Guys,

I need some help/advice. I'm literally in the middle of installing my new ZZ4 GM Crate engine with the Aluminium L98 heads. When I try to install the standard GM TPI manifold base the front and rear bolts line up and install fine. But the pair of bolts in the centre on both sides seem to be 3-4mm out.

I've tried torquing the others down to the proper specs but it doesn't solve the problem. I'm using the correct gasket thickness and not using excessive sealant etc.

Any advice would be much appreciated. From my searching I haven't found any problems like this with ZZ4 and the stock base.

Thanks.

 

Is it that they don't line up, or is the angle of the two center bolts different?

 

That's correct Apeiron, they just don't line up. I was thinking I might need to drill the holes in the intake manifold a bit larger possibly?

I'm in garage with the car, engine and laptop at the moment.

 

Those heads use the early bolt pattern, not '87 & up.

 

Dyno Don, are you sure? Summit and GM say the heads are 87-91 Corvette Aluminum L98 heads.

http://store.summitracing.com/partde...9&autoview=sku

 

Wasn't the D port design in the later years? You might be able to tell that way ???

 

the zz4 heads use the earlier bolt pattern same as the aluminum L98 heads

 

you should beable to elongate the intake holes with no problem.

 

Thankyou gents. I elongated the holes with a Die Grinder and a file. Washed the parts and offered them up.

From examining the intake manifold base more closely it appears to be an '87.