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I am in the process of tearing down a B20 to put a K cam in it, do some headwork, and possibly re-ring, etc.
The motor was recently freshened up, and it has a seemingly brand-new fiber cam gear in it, mated to a much older looking steel crank gear. My questions is whether, if pulled with care, these fiber gears are reusable. Some people say no, others say just be careful with it.
If it must be replaced, is there any sense replacing it with an aluminum gear and mating that to the existing steel crank gear? I know the best scenario is buying matching steel gears, but that's a lot of money I'd like to avoid.
Any thoughts on my best option?
reuse fiber gear?
buy inexpensive aluminum cam gear only?
pony up for a steel gear set?
Thanks,
Tyler
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posted by
someone claiming to be
on
Wed Dec 31 18:00 CST 1969 [ RELATED]
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There's nothing wrong with reusing the fibre gear provided it is within specs, just use caution removing it. The K cam is much kinder to the valvetrain because the D was actually Volvo's 1st attempt at a race cam for the B18B. Make sure you install the K cam 4-5° advanced too.
How much oil does it use? When you pull the head, you can get a good look at the top rings, see what size the bore is and how much lip it has.
Dual or beehive springs depend on how much and how good the porting is on your head. Dual springs extend the life of the seats and once the intake seats are worn, there is no way back and you have to spent all that time/money/effort on another. On my best head, I have used 3 new sets of springs over time and avoided loosing the head via seat wear. How much money do you want to spend?
--
69 142S Overdrive + 69 164S Manual
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posted by
someone claiming to be
on
Wed Dec 31 18:00 CST 1969 [ RELATED]
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I think Tfrasca has solved his timing gear problem.
I saw him PMing RedWood Chair over on Turbobricks about the used steel set he has for sale.
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posted by
someone claiming to be
on
Wed Dec 31 18:00 CST 1969 [ RELATED]
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A trick I learned from a Marcos racer is to narrow the cast iron/steel gears by half. I'll do that one day, but it sounds like a lot of work.
--
69 142S Overdrive + 69 164S Manual
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posted by
someone claiming to be
on
Wed Dec 31 18:00 CST 1969 [ RELATED]
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Planetman is right, I bought a used set of steel gears in great condition from Ken.
I'm curious about two things though:
Advancing the K cam 4-5 degrees? This is done through clocking the cam gear a tooth or two? What do I gain from this versus running it at 0 degrees (aligning the marks on the crank/cam gears)?
Milling the timing gears in half. To reduce rotating mass?
Thanks for all the input. I'm getting excited to gather the pieces I'll need.
TF
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posted by
someone claiming to be
on
Wed Dec 31 18:00 CST 1969 [ RELATED]
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Milling the gears to make them lighter, probably for racecars only, purely to save weight.
Cam timing is done with offset keys. 2 valve engines of every brand with limited breathing typically require 4° of timing generally gives the best average torque. The factory spec is 0, but they don't actually set it, the parts just get tossed together and you get something around 0. The worst timing I have seen from buying a cam and tossing it in is 10° retarded. Degreeing in a cam is an essential part of engine building, i consider it as important as ignition timing.
--
69 142S Overdrive + 69 164S Manual
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posted by
someone claiming to be
on
Wed Dec 31 18:00 CST 1969 [ RELATED]
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Aluminium is OK so long as it,s a matched set. Putting it onto a worn crank gear would be horribly noisy. If you do fit cam gear to original crank gear make sure there is backlash between the teeth.
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posted by
someone claiming to be
on
Wed Dec 31 18:00 CST 1969 [ RELATED]
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If you are using dual valve springs, then steel gears are the way to go.
Even though it costs me a guaranteed repeat job, I always suggest to my customers to upgrade to the steel timing gears set. Yes, the steel gears can be noisier, but the customer will never have to pay for another timing gear job. And even when the camshaft wears out, the steel gears can be reused.
