The V8 Owners Forum -

My engine is an old P6 engine with carbs. It had all the usual oil leaks (pouring out!!), so I've just had it out, done the front & rear crank seals (new type replacements), sump gasket, timing cover gasket, composite head gaskets, compo valley gasket, rocker gaskets. The dizzy's been out of course but nothing else has been off.

Put it back, refilled it, and now it sounds like a bag of nails - it was sweet as anything before. It runs, but it's noisy - sounds like something happening on one cylinder, as it seems to be just once per rev. Obviously I haven't run it for long.

What could I have done wrong? My first thought is a misplaced pushrod so a valve is jammed open maybe? But they seemed OK. It turns over nicely enough manually with a socket on the crank pulley. I haven't opened the oil pump so I didn't think it would need priming. Not many other ideas.

I'd really like some pointers before I go poking about and taking it all apart again. I'm thinking compression test first, then check for oil pressure.

Any ideas please?

Whip the rocker covers off, start the engine and see if you're getting oil to the top end.
Have you checked the pressure guage? What does it read?
Did you fill it with oil? - might sound obvious but you wouldn't be the first!

The composite head gaskets being thicker (and providing a better seal) raise the head slightly compared to the original tin gaskets. This lowes the compression by approx 0.6.

When using the composite gaskets though on your 14 bolt heads, the rocker assemblies are also slightly further than they were originally from the camshaft. Now the lifter preload, the distance between the flanged head of the pushrod and the distance that it fits into the lifter has now decreased below original specification. As such, there is less free movement between the pushrod and the lifter.

To correct this problem you can either replace your composite head gaskets with tin ones, or you can have the base of each pillar that supports the rocker shafts machined by the necessary amount to bring the lifter preload back to the appropriate clearance.

Hope this helps,
Ron.

Sounds more of a rediculously simple problem to me rather than anything else. Yeah a composite gasket lowers compression but I'd still think it'd run, unless it was a low compression engine to start with but I think P6s were the highest compression.

I would say a simple carb adjustment and timing may make an improvement. If you have had the engine out with oil filter off at all sorts of angles, the pump may need priming which may account for shite running if lifters are not being filled up, so prime the pump also.

I don't know if the P6 had an oil pressure gauge, but I would never start an engine I'd had apart without a pressure gauge of some kind, you can buy screw on testing gauges. My old man's that I used is a Draper, you screw it where the oil light switch would go. Just so you know what is happening. Also, I like to prime the pump with rocker covers off so I can check oil comes out.

Filled with oil, yes!

It does run, and I don't see compression as being the sort of thing that will make it noisy. It's not fitted in a P6 though; it's in a VW T25 (!!). So no oil gauge, but I think I have one in the shed somewhere.

Carbs have not been touched; they're still set exactly as they were before, and I did run it for just long enough to set the timing to 4 degrees with a good strobe.

So how can I prime the oil pump now then, if that's the problem? The V8 engine manual is not too helpful about things like that.

asahartz wrote: So how can I prime the oil pump now then, if that's the problem? The V8 engine manual is not too helpful about things like that.

If it's a P6 engine with P6 style gears, you just whip the dizzy out, put your priming tool into a drill and engage the end of the priming tool with the oil pump down the dizzy 'ole.
I used a flat head screwdriver with the handle cut off as my priming tool.

However, there are two different types of tool a male end and a female.

You just turn the pump over with the drill untill you see pressure on the guage or you see oil oozing around the top end of the engine (take the rocker covers off).

I never said that a change in compression would make it noisy!
I was just providing some general information then I wentt on to say what would make it noisy.....

The change in lifter preload now being outside of specification, and what you will need to do to correct the problem.

If the clearance is below 20 thou, which could now well be the case given you have used composite gaskets with 14 bolt heads, then without correcting the clearance you could well experience top end engine failure..ie bent pushrods, broken rockers etc.

Ron.

Surely the thicker comp gasket would reduce lifter preload not increase it which could lead to a tappetity engine and correct preload would require the pillars machining.

