1206 std pushrod location

[Tom68]

Should you be gasket matching to a 1206 if you're not offsetting pushrods ?

The height is a good thing if your heads and manifold have enough material but thinning the divider wall at the pinch can only go so far whilst you chase the width further into the port.

[6.50camaro]

I have thought this same thing. So the last few sets of heads I did I kept the port width at 1.25 and went for as much height as possible. The sportsman II's I did are at 1.25 x 2.21, SCE 211102 fits that with a little trimming on the height. the 441's are sizes for mr.gasket 5821 1.25 x 2.13.The sportsman II's did nice in my opinion. Went 6.40 in the 1/8 on my flat top 422 and since that's my cutoff safety wise on the car, [8 point roll bar not full cage]
I can't complain. There could be more there. That was only the second run on that engine combo with those heads. The 441's are still being finished up and will be tried this year on a 383 hyd. roller engine. Dan

[mag2555]

The push rod pinch acts like only half a Venturi at high flow rates which is not good.
It compresses the air stream on to the common wall which makes that localized flow speed up even more.

One the air mass gets passed the tightest point of the pinch it expands and slows again.

Any unneeded expansion and contraction in the air stream on its way from the plenum to the crown of the short turn only serves to narrow up on the given motors power band and makes the motor act more cammy until it does get up into the power band, while also reducing peak Hp.

A sudden pinch/ contaction in port area has a even more profound effect on the power band.

This means it’s actually better if you have to deal with whatever amount of push rod pinch area to start the neck down to that minimum area as gradually as you can up in the manifold runner before the head flange.
When I am dealing with a head with a push rod pinch area and I am gasket matching the manifold to the head I at least aways left the port match on the push rod side near 1/4” smaller if I have that option.

[1980RS]

I have run 1206 on my SBC's with the stock pushrod locations with no problems.

[6.50camaro]

I have run 1206 on my SBC's with the stock pushrod locations with no problems.

Yes they will work and run, but is it the best. You can't get a 1206 opening on a lot of newer intakes they have cut so much material out to make them cheaper to produce.
About the widest I have been able to go is 1.08 without going though the wall on the pushrod side and keeping a reasonable and safe for me wall thickness. 1.10 if your careful. That 's about 18% reduction in width on just one side for 1206 1.31 wide gasket. Even at 1.25 wide that around 14%. What did chevy do with the Vortec heads they made the port opening narrower and taller. Did this help with more constant air speed through the pinch?
Not being argumentative just an old school hot rodder trying to learn and understand. Dan

[Monza355]

I have thought this same thing. So the last few sets of heads I did I kept the port width at 1.25 and went for as much height as possible. The sportsman II's I did are at 1.25 x 2.21, SCE 211102 fits that with a little trimming on the height. the 441's are sizes for mr.gasket 5821 1.25 x 2.13.The sportsman II's did nice in my opinion. Went 6.40 in the 1/8 on my flat top 422 and since that's my cutoff safety wise on the car, [8 point roll bar not full cage]
I can't complain. There could be more there. That was only the second run on that engine combo with those heads. The 441's are still being finished up and will be tried this year on a 383 hyd. roller engine. Dan

How are the 441 heads set up ? Will this engine be ran at the drag strip in your Camaro ?

[6.50camaro]

I have thought this same thing. So the last few sets of heads I did I kept the port width at 1.25 and went for as much height as possible. The sportsman II's I did are at 1.25 x 2.21, SCE 211102 fits that with a little trimming on the height. the 441's are sizes for mr.gasket 5821 1.25 x 2.13.The sportsman II's did nice in my opinion. Went 6.40 in the 1/8 on my flat top 422 and since that's my cutoff safety wise on the car, [8 point roll bar not full cage]
I can't complain. There could be more there. That was only the second run on that engine combo with those heads. The 441's are still being finished up and will be tried this year on a 383 hyd. roller engine. Dan

How are the 441 heads set up ? Will this engine be ran at the drag strip in your Camaro ?

