ok ive got a stock botton end 350 with motown heads 2.05 valves 205 cc runners zz4 cam 208 221 475 510 and a dual plane intake 750 carb went to the dyno and only got 257 rwhp and 300 rwtq the zz4 moter puts out 355at the flywheel and 400 tq so whats up with mine soom one said my heads where to big

 

i don't know abotu that, it definately could be, but i doubt it....sounds like something isn't tuned right...is it running good??

 

the car runs great iam running 8.4 in 1\8 and 13.3 in 1\4 so yes it runs good just think it should be doing better iam changing the cam tomorrow

 

yea i doubt the heads are hurting you...it sounds like you have a pretty good setup, i'm thinking the cam is holding you back too....change that, tune her up, and see how she does from there...

 

I don't think the heads are too big, the cam is just too small.

 

The heads are fine. You need to question a couple things first. Is the cc the same as on the ZZ4 cyl heads? If not (larger cc volume), then you will have a slight loss in compression and a slight loss in horsepower. Did you measure your piston deck height before you put the heads on? This way you can roughly calculate the thinckness of the proper head gasket to use to get the correct compression ratio. What type of exhaust system do you have? Headers will add another 10-20 hp. The cam is fine but it is not a upper rpm pulling cam, it was designed for low to mid-range performance. If you want to help it out considerably you might consider a Edelbrock RPM Air-Gap manifold. I installed one a couple of months ago and it dropped my e.t by 2/10ths in the 1/4. I think that because you have a lot of breathing capability thru the heads now you could benefit with a little more cam (such as the Hot Cam or something with no more then 230/236 duration). You are roughly at about 308 hp at the flywheel, that is not too bad. You have to keep in mind that when they dyno the ZZ4 they do it without much engine load and they use full length headers in the process and the carb is set up correctly for A/F mix to maximize hp. I think you did pretty well with what you have. As I mentioned, a little more cam would wake it up considerably. I would take it to the track and see what kind of times it will turn. The dyno is not always 100% correct. Different dynos give different numbers...

 

iam putting a new cam in her today duration@.050 is 230 int and 236 exe with 544 int and 554 exe 112 lsa hope this one does better thanks for the info

 

That is a very nice cam selection for the heads you have. Should be good for around a 50 hp increase over what you have.

 

Although the ZZ4 is rated at 355HP, you will never see it. In installed trim, with all F-body accessories and manifolds, GM rated the ZZ4 at 308HP.

A larger, better matched cam should put you well over the 300RWHP number. A CC305/XE230 or CC306 would do very nicely.