Chevy Cast Iron Intake Manifolds -- Are any of them desirable?

[Sonny]

General question, please. Are any of the small block cast iron intake manifolds from the Chevrolet 60s and 70s eras especially desirable?

I'm sorting through my late father's obsolete parts collection and have come across several four-barrel manifolds. It seems appropriate to see if they have any value before pitching them in the scrap iron pile.

Thanks in advance.

[Cliff Ruggles]

They are all excellent, even the later EGR versions.  For the most part all the cast iron intakes are the same basic design.  There are a few specific versions that are more sought after than others for racing classes where you are required to use one, but really not that much difference in them to seek out the Holy Grail stuff.

The cast iron is actually your friend with these things, they improve thermal efficiency with a wet-flow system and allow for leaner A/F ratios compared to aluminum.

I know that the stock intake is typically one of the first items on one of these engines to be replaced, as folks buy into the BS that their engine will make more power with an aftermarket aluminum intake.

If anything at all the larger runners may make a few more ponies WAY up in the RPM range, and that's only if you have the cam and heads to support it.  In most cases about all you do is take a few pounds off the engine and kill off some throttle response and low-end power, and often hurt mid range power as well.

Several years ago we did a back to back dyno test with three intake manifolds.  The engine was a Pontiac 428 with 260cfm aftermarket aluminum heads, 10.6 to 1 compression and custom ground HR camshaft with 236/242 @ .050 specs.

With a stock Pontiac HO aluminum intake it made 487hp.  An Edelbrock Performer made 491hp.  My factory iron intake made 497hp!

To this day folks on the Pontiac boards cry "foul" because I modified the iron intake under the carb to be the same shape (two large openings instead of two round holes) as the RPM, but did no porting in the runners just cleaned them up and matched them to a stock Felpro gasket.

The RPM got the same treatment as we also port matched it to a stock Felpro gasket.

So with 434cid and a decent size roller cam, plus aftermarket high performance aluminum heads the stock intake outran the RPM.  The RPM is also over an inch taller with larger runners.......HUM.....something to ponder on here far as putting a bigger aluminum intake on your engine and tossing out the factory iron one.......Cliff

[Sonny]

Wow! I like your reply very much, Cliff. The breadth and depth of your knowledge and experience is amazing. Thanks for sharing it. I'm happy that I found your forum. Those old factory intake manifolds will be coming home with me and will *not* go in the scrap bin destined for the recycling center.

[Mudsport96]

Here's a thread I had before about manifolds.
I think it was super chevy putting up numbers for as cast and ported edelbrock manifolds. And the David Vizards stock and ported iron factory manifolds.

https://cliffshighperformance.com/simplemachinesforum/index.php/topic,3260.msg14178.html#msg14178 

[Sonny]

That was a great post, Mudsport. Thanks for pointing me to it. Several of the comments hit some sore spots I've experienced with my aftermarket intake:

• throttle linkage
• kickdown cable
• fuel line

Re-fitment of those items was time consuming and added expense. Hindsight says for my bone-stock 350 SBC I should have considered simply giving the factory manifold a good cleaning and a coat of 'manifold gray' paint to obtain the aftermarket look. 

[Pav8427]

Would this also apply to BBC intakes? Always thought the early hi rise q-jet intakes 'looked' good.

[Mudsport96]

That I do not know, I dont dabble much in big block engines. If I have time I'll see what I can find

[Cliff Ruggles]

The early "high rise" are excellent aside from having the exhaust crossover "channel" under the carb to deal with.

Even the later "flat" intakes work good.  We've helped some folks out with "factory appearing" cars that are required to use them and made excellent dyno and track numbers with them......Cliff