Coolvet

I have 2 questions about this porting procedure:
1. To port match the intake ports, what template do you use? On previous heads I ported, I used the inatke gasket, but on the LS1/6 the intake gaskets do not match the port opening?
2. A previous member said you can open the exhaust ports out to the exhaust manifold gasket. Is that recommended for LS6 heads as well? I had been told that it was better to just polish the exhaust ports rather than open them up because this creates a negative pressure that helps get the gases out faster. What is the current recommendation?

C_Williams

1. You do not want to enlarge the openings by any significant amount. Just scribe parallel lines (top to bottom and side to side)approximately .060 from the present casting.

2. Match the exhaust gasket on the top and two sides; the bottom of the LS6 port is straight, blend this feature in to the two sides.

Jantzer98SS

iTrader: (54)

This is how I started, I winged it with no prior porting experience. Results so far 10.82 @ 125MPH NA stock shortblock. If you're on a budget, the stock valvejob is very good. The best advice I can give is to not open up the intake port, smooth the walls, remove the rocker boss which will leave a hole so don't be alarmed, remove material around the guide boss, but keep the general shape, and smooth the bowl into the seat. If you have 98 heads, either have the valves backcut or use the stock newer LS1 valves that are backcut. You'll see good gains from mid-low. It's probably one of the better mods you can do. With tons of flow bench time, I know how tricky the ports are. You will make/break these heads on the straight wall side entering the bowl area and the shape of the short side. It's very tricky and I don't get it right everytime. Sometimes takes a couple trips to the flowbench to get it shaped like it needs to be. I wish I could tell you how to do it, but I can't. I wouldn't open the exaust runners to match the gasket, they don't need to be that big. The gains are achieved in the bowl/guide area further up in the port. Also don't grind any material from the short sides, the flat sides. FWIW, the heads on my car now don't flow crazy numbers like people post on here (300+), in fact they only flowed around 270-275ish. But they ran well. The heads I will be running later this year flow 300. My port work has improved considerably and it wouldn't have been possible without a flow bench.

If anybody is looking for budget port work drop me an email, maybe I can help. Sometimes there is no need to pay for aftermarket valves, guides, and valvejobs etc. etc. Stock is pretty darn good.

Abdullah

iTrader: (2)

here what i found : i guess maximum valve sizes on LS1 heads are 2.08 and 1.60 valves but you will need to install different seats for that. maximum valve sizes without changing the seats are i think 2.02, 1.57 valves. begin working at the bowels, you have to make the bowels as concentric as the valve seat for both intake and exhaust ports. remove material around the valve guide boss but there is a pump at the valve guide boss of the intake port at the fast wall side that should NOT be removed as i can tell just remove the other materials around the valve guide boss. also you will need to do some roof work just enough to match the opened up bowels also there is a another pump on the intake side at the pushrod wall that should be removed just remove enough material to make the pump's place even with the intake roof and pushrod wall. the port floor and the short side radius need some work on the LS1 heads where on LS6 heads they overcame this problem i mean on the LS1 heads the short side radius is uneven with the valve seat so you have to make the short side raiud concentric with the valve seat and to do so you have to remove just enough material to match the valve seat from the short side radius all the way to the floor to the opening of the intake port. for the fast wall ( the wall opposite to the pushrod wall) will need to be a straight shot into the bowel seat but try to eat very little from the ports side walls of the intake espesially the pushrod wall (low flow area). that what i could tell from picutres of ported 5.3 and 5.7 LS1 heads. some one might chime in to clarify more. any one can help and confirm what i found? .

Cal

iTrader: (1)

Abdullah, that's some good detail, thanks for the info. Have you tried porting using this information, and if so, what kind of results did you get?

Abdullah

iTrader: (2)

Cal, actually no i haven't tried porting LS1 heads yet but maybe i will do it later. i got sucsuss porting LT1 heads they were very close in terms of 1/4 mile numbers to my professionally ported LT1 heads in my website. i'm doing AFR 220cc LT4 heads LT4 intake and Custom cam at GTP for my vortech YS-trim blown 396 for my 94 Z28, so i think if no one here wants to help providing some info for porting the LS1 heads i think Craig @ GTP can answer my questions.