Ok guys, searched for a while and came up with a lot of intercooler topics, EGR, Build threads, etc. I am wondering about the maximum power/boost of a S4 TII engine. Engine will have a small bridgeport on it. I heard that the rear iron is weak and will crack near the dowel pin area. Any info on this?

 

400 is right around the failure point of a factory block. Just machine it for extra dowels and it will be fine.

 

Thanks. Seeing how 400whp would amount to around 460fwhp, I will get it doweled.

 

400whp is about the limit for s4 irons. Above that you can go with the beefier s5 irons and you will be good to over 500whp.

 

Irons do not break due to power, they break due to detonation. Most broken irons can be traced back to massive and severe detonation, caused by wildly rich AFRs or ignition misfires due to EMS noise.

Over 400HP will not be an issue. I'm running more then that on my S4 block. Not saying that the S5 irons are a worthless upgraded because if you have them, use them.

Also don't waste too much time on a "small" bridgeport. Either half bridge it properly, or go to a full bridge.

You also don't need a bridgeport to make 400HP. I'd suggest sticking with a street port so you can get decent gas mileage and have a car which is much easier to tune (ie. it actually pulls vacuum).

 

I detonated the living daylights out of my s4 irons and never cracked them. People do have more problems over 400whp though, mostly because those motors are running on the edge. I have recently switched to s5 irons for this motor I am building. When comparing the casting around the dowel pin landings, I have concluded that these particular irons are about 20% thicker in that area (both front and rear). Not all s5 irons are made the same though. These particular ones came out of a JDM 91 turbo engine.

 

Wildly rich AFR break irons? I know that you can have a rich missfire, but I thought rich miss fire wasn't violent. I guess all misfires are bad