Josh B

Has anyone on the board put the 48mm intake valves from a 2.7 liter 944 head into a ceramic lined 951 head - replacing the stock 45mm intake valves?

Do the exhaust valves have to be enlarged by the same ratio? By my calculations it is a gain of just under 14% of additional intake?

I have a low mileage head and some good 2.7 liter intake valves and am considering taking them to a machine shop and having them installed. Wanted to see if anyone has already been down this road.

I have a PB on the car and would expect that fuel would have to be added to account for the extra intake?

carlege

NIZE on pelican parts has done this and have very good success with it. There might be some machining to do it.

Josh B

I was emailing him and reading up on his thread and he went a lot further. Used aftermarket valves and went on the intake from 45mm to 50.8mm and on the exhaust from 40mm to 44.5mm. The valve stems were a small diameter as well so he had to change out the valve guides. I think cost wise he was around $2500 if not more.

carlege

yep just found the thread. i wasnt sure what valves he used.

Matt Sheppard

I have a 2.5 T head that Chris Cervelli did up this way.

I found that the 2.7 intake valves were a bit shorter than the 2.5's and had to get the seats cut deeper to get the stem height in line with the stock valves.

P.S. I have a set of (4) 2.7 int. valves available if anyone is interested

Josh B

Hey Matt,

Did you run that head on your car? Did you notice a difference in your AR values and have to correct? Do you recall how much shorter the valves were - mm or 2? How much for the set of 4 valves?

Thanks,
Josh

944obscene

I thought Chevy SB valves were a popular alternative. What would it take to get those in? And would that cause issues using the stock 951 Exhaust valves?

fast951

It can be done, but it takes much more than just cutting the seats to use with the larger valves. Lots of work involved, and unless a flow bench is used, there is no way to get any porting done.

Matt Sheppard

John is correct. Bigger valves are useless without the port blending and flow bench testing. Chris did an admirable job on my head but said it only netted him 30 HP over the stock intake valves on a 2.5 engine and a GT 25 turbo pushing it. Since I was planning to use it on a 2.7, I figured the increased swept volume would benefit a bit more. It puts the outside of the valve pretty close to the edge of the chamber so unshrouding it would def. benefit as well, but only in the case of using the bigger piston.

Josh: I never used the head, I did not build the 2.7 and the ceramic port in #3 was cracked anyway so I wouldnt want to chance it. You have a PM.