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Intake to Head--Port Alignment

2K views 10 replies 6 participants last post by  jaw22w 
#1 · (Edited)
My hot rod is down for 7-10 days waiting for a coil over shock to be rebuilt. So decided to replace rear trans bushing and seal. Motor has to come out to get trans out. So while the motor is on the stand. I decide to take a look at it. New build, only 250 or so miles. Motor runs great. I get the carb off, look down the runners, and the intake is sitting slightly low, causing a slight step up on the port floor to get to the head. Heads and intake are port matched. Removed intake. Originally had a 1206 gasket. So I mocked up with a 1266. That's the thick one, .120", I think. This raised the intake a bit, but still a little step up. Then just for grins, I mocked up a 1206 on top of the 1266. With both gaskets in there I get the best port alignment. The floor of the port @ interface is level. End gaps are .250".
Of course the heads are milled, the block decked, etc., but I have never run into this.
What do you think of running double intake gaskets? Will this likely lead to sealing problems?
Thanks for any input.

EDIT: I was thinking if I put the 1266 (no printo seal} on the head, then the printoseal of the 1206 towards the intake, this might work. Probably glue the 2 gaskets together and let cure before installing. I should have caught this during the build, but didn't.
 
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#3 ·
Well, I am retired and have a lot of time to devote to my hot rods.
So the port floor is of very little consequence? If port alignment is a waste of time, then why do we spend so much time and money on port matching. I'm certainly no pro, but it seems to me that the better the ports are lined up the better the flow. Since they are port matched they should fit together "perfectly". If the bottom has a step the top does too, effectively decreasing port size. Also I thought that the raw fuel running down the port floor had a big effect. A step would interrupt this flow, no? Like I said. No "pro" here.
So, you would do what? Throw the 1266 on there and live with the step?
 
#4 ·
Application of intent.

Port Matching has merit on a serious race engines where everything it being optimized for the reason you gave already. There's always more to the story though. Every combo is a little different and every combo has slightly different needs and wants as well as every small adjustment is compromise to something else. Bearing all this is mind, your net gains on something like port matching vs all the other inefficiencies your engine has nets very little gain for the time or expense involved. You would be way ahead spending the time optimizing the carburetors fuel curve for instance. Because your retired and have time than that's great too. I'd do the 1206 and grind away to your heart content. A day at the dyno playing with timing and fuel curves is one of the best bank for your buck expenses there are.
 
#6 ·
These heads and intake are already port matched. Any amount of grinding anywhere will cause a mismatch not correct one. The only way to correct this issue is to raise the intake. The only way to raise the intake is to use thicker gaskets. While I am installing the intake, why not make it the best I can? I am unaware of any gaskets thicker than .120". Can you lead me to them?
 
#7 ·
In my opinion, if both the head and intake ports match the same size gasket, your doing the right thing to raise the intake to the correct height for better alignment.
If you can get that height by gluing several gaskets together, have at it. All of the .120 thick gaskets that I have seen are just two .060 glued together.
One thing you might want to be careful with when using thicker gaskets is to be careful when bolting intake on. Due to the thicker gaskets it will be easier to distort/warp the intake. I would make multiple passes tightening down from the center out.
Like already posted, the push rod pinch is usually the largest restriction in the port before the valve seat. With that in mind the port misalignment difference in actual total air flow numbers will be small.
I agree that when you build a performance engine you want to do every thing you can to optimize performance/hp. Every little bit adds up.
Best of success on your hotrod.
 
#8 ·
The only gaskets I buy are head and exhaust gaskets, everything else I make from roll stock. Here is the stuff I use for just about everything, not expensive and super easy to trim with an exacto knife.

I use Permatex Spray Tack non-hardening sealant to stick the gasket down, better than Printoseal if you ask me plus the gasket is reusable later down the road.

Gasket Sealants : Permatex® High Tack™ Spray-A-Gasket™ Sealant

Looks like you want the 0.125" stuff for your application, Ive also seen this stuff in green which is a different binder but still good for intakes.

Asbestos Free Synthetic Composite Compressed Sheeting
 
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#9 ·
Then just for grins, I mocked up a 1206 on top of the 1266. With both gaskets in there I get the best port alignment. The floor of the port @ interface is level. End gaps are .250".
What your describing is the gap between the intake and the 'china wall', correct? If it is, then yikes. That will require a thick bead of silicone to seal and I'd be concerned that it would require resealing about once a month.

If it was mine, I'd be doing some checking with your porter on what kind of gain, if any, you're going to make by correcting what you've found. If I remember from one of your previous threads, you bought the heads and intake from Chad Speier, if yes, then I'd contact him and bounce your situation off from him.

Just so you know, 64, retired, and lots of time to mess with your hotrod - you don't have to rub it in - jealousy is prevailing on my end:D

Jim
 
#11 ·
Yes, it is .250" at the china wall. Seems like a lot to me too. Kind of scary.
A call to Speiers might be in order, today.

Not trying to "rub it in" LOL. Just stating that if I am "wasting my time" then I have a lot of it to waste. If I can make something better with a little time investment, it's all to the good, although as those hours and days start getting in shorter supply, they start getting more valuable. It's a sliding scale.:cool:
 
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