Volvo RWD 140-160 Forum

.040 overbore, block decked to .003, crank and rotating assy balanced...

46 CC Chamber (as measured) plus swept volume...etc... says 10.8 to 1 CR

Suggestions where to enlarge chamber to get back to 10 to 1???

OR

Do I just need to find an "F" Head!!!???

Ron
Sonoma

1.Widen the chamber to 92mm front to rear if it's not already, use an old head gasket as a template.
2.Put an eyebrow in the block on the inlet side only.
3.Remove metal from the sharp corners each side of the plug.
4.Try and make it flat to concave around the side of the chamber leading up to spark plug from the inlet valve.
5.Lay back the quench area on the spark plug side.

OR Do I just need to find an "F" Head!!!???

Well if you can port the exhaust (which is harder than you think) the F head is capable of flowing a lot better on the exhaust side.

If I were you, I'd queue up for a VPD head. Which one you want would depend on what you want to do with it. If you want fuel economy & are staying with D-Jet injection, the economy F head which just has porting on the exhaust & dual springs is what you want, I think it's $650.

If it was mine I'd RUN it!!
--
George Downs, Bartlesville, Heart of the USA!

Thicker gasket?

Ruins the squish, and it will make it ping worse.

Actually, 10.8:1 isn't *that* bad with modern 93 octane pump premium as long as you build it with nice tight squish. Get a good measurement on the deck height of the pistons at TDC, then get a gasket (Cometic MLS or copper) of the right thickness for a tight .032" clearance to the head. The piston *almost* touching those flat sides of the head rather violently snaps the air into the combustion chamber area, which creates a lot of swirl that helps prevent detonation.

Alternatives include enlarging the combustion chamber. One no brainer is to take the sides out to match the bore. Then make a little more clearance around the intake (unshrouding). Possibly shrink the island around the plug some, but bear in mind that those flat shelves are there specifically to promote squish.

Here's what I did to an R-sport head I got on eBay. It came to me ridiculously shaved down, to something around 12.5:1 on top of a 2.0L bottom end, even worse on my 2.1L. I enlarged the chambers as much as I felt I could, and even then had to team it up with dished pistons (B21FT) that gave me another 12cc. Ended up in the mid 10's CR. With a nice tight squish it doesn't want to ping at all on 93 octane. With 87 octane regular, it will ping some.
--
'63 PV544 rat rod, '93 Classic #1141 245 +t

Get a good measurement on the deck height of the pistons at TDC, then get a gasket (Cometic MLS or copper) of the right thickness for a tight .032" clearance to the head. The piston *almost* touching those flat sides of the head rather violently snaps the air into the combustion chamber area, which creates a lot of swirl that helps prevent detonation.

Swirl DOES NOT come from the quench areas, Swirl comes from the bias of the inlet port & can be improved on with correct porting of the inlet port. The flat areas of the head are quench areas, not 'squish', they quench the ignition of gasses which is happening at that spot, the purpose of which is to reduce the the chance of preignition. Ideally the quench pads is as far away from the spark plug as possible.

Four valve engines don't have swirl, they have something called tumble instead. Some four valve heads try to induce swirl by having the two inlet valves open at different times, or by having separate manifold runners for each valve & then using a throttle in one of the ports to close it thus increasing velocity & inducing some swirl at low rpms.

.032" isn't bad, possibly the minimum, but there are many reputable engine builders who have lost power by going from .040" to .030", most notable Bill Jenkins.

I aim for something around .040" myself, but if it ended up being .030", I wouldn't worry, and if it was closer to .050", I wouldn't go out of my way to spend money to make it tighter because it makes so little difference.

Paul, sometimes I agree with you, and sometimes I don't. This one is definitely a don't.

You are correct about the quench, but quench is much improved by reducing the volume under the quench areas by bringing the head closer to the pistons. You are also correct that swirl does not come from squish, but tightening the squish has a number of significant benefits. In no particular order:

Intake charge trapped under the quench areas does not burn, and is wasted.

