LQ1 turbo, 91-95 or 96-97 head

[brian89gp]

How much of a benefit would the 96-97 head over a 91-95 head be in a turbocharged application? Assume that either would also have custom headers.

[timg]

That's a good question that I don't think anyone has answered. I know the 95 heads are much easier to build headers and turbo manifolds for. I do have a 97 engine I'll be rebuilding soon, so hopefully I'll find out. I would tend to think the intake manifold makes a lot more difference than the exhaust ports. I think there are combustion chamber differences too.

Tim

[brian89gp]

Been a long time Tim.


"For better boost response, minimize the exhaust volume between the exhaust ports and the turbine inlet "

http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech102.html#c

Would seem to suggest not to over size the primaries. If the primaries would be sized on HP (indirect measure of exhaust gas flow), would it matter if the exhaust port is restricted down to a certain primary size inside of the head (91-95) or outside the head in the header itself (96-97)?

[SappySE107]

The 96-97 heads are a clover leaf combustion chamber that is 51.5cc. The 91-95 is pent roof and open, with 54cc chamber. I have not flowed the heads to compare, nor have I measured the export volume between them either.

I wouldn't be concerned with which is better, just build one with a turbo and enjoy it because its gonna make a lot of power.

[brian89gp]

True that. Designing from scratch so just trying to figure out the best and if it is worth the hassle. Part availability on the 91-95 heads are also a lot better.

[pocket-rocket]

The newer style heads like to drop exhaust valves, so keep that in mind and have yours checked if you go that route. Having the guides machined with a groove and a clip installed to prevent them from falling would rock as well. I've yet to see the older style have this problem, where as every newer set I've seen has had it happen (some more than others).

[SappySE107]

valve guides, and they all do it. The heads on my 92 were done with all new guides with the clips on them so they will never fall into the ports.

[RedZMonte]

I wouldnt worry about swapping heads on a Turbo car as well.. I did swap from the '95 intake to the '96-7 intake and it feels much smoother. between the intake and leaning it out a tiny bit i picked up IIRC 30whp. if you look in my photos you will see the difference in the intake design, im glad i did the intake swap.

S

[pocket-rocket]

valve guides

Thank you. That's what I meant, guides.