Gasket Matching

[robinsonwr]

I was reading the thread about grinding on Stealth's and had a question arise. I know with the wealth of knowledge you will lead this Mopar newbie to the answer. What gasket part numbers or dimensions should be used to gasket match a set of Stealth heads for a 512 build. I just picked up an Indy dual plane that will need to be done also. I appreciate your help in advance, thanks.

 

[Herr_Poopschitz]

As was outlined in the other thread, gasket matching alone is not worth the time/effort. There are other places in the port to focus effort.

 

[robinsonwr]

Yes, understand what you are saying. I also know in some cases bigger is not better. I just wanted to know a general port size to start with. The rest of the port work will be accomplished in due time.

 

[GTX MATT]

They're not perfect, but the paper gaskets that came with my fel pro valley pan were pretty close. I had to hack the crap out of the valley pan though.

 

[Herr_Poopschitz]

Yes, understand what you are saying. I also know in some cases bigger is not better. I just wanted to know a general port size to start with. The rest of the port work will be accomplished in due time.

The cross section at the pushrod pinch is gonna be smaller than whatever gasket you lay on the head. This will be the critical dimension from the gasket surface to an inch or so into the port...not at the gasket surface. For 500", I don't think you can make this area too large w/ the given material in the head, unless it's a low rpm torque/truck engine. Gaskets seal, not define a port.

Intended usage? Camshaft? RPM? Engine details please.

 

[robinsonwr]

The intended usage is street/strip focusing on cruising. The build will have an affective RPM range to around 6200. The camshaft is a custom grind hydraulic roller from Competition Cams (230/236 @ .050, advertised 281/287, 622/625 lift w/1.6).

 

[Cranky]

I like to lay my intake on a completed short block and 2 bolt it and then take a look at what's laying ahead. There are times when you won't have to do much if anything and there are times when the intake won't fit worth a damn....that is if you can see down into the ports using whatever you can to help view it. Of course, intakes with fairly straight runners will be the easiest to work with but you can also use dykem blue, clay or anything that will leave a foot print to see how it's sitting. Also, if your head ports are bigger than the intake, that's not nearly as bad as being the other way around. I'm all for not grinding if I don't have to.

 

[dvw]

If you see .5% on a gasket match I'd be surprised. In my opinion it's a waste of time. The valve job and transition in the bowl is where the power is. The entire port is small for a 512" But the most bang for the buck, bowls and VJ.
Doug

 

[Herr_Poopschitz]

The intended usage is street/strip focusing on cruising. The build will have an affective RPM range to around 6200. The camshaft is a custom grind hydraulic roller from Competition Cams (230/236 @ .050, advertised 281/287, 622/625 lift w/1.6).

Seems like an awfully small cam paired w/ small heads to spin that kinda RPM on that big of an engine. Those are mild parts on a 440, much less an additional 70 inches.

 

[cryplydog]

I always fit up my intake to the bare head and make sure its in a happy place as in the middle of any end to end or diagonal slop then tighten a couple bolts down . you need good lighting and look and see what you've got . I like spray dykem or the liquid layout fluid. core shift being what is never seems to stand still or in the same place do to many variables. the only time I remove material from the head is when the a/f mixture is running into a direct obstruction due to misalignment. once you get them to where you like, match mark man to head as to not get them on backwards. no matter what brand of engine, I've seen from one extreme to the other. you don't know unless you check and verify. do you think builders who deliver huge power/torque #s check all of these areas?

 

[Herr_Poopschitz]

This is a pic I took when I was putting my Mustang together. The intake had poor 'gasket matched' 'port work' performed on it as I bought it second hand (ebay). This port in particular had a pretty large opening at the mating face, larger than the other 7. I don't have access to a TIG, and I wasn't gonna pay someone to fix it, since it wasn't 'too' bad. I reworked the intake to overcome the small tube feeding into a large tube discrepancy that had been left by the 'gasket match' to get some kind of taper back. After porting these heads and mocking everything up, I found a little bit of an 'obstruction' in that the intake's port was still a tad larger than the head opening. I think I took this pic the second time I put it together...I had laid back the pushrod side wall just a tad, but you can tell I didn't get the corner pulled back far enough. I pulled it back apart and accounted for this transition. Did I need to? Not sure...air doesn't flow much in corners. One thing I do know...a gasket wouldn't have helped resolve this issue.

There are all kinds of theories on the mating surface mismatch. Some builders prefer the intake opening to be smaller than the head to help w/ reversion. Some prefer the exact opening on both intake and head as there's no transitions that must be made. Some don't worry themselves w/ small 'lips' - boundary layers mean little to no airspeed, ergo, no flow obstruction.

I'm not sure the OP was just concerned about mating surface obstructions...anyway...for Stealth's on a 512, make the port as big as the casting physically allows.

 

[Budnicks]

I was reading the thread about grinding on Stealth's and had a question arise. I know with the wealth of knowledge you will lead this Mopar newbie to the answer. What gasket part numbers or dimensions should be used to gasket match a set of Stealth heads for a 512 build. I just picked up an Indy dual plane that will need to be done also. I appreciate your help in advance, thanks.

what is it's intended use ?? will it be a track only car or a street/strip car... I don't know if gasket matching makes a real big difference, but it doesn't hurt either {I've done it on every car I've owned that I changed a set of heads on}, if it's done correctly, just don't go crazy with out know what your doing, just clean them up, mark what side goes where, in relation to the manifolds & blend in 1" or so, the biggest gain will be in the bowls/pockets, short side radious & valve size & type of valve job what angles etc., the rest should really be left to an expert or experienced head porter or you can screw up the heads, if you take material out of the wrong place & screw-up port velocity, change where or if, it makes more power... maybe IQ52 will chime in here, he can explain it much better than me... IMHFO no one book is the best, there are many more, than I show below, but they will give you a good idea or what & where to grind... IMHFO no one head is the best, no one builder has an exclusive on making power... But you should build the engine & especially the cylinder heads, for it's intended usage, that's the single biggest HP improvement you will make on a BB Wedge Mopar, heads have always been a big choke point... Spend the money right the 1st time... But I would highly suggest buying a few books, educate yourself on the cylinder head flow principles, before you start grinding away & some books & some heads also are better than others to start with... The inexpensive Stealth can be made to work, it depends on your budget, your abilities &/or knowledge & what your true expectation are... Some builders even big name ones, have many different theories than each other, about port size vs velocity, or port volumes & how it helps &/or hurts the flow vs valve size etc., the bigger the ports basically the higher the RPM's that will benefit the most, but port volume can effect power thru-out the RPM Range, or mess it up too... I like to use a combination of a few theories, to get a consensus & go from there... I highly suggest that you consult a professional head porter, if you have any doubts, it's allot easier to remove more material, than to fix a head, that is hogged out too much, FOR YOUR INTENDED USAGE... good luck & happy Moparing

 

[cdr]

what i have found is on the roof of the intake where it meets the cyl head ,almost all intakes have a little change of direction to match the angle of the port on the head,if you just grind that area to match the head port it will almost ALWAYS kill air flow. without a flow bench it is all just a guess.that indy intake should flow plenty UNTOUCHED .

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mine flows great out of the box