Exhaust gases trapped under the squish areas are not completely expelled and dilute the next intake charge.

Burn rate is made faster, requiring less ignition advance and allowing higher compression without pinging.

The faster burn transfers energy to the pistons more efficiently.

Less heat is transfered to the head.

All this is quite well documented, going back to Smokey Yunick in the 1970s. It works in Formula One, it works in two-strokes, and it works in old Volvos (it does not work on flathead engines, and does not apply to Hemis). Aaro, Parker, Hueppchen, and I all agree on this and have demonstrated it many times over.

I'll quote Smokey Yunick for you: I’ve also heard there are some builders who claim an engine will make more power if you let the “piston smack the heads a little.” I think this sort of talk is mechanical nonsense and I would not recommend it under any circumstances.

It is hard to recommend a desired quench clearance that will be correct for all engines, but I think 0.038-inch of clearance between the quench surfaces is an absolute minimum in an engine with a 4.00-inch bore and about 0.007-inch of piston-to-wall clearance. However, if the piston clearance is greater, say 0.009- to 0.010-inch, this may not be enough. A safe figure for all around performance is 0.040-inch. Anything up to about 0.045-inch is probably okay, and I wouldn’t worry about a little extra clearance as long as it was close to these recommendations.

But remember, if you let the quench clearance open too much – to 0.060-inch or more – you’re going to lose power. This much opening at the quench will allow excessive amounts of the intake charge to remain in the quench area as the piston reaches top-dead center, and especially if the piston has a high dome to obstruct the spread of the flame front, these gases may not be properly combusted during the ignition phases. This significantly reduces combustion efficiency.

Bill Jenkins likes to use .010” beyond ‘smacking clearance’ & that overly tight squish contributes to pumping losses. .050"-.060" static for a steel rod oval track motor.

Aaro, Parker, Hueppchen, and I all agree on this and have demonstrated it many times over.

I don't know who Mr.Hueppchen is, but I seriously doubt that Aaro or Parker could show a single HP difference between the same engine running .030" or .040" of squish clearance.

I've encountered two schools of thought among builders who believe in tight squish/quench on the first place (and a surprising number don't). One is that anything tighter than .040" doesn't accomplish anything. The other is that tighter is better, as long as there's no piston-to-head contact, and obviously that minimum safe static dimension will vary depending on the design and metallurgy of the specific pistons, running clearance, rods, redline, etc.

Smokey Yunick is often quoted as saying that .040" is about the minimum safe clearance -- I don't know what engine he was talking about, specifically -- but I can't see where he ever suggested that tighter wouldn't accomplish anything if it could be achieved without actual contact.

I find
this article to be a good overview, and it suggests much less than .040".

I've run .030" with forged pistons (Ross, they "grow" less than most other brands), .004" running clearance, and H-beam rods with no problems at 7500 RPM.

In any case, tight squish is NOT an internet myth, and decking a block is not a waste of money. It varies quite a bit, but factory B20s usually have the pistons a good .020" or .025" below the deck. Add a .035" carb head gasket (which is what the ones advertised as .030" actually crush to), and you end up with .055" or .060" clearance. Gaskets for injected heads crush to around .055", so you potentially have .080" clearance without decking. And then there are the .080" compression-lowering gaskets... which seem designed to guarantee more pinging and less power all at once.

I've had two cases where engines that already had good basic performance mods came to me, and all I did was deck the block. Both were completely transformed by this procedure -- same cams, same porting, same exhaust, same everything else. Even the exhaust tone became much crisper. Customer reaction upon returning from his first test drive: "Holy sh*t, Martha!"

Works for me...

I can't see where he ever suggested that tighter wouldn't accomplish anything if it could be achieved without actual contact.

Smokey Yunick didn't, but Bill Jenkins certainly has.

