I saw it mentioned somewhere here that the cathedral to rec port head adapters can cause tuning issues or at least some quirks at idle. The adapters seem to be really popular, so how big of a deal is it really? I can't see myself going for aftermarket heads, maybe some used rec port heads which would still cost a bit more than the adapters.

The plan is for the LSA to go on sig truck, it's not for racing and doesn't need every last drop of HP, but all the down low torque to get that 6500+ lbs moving is most desirable. I really want it to be a low maintenance power increase, so whatever is more reliable, or better to tune for drivability is going to be preferable.

 

The adapter plates will still get the job done. They have been used by many over the years and the tuning issues aren't that big of deal. It's not the perfect setup but it'll be fine. Tune it in speed density and have all the proper injector data, makes things easier on the tuning side.

 

I am a mega hater on adapter plates. So I vote swap to a rectangle port head, OEMs can be had for relatively cheap.

My thinking behind adapter plates is mainly why? You have an option to eliminate another hypothetical point of failure. It's like when you are doing an EGR block on the early trucks. A used intake without the port is barely more expensive than the block plate. Just one less thing to leak
If you are on a tight budget, and we all have been there, then yes they will for sure work fine. Even out of a tight budget they will work fine.

 

i think an adapter plate made of phenolic material would be a great heat barrier in a blower application and even add an air gap between the blower tub and the block.

 

this is one of the benefits (also some companies using a high-temp stiff nylon that doesn't occasionally get brittle & flake apart like phenolic)... but one of the downsides is the weird turbulence it often causes that disrupts the fuel spray... which causes the issue to tune around.

i second the vote to use square port heads since you've got the 4" bore required. if you want the spacer benefits, space the blower lid away from the intercooler brick.

 

An uncomfortable truth. lol

 

Phenolic spacers did sound interesting, with their claims of less heatsoak... but I'm pretty sure these blowers mounted directly to the heads on the CTS-V cars so it must not have been that big of a deal. I guess if you start looking at some max effort build or road racing that may be more of an issue.

I'll probably check FB market occasionally for heads but there isn't much going on for LS parts selling in my area. It's all Gen 3 partouts anyway.

 

Just check car-part. Last time I shipped cylinder heads I think it cost me $30 each? Most places don't box them up correctly though.

 

turning at factory speeds, it's fine (not that any amount of heat reduction is unwelcome); it's when you start over-spinning little blowers on big engines that you make problematic amounts of heat.

the other side of the suggestion (that i think is more effective than spacing the heads) would be to space the top of the blower up so that it improves the airflow through the intercooler brick & helps reduce IATs further.

 

I only picked up about 6 degrees of IAT with my 408.