I personally don't like the aluminum camshaft gear as we broke 1 on our race car a long time ago, but we were running dual valve springs.
And AFAIK, you can't get the aluminum cam gear by itself, it should come with a new crankshaft gear. FYI, the crankshaft gear that comes with the aluminum timing gear, doesn't come with pre-drilled holes for removing from the crankshaft.
It is possible to reuse the fiber gear. Just check to make sure the gear isn't worn by checking for excessive play and check that the metal hub is still firmly bonded to the outer fiber gear.
New aftermarket fiber gears are available and I usually have them in stock.
--
Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
hiperformanceautoservice.com or oldvolvosonly.com
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posted by
someone claiming to be
on
Wed Dec 31 18:00 CST 1969 [ RELATED]
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As always, thanks for the info, Eric.
The aluminum gear I was going to get was second-hand, hence the fact that it didn't come with a crankshaft gear.
I'm leaning toward just buying a steel set from you. I had been looking at the prices on another popular Volvo parts site, but your price is nearly $100 less. That makes it a better option for me.
While we're on the subject of valve trains- do you think I'll be ok with stock springs with a K cam? If I keep stock springs, is there any sense using HD lifters/pushrods? I drive this car strictly on the street, and don't plan on revving over 5k often, if ever.
That being said, I'd like to do this once. I'll be having my F head decked a bit to get near the 10:1 CR range, adding the K cam, but everything else is stock. SU carbs, too.
Any input on that?
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posted by
someone claiming to be
on
Wed Dec 31 18:00 CST 1969 [ RELATED]
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IMO If you're never going to rev the engine beyond about 5K, the K cam still has a bit in hand there, spending extra money on "heavy duty" items will be a waste. If needed, spend the money getting the SU's properly rebuilt. Good quality new valve springs a good idea of course. Consider getting your rockers rebushed and if the rocker shaft shows signs of wear replace that. The valve gear will run quieter and control the valves better. A couple of pounds off the flywheel and rebalanced will feel like extra power. Flywheel balance should include the clutch cover if possible.
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posted by
someone claiming to be
on
Wed Dec 31 18:00 CST 1969 [ RELATED]
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Planetman suggested checking the fiber cam gear for solid attachment to the steel hub. If the gear is separating and is well along you may be able to see the gap - or even find play. What I look for is oil streak stains emanating from the hub outwards - a sure sign that oil is working its way between the two.
As for the cam and choice of related parts--all the steel gear sets I've seen have twice the number of teeth as the fiber gear and crank gear--meaning they have to match.
I started with a B18 in a '68 144 and later transferred the K cam and all the rest of the parts to a '69 144 B20. My cylinder head is from a carbed 44mm exhaust valve B20 motor--milled a huge amount to bring compression to over 11:1. The cam, lifters and fiber timing gear now have in the neighborhood of 200K miles. I attribute the long life to the SB Chevy lifters (and tubular pushrods needed because the Chevy lifters are a different length than stock). As a serviceman I've had to change many worn out cams and lifters - even in motors that have had regular oil changes. I think the Chevy lifters and the cam just seem to get along better.
My car has been run in about 35 Time Trial track days and will rev to 7k with stock springs. Good luck with your build. -- Dave
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posted by
someone claiming to be
on
Wed Dec 31 18:00 CST 1969 [ RELATED]
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Good to know. I don't need CR numbers that high, but I'll basically be building the same motor as you. I say that I won't likely rev past 5k, but the current B18 in my 142 falls on its face at 4500, and sounds like it's going to explode at 5, so maybe that where my reticence comes from. If I build a motor that is still pulling at 5k, I'm likely to wring it out every so often.
Regarding carbs, I already spent the money to have my SU HS6's properly rebuilt (new throttle plate bushings, and all new brass parts), so I'm good to go there.
The flywheel felt ungodly heavy when I pulled it, so I'm also thinking about weight there. Any ideas how much it can lose without starting to feel like a honda civic in traffic?
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