I've run .030" with forged pistons

What was the difference in performance between running .030" & .040" squish with everything else being the same?

Smokey Yunick didn't, but Bill Jenkins certainly has.

I don't know who Bill Jenkins is, but in the article I referenced, David Vizard calls for .030 and even .024 if you have super pistons and rods. We both know who he is, and he's clearly in the "tighter is better" school.

What was the difference in performance between running .030" & .040" squish with everything else being the same?

I haven't put it to the test. Have you?

Who is Bill Jenkins? He’s a guy that’s accomplished more than Smokey Yunick & David Vizard put together. If you can find a copy of his book, grab it, it is 10x more useful than the half dozen or so of Vizard’s books which I have.

I read the Vizard article. He says: “Most small-block Chevy engines have a static quench clearance of 0.055 to 0.065 inch. On a typical 400hp 350, cutting the quench clearance by 0.010 inch and holding the CR constant is worth about 3-4 lb-ft.” From the way he wrote that, we can assume that he has actually tested that part of the theory. That would mean going from .060” to .050” in a 120 cube B20 is worth 1 lb-ft. He then says: “This means decking the block (or using a skinny head gasket) to get the quench down to 0.030 inch is worth about 12 lb-ft.” This looks like he is simply jumping to a conclusion, but in a race engine, I'd go closer to .030" depending on how good my parts are, I just don't see how it could possibly be worth anything risking everything by shaving off another .006".

Did you read the rest of the article? There is way more power to be had by degreeing the cam & tuning the exhaust. Much greater bang for the buck in those parts of an engine. Notice what he says about what each lobe should be like too.

In any case, tight squish is NOT an internet myth, and decking a block is not a waste of money. It varies quite a bit, but factory B20s usually have the pistons a good .020" or .025" below the deck. Add a .035" carb head gasket (which is what the ones advertised as .030" actually crush to), and you end up with .055" or .060" clearance. Gaskets for injected heads crush to around .055", so you potentially have .080" clearance without decking. And then there are the .080" compression-lowering gaskets... which seem designed to guarantee more pinging and less power all at once.

What brand of pistons? Every stock one I’ve pulled apart has had the pistons .005” to .010” down + B20B & E have the same .028” crushed gasket, so I never take anything from a stock block.

I've had two cases where engines that already had good basic performance mods came to me, and all I did was deck the block. Both were completely transformed by this procedure -- same cams, same porting, same exhaust, same everything else. Even the exhaust tone became much crisper. Customer reaction upon returning from his first test drive: "Holy sh*t, Martha!"

So the only thing you did was deck the block & fit a thinner gasket? Nothing else was done at all? The head & cam were untouched, the carburettors & ignition were untouched, compression ratio was unaltered. What was the clearance before & after?

Who is Bill Jenkins? He’s a guy that’s accomplished more than Smokey Yunick & David Vizard put together. If you can find a copy of his book, grab it, it is 10x more useful than the half dozen or so of Vizard’s books which I have.

Oh, Bill Jenkins the drag racer / builder. I didn't know he had a book out -- will check it out.

read the Vizard article. He says: “Most small-block Chevy engines have a static quench clearance of 0.055 to 0.065 inch. On a typical 400hp 350, cutting the quench clearance by 0.010 inch and holding the CR constant is worth about 3-4 lb-ft.” From the way he wrote that, we can assume that he has actually tested that part of the theory. That would mean going from .060” to .050” in a 120 cube B20 is worth 1 lb-ft.

I wouldn't assume that -- the Chevy heads he's dealing with have much better swirl than a B20, and the B20 could therefore benefit more (not that squish causes swirl, but it does help mix intake throughout the chamber).

He then says: “This means decking the block (or using a skinny head gasket) to get the quench down to 0.030 inch is worth about 12 lb-ft.” This looks like he is simply jumping to a conclusion...

