1970 351C 4v intake manifold

magnoliamach1 · Sep 30, 2009

I currently have an Offenhauser intake on my 1970 351C 4v car and would like to replace it with a stock manifold. I have located one with the stamp code of DOAE-9425-L. I have an interchangeable parts manual that says my motor requires DOAZ-9424-C. I am new to this and still trying to figure out the codes. Any help would be appreciated.

2+2GT · Sep 30, 2009

magnoliamach1 said:
I currently have an Offenhauser intake on my 1970 351C 4v car and would like to replace it with a stock manifold. I have located one with the stamp code of DOAE-9425-L. I have an interchangeable parts manual that says my motor requires DOAZ-9424-C. I am new to this and still trying to figure out the codes. Any help would be appreciated.

DOAE-9425-L is in fact the casting number for manifold p/n DOAZ-9424-C.

The 1970 351C 4V intake was unique, having a hot air passage under the carb spacer/gasket. This also requires a unique 1970 gasket with a stainless steel insert, these are available new.

View attachment 243939

magnoliamach1 · Sep 30, 2009

Thank you 2+2. I will try to find an intake at a local shop to get an idea and mental picture of what it should look like. The picture you sent, is it available?

D.Hearne · Oct 1, 2009

magnoliamach1 said:
I currently have an Offenhauser intake on my 1970 351C 4v car and would like to replace it with a stock manifold. I have located one with the stamp code of DOAE-9425-L. I have an interchangeable parts manual that says my motor requires DOAZ-9424-C. I am new to this and still trying to figure out the codes. Any help would be appreciated.

What you're dealing with here are two different numbers. The D0AE-9425-L is an engineering number found on all Ford parts (not the same exact number but all Ford parts are cast/stamped with an engineering number, also known as the casting number) The other number you posted is the actual Ford Part number found on the part's original packaging, if you had bought that part from a dealer. You will never find this number on the part itself. Most likely the engineering numbered intake you found in the correct one. And possibly is the same part numbered part. If you're really looking for the exact correct part (as in doing a concours restoration) you'll need to look up the part number in a Ford parts book and get the engineering number found on the intake and look for an intake with that number. Of course the date code will also need to match for that as well.

D.Hearne · Oct 1, 2009

2+2GT said:
The 1970 351C 4V intake was unique, having a hot air passage under the carb spacer/gasket. This also requires a unique 1970 gasket with a stainless steel insert, these are available new.

All Ford factory intakes had an exhaust cross overpassage running thru them. This wasn't a feature unique to one specific intake. It would be unique to find one that didn't have one.

2+2GT · Oct 1, 2009

D.Hearne said:
All Ford factory intakes had an exhaust cross overpassage running thru them. This wasn't a feature unique to one specific intake. It would be unique to find one that didn't have one.

Well, yes and no. Pretty much all Ford (or Chevy, etc) V8 manifolds have a heat passage running through them, internally, but the 70 351C 4V is unique in that there is also a groove or slot on the top, as shown in my link. This requires a one-year-only stainless steel core carb gasket.

D.Hearne · Oct 1, 2009

I'll bet that if you flip the intake, you'll also find that the passage runs under it as well. The top passage was meant for an EGR system. Many 70's Ford intakes had this feature as well as that intake you posted. They ALL sucked big time. Good for rotting the carb spacer out above it, which it fed exhaust gasses into for the EGR.

2+2GT · Oct 1, 2009

No, you're wrong about the EGR. The upper pic is the 70, with crossover, which is probably meant to eliminate carb ice. The carb gasket will last indefinitely if you use the right one, which has a stainless steel plate along that heat passage. The lower is the EGR-equipped manifold, note that the channel for the EGR is much larger, and located differently, than the heat crossover on the 70:

View attachment 243845
View attachment 243846

D.Hearne · Oct 1, 2009

Wrong about the EGR ? Nope. Ford made many different intakes and parts as the need arose for different polution control mandates. The 70 intake was just one in a string of experiments. The 83-85 Mustang HO 4 bbl intake had one bean sized hole to route the EGR up into the carb spacer. Want to explain that ? And if you really want to prove your point, show us the backside of those intakes.

magnoliamach1 · Oct 1, 2009

D. Hearne and 2+2GT

Thank you for the discussion. It has helped and I feel comfortable buying the manifold if it is in reasonable shape. Where do you find the Ford manuals? Are these the 5-volumn sets I've seen advertised on CD or hard copy?

