Valley gasket for decked heads?

Antonyj · Post by **Antonyj** » Thu Nov 13, 2008 8:07 pm

Does anyone know of a way to adapt a valley gasket for use with a block that has been decked?
Obviously the heads sit further down the V now.

Also, the new manifold needs to sit lower as the bolt holes dont line up(and therefore the ports), is there a way of calulating the amount required to be skimmed of the faces?

HairbearTE · Post by **HairbearTE** » Thu Nov 13, 2008 8:35 pm

The gasket will have to be made by cutting in half the gasket, removing an amount and then joing back together. You might even want to use two gaskets from which to make your one. For the inlet you can take the same amount off the faces as you took off the heads/or block. (this assumes you are going to use the same style of head gasket again)

Post by **katanaman** » Fri Nov 14, 2008 12:49 pm

I use two gaskets and pop rivet them together with some RTV along the joins.

sidecar · Post by **sidecar** » Fri Nov 14, 2008 1:27 pm

How much do you have to machine off before the gasket won't fit?

The reason that I ask is that I've had 70 thou taken off my 36cc heads in order to use them on a 4.6 block and can still use a normal tin valley gasket. I am using comp head gaskets so that accounts for 20 thou out of the 70 but that still means that my heads sit 50 thou lower than normal. (Assuming that comps are 40 thou thick and tin head gaskets are 20).

I have opened up the ports in the valley gasket to match the stage III inlet ports. (Because of that I've reused this gasket many times but I've not had a problem with it!)

My edelbrock 180 has also been machined to fit but with hindsight I should have had the inlet tracks on the heads machined instead as this would have been cheaper. Russell Ram explained how much has to come off the manifold to me very well. As the engine is a 90 degree V then if you shorten two sides of the square that the cylinder banks form then you need to shorten the two sides that the inlet manifold form by the same amount, this keeps the "square" a square! Having said that there is some leeway before you have to do any inlet machining.

I seal the tin valley gasket round all the ports and waterways with a thin smear of silicone on both sides of the gasket, I leave it to semi-cure before fitting. In fact the problem is getting the bugger off again!

HTH,

Pete

CastleMGBV8 · Post by **CastleMGBV8** » Fri Nov 14, 2008 1:55 pm

Pete/Anthony

Thats what I had done with the Buick 300 heads, machined the inlet port faces whilst the engine was still in the machine shop, I gave fim a inlet manifold and comp gasket so that he could get it to line up properly and with a couple of skims off the heads port faces, it all lined up correctly.

I did it that way so I could swap manifolds later without a hassle as I intend to go hotwire in the near future.

Unfortunately didn't ask what he had to machine off, but the decks were machined 40thou and the heads 30thou

Kevin.

Post by **katanaman** » Fri Nov 14, 2008 2:04 pm

yes I machined the inlet side of my heads as well. You have to be careful of the step between the block and the heads when you do that or you could get a leak. Easy enough to sort out though when your aware of it.

sidecar · Post by **sidecar** » Fri Nov 14, 2008 2:14 pm

Looks like I am the only muppet that paid out a small fortune to have the manifold machined instead of the cheaper head option.

Boosted LS1 · Post by **Boosted LS1** » Fri Nov 14, 2008 5:39 pm

Hi Anthony,

I've seen tvr hammer over the edges of the gasket into the intake ports before now. The bolt holes in the gasket shouldn't be hard to address.

Mike.

CastleMGBV8 · Post by **CastleMGBV8** » Fri Nov 14, 2008 7:01 pm

Interesting point is that the ports on the comp valley gasket at 44mm. x 25mm. seem to be larger than on the tin version and they matched the standard port areas of the Buick 300 heads exactly, which was a happy coincidence.

On my original engine which had 20 thou off the heads there was no problem getting the Edelbrock manifold to fit, but whether the manifold and head ports lined up correcty is another matter and at that time I was on a learning curve about Rover V8 engines so wasn't aware of that issue.

My understanding now is that it is more important to get the port roof areas to line up .

I also don't know if the tin and comp valley gaskets are as different in thickness as the head gaskets becacuse if the tins are thinner then that would give a bit more leeway as the heads would sit lower.

Kevin.

Antonyj · Post by **Antonyj** » Fri Nov 14, 2008 7:41 pm

I have sat the serp inlet manifold on the engine with no gasket, and the bolt holes dont line up, so I must assume that the ports dont either.

So as I see it I need to measure the measure the same point between the heads and then machine some off each face of the maniold.

Have to get measuring......

spend · Post by **spend** » Sat Nov 15, 2008 1:45 pm

Try it with a comp gasket first Ant, I'd agree with Mike there seems to be quite a margin of movement available with the bolts?

Mark very carefully the exact position you want the in/ex manifolds to fit if you do any 'accurate/marginal' port matching, rather than rely on the bolts lining things up

.

Just reaming out the bolt holes might even get you a much better located inlet? ie a fixed location.

Antonyj · Post by **Antonyj** » Sat Nov 15, 2008 2:29 pm

SO need to check the actual port alignment first , then see how it lines up.

Cheers

All clear in my mind now.

CastleMGBV8 · Post by **CastleMGBV8** » Sat Nov 15, 2008 3:28 pm

Antony.

How much machining, heads and or decks was done and for what reason, only normally necessary when you have built a stroker engine with non rover rotating parts to optimise deck heights and adjust compression ratio.

Whats the engine going to be used for and are the heads ported?

What type of head gaskets are you using?

Kevin.