Unless he knows that tighter is better, and the improvement is linear. I can't tell from the article either.

but in a race engine, I'd go closer to .030" depending on how good my parts are, I just don't see how it could possibly be worth anything risking everything by shaving off another .006".

I've never dared go tighter than .030, and usually a bit larger than that, depending on the specific parts. But when I was first building the MPPE and trying to understand why this matters, the racing machine shop I was using decked the block for .037" clearance. Mike Aaro jumped all over me and I had to take it back and have another .005" taken off, so he, at least, thinks every little bit counts.

Did you read the rest of the article? There is way more power to be had by degreeing the cam & tuning the exhaust.

I'm not about to dispute that for one second.

Much greater bang for the buck in those parts of an engine.

Decking is cheap, and I maintain there's quite a lot of bang to be had from it, and also for other mods that can be taken farther because of it.

Notice what he says about what each lobe should be like too.

Yes, I hadn't heard that one before -- interesting. Why does a slower valve velocity work better for exhaust? I understand how a B20 might want longer duration on the exhaust side, but why not high velocity as well?

What brand of pistons? Every stock one I’ve pulled apart has had the pistons .005” to .010” down + B20B & E have the same .028” crushed gasket, so I never take anything from a stock block.

I'm talking about factory engines with no prior rebuilds. On the ones I've bother measuring, the pistons are generally down .020" or more. The current Elring B gaskets crush to .035" (they are different from the old ones), and we don't have the .030" nominal E gasket here -- the injection ones are all .050" nominal now. The Elring big-bore gaskets are marked as crushing to .047", but actually go no thinner than .055". Bottom line is, these days I just tell my machinist what I need the deck height to be, and I don't even bother with taking "before" measurements anymore.

So the only thing you did was deck the block & fit a thinner gasket? Nothing else was done at all? The head & cam were untouched, the carburettors & ignition were untouched, compression ratio was unaltered.

That was absolutely the only change. Same pistons, same cam, injection untouched (it was a D-jet engine). Compression did come up slightly from decking, of course, but I don't think that accounts for much of the improvement.

I originally said this: I aim for something around .040" myself, but if it ended up being .030", I wouldn't worry, and if it was closer to .050", I wouldn't go out of my way to spend money to make it tighter because it makes so little difference. and I stand by it.

The rawits has stated that he is on a budget, so I would have spent the money on machining the spring pockets for better springs or something else that is more important.

That [decking the block & reducing the quench] was absolutely the only change. Same pistons, same cam, injection untouched (it was a D-jet engine). Compression did come up slightly from decking, of course, but I don't think that accounts for much of the improvement.

If the reduction in clearance didn’t automatically force a change in the required amount of ignition timing, then the timing must have been wrong for the motor before you touched it. Also, if you made an insignificant change to the compression ratio, then you must have removed an insignificant amount from the deck. Additional compression ratio is always going to be a bigger factor in power development than altering quench. Perhaps a simple adjustment of D-Jet fuel + alter the ignition timing is all it needed in the first place.

I'm talking about factory engines with no prior rebuilds.

What brand of pistons? 6 or 8 bolts?

I've never dared go tighter than .030, and usually a bit larger than that, depending on the specific parts. But when I was first building the MPPE and trying to understand why this matters, the racing machine shop I was using decked the block for .037" clearance. Mike Aaro jumped all over me and I had to take it back and have another .005" taken off, so he, at least, thinks every little bit counts.

Do you actually believe that there is a worthwhile difference between .032” & .037”? Mike Aaro doesn’t impress me much, especially after you told me he opened up your exhaust ports to gasket size, that a very basic porting mistake. He really should have been able to tell you exactly how to jet your Webers since he provided the head & told you what cam & headers to use.

Notice what he says about what each lobe should be like too.

Yes, I hadn't heard that one before -- interesting. Why does a slower valve velocity work better for exhaust? I understand how a B20 might want longer duration on the exhaust side, but why not high velocity as well?