They are home ported from around 160cc stock to 180-185cc, pushrod pinch from .97 x 1.80 to 1.08ish x1.90 intake face from stock to 1.25 x 2.13 . 1.94 1.50 valves throats are at 89% intake 87.5% exhaust . right now they are out getting angle milled .100 should bring the chamber down to around 64cc. they are going on a 383 short block I have had for about 8 years and has been mothballed since. This was my first bracket race motor back in 2014-2015. It will have a Lunati VooDoo hyd roller 243/251@ .050, Holley strip dominator intake, 750 Holley DP. Just for fun to see what I could do with these Old heads.

[jsgarage]

Something that's bothered me a little since the '60s: why do many engine builders let the intake gasket manufacturer dictate the size of an engine's intake ports? Is there really any deep science in the sizes & shapes they provide? Or is it just that the gasket provides a convenient stencil? If that's all it is, why not just pick a gasket that's a little bigger than the port, add it to the head and wipe a little Gasket-maker or RTV on to fill the tiny gap thats left so the air/fuel flow is not disturbed by the void. It would come right off with the gasket when its time to change. Am i (as usual) missing something?

[FC-Pilot]

Something that's bothered me a little since the '60s: why do many engine builders let the intake gasket manufacturer dictate the size of an engine's intake ports? Is there really any deep science in the sizes & shapes they provide? Or is it just that the gasket provides a convenient stencil? If that's all it is, why not just pick a gasket that's a little bigger than the port, add it to the head and wipe a little Gasket-maker or RTV on to fill the tiny gap thats left so the air/fuel flow is not disturbed by the void. It would come right off with the gasket when its time to change. Am i (as usual) missing something?

You bring up a great point. Right or wrong, this is what I do. I either get a gasket a touch on the small side, or a flat general gasket and make an intake gasket to match my heads intake port. Then I see how the intake matches up. Between the two I transfer the measurements back and forth as I don’t want to make the port too big before having to shrink it down for the pinch. I don’t want a big opening and then have to shrink it a bunch for the pushrod pinch. This way I can max out the pinch as needed, and then adjust the flange as needed. I don’t care about what gasket number or gasket size. I just care about having the sizes properly matched and then as smooth of a size transition through the pinch as possible.

Again, right or wrong this is how I do it.

Paul

[Bigchief632]

Something that's bothered me a little since the '60s: why do many engine builders let the intake gasket manufacturer dictate the size of an engine's intake ports? Is there really any deep science in the sizes & shapes they provide? Or is it just that the gasket provides a convenient stencil? If that's all it is, why not just pick a gasket that's a little bigger than the port, add it to the head and wipe a little Gasket-maker or RTV on to fill the tiny gap thats left so the air/fuel flow is not disturbed by the void. It would come right off with the gasket when its time to change. Am i (as usual) missing something?

That's what MTEngines was getting it earlier in the thread. Just use a 1206, it doesn't matter if it matches the port exactly. It'll seal just fine. Or, if you want the port a little bigger than that's in between 2 gasket sizes, oblong bolt holes, shift it up, and or trim some of the 1205 to make it what you need, there's no "rule" that says you're bound by the gasket size.

[SpeierRacingHeads]

This 23 degree of mine measures 1.390 x 2.400 at the opening. Close to a 1209. It's thin between but seals up just fine.

[Tom68]

This 23 degree of mine measures 1.390 x 2.400 at the opening. Close to a 1209. It's thin between but seals up just fine.

Beautiful.

Offset rocker on that one ?

[Tom68]

I have run 1206 on my SBC's with the stock pushrod locations with no problems.

No doubt, the intent wasn't whether the gasket would form an effective seal but whether gasket matching your ports to a 1206 with no pushrod offset was a power increasing worthwhile exercise. I'd say probably yes if you can immediately raise the heads port roof after the gasket face to recover the otherwise lost area.

Of course this is also power dependant, up to 450 HP probably no concern one way or the other, up to 550 HP getting tricky, over 550hp, getting very fussy about msca at the pinch unless there's a lot of available height.

Nonetheless I'm still staggered at the power levels now commonly attained with low roof 23 degree heads considering all the 80s and 90s raised port and also massive pushrod offsets.

[SpeierRacingHeads]

This 23 degree of mine measures 1.390 x 2.400 at the opening. Close to a 1209. It's thin between but seals up just fine.

yes .500. It has 3.02in² at pinch and MIN of 2.98² at the throat.

[SpeierRacingHeads]

Also, this is what I have to do for the 300-25 to match a 1207 gasket.