Clark455

I think most everybody knows what happens when you mill cylinder heads down a ways to reduce the combustion chamber volumes. You need to run shorter pushrods and then you also have to machine your intake manifold to properly fit. I took the bait on these a while back when building my 403 rev monster:

69cc Olds 403 Cylinder Heads

These heads above are the Speedmaster big block Olds heads with the head bolt holes drilled to accommodate the larger later model 1/2" head bolts. Great! 69cc's and already drilled head bolt holes - exactly what I needed.

I bolted them down to the engine, mocked up and ordered the custom pushrods, later assembling the valve train - no problems.

Then OOPS - I went to install the Edelbrock Performer 7111 intake and that aha moment hit me - you know the one, where you should've known better but didn't (we've all been there at one point of another as gear heads). The intake bolts were nowhere near lining up, slapping myself as I should've know this is how OldsRocketParts managed 69cc chamber volumes - milled decks, not some kind of different castings. YES - OldsRocketParts *REALLY* needs to mention this in their online listing for these heads, as I can only imagine how many guys have ended up at this same point wondering what to do about their intake bolts not lining up.

I know this could arguably be shunted off into the parts for sale section, but the tech info here is what will come in handy for guys milling heads on their builds. I ended up calculating that I needed to take .080" off of each side of the intake (where the intake gaskets meet the heads), then take .060" off of the end rails (the front and rear ends of the intake where the oil seals are). I got lucky that my calculations resulted in the intake dropping right into place perfectly, as I had expected to possibly have to go after it again. What I did initially was set the intake down WITHOUT any gaskets in place, seeing that the bolt holes almost lined up, but finding the end rails literally sitting metal to metal. I measured the thickness of the Edelbrock 7284 intake gaskets, coming in at +/- .062" which is how I determined that milling .080" off of each side of the intake was going to do it. I shot from the hip on the end rails, knowing I was going to be using RTV, deciding that .060" would be about right.

Having been down this road milling many heads over the years in efforts to raise compression ratios, I have often wondered how many other people get through this. I have seen many cases where guys have just elongated the bolt holes in the intakes to get the bolts in, but not realizing how far off the port alignment is when the intake manifold is NOT machined in accordance with heads being machined. I'm not sure how others may decide how much to machine their intakes, though the formula above is what has most always worked for me, so maybe this may help others.

At any rate, I was going to build two 403's just about identically, so I had two of these intakes machined. The line I had on a second 330 Olds forged crank fell through, as the guy sold it out from under our deal. After scavenging around for another forged crank for a while, the machine shop called me and said that my second 403 block was found to have a crack in the cylinder head deck, so that scrapped the build on the second 403. As a result of all of this, I now have a second machined Edelbrock 7111 Performer RPM intake on hand with no use for it. If you may be interested in it, take a look at Ebay listing 285437011984 (just copy and paste that number into the Ebay search box and it will pop up the listing). I'd rather sell it to somebody here on the forum that could use it. If you may need this intake, send me a private message (I will sell it to you through a Paypal transaction so that you don't have to pay all of the fees and sales tax) (lower price for a ClassicOlds forum member). You may also be interested in this '83-'84 Hurst Olds A4 intake - enter this number into the Ebay search: 285447263054

Hopefully this info on how I determined how much to have the intake milled to properly interface with the milled cylinder heads may help others!

Paul...

rickw30

I recently went through the same scenario.
Got to the point of mock up for port matching and it hit me. I knew it had to be done and had that "senior" moment.
I did the same as you but I had the luxury of knowing the head mill # and incorporated that into my calculation.
Worked out perfectly.
Elongating the intake bolt holes just wasn't going to do it for me and would pose other potential problems when port matching. I would loose to much sleep at night doing it half assed. It has to be done correctly.
Very good point about those heads. This scenario should be clearly noted to potential buyers.

oddball

I've had to mill every edelbrock intake because they're nowhere near flat, even new out of the box.

cutlassefi

^^^^^^^

CANADIANOLDS

I’m the luckiest guy in the world….never had to mill an Ebrock intake. ..they must like me, I get sent the good ones.

the other thing about cutting the intake to drop it when heads or block have been cut a bunch….I don’t agree with. There is a benefit to having the intake sit up higher…the higher the better if you plan on having a way better port/intake runner alignment. That’s your chance to fix what the factory F’d up

you can double stack the intake gaskets , cut the heads +.100” and still make it work.

skyhigh

I was just at the machine shop today and he had my speedmaster heads cut sown to 68 CC or so and he said he didnt touch the rpm intake and it will align, so you dont have to take off the same amount as others have suggested, but Dale made some good points about the double gasket and what not if you do run into issues.

jmcghee

Dalle, what do you do on the end rails?

