What the theory on the slanted intake port roof on the LT1 heads? Its seems that since most of the flow favors the port roof, that removing ths slant would provide more flow up top. I've also heard that removing the slant is bad practice on these heads. Opinions please.

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94 Formula M6 4.10 Strange 12 bolt Spohn Subs,LCA,LCA Brackets, & PHR,Moroso Cold Air, B&M Ripper w/ T handle/w switch , Hurst Line Loc,ET Streets, FLP's with B&B Triflow's, Taylor Wires
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CC306, R lifters, Pro Mag 1.6's
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3710# Pig Fat Race Weight
335 RWHP best 60' - 1.76
Best 1/8 - 8.05 @ 86.5
No 1/4 times yet

 

I always figured it was there to help promote swirl. Although all of the aftermarket/ported head i've seen do not have the same slant to the roof.

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Jason
93 TA, M6

 

For one thing, look at the intake, why would you go from a slant to an abrupt flat roof in the head? Let it do that in the bowl.

 

Long time no see Doc

Is the port roof on the intake manifold really slanted? I thought it was flat but I'll admit I didnt pay much attention to it.

Anyways does anyone have anything else to add on this subject? I would really like to know more about why its done that way.

Thanks!



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Jason
93 TA, M6

 

Removing the slanted roof will add more volume but you will have less preasure.Most of your A/F mixture will flow in the lower half of the port. If you remove the roof you disrupt the flow. If you have a cam over .650 lift you may gian from removing the roof. Steven

 

Are we talking port roof or port wall. The oem lt1 and lt4 heads/intake I've delt with have a parallel/flat port roof, but one wall is slanted in on the intake of each.

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I'll be back

 

Here's a picture:

http://nuke61.homestead.com/files/He.../RoofSlant.JPG

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Hear LT1 cam WAVs, DIY head porting: members.***.net/gmarengo

'95, !CAGS, CAI, ForceII, Hooker Shorties, 14.2@103

 

Or... A=LT1, B=LT4

http://home.tir.com/~steveher/intake.jpg

 

http://home.tir.com/~steveher/intake.jpg
Fred, ?

Anyway, the port roof on both LT1s & LT4s I've come in contact with, are true/parallel with head mtg surface. This allowing 1/64-1/32 for casting irregularity. It is the short side port wall slant that is very prominant on the LT1. But the corresponding intake/plenum wall is dead square, which makes for a restriction into the head. The wall slant to me looks to be by design.

The LT4 head short side wall appears to be square by design, allowing for slight casting irregularity. However, the corresponding intake/plenum port wall has a definite/deliberate slant designed into the wall. This however, will not pose a restriction/blockage, being smaller than head port. Ironically, the deliberate LT4 plenum slant mimicks the deliberate LT1 head port!

I trust I didn't loose anyone explaining.
My reasoning on the LT4 plenum port slant is for reversion for the LT4 cam specs. Agree? The LT1 head port slant defys logic to me. I'm listening.

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I'll be back