Best '60s or '70s GM small-block intake?

[Wayne Kever]

Thinking of replacing my L79 intake with an LT1, which my engine man says works about the same as a Performer RPM. Gotta keep that stock look!
I've noticed that the aluminum Qjet manifolds of the same era are a whole lot cheaper than the LT1 manifolds. Does anyone have any information on the relative performance of the Qjet versus the LT1 manifold? Any other small-block intakes of the era worth looking at? The 350HP 350's had the Qjet, while the 370HP LT1 had the Z28/LT1 intake.
_______

Wayne

'67 327/350HP, M20 wide ratio, 3.90 gears

[Duke W.]

Re: Best '60s or '70s GM small-block intake?

The LT-1 inlet manifold is probably the best SB street high performance manifold out

there, including aftermarket, but I have never seen any scientific comparison data.

The LT-1 inlet is taller any used on C2s, so I don't think it will fit under a C2 SB hood

with an air cleaner. Remember that the LT-1 Sharks had the BB hood to provide

adequate clearance.

In terms of power for a given long block configuration, I think more can be gained with pocket porting and a three angle valve job. The valve throat region is where most of the flow restriction is at high revs.

Duke

[Joe L.]

Re: Best '60s or '70s GM small-block intake?

Wayne------

No 350 hp small block, 327 or 350 cid, ever ORIGINALLY used an aluminum manifold designed for use with a Q-Jet carburetor. The only aluminum manifolds ever originally used on Chevrolet small blocks which were designed for use with Q-Jets were those used on late 70s to early 80s Corvettes and Camaro Z-28s. There were several different casting numbers, but all were otherwise fairly similar. All were low rise designs and were designed for use with EGR. None are really considered to be a performance manifold; they are really just a "lighter" version of the cast iron manifolds used during that period.

The best aluminum manifold ever used originally on a small block was the 70-72 LT-1 manifolds of casting numbers 3972110 and 3959594. However, these manifolds are designed for use with square bore, Holley carburetors. I do think that either of these manifolds will fit under the 63-67 small block hood. For 68-72 applications, though, the LT-1/big block hood is required.

To obtain the equivalent performance of the LT-1 manifold with a Q-Jet carburetor, one has to use an aftermarket manifold. The Edelbrock Performer 2101 is such a manifold. This manifold is designed for use with a Q-Jet or square bore Holley carb and is otherwise very similar in overall design to the GM #3972110 and 3959594. It will fit under the hood of any 63-67 and will also fit under the small block hood of 68-72 models since it is a bit lower profile than the GM manifolds. Not much, but just enough to fit under the 68-72 hoods.

[Clem Z.]

Re: Best '60s or '70s GM small-block intake?

if you use a performer manifold make sure you use a oil heat shield under the manifold because they have poor fuel distribution because 4 of the the intake runners are exposed to the hot oil and these 4 runner have extra heat inducted into the fuel charge. moroso sells one that fit in the tappet chamber.the best type is to make your own to cover the manifold bottom but this will take some machine work. also i am enjoying the sunshine here in fl. till march 7 and now i am on the local library computer.see you all later when i get back home.

[Christopher R.]

Re: Best '60s or '70s GM small-block intake?

Joe,

1. Whadda y'know about the 3917610 manifold? It was used in the first Z-28s.

2. I'd like to understand Chevrolet high performance aluminum intake manifolds in general. You just gave me a big piece of the puzzle with your statement on the aluminum intake manifolds that took Q-jets. How did the aluminum intake manifolds of the '62, '63, '64-65, etc. differ? Why did Chevy change them almost every year? What about the iron intake manifold Chevy currently offers as a budget replacement for the Z-28 manifold?

[Joe L.]

Re: Best '60s or '70s GM small-block intake?

clem-----

Yes, a MANIFOLD-MOUNTED heat shield is advisable. But, you don't need to start from "scratch". A functional, if not pretty, heat shield can be cobbled together by modifying GM heat shield #6271071. This shield was originally used on 73-81 Corvette and other Chevrolet intake manifolds. By doing a little "cutting and bending" it can be made to fit other manifolds, including the Performer. It can then be attached by using the shield for a drilling template and drilling and tapping four small holes for 8-24 machine screws. Install the screws with Locktite thread locking compound.

The GM #6271071 heat shield is still available from GM for a current list price of $8.14.

