Those of you that have ported the head on your LSJ. I can see from pictures and threads on here that a TON of material can be taken out on the exhaust ports to gasket match the heads. But, from what I can see in the few pictures I've found, the intake side looks as if there is a minimal amount that can be done to it. Have you ported the intake side as well when you ported the exhaust side?

Just wanting to know what I'm getting into, This will be a memorial day weekend project and i like to go in prepared.

Thanks

 

I had planned on doing this once i have a free weekend, from what i read the best way to go about porting is to use the gasket to match the ports. The most imporant thing to remember is to take your time thats the best advice i can give. I would read up diy manifold porting.

 

Thanks-

I've ported several sets of V8 heads, I was jsut kind of curious if there any gains to porting the intake ports, or if the big restriction is the exhaust side

 

Both sides are restrictive, but the exhaust side is worse.

 

youre going to be porting this in your garage? with what?

 

The bottle neck is the exhaust.....I would never describe the intake as restrictive though.

 

think of it this way. the old GM race head for the LSJ was exhaust ported only.

 

In my dad's shop, with a die grinder..lol.. This will be my first aluminum head to port, but I've done a load of steel heads.

That's the kind of info i was looking for!

 

u mean cast iron? i didnt know anyone used steel heads

 

Well, yeah.. We call them steel at my local race track.. lol.. They are cast iron i suppose :P..

 

die grinder head port FTL I wouldnt even port the outlet of a supercharger with one man. Anyways as has been stated above exhaust is all you need to worry about and gasket match is the best/ safest way. I'm pulling my head off anytime now as well but im getting a proper hand port done

 

What is the proper way exactly? All the reading I've ever done for v8 heads say that so long as you use the proper bit and leave the proper finish, a die grinder works.. but i'm always up for learning!

And all i'm planning to do it gasket matching

 

Yeah you could be right im just thinkin of the die grinder I have at work with the bit thats on it wouldnt go near my head. I'm sure my guy has some sort of dremel tool used for this.

 

They make as many different bits for die grinders as they do for dremels.. we're in good shape .. and we've got a valve on the air line that lets me speed up or slow down the tool as i see fit..

 

take pics

 

Not that I disagree with you, but don't most LSJ ported heads have expanded inlet and outlet ports? I would think there's gains to be had by doing both, but I could be wrong.

I really wish I had that airflow thread handy right now.

 

Just for ***** and giggles, lets turn this into an informative thread. LOL.

Billabong's stock head flow numbers
Old. Intake / exhaust
.100 lift 59.9 / 50.1
.200 111.6 / 84.7
.300 164.1 / 116
.400 189.2 133
.500 190.7 129.4



Billabong's ported head flow numbers
new intake / Exhaust
.100 83.6 / 70.0
.200 151 / 132
.300 198.3 / 165.4
.400 238 / 173.3
500 251 / 199

ralliartist's head flow numbers
----Intake / Exhaust
Lift CFM---CFM
200-- 160/145
300-- 225/170
400-- 265/185
500-- 285/190
600-- 290/190


ZZP stock head flow numbers
Lift Intake/ Exhaust
0.200"-- 152/ 138.5
0.300"-- 216.5/ 156
0.400"-- 242/ 161

M2Race/OTTP Stock head flow numbers
Lift CFM/I CFM/E
200-- 155/ 126
300-- 223/ 143
400-- 253/ 147
500-- 261/ 149

M2Race/OTTP Ported WITH +1MM OVERSIZED VALVES
LIFT CFM/I CFM/E
200-- 165/ 151
300-- 235/ 186
400-- 278/ 199
500-- 298/ 206

There's going to be some number variation because of the testing bore size. But everythings pretty close.

Hope that helps someone.

 

*hug*

So, those numbers are based on porting both sets.

And in stock form the intake outflows the exhaust, so there would be some benefit to porting only exhaust as it would catch the exhaust up with the intake. But there's even more benefit to porting both sides?

Would that be a truthful statement?

Will the stock intake manifold flow enough to keep up with porting the intake ports, or would the restriction then be the intake manifold? (This is a sick hobby we have... )

 

Whats the stock lift for the valves?

 

From the research I've done, you want your exhaust to flow about 80% of your intake on a supercharged car. Mine is at 79%.

The stock intake manifold isn't the problem. WHile it is a tad restrictive, and a few innovators have gotten some gains with a tad bit of modification, it's not enough to warrant the cost. In all reality, it's fine if you are staying supercharged.

the stock cams provide a .395 valve lift.

 

Awesome, Thanks for the info.

Wonder what happens if you get them flowing 1:1?

 

won't make as much power.

this is a science. A lot is involved to come up with all these numbers.

 

Since we're talking valve lift a little.. what ratio are our rocker arms? We have 3.95 cam lift, but whats that multiplied by when it goes through the rocker?

 

The rocker ratio is 1.69. The valve lift of .395 is with the ratio. The Hot Rod article says they are variable ratio. I'm not exactly sure what that means.

The flow numbers are interesting. I messed around with the old Quad 4 heads on the flow bench, it was a much better flowing head. Had the same issue though, the exh was weak, but easily fixed by enlarging. Remember that most of the flow is affected by the valve job and the bowl under the valve. And how the bowl turns into the runner.

Great ported numbers Ralliartist. Those match pretty well with slightly modified Quad 4 heads. I agree with the 80% ratio. AFR seems to make this work well on NA small and big block heads as well.

When porting alum, use a bit that can clean itself easily. The alum will stick to it, so use plenty of WD40, or even ATF on the bit. Lube it all the time. Otherwise you will spend 50% of your time cleaning the bit. Slow speed seems to be better than high speed. I think a variable speed electric die grinder works best.

Ron