2.7 Heads

Barskov · Barskov's Garage

Hi there

looking for advice on this set of heads i have unfortunatly purchased along with a 2.7 l engine in many parts.

it seems like these were taken to a very agressive machinist , its hard to determine how much of the mating surface that have been taken off , but its almost down to the valve seats as shown on the pictures ,

Can these be used or are they only to be thrown into the Alu recycle bin ??

Regards Uffe

cgarr · cgarr's Garage

Check the measurement from the top (cam carrier) to the sealing surface, stock is 84.5mm or 3.3267 and you can go down to 3.3167 but I have seen them used down to 3.3017 in other words .025 taken off the surface but this was in a special built race engine where other parts were adjusted.

Walt Fricke · 10-04-2011, 10:12 PM

Aggressive indeed. But done right?, as witness removing some of the finned surface as well so it won't interfere with the cylinder fins outside of the spigot area.

You can get 1mm thick cylinder base shims to help restorethe needed piston to head clearance, gaining back 0.75mm over stock 0.25mm shims. And maybe other ones on a custom basis?

Barskov · Barskov's Garage

thanks for the help both ,
I bolted on 4 of the heads to the cam tower and get consistant measurements around 83,80 to 83,89 mm , I think I will try to look for some used heads to rebuild instead , I guess the solution with shims can be used but I rather not , planning to use JE pistons and S cams.

JohnJL · 10-05-2011, 06:07 AM

watch those valve-to-piston clearances!

Rexs-911T · Rexs-911T's Garage

What is the minimun recommended valve to piston clearance

Walt Fricke · 10-16-2011, 09:49 PM

Rex - I think Porsche calls for 1mm, which would be about 0.100". I'm using 0,080 exhaust (and in fact I have a lot more) and 0.040 intake on my race motor. Only a bunch of chassis dyno runs on this yet, but so far so good.

You'll find a variety of opinions on this, I think. As you will for piston to head clearance.

VitoV · 10-17-2011, 06:14 AM

Quote:

Originally Posted by Walt Fricke

Rex - I think Porsche calls for 1mm, which would be about 0.100".

A typo, Walt? 1mm is around .040". (Forgive the nitpick.)

Walt Fricke · 10-17-2011, 01:48 PM

You are too kind. More like brain fade. Forget what I said about Porsche's specs for this.

Looking it up in Wayne's book, I see that he calls for 2mm exhaust and 1.5mm intake valve clearance (and he spells out one of the methods of checking this). That would be 0.080" exhaust and 0.060" intake roughly, if I did the mental conversion well enough this time.