Thread: 350 cylinder head swap

Tweet

I have a 79 chev 350 with a cracked head. I have some later model vortech heads and I am wondering if they will work. The head gasket seems to match up but there are two holes missing to attatch the intake manifold. If I drill and tap these two holes will the heads work?

Welcome to CHR!

The intake bolt angle for the Vortec (1996 and onward) is drilled at 72 degrees versus 90 degrees of 1995 and earlier heads. Vortec heads are tapped at 5/16 – 20 thread. Earlier heads use 3/8 -20 threads.

You can drill and tap the cylinder head for the early style intakes - but you must be very careful and if you make a mistake, the heads may be unusable. Gaskets don’t line up real well and a major danger is drilling to deep on the outer bolt holes and penetrating the water passage. Better bet is one of these GM part numbers:
Part # 14097499 - stock cast iron Vortec intake
Part # 12496820 - low rise dual plane with EGR provision and dual (spread/square) bore bolt pattern.
Part # 12366573 - high rise dual plane manifold with a square bore.

Or one of these Edelbrock Vortec manifolds:
Part # 7116 Performer RPM manifold
Part # 7516 Performer RPM Air Gap manifold

Others may chime in here.. Again, welcome to the site. Hope we can help you in your hot rod journey and that your time here is long and fun too!

Regards,
Glenn

Welcome Racemaster! Glenn's leading you right.

Glenn is the real deal...... Here's some other info to help guide you.....
http://www.crankshaftcoalition.com/w..._cylinder_head
Knowing what I know, I would STRONGLY advise that you read everything you can about the L31's.....
The Edelbrock 7116 is the hot tip for intakes.....
Want it in black? 71163
Want it in enduroshine? 71164
Want to mount a Quadrajet? #2516 is a high-rise, dual-plane intake designed for use with 262-400 c.i.d. Chevy V8 engines with 1996-later Vortec (L31) cast iron heads. Accepts square-bore and spread-bore carbs. Recommended intake gasket: Edelbrock #7235.
Any of these dual-plane, high-rise intake manifolds will make more power from 1500 to 6000 than any other carburetor-type intake manifold you can bolt onto the motor.
I also very strongly advise that you magnaflux the heads for cracks before you do any work or spend any money.

.

Welcome to CHR, Racemaster!!!! Tech and Glenn gave you the real deal info!!!! Hope you enjoy your time here!!!!!!

A few years back I modified a manifold by slightly opening up the bolt holes and then made some wedge shaped washers to compensate for the different angle. That worked. This motor Im working on now has been modified one way or another for many years. I have a pair of new head gaskets and some intake gaskets so I was just going to clean up the vortech heads and put them on. Still have to figure compression ratio, pushrod length, etc. but the basic idea is to do this with parts on hand and spend zero cash. So my next question from your response is; are these heads prone to cracking?

I thought to add, this is a 79 Camaro Z-28. The suspension was shot and I had an 86 Bronco with a dead motor. So, I took the body off the Bronco and put the Camaro body on the Bronco frame. "Broncamaro" Had to make an adaptor for the TH400 to the ford(new process) transfer case and motor mounts to move the motor forward and up a bit. Then the headers would not fit so I went back to the stock manifolds. Lot of fun to drive and I get comments everywhere I go. Driven daily. Have a spare motor in it while I deal with the cracked head problem.

I read the link you gave. Crimeny! Seems like I have a bit more work to do than I thought. Maybe I will try to weld the cracked head instead. That in itself is also a lot of work. Have to pre-heat the head etc,etc. Ah well, if it was easy it would not be any fun.

Originally Posted by racemaster

So my next question from your response is; are these heads prone to cracking?

Yes, most of these motors you will find in the boneyard are there because the head(s) cracked.

.

I agree with Tech – The last set of cast iron Vortec heads I bought at a wrecking yard had several cracks on both heads that were not apparent from the outside with the naked eye. The heads were very clean and I thought they’d be fine; however, the machinist I use tells me that finding cracks in Vortec heads is pretty common especially in the area under the exhaust valve. Fortunately the yard I bought them from is local and managed by a good man and we agreed up front that I would end up with two heads that would magniflux and show crack-free. I actually took four more heads and ended up with three good ones and one more zinger. So out of a total of six heads, three were good, two cracked beyond repair and one was “fixable” but the wrecking yard manager thanked me and chucked it in the scrap heap to go along with the other recycled iron. This yard only charges $50 per head and because it cost me a bunch of time, I wrangled a tilt column from a 1971 Chevy pickup (no key – column shift for another project I was working on) out of the deal as well. I always pay these guys in cash and try to be reasonable in my expectations.

I see the lads at Phoenix Automotive are selling guaranteed re-manufactured Vortec heads for $500 a pair. These look pretty decent and this is a good price for a ready to bolt on high performance head.
Chevy 5.7 Liter Vortec Cylinder Heads (PAIR)

Sounds like you got quite the ride your workin' on! Would be great to see some pictures of this one.

Let us know how you decide.
Glenn

The only photos I have are on my phone and I dont have a clue how to get them on the computer. I will find out. After reading all the tech info I think I am going to try fixing the cracked head and file 13 the vortechs. Thanks for all the advice.

the vortec heads are probably the best option , but you do need a manifold that is designed for them for the best performance-----there are bolt/shim/adapter/washer? kits available for the different angles