61driver

As I persue to build my 350 to 1970 LT1 specs I am running across a lot of intake manifolds that are being sold as LT1 intake , but the numbers do not match the 370 hp engine numbers from corvette by the numbers or How to hotrod your SBC...are all these manifolds the same regardless of what HP engine they were put on? Will they all do the job with an LT1 cam? Is there an aftermarket equivelant? SOme of these are selling for more than $400 is that too much? As always thanks in advance. (and if any ine is selling one please drop me am PM.)
Ray

wesmigletz

The 67/68 Z/28 intakes had an oil fill tube. I think the 69 and up had an undrilled aluminum pad for a fill tube. The 67-69 Z/28 intakes look very similar to the LT-1 intake to me. I used to have a GM service replacement LT-1 intake. Wish I still had it.

GCD1962

You have a pm

DZAUTO

The 67-72 Z/28 and 70-72 LT1 intake manifolds are the same design in regards to the carb base/plenum/runners. There are some variations in water outlet position and oil filler tube.
The 67-8 water outlet/thermostat position was different from the 69-72 manifolds. Also, the 67-8 manifolds had a threaded hole for a temp sender next to the water outlet. That threaded hole was moved over to the right side on the 69-72 manifolds.
The 67-8 manifolds had a hole up front for an oil filler tube that was pressed in. The 69 manifolds had the repositioned water outlet as well as the hole up front for an oil filler tube, BUT, the 69s had a welch plug installed in the hole. The 70-72 manifolds had the boss for the oil filler tube hole completely cast over. I supposed if a person had a 70-72 manifold and wanted to machine a hole in the boss for the oil fill tube, it shouldn't be a problem.
Those are the differences, in addition to different casting numbers:
3917610 for the 67-8
3932472 for 69
3972110 for 70
3959594 for 71-2.
At one time, one of these could be picked up at swap meets for $50-75, but not anymore. I think $400 is waaaaaaaaaaaaaay to high, unless it is an NOS manifold. The last one I bought at a swap meet was about $150.

longbros

Hey DZAUTO,

In your table of manifolds and part numbers, you did not list part number 3972114. In my Corvette parts book, it lists this as the 68-70 350 w/ special high performance. I seem to recall, that the 3972114 was a service replacement for the 70 LT1 3972110. Is that correct, and are there any differences? Also, what about the 3972116, is this the same manifold but different application.

JohnZ

Don't confuse CASTING numbers with PART numbers - they're usually (but not always) different, and the parts book doesn't show casting numbers. The 1970 LT-1 intake was CASTING #3972110 (which was P/N 3972114), and for '71-'72 LT-1 it was CASTING #3959594 (which was P/N 3991004). All you can go by is the casting number, as the part number wasn't shown on any intakes - only the casting number appears on the part.

longbros

JohnZ,

Now I am really confused. I see what appears to be, at a glance, the same manifold on Ebay and elsewhere with the cast numbers on the manifold of 3972110, 3972114, and 3279116. I thought the manifold with the number cast into it of 3972110 was the original 1970 LT1 manifold. I had heard or read where the manifold with the number 3972114 cast into it was a service replacement manifold for the LT1. I don't anything about the manifold with 3972116 cast into it, but as I said above, they all look the same at a quick glance. Thanks for helping me sort this out as I also am looking towards building an LT1 engine, and would be happy to use any of these manifolds if they all perform the same.

DZAUTO

I have SEEN the service replacement manifold (years ago) and at that time, it never occured to me to check the number on it. So I don't know what the casting number is on the service replacement. AT ONE TIME, long, long ago (no, this is not a Star Wars story), you could buy the same manifold from the parts dept that was installed on production engines. Then, later, the service replacement became available. There is one particular visual difference with the service replacement. Where the manifold mates with the head, the service replacement has a raised ridge around the intake runners (kind like most other manifolds), whereas the production Z/28-LT1 manifolds have smooth intake runners all the way down to the edge of the manifold where it mates to the head. To the best of my knowledge, ONLY the service replacement manifold had these raised ridges.
Now, one other thing. At one time (its now discontinued), there was also a cast iron twin to the alum Z/28-LT1 manifold. The reason was to satisfy some class rules that required a "factory" iron intake as well as for marine applications. That sucker was heavier than a regular iron 4bl manifold. Probably about as heavy as an iron BB intake!

61driver

My understanding is that there is no differance in performance with all these differant intakes. All are acceptable with an LT1 camshaft??

DZAUTO

Correct.

61driver

Thanks for all the replies. see you on the next dilema.

Ray

6T5RUSH

DZAUTO,

I had to jump in here and let you know I am using a GM Service Replacement LT1 Intake. As I'm penning this, I am providing you with the info on the GM Service Parts Operation cardboard box it came in. That Part No. on the box is 14044836. That same Part No. is also cast on the intake itself. The front of the intake has the firing order cast in. The rear of the intake has 14044836 cast in. I bought this piece from REDVETTRACER in the original box...never been used.

Although I do not have a website, I can e-mail pics of the intake if anyone wants 'em.

Regards,

Jim