D.Hearne · Oct 2, 2009

The parts manuals I'm thinking about are big suckers. Bout 20 lbs each that they used at the parts counters at the dealers. Might find one at a swap meet.

2+2GT · Oct 2, 2009

The 70 351C 4V differed from the 71-73 in that the 70 was a square bore, while the 71-73 was spread bore. A one-year-only deal, with no EGR.

The Mustang etc (73 and later) had EGR , and ALL of them had the lower heat passage as well, but the 70, 71, and 72 manifold had no provision for EGR. The 73, the first year for Mustang EGR, the manifold had an ENTIRELY different slot, look closely and you'll see the 70 slot wraps around the primary venturis, and goes no where near the rear of the carb, which is where the 73 and later EGR was mounted. This requires a unique carb gasket with an internal stainless steel heat shield. Failure to use this special gasket with early 351C manifolds guarantees gasket failure.

The 71-72 BOSS 351 and 351HO had the lower crossover, but no such channel on top:

2+2GT · Oct 2, 2009

2+2GT said:
The 1970 351C 4V intake was unique, having a hot air passage under the carb spacer/gasket. This also requires a unique 1970 gasket with a stainless steel insert, these are available new.

View attachment 243716

This is the unique 1970-only carb gasket I mentioned. It's basically two special gaskets bonded to a stainless steel core.

D.Hearne · Oct 2, 2009

The one fact remains that there is another passage under the intake plenum (just as there are on most other Ford intakes, the 83-85 HO 5.0 included)) and the one that surfaces under the carb may or may not have had a dual function (EGR and carb heating) In the case of EGR and heating, both functions are detrimental in the engine's power production potential, unless you're talking about extreme below freezing cold weather operation. If you're not going to run the engine in those temps, that passage should be filled or blocked and the under plenum passage too as well.

2+2GT · Oct 2, 2009

Carburetor ice, which I mentioned in passing above, has nothing to do with extreme below freezing cold weather operation, in fact carb icing is extremely unlikely at extreme low temperature. While carb ice is of more concern in aviation (when the engine quits you die, instead of pulling over) it is not unknown in autos.
What is carburetor ice? - Ninja250Wiki
Carburetor icing - Wikipedia, the free encyclopedia
Automotive
Ford Mustang relevant: Classic Mustang Forum + Classified Ads :: View topic - Whoa! Better keep mine if they're this spendy to replace

While this chart is published for aircraft, note that icing can occur at 30°C, or 86°F, and does not occur below -15°C, and most icing takes place above 0°C, the freezing point of water:

2+2GT · Oct 2, 2009

magnoliamach1 said:
Thank you for the discussion. It has helped and I feel comfortable buying the manifold if it is in reasonable shape. Where do you find the Ford manuals? Are these the 5-volumn sets I've seen advertised on CD or hard copy?

The Ford Master Parts Catalog is available on CD, and if you need to look up part numbers, that's the way. The hard copy takes up about 2 1/2 feet of shelf space, and costs considerably more than the CD.

The part numbers are not the numbers you find on the parts, strangely. Those are engineering numbers. You can get guides to them, too, fairly cheap.

ddonaca351 · Oct 3, 2009

Also worth mentioning ( I might have missed it among the mud slinging ) is that the 70 is set up for a square bore carb.

The boss man and several others are for spread bore carbs.

D

Pm me if ya need to buy a factory 4v man off a 70' M code 351C stang.

2+2GT · Oct 3, 2009

I mentioned that about halfway up, but you'd be hard-pressed to find it:

The 70 351C 4V differed from the 71-73 in that the 70 was a square bore, while the 71-73 was spread bore. A one-year-only deal, with no EGR.

67efivert · Oct 3, 2009

amongist all this bs did u find out what u needed to know ?

timeless2 · Oct 4, 2009

Let's keep her on topic, guys. This is a good thread otherwise. If you don't have something constructive to say, just push the |/O button.

1970 351C 4v intake manifold

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