I’ve been saying that for years, my very first low budget engines I was building myself in the late 80’s when I was a lowly paid apprentice + the Australian dollar was terrible featured 4 dual springs on the intake to save money + a dual pattern cam with a fast & high lift intake lobe & gentle stock lift exhaust lobe. The reason is two fold, the exhaust valve has to open against seat pressure + exhaust gas pressure on the valve head, so it can’t be as tough as the inlet. Reason two is the exhaust valve is smaller, so it just doesn’t need the same lift.

....the Chevy heads he's dealing with have much better swirl than a B20, and the B20 could therefore benefit more (not that squish causes swirl, but it does help mix intake throughout the chamber).

I don’t agree with that at all, I feel the number one reason that you can make a decent engine out of a B20 is because the inlet port provides good swirl & it’s easy to modify it to make great swirl. I still prefer to call it quench rather than squish too as I believe the primary point of having it is to extinguish any pre-ignited pockets of air/fuel mixture at TDC. If the gap is too wide, you don’t get quench action & the combustion chamber then reverts to being like an open chamber design which then forces you to run a lower compression. The squish action stirring the mixture is a very minor thing IMHO.

Bill Jenkins book is great. Long out of print but you can find it on Amazon or eBay.

Every virgin block that I've seen has the pistons .015-.018 below the deck.

I don't think the question is if tight squish helps but rather how much. For the cost of a heavy clean up cut on the block and a $20 Elring .032 thick gasket it just seems the to do.

Charlie

I don't think the question is if tight squish helps but rather how much.

Quoting from http://www.rbracing-rsr.com/squishcalc1.html (these guys build land speed record-setting Harley engines):

"It's a simple fact: The closer the flat of the piston to the flat of the combustion chamber, the more power you will make. In a race engine with all the factors considered you practically want the two surfaces touching one another. In F1 they machine each piston individually even for the spark plug relief."

Quoting from http://tinyurl.com/ojs46g:

"Most conventional ports do induce a very small amount of swirl, but this is not important as far as generating much turbulence. Rather, the biggest benefit is obtained by reducing the squish band to it's safe minimum (about 0.020-0.040 in, depending on the particular engine used). This will have a far greater effect on increasing the turbulence in the combustion chamber than any other modification."

And from the next paragraph:

"It is important to realize the two important functions of reducing the squish band clearance: (a) to enhance turbulence due to rapid ingestion of gas into the combustion chamber, hence increasing the burning rate of the mixture and (b) to reduce the volume of the unburned gas in the boundary layer of cool gas near the piston top and cylinder head surfaces. Typically, gas trapped in the squish area doesn't burn, even if the squish band clearance is relatively large. The cooling effects of the large surface-area-to-volume ratio of this region will prevent any ignition of the fuel-air mix therein, even if the squish band clearance is rather large. Hence any gas caught in the squish band will not be burned near TDC when it does the most good, but later during the combustion process when one cannot extract as much work from the late-burning gases. The amount of gas trapped in the squish band can actually be a substantially greater amount than just the relative volume of the squish band because the pressure wave from the ignition process literally crams a lot of the unburned gas into crevice areas like the squish band. Reducing the squish band clearance will decrease the amount of unburned gas substantially, leading to more complete and faster combustion, lower emissions and improved power."

My machinist, Ed Trihey, has built scores of record-setting engines (he's mostly known in boat racing circles, but also has had much success with cars), and he's never once said to me, "Don't run the clearance that tight or you'll make less power."

YMMV...

http://www.rbracing-rsr.com/squishcalc1.html & http://tinyurl.com/ojs46g

They are correct, but in both cases they are talking about Harley's which have Hemi heads. Pure Hemi heads are possibly best two valve design for breathing, but the worst design for combustion. The intake gives no swirl like some other two valve head designs are capable off & no tumble either which four valve heads have. Addition of quench is essential to Hemi, partially because it reduces the combustion area.

