I've been talking to some friends who do port work and I have been getting mixed information. Some say the bowls should be smooth and relatively shiny and others say I need to leave it a tad bit rough to cause some turbulence. Looking at the GTP and the ARE heads im beginning to wonder myself. Can anyone clear this up for me? Im going with a small cam and want to pull the most out of it. 218/218 .531/.531 with 1.6 ratio rockers on a 112 lsa.

 

Is that a custom cam? If so, you should probably increase the duration at the exhaust. You might me the first to try an even split cam on a LT1. LT1 heads are not know for their exhaust flow.

Just a suggestion.

 

Crane makes an even split cam for the LT1...

It sound like what he's talking about. Its got a 218/218, 280/280, 116 LSA at .498/.498 with 1.5s.

Adjusting the math and it comes to .531/.531 with 1.6s.

Having it twisted to 112 LSA would be a custom grind.


MeanGreen, am I right? Are you looking at the Crane Cam? I was and I'm still thinking about that cam. What was your decision to make you get that cam?

 

Cool, is anyone currently running an even split cam?

 

Most people here are on the Comp Cams. But, after reading David Visards books, the split cam should be more torquey. The higher exhaust duration is to compensate for exhaust restrictions. But if you really open your set up, you'd want to tighten your exhaust duration. Note, I'm not a cam designer but I love to read tech manuals. In this case, Visard would recommend the split if possible. Since most designers don't do that for the LT1, Vizard recommends a 1.6 RR on the intake and 1.5 on the exhaust to compensate for the excessive exhaust duration.

1.6s do not increase duration, they only increase the area under the curve which could increase the low lift flow rate.

 

Wasnt this post asking about the bowls in the heads whether they should be smooth or rough? Theres plenty of threads about cams here.

 

Sorry, well dont know much bout it, but mine are smooth and shiny

 

Yes it is the crane cam you are talking about. I went with this cam because a friend of mine had luck with it in a supercharged car and I wanted a small cam that would not sacrifice anything. I bought it used of my friend and I was under the impression it was a 112 lsa but if its an 116 I am even happier. Low emissions and decent duration on both sides should make for some good numbers. Im thinking that the even duration may be a problem but if I work the heads around the numbers I should be able to pull some good torque out of it. I bought a set of 561 castings which flow a little better as far as my reading follows. Im not positive what the outcome of this combo will be but I will be sure to keep you all posted. To me this cam just seemed like the best street car option for me. This car will be driven daily at least 20 miles a day. I cant suffer too bad on the gas mileage and as far as me finding out its on a 116 lsa makes it a tad easier to hide with the exhaust tone. True duals and hooker long tubes with a 900 rpm idle should make it sound like a beast.

Here is my plan for the heads. I plan on a slight mill to get them squared. They already have need valve springs good for 600 lift. I might pull those off in favor of some lower seat pressure springs. Manley race flow valves of the 2.0/1.56 group should suffice. One last part of this is the bowl and port work. Im going to make sure they meet the gasket surface and work in from there. I am going to go ahead with my plans of a not perfect surface. Once I get them down to a shine and the material moved out the way I like I am going to hit them with 500 grit and put a nice crosshatch pattern in them to see what kind of flow numbers I pull out of them. I did this on a set of trick flow heads for an older 350 and I pulled some pretty good numbers out of them. We'll just have to see how it goes.

Got any comments post em up!

 

Great idea! Let us know how it works out when you're done.

Didn't mean to steal the thread earlier, I was adding some background to the porters who have matched heads to this cam. Since the cam numbers weren't present, I felt obligated to provide them with the data so they can give an informed response.

 

I have ported several heads and I would have to say when we get them flowed it really doesnt matter if they were polished or not. I like to finifh them up with a paper roll (light grit) and then let it be, Ive been told that it helps atomization to not polish.

 

Exactly what I wanted to hear.

 

Put a drop of water on a peice of glass and blow on it. The drop remains a drop and "rolls" off. now put the water on a sheet of sand paper and blow on it. The drop will kind of spread out and not pool up. When you polish ports on anything except an alcohol motor the fuel will puddle up on the smooth surface. Go the way you were going w/ the int. ports but polish the exhaust ports pretty well as there is no feul to puddle up. Good Luck

 

Yet another great idea! I like em. Keep em coming.

 

i don't know much about cams, but i know that i have a comp cam and i love it.
-J-

 

That is a great idea Marktisch! Has anyone flowed numbers with only the exhaust port polished?