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Hi, going through all that's to be done on my 1965 121 (i.e. preparing the parts order and counting my cash...), I've now come to the fuel system.
Carbs:
For several 10km, I've had the following problem with my HS6's: with the air filters off, when I rev the engine up the two pistons of the SU's go up smoothely almost to the max. At one point, the rear one keeps going up while the other one falls to mid-level of the carb's throat and stays like that. I beleieve it does the same when driving (haven't been able to check ;-)).
Option 1:
These SU's are a bit worn and would deserve a good overhaul, but I doubt a complete overhaul kit will do the job: changing the bushings and all that's in the kit won't solve what I believe is a vacuum problem. So is there a place where one can source the suction chmber and piston for an HS6 carb? at what price? I think it's the only way to get my SU's back on the road. Am I wrong?
Option 2:
I know there are places that sell rebuilt SU carbs, but considering the price, I thought: hey, why not get 2 Weber DCOE 40 instead? I can get a pair for not so much money (1/3 of the new SU's) that are set up as follows: venturis are 32, main jets 130, aux.venturis 4,5, air corrector jets 200, emulsion tubes F9 idle jets 50F8, accel pum jets 35. These units would be on a standard B20E. Do you think they would be suitable without having to change all the settings (adressing the weber converted Volvos owner's here...).
Ok that'a all folk, my post is long enough. Sorry for that, but I think every detail is needed to answer, richt? Thanks in advance for you inputs! Cheers, Séb
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If I were you I would make sure the cam hasn't gone south. Seems really
strange to me that the carbs would operate that differently but only PART
of the time! Check your valve lift and make sure they all lift the same.
Should be a little over 3/8" at the valve spring retainer.
--
George Downs, Bartlesville, Oklahoma, Central US
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posted by
someone claiming to be anthony
on
Fri Oct 15 21:14 CST 2004 [ RELATED]
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Hello George,
I had a problem like that on my SU, the pistons won't go up the same level. Although the springs and everything match, but still. It's because the air wants to travel through the carb it can pass easier (Because volvo has such a big syncro tube.) So what I did was chopped the intake up into 2 pieces ,closed up the old big holes, and made a syncro tube myself out of 8mm tubing. This seems to work quite well as the syncro tubes can really take effect only during idle. Now the pistons go up about same height on both carbs with throttle on. And helped some strange mixture problems I had with one going lean in some conditions. :)
But overall, I guess I went through all that because I was bored.
Not much use of doing that, really...
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Those jets are a good starting point. You'd be able to drive the car.
Note what JohnMc says about how hard it is to really tune Webers correctly, though. The performance difference between "pretty close" and "really right" is significant, and the economy difference is huge.
Webers are great if you are prepared to learn a lot and spend a bunch of money experimenting.
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posted by
someone claiming to be Rhys
on
Fri Oct 15 11:39 CST 2004 [ RELATED]
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Is that your engine Phil? Outstanding!
Rhys
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Technically, it's my wife's engine... but I pretty much stole her car 20 years ago.
8^)
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But it's not RED!!!??!!
--
George Downs, Bartlesville, Oklahoma, Central US
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The car used to be white with a red interior. She always loved the car, but never liked those colors. So when we redid it, she wanted nothing white or red, including the motor.
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I replaced a fairly decent and well tuned set of HS6's on my PV's engine with some DCOE 40's with 32 mm throats last year. it is true that Webers are much more tuneable than are SU's, however left unmentioned in that statement is that tuning them involves buying expensive unreturnable little intricately machined brass bits in sets of 4. Unlike SU's with a spring or a needle in sets of 2. There is no overall mixture adjustment on a Weber like there is with the SU. You can accomplish a minor tweak by messing with the float bowl fuel level, but mostly you have to swap parts. There is an idle mixture adjuster screw, however.
As with most things relating to the fuel system it's very easy to get it to run at all. Pretty easy to get it to run pretty good. And very hard to tune it very well. I have a wideband O2 sensor on my car so it gives me a better clue as to what is going on in various operating conditions. I got a nice imporovement by changing from the original style mechanical pump to an electrical one with apressure regulator - the mixture seemed more erratic before - I suspect the mechanical pump and its squirts of fuel were giving the DCOE's some fits. I've put some 36mm throats in and while they didn't work well with the 'D' cam (major bog when pressing on the accelerator at low speeds) I tried them again once I had put a modified head and 'R' cam on the engine and they worked quite well. And then the #2 rod bearing spun...
