atljar

From this post....
http://web.camaross.com/forums/showt...lowbench+games


Now I decided to try a little porting. Just done the intake side so far, but here is what I got.

I have not touched/unshrouded the chamber. Still stock valves and stock valve job.

What I did... Just took off casting marks from floor. Opened the bowl up a lot, tear dropped the valve, tried to straighten the pushrod pinch as much as i could. On the short side radius, i just kinda blended it so it was smooth but kept its shape. I did two ports so far, they are at least consistent on the bench.

NO INLET RADIUS
INTAKE BEFORE / INTAKE AFTER
.100 55 / 58
.200 118 / 117
.300 157 / 166
.400 174 / 198
.500 180 / 213
.600 180 / 216

WITH INLET RADIUS
INTAKE BEFORE / INTAKE AFTER
.100 60 / 61
.200 121 / 119
.300 166 / 175
.400 195 / 213
.500 198 / 218
.600 DNF / 237


Really weird I gained at .100, but lost at .200. Maybe its where some shrouding is taking place.

Numbers arent all that great, but with a valve job and some chamber work I dont think they would be horrible to run.

Any secrets in getting the low lift numbers up?

NightTrain66

low lift flow (.200 and below) is ALL valve job and chamber shrouding.

Just look for a compromise in a valve job that flows well low, mid and high lift since some things that work well in one placemight hurt (or KILL) flow in other areas.

Just keep playing with the bench and test after EVERY change made.

Lloyd Elliott
972-617-5671
Eportworks.com

atljar

Thanks again for posting on this lloyd, nice having someone who does it for a living respond.

I have been porting, checking, porting, checking etc.

Any thoughts on a radius valve job? I think I may give it a try instead of a typical 3-4-5 angle type of thing. Also might try a bowl hog on the seat and guide machine on another port and see how that compares to a hand port.

SStrokerAce

No dont do a radius VJ on the intake.

How much are you going to open the bowl compared to the intake valve size?

Bret

atljar

Thanks to you also bret, always seem to be posting on this also! Why not a radius job on intake? Exhuast?

I always had heard make it about .004" smaller than the diameter of the valve size.

These arent going on my car or anything, just trying to learn. Thanks again.

MachinistOne

I talked about this with Lloyd when I contacted him about porting my heads after I shot the valve job, basically there are generic radius cutters that machine shops can buy, but our radius cutters were developed on the flowbench and engine dyno with Flowmaster inc. when we were doing their machine work for them as part of the GMPP 502 project. Different cutters for INT and EXH with different radi and seat widths.

For example, I just did a set of dart iron eagle 200's for our GTA car, we flowed the stock 5 angle, and a custom 5 angle, and our radius cutter... the radius on the intake was good for 10-15 cfm across the board.

NightTrain66

I have always had better results with angles on the intake but I am open minded enough to realize that I might not have tried the right radius cutter on the intake.

I use angles on the intake and radius on exhaust. Get a WIDE top cut that has a radius at the end and blends into the chamber. This helps low lift alot. A back cut on the intake valve helps too. Just play with angles since it changes with the rest of the valve job.

Most people make the venturi diameter anywhere from 83 to 93 % of the valve diameter and this will change alot of stuff. More air can come through a bigger hole but you have less distance (fewer angles and/or narrower angles) to direct air AROUND the valve. Everything is a compromise and when you find something that works, you stick with it and tell no one the exact angles and widths that you use.

Lloyd Elliott
972-617-5671
Eportworks.com

MachinistOne

Everybody has their own way of doing things, and many times although the means are different, the results are the same. I know that Lloyd has by far more time on the flowbench with these LT1 castings than I do, so what he has found to work best I would not question. Just throwing out there that I have seen good results with the cutter we developed, just not specifically on LTx stuff, I will need to look through the build sheets for the LT4 heads we did a while back for a more accurate apples to apples comparison. The thing that's intresting about head work is that I could throw a radius cut on Lloyd's heads and it may not flow as well as his 5 angle, it's all about making everything work together, little changes in other area's of the bowl can change the way the air likes it's transition's. So as soon as I come up with a set of good cores, they will be sent to Texas for some porting.