Looks like a casting flaw. If it was that way from the factory, it's a wonder it ran great up until last month. I've been chasing a vacuum leak for a while, but never expected this! On both 5 and 8. [/IMG]

 

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Wow good job finding that definitely a factory flaw Hell it could take months to find something like that.

 

looks like a good time for an upgrade

 

No luck finding aftermarket 2V intakes. Edelbrock makes a 4V but it's illegal in California because the 4 barrel wasn't offered on trucks. If there are any options besides a junkyard, I'd sure like to hear about 'em.

 

As original, there is no such thing as a 400 (or 351M) with a 4V, all were 2V's. Passenger Cars, Bronco's, F100/350's and Econolines.

No 302 installed in any truck, Bronco or Econoline came with a 4V either.

1974/76 F100/350's w/390's offered an optional 4V (VIN engine code M).

All 1973/76 F100, 1973/79 F150/350's with 460's are 4V's, but...1978/79 F150's sold new in CA were not available w/a 460.

 

Edelbrock 3771 - Edelbrock Performer Intake Manifolds - Overview - SummitRacing.com

 

couldn't you just epoxy the low spots?

 

That's what I just got done doing. Used JB Weld. I'm just not sure how long it will last when it gets hot. Probably a long time. Just wanted an option, because next summer I'm doing a full resto, but I still have to keep it CA smog compliant.

 

a two-part epoxy should last forever if the manifold is clean when you lay it down.

 

edelbrocks intake is smog legal. I live in california and thats what I have on my truck. When you buy it they give you a 2 barrel adapter plate that has your egr valve hookup. I also run all MSD ignition with pro billet dist, ignition box, coil. also all smog legal. just make sure you save all the stickers they give you with carb numbers. Smog tech will look for them. Just passed smog last spring with no problems and all the aftermarket stuff actually brought numbers down. Its also really easy to take the adapter plate on and off in between checks....

 

Any good machine shop should be able to weld that up.