So I just picked up a L48 350 out of a 79 z28 yesterday and im starting a list of what im going to get for the rebuild but not sure how to cope with the (76cc) low compression heads, im going with factory spec internals besides a high lift cam, gear drive, and 1.6 roller rockers, I was thinking about a single plane high rise and My plans for the low comp. heads were to mill the heads, thinner head gasket and possible larger valves (2.02 and 1.6). From what ive read the heads are practically use less unless your force inducted. I have a set of early model vortec 54cc heads off my old 305 if it came down to swapping...give me some ideas on what I should revise/add to my list!!!

 

I've never seen those heads fail to keep a self-closing door open. I also haven't seen a better use for them.

Single plane + low compression = dog

Ideas:

Have no idea what your plan is for use of the car. Kinda need that before making specific recommendations.

But, in general:

IMHO, gear drive is pointless.

1.6 rockers should be reserved for a cam designed for 1.6 rockers. Like an LT4 Hot Cam. Otherwise, stick to 1.5:1.

 

Gear drive, "high lift cam", and single plane do not mix well with factory heads, even if they were decent factory heads, which ANYTHING 76cc is most definitely not. You cant make a turd fast just by throwing fancy parts on top of it. It's still a turd with icing on it.

I suggest you ditch that block altogether and get a modern roller block and go with a roller cam. Save that gear drive money and spend it on an xr276 and some Vortec heads. A good dual plane (any edelbrock intake that says "RPM" in it), vortecs, and an xr276 with a reasonable 9.5-10.0:1 compression ratio will get you 350-375hp.

305 Vortecs are not the same as the 350 vortecs. They are significantly different.

 

Just because certain parts are used on a 1/4 mile car doesn't make them good choices for the street
I wasn't going to say so but appears the OP has been reading too many mag articles on how to "Hot rod your engine "

 

Throw those heads IN THE TRASH.

(speaking strictly as a former 79 Z28 owner who did JUST EXACTLY THAT, in about 1981...)

DO NOT spend even so much as ONE PENNY on them. Every dime you waste on those turds, puts you one dime further from improving your car.

You should revise your list to include some other heads - preferably BETTER ones - than any of the ones you mention in your post. About THE ONLY stock heads worth spending money on these days, are the Vortecs (the REAL ones, not the 305 ones that just got slapped with the label); 906 or 062 casting. Other than that, aftermarket.

Spare yourself the humiliation of putting a gear drive on that thing. The world already has entirely enough poseurs in it. We could use more ACTUALLY FAST cars instead. Just use a GOOD QUALITY timing chain, it's all you'll need.

Not sure what you mean by "factory spec internals". If you're rebuilding the short block, don't put those imitation dog turd pistons back in it. Use some common sense instead. Put in flat-tops.

 

thanks for the input guys, I just pulled the heads off and oil pan and discovered it has the 4 valve relive pistons heads and is a 4 bolt main!!! so that kinda changes my plans for this motor entirely

 

The number of main bolts isn't really important. It's good for trucks to have 4, but for a performance engine by the time two bolt mains become an issue you need to be using an aftermarket block like a Dark SHP block.

It's far, far, FAR more important to get a roller block. Retrofitting roller hardware into a non roller block costs a ton of money, far more than machinework on the block and a roller cam is a vast, vast, vast improvement over old hat flat tappet stuff. And the pistons in it now dont really matter because the bores will probably be oval'ed out and worn. You'll need to have them bored until they are round again and get new pistons. The 76cc heads are huge low compression chambers regardless of the pistons and they are junk even with a giant domed piston in them to get the compression up.

 

How deep is the dish?

Are they factory or replacement?

Any idea how old, how many miles, etc. the short block has on it?

What kind of condition are the cyl walls in?

If the short block needs to be rebuilt, no sense in doing it to a 70s block with the crappy quality control from those days, and no roller provisions; might as well get a newer one.

4-bolt main is only of value when you want to tell somebody you have 4-bolt mains. It offers no practical benefits beyond bragging rights. Don't get all starry-eyed over that; concentrate on stuff that matters.

 

Yea

It's a nice surprise when you buy a 2-bolt main and wind up with a 4-bolt main but for the most part a 4-bolt main block isn't all that necessary for most street applications. We had a mid 70's 350 2-bolt block machined and built into a 388 motor. After 8 full years of drag racing first running 11.20's then later running 10.80's with the motor spinning 7K through the traps the motor was torn down the bearings still looked good.