L88 heads #3946074

[Joe L.]

Jeff----

The "074" heads are open chambered and you can use them on your engine with the parts that you described. These heads were used on 1971 LS-6 engines. I don't like them, though. The port volume is too large and will sacrifice street driveability.

[George Daina]

In reply to Uncle Joe's post.....

the intake volume is the same as previous sq. port closed chamber heads. Where they differ is in the exhaust ports and combustion chamber design. By swithing the closed chamber with the open chamber, one picks up an easy 30-35 HP. Another head you might want to consider is the Bow Tie 077 over the counter head. This head makes considerably more H.P. than either the 074 or the 842.

Streetability, not a bid deal, just ask any 427/435 owners. Granted, it may not behave like your normal beater in traffic, but that's the price you pay for higher performance.

[Joe L.]

Re: In reply to Uncle Joe's post.....

George-----

Well, you're "sort of" correct. The GM #3946074 aluminum cylinder head DID have the same size intake port volume as previous rectangular port heads, both aluminum as well as cast iron. This volume is 325 cc. However, the successor GM aluminum cylinder head, GM #14011076, had considerably smaller intake ports at 290 cc. Of these early aluminum heads, this is a far better head for street operation. In fact, in my opinion, it's one of the best big block, aluminum SERVICE or PRODUCTION heads which GM ever manufactured. But, it did have its limitations and pitfalls and was discontinued by GM some time ago.

In my opinion, the absolute best(to date) big block, rectangualr port, aluminum cylinder head for STREET operation which GM ever marketed is the one which they market today. This cylinder head comes in three versions. First, the bare cylinder head which is a direct replacement for the GM #14011076 cylinder head is GM #12363408. This cylinder head has as-cast ports. The second version is sold bare under GM #12363410 and is the same as the first, except that it has CNC machined ports. The third version is the GM #12363410 cylinder head sold complete and outfitted with 2.25/1.88" stainless valves. This head is GM #12363400.

All of these modern cylinder heads have 315 cc intake ports, which is larger than the 14011076 head, but smaller than the 3946074 cylinder head. They have a vastly improved, semi-open combustion chamber of 118 cc and HARDENED, INTERLOCKING valve seats, NEITHER of which the 3946074 or 14011076 cylinder heads had. Unfortunately, their external configuration is somewhat different than the original-style 3946074 or 14011076 cylinder heads. Notwithstanding that fact, though, these ARE the big block heads to use. Absolutely. Positively.

[George Daina]

Uncle Joe....

I wasn't aware that GM had a 076 head. The 077's that I'm refering to are known as the "D" port heads. The exhaust port is shaped like a inverted D and the port is raised, with a hump in the middle. These heads use 2.25" intakes and 1.88" exhaust, intake ports volume is 325 cc's and produce gobbs and gobbs of H.P.

[Joe L.]

Re: Uncle Joe....

George-----

I believe that 14011077 is the CASTING number for the GM PART #14011076 cylinder head. These heads are factory-fitted with valve seats for 2.19/1.88 valves, but the intake valve seat can be easily enlarged to the 2.25" size. These heads were NEVER supplied by GM complete with valves, etc. They were supplied ONLY as bare heads and only for SERVICE. They were never used on a PRODUCTION engine application. The intake port volume on these heads, which you correctly identified as being called "D-port"due to the exhust port configuration, is 290 cc. The cylinder heads which they REPLACED, GM PART #3906472(cast 3906474), were 325 cc.

[George Daina]

What we have here was almost a failure.....

to communicate. Yep, I was referring to the casting #. I had two sets of these, still have a set, new in the boxes, the other set I peddled a few months back, complete. In about a month the new set will find a new home, outside the box, inside the 68's engine compartment.

[Joe L.]

Minor Correction to Above Post

I made a minor error with respect to the intake port volume of the 14011076(CAST 14011077) cylinder head. The intake port volume is 295 cc NOT 290 cc. I'm sure that all of you eagle-eyed enthusiasts caught that, but didn't want correct me. But, this just goes to show what can happen when I try to provide information from memory and without my references at hand.

[Jeff M.]

L88 heads #3946074

the 69 L88 heads #3946074 are open chamber heads as i understand it. Can i install these heads on a 71 with open chamber pistons that are LS6 configuration. How will these heads flow with 9.5/1 pistons and a 71 LS6 intake