I started working on an LT1 intake port last week. I did some work thursday, then friday I flow tested it. It got up to 255@.500 and backed up a little above that. Today I did more work on the heads and here are the results.

Aluminum LT1 head
stock 1.94 intake valve with 45° seat angle and a backcut
4.030" test bore
Superflow 600
1/2" radiused clay intake

.200 - 146
.300 - 195
.400 - 231
.500 - 256
.600 - 265
.700 - 266

That comes out to just a hair under 90cfm per square inch of valve size which is considered to be pretty dang decent in a 23° head, so I'm pretty happy with it. I know there is plenty of room to go in this head. I'm thinking that the valve is starting to become the restriction so I'm thinking about whether or not to put larger valves in it... But I'm also thinking that since I already have these valves, I should use them. Then put the 2.055/1.600 Ferrea valves that I have sitting on a shelf in the next set of heads I do...

 

Good deal Cheston, you done with Sam yet?

 

thanks. I graduate in April.

 

Cheston,

Here is a good thread that might be a good read in terms of low lift flow and backcuts for you. Might as well play with the valves and valve jobs while they are still that size....

Link

At .500 you have a Dis Coef of 86.6cfm/sq in which is pretty good. Realize that Super Stock race ports are around that and one port can be worth 50hp over another at that level, same flow etc..... Guess that's where the years of work you get to play with after SAM come into play.

Good Luck,

Bret

 

thanks Bret. I think I'll be spending some time reading that site

I was thinking about offset doweling these heads also. That should be able to push me over 270cfm peak and help my lower lift numbers a bunch. Angle milling is another option that could help. I flowed it to .700 because the cam that I would run with these heads would have well over .600 lift. I took a little too much out of the pushrod area and broke through, but it can be welded up. I was planning on using .150" offset 1.7:1 rockers anyway While those parts are getting welded I might as well get a little bit of welding on the roof so I can bring that up a bit more...

 

I did some more work today and lost a little low low, but picked up a good bit of mid lift.

.100 - 68
.200 - 138
.300 - 198
.400 - 240
.500 - 264
.550 - 265
.600 - 266

Something is definitely a restriction in there somewhere...

Is there any interest in me continuing this thread a little at a time, or should I just wait for the "final" numbers.

 

I hit the bench a few times today with interesting results.

First time was with the intake manifold on. The intake is totally untouched.

1 - 67
2 - 140
3 - 191
4 - 225
5 - 244
6 - 247
then I pushed it all the way down and it peaked at 250cfm.

Took the intake off and here is what it flowed (I did some work to it since last time)

1 - 70
2 - 150
3 - 207
4 - 243
5 - 262
6 - 266
7 - 267

A friend noticed a ridge in the short turn, so I did some work with sand paper and a little bit of cartridge rolling to take it out and to clean it up a bit.

1 - 71
2 - 149
3 - 208
4 - 246
5 - 267
6 - 272
7 - 273

Remember, all of this work so far is using a stock 1.940" intake valve with a backcut.

I still think there is some CFM left in these heads with the tiny valve

 

hey i'm finishing up my heads right now, i don't have access to a flow bench so i'm waiting till they are done to have them checked.

maybe you could pm me or just post. i have some questions.
regarding roughing.
your supposed to flatten the roof out leading into the bowl correct? should it still have a gental curve or should it be pretty flat, i know the factory has alot of stock there.


how do you polish up the bowls? can't get a flopper in there and sandpaper rolls aren't very good for working the tip in the radii. i was thinking of order some 3/8 floppers but i'm worried i'll tear through them. also what do you use to get deep into the intakes??

i pretty much have them roughed i just gotta figure out how to polish them!
i'm also worried i took out too much stock in the bowl just behind the guide i guess the bench will tell.

the only place i broke through was into the bottom of a stud hole for the rockers on the intake. what kind of epoxy should i use??

thanks,
mike

 

I've used cartidge rolls (sandpaper rolls) screwed on a 4-6" mandrel. I'm not very good with those yet. I have also use just sandpaper by hand. Some of the other guys use stones to help smooth, but I haven't tried that yet. They also have some kind of a brush thing that is awesome on the chambers. The last time I put the head on the bench 2 others told me I was wasting my time since it wasn't "pretty" enough. I guess picking up 8cfm up top and a little bit everywhere else is wasting my time?

Everybody is telling me that you don't really worry about epoxying the stud hole. It gets sealed by the stud. But will also by using an epoxy to seal it. I'm not really sure what it's called. I've got clay from the bench in there now that I'll need to clean out first though. I also broke through in the pushrod pinch, but I'll either get that welded or will epoxy it up.