I just bought a used throttle body and intake manifold. Plan to port at an angle to counteract the imbalance flow to cylinder 4. According to Buschur, cylinder 4 gets 327 cfm, 3 gets 308, and 1 & 2 gets 300. Cylinder 4 gets a whopping 9% more are than 1 or 2. I am also planning on match porting intake manifold to head. Does anyone know the intake port dimension in head? 40cm wide by 30cm high?

I'll hone the runners as deep as I can. That is a serious bend at the plenum.

 

When you start cranking up the boost, no 4 nearly always ends up going leaner than the others , it detonates first and shatters that piston first.
Porting it won't fix the problem, a different intake manifold is required.
The easy fix its to put the highest flowing injector into no 4.



But it's a bit pointless when no 2 piston is broken.

 

 

I was thinking about shaving down the splitter wall for cylinder #4 inside the plenum. And taper it to bypass. I don't think I'll need much to adjust for 9%.

 

I think he meant broken piston ring on your other thread.

 

The early models break between the top ring and the 2nd ring, the side of the piston.
When it's really bad they break between the 2nd ring and the oil ring.
The later models break above the top ring because the rings are moved upwards on the piston.
But they'll also break below the top ring when the abuse gets worse.

 

i have ported my intake quite a bit. as much as i could without cutting it open. i havent really noticed a big difference between cylinders when pulling my motor apart, or on spark plugs.
here are pics of it untouched: https://www.evolutionm.net/forums/sa...ort-block.html
i can run the 4th piston up for a better pic if you really care, but you can tell its not much different than the other 3.
at the plenum, i welded a 1/4" plate over the flange and then filled in the best i could behind it on the sides. the factory casting necks in a lot right at the tb opening. Then opened it up to my tb (70mm ebay junk) and opened the plenum up as much as i could without making any new holes.
when i did the runners i basically opened it up in a straight taper as far in as i could with a 6" bit. taper should be largest at the plenum and go down evenly all the way to the valves. usually 3-8* but thats a much heavier topic than i can debate. i strongly suggest not using the gasket or the opening at the flange as a template. if you look at your head, or the pictures of mine in the thread i linked to in a previous post, you can see the factory fillet cut at the flange. you really should measure the port without the fillet and apply that to the intake.
the way i used to 'gasket match' aftermarket bbc stuff was using a small square and color all over with sharpie then you can scribe vertical and horizontal lines up the gasket face past where the intake goes. then bolt the intake on and transfer the scribe lines, unbolt and use the square to extend your transferred marks into full lines. that will give you your sides and top. leave the radius in the corners as big as you can.

 

I've blown a hole in between 1st and 2nd ring with too much timing in a LS. ran ok after, just lots of smoke.

 

I'm trying to find out what the dimensions are for intake ports on head. I'm too lazy to pull head off to measure.
This is the bottom end

 

do you think the pistons tell a different story than the spark plugs? if it was 9% leaner on 4 you would see it on the pistons

 

oh, I didn't get the hint
Tuner should tune it rich enough for #4 to make most power and rest to run extra rich. I want to try to get rhem all closer so all cylinders run closer AFRs.

 

Oh and match porting is between the aluminum pieces, not gasket.

 

theres a big fillet cut in the head gasket surface. dont be tempted to open the head up to that size.

 

oh no, I'm only experimenting on an evo 9 intake manifold and throttle body. If I can get #1, 2, & 3 to similar flows of #4 then it should increase power (from #1, 2, & 3) with same fuel (which is wasted running these cylinders richer than #4).

 

intake gasket surface on the head is what i meant.