My machinist, Ed Trihey, has.....never once said to me, "Don't run the clearance that tight or you'll make less power."

What clearance did he recommend?

They are correct, but in both cases they are talking about Harley's which have Hemi heads.

Not so. In the RB Racing article, read the paragraph immediately following the one I quoted, and look at the illustration further down the page. The other article on motorcycle.com does use a Hemi in the illustration, but does not ever mention that the advice applies only to Hemis, and the site is not Harley specific.

What clearance did he recommend?

Whatever I think is the minimum safe clearance for any specific engine.

Not so. In the RB Racing article, read the paragraph immediately following the one I quoted, and look at the illustration further down the page.

Harley's have their valves in a Hemi layout.



None of their heads look anything like this, the illustration is a bad joke, there is no engine that looks anything like that when cut in half. The layout shown in the picture has quench covering half the piston, which make it very bad.

From the RB Racing page: It's a simple fact: The closer the flat of the piston to the flat of the combustion chamber, the more power you will make.

That might be true if you were to ignore pumping losses, but it's like raising the compression, were there are diminishing returns due to pumping losses.

Bill Jenkins book is great.

I really liked his explanation of balancing Cam LCA, Rod Ratio & Head Flow.

Back in those days when the head was the limiting factor on an SBC, it really helps to have a longer rod ratio and/or tighter LCA. These days were you can get the required CFM & CSA from an off the shelf head for SBCs, the rod ratio becomes insignificant & the LCA can be widened.

Other people discussing the same topic!

http://speedtalk.com/forum/viewtopic.php?t=17123

They cannot decide either!

No one could possibly argue against bigjoe!

One no brainer is to take the sides out to match the bore.

At .040 over, cylinder bore is 90mm and the chambers are already 92mm across.

Then make a little more clearance around the intake (unshrouding).

NOT outboard of the valves, which will actually hurt flow. The major squish area -- the flat edge opposite the spark plug -- can be cut back somewhat, as can the outer edges of the wedge the plug threads through.

Then make a little more clearance around the intake (unshrouding).

NOT outboard of the valves, which will actually hurt flow.

Where are you thinking of?

The major squish area -- the flat edge opposite the spark plug -- can be cut back somewhat, as can the outer edges of the wedge the plug threads through.

I'd get rid of all the squish around the spark plug first before touching the major quench area.

I'll post pictures tomorrow. we didn't touch quench, just unshrouded valves. Rich uncle came through with more cash...so we did the dual spring thing.
Dema Elgin suggested a 274 deg duration cam with net lift of .427. Exhaust lobes ground 2 deg advanced. I remember him saying the lobes are much like SB Chevy's. Odd...he notes .014-.016 for intakes, .016 for exhaust. I asked for 150HP between 2500 and 6000 (not rear wheel)

I apologize for using an unknown cam builder, but when we talked for a while, and found out about our shared experience from SCCA early '70's (I was a Fire Control guy, he raced HP Sprites)...I must have pushed him back on track many a time along with his buddy Bernie Storc)...I had to try one of his cams. After all, it's just a street rod.

Nice thing, there's a dyno shop next door; $ 150 for three runs. we'll dyno after break in.

Do you know lobe lift & duration at .050"? Is it a 685-16

Has the cam been ground yet, if not, I REALLY think you should ask for a dual pattern cam. I'd request an 'A3 Cosworth' for the exhaust lobe, they know exactly what that is, they list the larger A6 & A8 at the Elgin website.

Elgin is not unknown, I have sent people here to Elgin's writeup in the past. It's a good read.

I remember him saying the lobes are much like SB Chevy's.

What cam profile you can use is determined by the diameter of the lifter. Volvo is the same as SB Chevy, BBC, English Ford pushrod motors, Datsun 1200, pushrod Toyota 1300's, etc. The lobes I have used have been from all those & more.

Again, I really think you should get a dual pattern cam if there is still time, I will email them myself if you like.

