Tractorsport Flowbench Forum Archive

Posted: **Mon Sep 21, 2009 2:24 am**

Well i guess i need to start from the start. those that have read my bench thread will find some repeat here.

These heads, that I'm about to start porting on, were rebuilt some 15 year ago. Do to dropping a intake valve, stuffing it through the piston, cracked the cylinder wall. Beat the crap out of the combustion chamber.
Required a seat insert in the intake to save the head. had all exhaust seat replace so that i didn't have to worry about unleaded gas any more.

Because the newly installed seats left a bump in the port bowl, i ground the bowl out a lot, and then made plastic templets to match the other Intake and exhaust bowl areas.

I had all new valves, and bronze guide installed while it was there.(1.88 intake and 1.60 exhaust)
bolted them on my 340 and the car slowed down by a full sec.

after 3 mouth, i had enough of these head. (The eng would pull to 7200 rpm but had nothing until 4500 rpm) they didn't work vary well with my 2800 stall.

Put my "X"(2.02) head back on. Runs low 14's in the 1/4 at 4400 feet.

A good 15 years later,.......... I have a flow bench and found these head in my friends barn. some what preserved..............

There real isn't much out there, on how to port one of these heads. So hopefully some one will be able to learn from the experience I'm about to get. :;):

I have been chatting with ray(coulterracn) a lot lately.
I pored/pulled my first mold, of my intake port, and posted it up in my Bench thread(Melamine?)

I asked Ray if he could give me some tip on how to port these head. I sent some picture of the intake port to him and he doctored them up, and the mold pic's i had posted.

He encouraged me to post then up on here for all of us to see and examine.
He "said" post them up on the bored and maybe we will both learn something

I will have to post the pic up tomorrow.

My goal is to get them to flow better at lower lift.......Or maybe i should say more efficient. My 340 has a .474" lift cam. And i would real like to squeeze a little bit more bottom end out of it.

If not, then it will be a grate candidate for my 410 ci Stroker(a, someday dream)

Thanks in advance.

Posted: **Mon Sep 21, 2009 2:43 pm**

I was afraid to remove this much metal, worried that it would slow the velocity to much.

stuck a probe in my intake port and change my mind!(429fps at 28" on the floor/ssr)

any way here are the pictures.

WOW THAT WAY SMALL

Have to see if i can fix it when i get home.

stay tune better pic to come.....................................

Posted: **Mon Sep 21, 2009 7:11 pm**

Maybe this one will be the right size

Posted: **Mon Sep 21, 2009 7:16 pm**

Gorden,
I hope it was ok to post a larger photo
Ray

Posted: **Mon Sep 21, 2009 9:29 pm**

Gordon, the area after the guide that is written it's safe to take metal away here...form it into a pointed fin, do not take it out. My testing has shown slight low lift flow increase when I add material there where there wasn't. The area behind the valve stem/guide has eddys and liquid tests showed the area from guide to seat to leave fuel behind, or none at all. Basically a dead area. Work that area a little at a time.

I don't remember that much bias in the port, but do remember how high the roof can be and deep the bowl can be. Can't remember any numbers though. That was also back in the days of no pitot tube. Was looking for flow gains and did'nt get much. But I probably slowed some speeds down without even knowing it.

Just some thoughts, I'm still learning too.

Posted: **Mon Sep 21, 2009 10:21 pm**

Can you post a view of the mold straight down. Trying to get a view of the wall turns. Is that a turn right at the very entrance? Also, a direct side view would hellp.

The low depression part in the roof of the mold, is that from casting that is forming a channel up inside the port. Might help to see a inside port photo. (tom c)

Posted: **Mon Sep 21, 2009 10:23 pm**

Posted: **Mon Sep 21, 2009 10:25 pm**

Posted: **Mon Sep 21, 2009 10:43 pm**

Posted: **Mon Sep 21, 2009 11:57 pm**

OK i thing i got it!!!!

I can't grind the roof out as far as the picture recommended, as there in a machined surface for a head bolt above each port, and is why the bump is there.
I can take about half of it out though.

The shaded area on the lower left side is were the head bolt surface is.

Posted: **Tue Sep 22, 2009 3:43 am**

Gorden
The last picture of the port entrance and the valve guide boss, The obstruction in the port to the left of the Guide, is that the boss below the rocker arm shaft bolt hole?

I think it's safe to remove some of this boss to help air flow around guide.

Ray

Posted: **Tue Sep 22, 2009 4:43 am**

Posted: **Tue Sep 22, 2009 8:46 am**

Posted: **Tue Sep 22, 2009 1:37 pm**

How about this. Since I am also still trying to learn how to apply alot of this new info, how bout a pic of the results. The port was ran with magenta dye in water at 28" @ .500, .550, and .600 lift. You can see where it stayed in heavy proportions to really stain those areas. So come to any conclusions. And lets try to apply what we learn.

Also, here is an old vid of the same port before some additional work. This was done in this sequence. I don't have my notes but I think it was started at .500 then up to .600 having turbulence issues. Then I backed the valve down to .100 and then back up to .600. This is just for some more ideas.

Posted: **Tue Sep 22, 2009 1:49 pm**

I'm looking at this closely for the first time myself. Notice the clean spot on the seat (undercut) at the top of the pic, and the wall over the SSR at the bottom. The different shades show activity.

Tractorsport Flowbench Forum Archive

Porting a Chy 340/360 head.