[67cruiser]

WOW, wondering how many guys are having a issue with there RPM intakes on the alaignmant of the bolt hold down area screws. My front drivers side was almost off 1/4 of the hole.Pass side center 2 are ok but is you use a bolt with washers made on to them the washer hits groove in the intake. Drivers side 2 center holes are off also.On new aluminum heads never milled . Standard .040 over block. IF ITS NOT ONE THING ITS ANOTHER!! Looks like valve covers are hitting top of intake also. Geeezzzzzzz. Double up the gaskets in valves cover may make it work.

[lfdsteve]

Had to have mine milled to fit FYI

Steve

[paul s.]

On stock deck height or SLIGHTLY decked blocks, the only problem I have seen is the valley cover/port interference as there is a lot of material there. A few minutes with a die grinder usually takes care of it.

[67cruiser]

Paul S. biggest area is the 2 center bolt holes on drivers side off about .100 to the rear area off. Im going to a Allen 3/8 BOLTS TO ACHIEVE i better fit. Yes i took some off bottom i have clearance there, only other place (as stated) is now my valve covers are
hitting the intake. Back to the die grinder!!!

[Matt Meaney]

mine didn't fit either.

put it on without the gaskets and it fit great. had the intake milled the thickness of the gaskets (.060) and all was good.

these are new parts, you don't expect them to just go together do you?

[lust4speed]

Every Edelbrock RPM manifold needs to be cut. Normal cut is .060" per side, and can be verified as stated above by test fitting without the gasket. Why Edelbrock doesn't read the letters and emails and do something about the fit remains a mystery.

While the manifold is too fat, Edelbrock did get the bolt holes and ports dead nuts on, and things fit excellent after milling. Bolt holes are good enough to use as an alignment help. The threaded holes in the heads should be dead-nuts centered in the holes both up and down and side to side. If you get them centered, the ports will be aligned. So never take a file or grinder to the bolt holes, fix the problem right by having the sides milled.

The .060" is correct for virgin heads, and if the heads were milled on the block mating surface without a corresponding cut on the head manifold surface, then this amount should also be added to the manifold cut. Say the shop milled .010" on a clean up cut on the deck of the block to get closer to zero deck height, and then did a .006" clean up cut only on the combustion side of the head, then the manifold is going to need a .076" cut on each side (.060+.010+.006).

Most shops don't automatically do the manifold side of the head which is odd because they charge extra for it and it's just more money for them. I always specify the additional cut on the head manifold surface to match the block mating surface mill, then I can change manifolds without having the replacement manifold custom cut. The Edelbrock is simply at the same width as a stock manifold after the necessary .060" cut, so it can be transferred to any engine with stock specs.

Also as mentioned above, the bottom surface of the manifold runners and possibly some valley pan shaving is going to be necessary to make sure the manifold is actually sitting on the heads and not resting on the valley pan.

[67cruiser]

Lust 4 speed, inquiring, how did you arive at .060 mill on each side of intake?? Was it trial & error thing???

[lust4speed]

We've probably had about a dozen RPM manifold milled in the GTO club. Not a big sampling, but when all of them turn out the same I start feeling pretty confident about the manufactured size of the manifolds. Someday maybe Edelbrock will surprise us and they'll make them the correct size.

As Matt mentioned above, the holes line up perfect without the gasket in place, and just about all the standard gaskets are .060". You might find some gaskets on either side of this thickness, but most are really close. Always best to set the manifold in place and eyeball the fit. We're lucky with the Pontiac geometry because the math is easy. If you take .010" off the head surface, then the same amount should be taken off the manifold mating surface of the head. If you look into the bolt holes of the manifold and note the distance it takes to center the holes, this is what has to come off the manifold. It keeps the math simple. Don't fall into thinking that since it's a 45° surface you have to take off twice as much (or maybe half as much). Since it is a V shape and there are two surfaces being milled on the manifold, the proportions are 1:1.

Eyeballing the bolt holes as the final check also lets you know if you have to make up for a previous head cut, So best not to just grab the manifold and head out to the machine shop. Keep in mind that the closer the better, but being close is good enough. I've seen manifolds the guys have stood on to get the bolts started and the cars still ran good. I'd like to think that they cost themselves a little horsepower, but who knows if it was even a measurable amount?

[67cruiser]

Please forgive my questions, butt if you take .060 off the intake(at least i see it this way) won,t that put the intake closer to the valley pan for even more interfierance?? Spelling sucks, sorry. I do know machine shop took .008 off deck side of my aluminum heads for clean-up nothing off the mating top intake side. My holes are off, id say just about .060.maybe also thats why my valve covers are lying on top of my intake??????

[lust4speed]

Yes, milling the intake drops the manifold closer to the valley pan. Might be sitting on the pan now, but will be .060" closer after the correction. If the manifold touches the pan, it will not seal against the heads. The necessary correction should be a two-part approach. First is to notch the valley pan where it contacts the intake manifold. Usually have to go into the pan about an eighth of an inch (.125"). Next thing to do is to file off the bottom of the intake runners to gain additional clearance. This can be done with a rasp or file, but this will take awhile. I usually use a grinder to get most of the material removed, and then do hand cleanup with a file. Normally you will remove enough material from the bottom of the runners to reduce the sealing down to a little more than an eighth of an inch here also. The wall thickness at the edge on the bottom probably starts out about .28" thick, and you will be cutting this thickness in half. Between the two cuts, this should leave a nice gap between manifold and valley pan. You will also need to clearance the valley pan gasket and the intake manifold gaskets to match the pieces. I attached a pic of the notches, but don't go that deep unless you have to. This one still sealed up, but things were a little tight.

[67cruiser]

Excellant answer, Thank You very much

[Don 79 TA]

if you dont need a valley pan with PCV look at Darrin's pan from nightmare performance
prenotched, and real shallow too
but definitely look there as you can get hung up there, especially with milled heads

would be nice if the t-hawk got updated and was notched (yes... it sort of is trial and error)

[tooski]

Put RPM on stock 68 350. Changed over to 400 zero decked w/48 heads. Changed heads to 6x cut .025. Crossover separated. Only mod needed was runner bottom clearance for the valley pan. I must have got a good one.

[Skip Fix]

My machine shop says it isn't just Pontiac Edelbrocks that need milling

[Matt Meaney]

Originally Posted by Skip Fix

My machine shop says it isn't just Pontiac Edelbrocks that need milling

so did mine. thought they did it on purpose, to give the end user the ability to "fine tune" it to their specific application.

[mchell]

mine required the usual "aftermarket" modifications......grind....grind....grind....oh, and grind a little more

[KEN CROCIE]

If you can find a '65 valley pan,it's notched from the fact.