Finally, DON'T forget to degree the cam in! At least 4 degrees of advance.

AS of today...it was not ground yet. It's 230 deg at .50, .295 lobe lift.

I asked Elgin about a dual pattern...he said it was unnecessary...he's at dema@elgincams.com (dema short for Dmitri)

What's your reasoning? Broader powerband, is what I want, not extreme horsepower at a narrow RPM of 4-7000 ...Who idles at a stoplight at 4K???

My full name is Ron Whitsitt, and my cam will be delivered to Jerry White at JNW Machine...how would you propose to tell a man whose been grinding for thirty years, that he's suddenly mistaken?

I suppose an anonymous note from a blind nickname is something this man really wants to deal with...

Now that the rich uncle died...maybe I should get a cam from you, one from Phil S., one from JP, and do some testing... because Phil commented to me privately "They think they know everything, and none of us actually do. No one does."

I asked Elgin about a dual pattern...he said it was unnecessary...What's your reasoning?

The exhaust port flows very poorly relative to the intake, that's the main reason for running extra exhaust duration with any engine, Also, you are running high compression, so you can open the exhaust valve earlier to reduce pumping losses because the mixture burns faster. (Low compression motors are slow burners, you have to open the exhaust port later with those)

Modern engines with four valve heads have so much exhaust flow that they can & do have less duration on the exhaust than the intake.

Now that the rich uncle died...maybe I should get a cam from you, one from Phil S., one from JP, and do some testing... because Phil commented to me privately "They think they know everything, and none of us actually do. No one does."

I'd simply specify a cam from Elgin, since that is the easiest way for you to get a cam, so if you want to do a back to back comparison, he'd be grinding both. The one I would use would be very similar to the VPD SP Cam if you are intending to use stock, unmodified D-Jet. There probably wouldn't be much difference between the four different cams, but I know mine would last longer & have less chance of flattening a lobe.

What specs did Phil recommend?

What specs did Phil recommend?

230 @ .050", camlift .300", 108 LSA, pretty close to the Elgin cam he's having made up as far as I can tell. It's not dual pattern -- I may try one next time around.

Thanks Phil, do you have any other duration@lift measurements for it?

No partial lifts on that one, sorry... At .012" lash and 1.46 rocker ratio, duration is 274 and valve lift .438".

Actually, Phil suggested a dual pattern cam from Schneider Racing...something with lower lift but greater "velocity", about 272 deg duration. A Phil S. "Special" street performance.

Since the rich uncle died, we went with 36mm SS Exhausts, stellite seats and some exhaust seat throat port work, opened and radiused really nicely...if I had $ 500.00 really extra, I'd put in on a flowbench to see how it worked.

I'm hoping to run the Mikuni HSR45's for now (currently on B20B)

Phil suggested a dual pattern cam from Schneider Racing...something with lower lift but greater "velocity", about 272 deg duration.

There is zero information about the cam in that sentence except Phil's, VPD & my choice are all dual pattern.

I'm hoping to run the Mikuni HSR45's for now

I was always under the impression that you were building a motor for D-Jet.

With Twin Mikunis I would say go with the what Elgin recommends on the intake, but I would change the exhaust to something with more duration. Elgin 71-15 or A-3 exhaust.

How much for Elgin's cam vs the others? Are you using duals springs from Elgins?

Yes, this is what I would do. You can enlarge the chamber a couple cc's and improve airflow a bit.

such talk makes me want to pull apart my 'mystery' engine.. but I can't do that. Can't fix that which ain't broke.

I estimate about 1/8" was taken off the head... I've peeked and the pistons don't look dished, but maybe they are.. spark plug holes don't provide the best view... Maybe some day I'll blow the thing and be forced to take it apart... until then, I'll give it my best effort ;-)

--
-Matt I ♥ my ♂

Spoken like a true enthusiast there, Matt! If you can borrow or buy(!) a borescope you'll see what kind of pistons you've got right now.