Check for exhaust flange leaks - its not unusual for the gaskets to get assembled incorrectly and lead to a blow at the head face that sounds like a loud knocking

Andrew

Darkspeed wrote,..

Surely the thicker comp gasket would reduce lifter preload not increase it which could lead to a tappetity engine and correct preload would require the pillars machining

Hello Andrew,

I think you have it spot on. I was looking at it from a different viewpoint, but certainly the pillars will indeed need machining to correct the problem.

I was mistaken with regard to bent pushrods...

Just lots of noise leading to pronounced wear I would expect?

Thanks,
Ron.

RoverP6B wrote:I never said that a change in compression would make it noisy!
I was just providing some general information then I wentt on to say what would make it noisy.....

The change in lifter preload now being outside of specification, and what you will need to do to correct the problem.

If the clearance is below 20 thou, which could now well be the case given you have used composite gaskets with 14 bolt heads, then without correcting the clearance you could well experience top end engine failure..ie bent pushrods, broken rockers etc.

Ron.

Din't mean to be rude mate.

Ahhhh yes, sorry he's reduced the lifter preload which may cause that I guess if some lifters have little or no preload? I was thinking purely in terms of the reduction in compression ratio.

Darkspeed wrote: Check for exhaust flange leaks - its not unusual for the gaskets to get assembled incorrectly and lead to a blow at the head face that sounds like a loud knocking

Andrew

No, I was very careful to get those right. That part should be a big improvement anyway; some previous numpty had put the manifolds on without any gaskets at all!

JC. wrote:

asahartz wrote: So how can I prime the oil pump now then, if that's the problem? The V8 engine manual is not too helpful about things like that.

If it's a P6 engine with P6 style gears, you just whip the dizzy out, put your priming tool into a drill and engage the end of the priming tool with the oil pump down the dizzy 'ole.
I used a flat head screwdriver with the handle cut off as my priming tool.

However, there are two different types of tool a male end and a female.

You just turn the pump over with the drill untill you see pressure on the guage or you see oil oozing around the top end of the engine (take the rocker covers off).

I was afraid you were going to say something like that! Due to the unusual location, I'll have to lower the engine to get the dizzy out...



This picture was before I did the gaskets and general cleaning & tidying, but when bolted up, the ignition leads touch the crossmember (hence the cutout)!

I recon you could get a caddilac northstar V8 in there! now that would be interesting.
Sorry shouldn't say things like that!
As has been said above it sounds like it sounds like Lifter Preload is out of spec. Cheepest solution would be to go back to tin gaskets and don't do up the outer row of head bolts. Next Skim the heads 20 thou or so to compensate for the composite gaskets. Better still skim and rebuild a set of SD1 heads and just swap them in when you get sick of the racket.
Mike

Surely it would have been easier and neater to use angle caps on the leads than cut the car about

Without a really good idea of what the noise is or where its coming from we are all reaching about in the dark guessing.

Oh and its not unusual not to have any exhaust gaskets on the early motors - they didn't have them from the factory.

For a check on oil pressure connect a test lamp to that oil pressure switch.

Andrew

kiwicar wrote:I recon you could get a caddilac northstar V8 in there! now that would be interesting.
Sorry shouldn't say things like that!
As has been said above it sounds like it sounds like Lifter Preload is out of spec. Cheepest solution would be to go back to tin gaskets and don't do up the outer row of head bolts. Next Skim the heads 20 thou or so to compensate for the composite gaskets. Better still skim and rebuild a set of SD1 heads and just swap them in when you get sick of the racket.
Mike

Actually there's not a lot of space.
I'd rather not go back to tin gaskets - they were pouring oil. But I might look for another set of heads. My nephew runs a head repair business so skimming is not a problem. I could always shim the lifters anyway.

Darkspeed wrote:Surely it would have been easier and neater to use angle caps on the leads than cut the car about

The whole back panel had to be cut away to get the conversion in anyway, so it didn't make any difference. In fact the water pump pulley is also cut off (there's a Davies Craig electric pump instead); even with a 2" extension panel in the back the pulley won't fit. I need another pump for the heater though...

I bought the complete conversion for £300, so I can't complain.