Another thing to think about before sinking a lot of money into Webers and parts for them is a modern add-on FI system like MegaSquirt - there are some posts floating around regarding that. Sounds more promising in terms of fine tuning - better to just tweak a table of numbers exactly as you'd like than swap parts and hope they will correct a problem without adding another one.
PS - fogot to mention - the power and throttle reposnce of those DCOE's makes up for any hassle and expense in setting them up! VROOM!
--
I'm JohnMc, and I approved this message.
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Séb
On the SUs, talk to Rhys Kent at:
http://www.sucarburetors.com
His posts on the forum here indicate he is very well versed.
I think his prices are really reasonable on his rebuilt SUs too.
I looked at DCOE Webers myself, but for daily driving it seems to me that the SUs will take a lot less care and feeding. Phil S made a very telling observation to me a while back on the dual throat webers: "The good news is, Webers are almost infinitely adjustable... the bad news is, Webers are almost infinitely adjustable."
I have a set of old worn SUs and even so, they are pretty forgiving and are still adjustable enough to be made to run well. Mine are going to go to Rhys at the first opportunity.
Be careful, Unless you have a great deal on the line for a new set of Webers equipped as you spoke of, you could end up with an old worn set that could end up being a real "basket of snakes" due to wear. Best I have seen for a set of new DCOEs a, manifolds and linkage is in the range of $1000 USD.
I'll bet Phil will chime in here with his observations shortly!
Cheers
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One good thing, among many, about DCOE webers is that they generally don't wear out. They have ball bearing throttle shafts and so do not wear shafts like SU carbs.
Also, although new sidedrafts are very expensive, list is more than $450 for a single 45DCOE, used 40 DCOE and DCOM carbs are available relatively inexpensively, often under $200 a set as these were OEM equipment on certain Italian cars. You still have to add manifolds at over $200, and air cleaners, and linkage. But the performance can be really nice.
John
v-performance.com
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posted by
someone claiming to be volvolio
on
Fri Oct 15 06:27 CST 2004 [ RELATED]
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Wow, that's a nice clean set of SU's there on the front page. Any idea around how much they charge for a cleaning and rebuild, fairly standard package with at least the teflon bushings?
- V'ster
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"Completely rebuilt including new throttle shafts and plates, new Teflon throttle shaft bushings, jets, float valves and gaskets, $350.00 exchange per pair.(Current US price $275.00) With gold cadmium plated ferrous parts, polished dashpots, and new fuel needles of your choice, $450.00 exchange per pair (Current US price $350.00)"
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posted by
someone claiming to be Rhys
on
Fri Oct 15 11:42 CST 2004 [ RELATED]
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Thanks to everyone for mentioning my company.
The carbs will perform like new, or better, regardless of the deluxe or standard overhaul. If new needles are required the standard overhaul increases by $33.00. In any event, the engine will perform like Volvo intended, which is smooth and reliably, albeit at a lower performance level than the Weber DCOE set-up, but as Phil says, with a lot less hassle.
Rhys
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Before you go and spend lots of money on new carbs, check the drop rate of the air pistons and suction chambers by removing them clean each piston & chnmber meticulously especially the circular grooves on the piston, drain the oil in the dashpot, plug the breather hole and remove the spring. Drop the piston into the chamber and if it's less than 5 sec to hit bottom, you will need new parts. Note, 12 sec, fantastic, 7 sec pretty good, 5 sec marginal, 3 sec, runs bad, less that 3 sec scrap them.
--
'89 245 Sportwagon, '04 V70 2.5T Sportwagon
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Thanks for the tip, Pete!
I'll do that one tonite.
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posted by
someone claiming to be Derek UK
on
Mon Oct 18 01:19 CST 2004 [ RELATED]
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After you have cleaned the dashpots and pistons, petrol or carb cleaner only, definately NO POLISHING, you could try swapping the pots over to see if the rise characteristics move with them. Sometimes the pot can be tightened down a few thou off centre. Might be just enough to give a little extra gap around the piston. Check when you're doing your drop tests.
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