Hey,

Rebuilt my 30hp 1200 for my oval and put it in the car, having adjusted her and given her a few runs.

I have two problems. Firstly, i replaced the gasket under the dynamo at the top of the oil fill/dynamo stand. However, it is leaking oil very badly, made another thicker gasket and its now worse! Even if it had the correct gasket, is ther supposed to be oil coming out of there? Filled the oil up to the correct level according to the dipstick. Unfortunatley its gone all over the clean case/inlet manifold and tinware :o(

Second problem when accelerating i have a serious lag-time on acceleration and she actually cuts out sometimes when i approach junctions and apply the clutch. She starts first time and idles perfectly. It seems clear to me that she is running lean as when the choke is out she runs beautifully, its just as soon as i disengage the choke that the problem starts. I have bought some gungum, which i intend to apply around the inlet manifold and exhaust.

I removed the new plugs yesterday ,they're a little black from overcompensating the mixture with the choke, checked the gap it was 0.5mm.

Am i on track to solving it do you think? would be greatful for any feedback or help, thanks in advance,


Cheers

As you were,

While you're waiting for a 30HP expert to reply...

Could the combustion gases be blowing past the piston rings for some reason and causing pressure in the crankcase? A compression tester should give you a good idea whether anything is seriously amiss here.

I don't know the answer to this... Should the cutout in the gasket be a fair bit smaller than the 'hollow' in the generator stand? I'm mentioning this just in case your 'template' gasket was half missing! :lol:

The engine casings look great by the way, how did you clean them? Looks like a lot of hard work and Solvol Autosol from here.

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Hi,
As you say, it sounds like you may have an air leak somewhere on the inlet manifold.
I've not tried this but have read that if you spray WD40(?) around the joins on the manifold while the engine is running, when you spray around the leak the revs will pick up.

As tman says above, it sounds like you could have too much oil pressure.
On a performance engine I would suggest adding some breathers but not sure of the cause or solution on a stock 30hp engine. Sorry!

If you don't have any luck here, I would post the problems over on The Samba vintage speed forum 
There are loads of 36hp engine builders ever there!

Malc

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Cheers guys,

all help is appreciated, i think i may post it on the samba as you suggest. The engine has new piston rings and seals, so i'd be surprised (doesn't mean its not the case though, you're right a compression test might be a good assessment, even if it just narrows it down.

I cleaned the case by hand as the outside of the case appeared rather soft due to age. I wire wooled it with a bit of meths, over the entire case! Took a while, trust me.

I shall try the WD40 test, i'm going to apply some sealant to the exhaust system hopefully over the weekend so i shall see how that affects it if anything.

Cheers

It does sound like piston blow by .Are the Barrels and pistons new ? .New rings are only worth fitting if your barrels were very low mileage with no ridges at the top of the barrrel .Any ridges will break the rings and if they do survive will not seal properly causing the problem you describe.It is also possible the rings moved on assembly so the gaps are inline giving the same problem.I personally prefer to set the timing with a strobe especially with an old distributor which could have weak springs or defective vaccum can.You can check the advance is working ok which could also be your lagging problem.I also use a leakage detector rather than a compression tester ,you would be surprised what a difference it makes.

Good luck.

Cheers for the comments,

Certainly i had the barrels out and they were ridge free, i will try to dig up some photos, i also honed them. When i assembled the engine, the rings were so tight in the barrels that i was unable to turn the engine over as the rings were wedged in the barrels, i adjusted the ring gaps and spent care and attention on the honing to get it smooth.

Its still possible of course but i would be very surprised as i had so much trouble with them being so tight, surely though, i would have excessive oily deposits around my heads and valves if this was the case though wouldn't I?

I shall definately get a timing strobe on the car soon, im not familiar with a leakage tester? How does that function? I'm actually very concerned about the connection between the vacuum advance and the carb body, if air was getting in here, would that be likely to be the cause of the acceleration symptoms?

The engine was running very lean when i bought the car, and appeared to have this prblem then before i rebuilt her.

Thanks for your help,

https://en.wikipedia.org/wiki/Leak-down_tester 

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it is very unusual to have to file the ring gap these days .In my experience either the piston ring groove has a build up of carbon stopping the ring from compressing or you were sold 0.5mm oversize rings.Its a real pain but you may have to strip the top end just to see how things look now you have run it.If it was just the lagging problem i would say to try other things but crankcase pressure bad enough to cause an oil leak at the stand is not good news.Building these engines is a pain because of the lack of good quality parts around .I paid nearly £300 for what i considered to Brazilian quality Barrels and pistons.Other parts are equally expensive and just as poor quality.

I rang vw heritage and checked that i had been sold the correct ones as soon as i found them tight, they were also very brittle. They verified they were the correct ones.

I will check with a leakage tester, (thanks tman for the info link) am i correct in saying that the oil filler has a breather that drips into the road? Surely any excessive pressure should vent through there??

I know what you mean, i bought a new oil pump cover as the old one was quite badly worn by the gears,. The new item is far from identical in fact doesn't appear to fit well at all. I shall replace the old item, when i next have the engine out. (Iassume this wouldn't be related!!)

I must admit i'm finder these old engines so fussy!!

Thank you again for all your suggestions.