I need help are the heads on my motor good performance heads it has guid plates big valves 76cc cast # 330545 . i know i can change pistons for more conpression. i would like to get 375 too 400 hp.any info to get that much power on pump gas? the short block is stock with good parts forged pistons pink rods steel crank thanks

 

What are the priorities? Driveability? Neck-snapping performance? 1/4 mile times?

If you want a real 375-400hp without compromising driveability, I'd replace the cylinder heads with a set that has 65cc or smaller combustion chambers. DART Stage II, AFR, Brodix all make really good 195cc or larger intake-runner cylinder heads that will easily support your performance goals.

I have a 300hp motor but it makes closer to 380-400ft lbs of torque. It is a blast to drive and runs 72cc DART Iron Eagle heads. The biggest difference between your cylinder heads and mine is that my intake runners flow better yet still provide excellent torque off the line (I think 180cc intake runners vs your 160-165cc if they are the '624' or '882' castings).

Combine the cylinder heads with a nice set of pistons, headers, intake, cam/lifters, carb setup, re-curve on the distributor and TRUE duals (and maybe an x-pipe) and you'll have a screamer and still very driveable.

 

To honest NO! The combustion chambers are too large and have lousy quech properties. GM made them that way to reduce NOX emissions. The late John Ligenfelter once lobbied the NHRA to try toballow the late cars to run early heads but, was turned down. John claimed a 20-25HP deficits were due to the bad design of these combustion chambers. While they will flow more air, they won't burn it as efficiently as an earlier 186-492 head. It's not only the amount of fuel/air you get in, its how effective and complete the burn is on the mixture. Late model Vortec heads have a well shaped chamber, and most of the aftermarket stuff including the RHS stock replacement small chamber heads but, not the RHS large chamber stuff.

 

thanks. I think I will buy better after market heads any one better for my 400 hp build? and cam picks maybe solid lifter or hyd roller?thanks

 

Summit has USA made aluminum heads and the Brodix IK 180 heads whole be good choices.

 

I agree with Solid. The old heads you will have to rebuild and the money you put into them would be better off spent on a new set of modern heads. You will be way ahead with newer design heads. Don't waste your money rebuilding the old door stops.

 

Certainly can't hit your power targets with those heads - around 350 FWHP is about the best you could hope for, even if they were massaged. And, as noted the "smog" type chamber negates a lot of the flow capabilities.

Need a lot more information about the engine before making a head recommendation - intake? Exhaust? Cam, and planning to change it? Gears? Usage? More info = better recommendation...and a realistic budget is key as well

 

I am get ready to rebuild the engineso pistons/heads/cam r up for discussion. the block is 4 bolt main the rods r gm pink rod the crank is a gm steel crank all the parts r in great shape Iam going to balance the rotating assm new rod bolts and see what the crank needs hope just a polish i have the stock windage tray 6qt oem pan 400 trans with a 26 to 2800 stall 11 inch converter/ 355 oem rear dont know what intake to run and realy dont want headers i have a 2 1/2 exaust by magnaflow.the ign is stock dist with crane pick up msd 6al box i have a new holley hp 750 vac sec.

 

There are a fair number of questions here Overall, the general approach is to select the heads and then build the rest of the engine around them - piston and cam selection must be made in combination with the heads and then the rest of the shortblock follows. Given the forged crank I would tend towards forged pistons for an all-forged bottom end.

For a 400 HP target from 355 CID, you're generally looking for a tier II 180-195cc head...ultimately budget will determine what your options are. AFR heads will virtually always be your best choice here...if you can afford them

You don't say if the block is roller-capable, but a roller cam is the best possible choice...if you can afford it Retrofit roller lifters aren't cheap - but are a great investment.

A decision not to run headers will cost you serious power at this build level - I would encourage you to rethink this.

The ignition and carb are fine; the carb is a touch on the big side but the HPs are *very* tuneable. Ideally you'd run a high-rise dual plane, but hood clearance becomes the question.

These are some very general comments for a very general question I would note that if you're starting from scratch it's worth thinking about the benefits of a 383 over a 355...but given that you have the crank that point may be moot. Certainly if you're looking at having the crank ground then it becomes worth checking the numbers both ways...cost of maching and balancing vs. buying a balanced 383 assembly.

 

With those being 1 year only heads they will bring some good $ if you sell them.

 

thanks for the info. the engine i want to rebuild is the # matching L-82 for my car .maybe i should put it away and build a 383. its easy to get more power that way .whats a good year block maybe a roller block but heard they r not good for alot of power what do u think thanks