CANADIANOLDS

permatex ultra …no rubber end rails. I do that on all builds

rickw30

That's what the machine says now ! Until you do a mock-up or try to port match.
I double check everything the machine does. If your lucky, it doesn't go back for some fixings.

skyhigh

He did mock it up so he says, prob fits better due to the thicker comp gaskets rather than the thin turkey tray is my guess, secondly that will be his problem if there is one lol

Bernhard

Dale is there a brand of intake gaskets that you prefer when staking gaskets? When staking intake gaskets do you apply a sealer between the gaskets?
I see that many manufactures list an Oldsmobile intake gasket that has .60 to .62 thickness and that the Chevy guys don't have to stack gaskets as they can buy a .120 gasket.
I assume that this practice can also bee done with the stock cast iron intake?

skyhigh

Im not trying to answer your question to Dale but BM sells a 0.90 printoseal gasket for the speedmaster head, or any ported head for that matter.

https://bernardmondelloracing.com/pr...nifold-gaskets

Bernhard

Thanks for the post good information to have.

rickw30

I mill the head, mill the intake port on head, mill the intake and port match. What ever it takes to achieve correct compression and port matching.
I order what ever thickness gaskets I need from cometic and they are at my door in 2 weeks.
I don't use the BS factory gaskets at intake end rails. I use '" the right stuff ' " by permatex and it's perfect every time.
Eazy cheezey... Done !

CANADIANOLDS

its more important to raise the stock intake than an aftermarket one because of the horrible angle change at the head on most of the ports…the lower plenum runners

Flatout gaskets makes .120” thick Olds intake gaskets. I usually make my own from .120” sheet though.

Flatout also has a spacer kit. .125” aluminum spacers with two .060” gaskets

the trick deal with the spacer is to use two .120” gaskets instead of the .060” ones 😎

CANADIANOLDS

yikes….🤣

Bernhard

Thanks for the reply Dale.

70W-32

Just an FYI to everyone, OldsRocketParts is part of Mondello Performance. Theyre are hiding behind an alias because they cant sell parts as Mondello Performance due to their lousy reputation for screwing customers.

fleming442

I knew it!! scheisty bastids

CANADIANOLDS

thats weird…not that I don’t trust what you say. I email’d them about a part and they made it clear they’ve got nothing to do with Mondello.

they have parts Mondello doesn’t carry and vise versa. Rocket parts trashes Mondello sometimes too.

Clark455

Harry / Junior over there at Olds Rocket Parts is great to deal with. Do you have anything to back up your claim? I for one don't believe that this is true - where did you hear that they are Mondello related?

olds 307 and 403

Olds Rocket Parts claims they are a former Mondello employee. Did you measure the chambers? Supposedly they guess and do a .050 to .060" cut which puts them short of the 69cc number from what 81cc they start at?
https://classicoldsmobile.com/forums...edmaster+heads

fleming442

That is the absolute 1st good review I've heard about them.

skyhigh

My machinist said my pair cc right where they were advertised at 77 and to get them to 70 he didn't take down as much as your saying, that being said when mine gets to the dyno and if I dont have the hp or torque that I no I should be around then I no he was blowing smoke lol

CANADIANOLDS

is this bs or true?

im not asking if the guy is a shyster like Mondello or not …he makes sure he has nothing to to do with anything Mondello when you deal with him

olds 307 and 403

Good to hear, hopefully he actually checked them. I know Mr Remmel has handled many sets and said they were larger than advertised. Maybe they are doing better quality control and they actually measure what they should now. I hope everything goes peachy on the dyno.