[Wayne Kever]

Re: Best '60s or '70s GM small-block intake?

Thanks, Joe.

Someone with a '64 told me he has an LT1 intake with his L76 air cleaner, so I have hope. He hasn't given me the casting number yet. That will ice it and I'll buy an LT1.

- Wayne

[Clem Z.]

Re: Best '60s or '70s GM small-block intake?

joe, you have to cover the whole bottom of the manifold to keep the heat from the 4 runners. i mill off the heat riser crossover bulge on the bottom,weld in a aluminum plate to cover the hole and then cover the whole bottom with a stainless steel plate spaced about a 1/8" from the manifold surface.

[hogan64]

Re: Best '60s or '70s GM small-block intake?

Wayne,

I am the person you have been in contact with via e-mail about the LT1 intake. The casting number I am using is 3959594. I am using the a stock 365HP Chrome Air cleaner with a SB hood (Holley Carb). It does have the stock chrome oil fill tube but I don't know if the boss was added to the intake or not.

Hope this helps,

Ted

[Joe L.]

Re: Best '60s or '70s GM small-block intake?

chris-----

Oops! I almost missed this one. Anyway, the 67-68 Camaro Z-28 manifold, GM casting #3917610, was the first member of the "family" of PRODUCTION small block manifolds that later included the 3972110 and the 3959594. From a performance and runner design standpoint, all of these manifolds are nearly the same. The differences involve changes to accomodate chassis and peripheral revisions over the years. The location of the water pump outlet, heater hose outlet, temperature sender fitting, oil fill tube fitting, choke stove configuration, etc. are the principal differences.

The 62-67 Corvette small block aluminum manifolds are, essentially, another "family" of manifolds with similar performance and runner design. These manifolds also differ from year-to-year based upon the same sort of things that I described above. I think that the evolution from this design "family" to the Z-28/LT-1 family produced a better performance potential in the latter manifolds. That's what evolution is all about. However, I don't think that the performance difference is large between the two "families".

The cast iron version of the LT-1/Z-28 manifold, GM #14096011, is still available from GM for a current list price of $204.64. However, since this manifold was never a PRODUCTION piece (and, consequently, was never original for any application) I don't see what possible advantage there is in using one. For $150, or so ("wholesale"), you get a non-original, excellent performing manifold that's HEAVY. For about the same price, you can get a non-original, equally excellent performing, Edelbrock 2101 aluminum manifold that's LIGHT. Why anyone would want to use the 14096011 is beyond me, under those circumstances. Plus, the 14096011 is square-bore flanged for Holley carbs; the current 2101 can be used with either spread bore (Q-Jet) or square bore (Holley or Carter) carbs.

[Joe L.]

Re: Best '60s or '70s GM small-block intake?

Ted and Wayne------

I believe that the 3959594 manifold either has a soft plug installed in the oil fill tube hole OR it has just the cast boss for the oil fill tube which was not machined out in the as-supplied manifold. Vaguely, I recollect that it's the latter of these two possibilities. The 1970 manifold, GM #397110, may be the one with the soft plug. In any event, the soft plug can be removed or the boss machined out and then the pre-69 style oil fill tube can be installed. No problem, at all. I expect that's what happened here and it's perfectly fine.

[bruce11495]

Re: Best '60s or '70s GM small-block intake?

The LT1 manifold is history!!!1 Put on a single plane manifold, Edel. Perf, the Air Gap is the hot one now. The LT1 manifold is a dual plane type and hurts the bottom end. If you need something above 3500rpm, than the Victor Jr is the way to fly. But listen to Duke and do the porting, also port match both the heads and manifolds to the gaskets.

[John H.]

Re: Best '60s or '70s GM small-block intake?

The dual-plane manifold helps the bottom end torque (vs. single-plane); the single-plane torque is flat at the low end due to its large plenum and runners which reduce gas velocity, but it makes more power than the dual-plane at high rpm. Torque is what creates acceleration and "seat-of-the-pants" feel on the street. In spite of the marketing hype, NASA-level instrumentation is required to show any difference between the standard Performer RPM manifold and the Performer RPM "Air-Gap" manifold; but, the hype sells parts.

[bruce11495]

Re: Best '60s or '70s GM small-block intake?

John...You're right! I stand corrected. It's so long since I've been asked that question, I remember the principal and answered the question too quickly. Sorry for leading anyone astray.