i have an 88 iroc with a tpi 305 and i wanted to know if the vortec heads will work on the motor i am getting conflicting feedback on it from friends one is tellin me that it will work if i drop compression and the other is tellin me that if compression is dropped enuff that it wont even run. i am planning to do a cam swap with a comp cam 266 HR14 heres the info on it, 266/276-210-220* @ .050 .500-.510 inch lift on the intake and exhaust with 114* lobe seperation. i want to know if the heads will work or should i go get a set of stockers and port em out myself. plus id like to know if my iroc will run with the 350 guys. heres the particulars on the ride LB9 305 700R4 and 3.42 posi rear. i was told that with the gears i should be able to run with the 350 guys but i think theres more work to do.

 

Vortec heads on a 305 work fine. I am running the vortec heads with the Felpro 1094 steel shim head gaskets, this kept my compression at 8.9 to 1 which was very close to the stock 9.0 to 1 compression. I am running the vortec TPI intake and ZZ-4 cam along with the other parts that are listed in my sig and the car runs strong. if you do not want to use the Vortec heads pick up a set of the Corvette Alum heads and use them instead.

 

what was the stock compression ratio on the 305, and if i do use the vortecs what is the absolute lowest compression ratio i can use???

 

why do you want low compression

 

i was planning on running the vortec heads which are 64ccs as opposed to the stock 58cc heads and wanted to know how much itll lower compression, i know if compression is lowered too much it wont even start but i wanted to know how low of a compression i can go before it wont even crank over.

 

I personally wouldn't go with anything lower than 9:1 for any kind of performance application. I would imagine it would run at around 5:1 I know that some run at around 7.5:1 for highly boosted applications.

bjankuski: isn't the stock 305 head gasket a shim style? The stock one on my 350 was a shim gasket, so i would have thought it would be the same for 305's. If so, wouldn't compression be much lower?