Cast iron head problems

SB671 · Post by **SB671** » Thu Jul 14, 2005 5:45 pm

We are running a set of 220cc cast iron kiwi pro heads on asmall block chev used for endurance racing
If temperature is not controlled to exacting specifications we invariably stick an exhaust valve and end up with another repair bill and DNF
There is talk of the easy fix which involves reaming the guides larger to give more clearance but this does not sound the best way to go to me
Has anyone had experience here with these heads or had the same problem with another brand head?

Mike Rogers · Post by **Mike Rogers** » Thu Jul 14, 2005 6:35 pm

In my exspearance with running cast iron guides in a race applacation you need to have a min of .0025 clearance valve to guide.It would be best to put bronze in there.

SB671 · Post by **SB671** » Thu Jul 14, 2005 8:06 pm

Thanks for the reply Mike
We are running that clearance but apparently these heads have a reputation for cooling problems and then hanging on to the valves. Guides are bronze so we were searching for anyone that may have mods on how to better cool the heads
Any clues here that may help us?

Mike Rogers · Post by **Mike Rogers** » Thu Jul 14, 2005 8:26 pm

What valves are sticking the center or outer ex.

SB671 · Post by **SB671** » Thu Jul 14, 2005 9:54 pm

Hi Mike
Centre Exhaust

I have heard that over there the NASCAR boys run coolant lines down the heads in a rail type set up . is this right and if so does it help?

Mike Rogers · Post by **Mike Rogers** » Thu Jul 14, 2005 11:05 pm

You run a coolant line between the to center ex. ports.I will try to find the diagram for it and how to drill it.Maybe Don has it or one of the other guys on here.

BRENT FAY · Post by **BRENT FAY** » Fri Jul 15, 2005 10:05 am

Are you using valve seals on the exhaust guides and if so what style. Customer of mine had these basic same heads on his limited dirt late model and ran gas or alky depened on how many lap feature 30-100 and didnt have that issue. Did tap head 1/4 npt below center ex ports and ran -6 line to water pump and modify the all teflon pc seals by running a SHARP .341 guide reamer thru the seals for the exhaust. It let a little more oil past the seal. You will ruin a few before you get 8 of em. Brent

John Haskell · Post by **John Haskell** » Sun Jul 17, 2005 2:44 pm

I have seen this on engines that don't get to breathe much at all. The heat value is longer, the dispersent at the end of the guide bore pinches down & that's it. What I have done in an process to stop this, takes more effort & investment in tooling.

Take a note of what your tooling finishes as far as sizing. The tooling you buy is made for mass production re-build style of repair. -------- We don't do this in this arena. What you will find when removing a guide in cast iron especially is, the guide is not very tight except at the very end if at all in what I've seen here.

The contact area is only on the high spot of the tooling as it bores,reams, or tears down through the casting. -------- What I did to correct this costs a bit but, you order or have custom ground, undersize reaming tooling & finish the bore with a hone & bore mic for the crush you choose. We all know what the contact area is in comparison, but this is what I do.

The transfer of heat into the guide & into the water jacket has got to be a ton better through common sense thinking. The press is better & you use a molly lube due to the fit. -------- Sure it takes more time & 'you' have made the extra effort on your end.

Most every time I have seen this issue show up, in my oppinion, the guide fit was poor in the casting. --------- If it's a marine & fesh water cooled, you know the water temp differance will get you every time if you don't open clearance & let the valve float in the bore untill they make the heat threshold to close down to their 'happy' clearance. It doesn't matter what it is, as long as 'you' know what the use will be.

Reaming is not done on race parts. You hone, & with a flood of the proper type of honing oil or, ---- it won't hone as it should. It should be semi-finished, all work completed & back in for the final with a polishing stone, final cleaning & if you don't have a sonic cleaner, use shaving cream and a good brush to get the cuttings out. --------- Also, if your not honing valve stems, you should. All of this stuff is done in 'Cup', and we should too.

One 'Cup' contact that I have, informed me, they set the clearance based on what the dyno tells them. If they set clearances like what you read about, they wouldn't finish a race & this has been learned through experience on what they use. It would be moot to tell you what they tell me because it is so differant from what we all are able to use.

SB671 · Post by **SB671** » Sun Jul 17, 2005 5:04 pm

Thank you all for the input on this problem

Post by **SchmidtMotorWorks** » Sun Jul 17, 2005 8:55 pm

Great input John!
I always like it when the answer is "better machine work".

Also, if your not honing valve stems, you should.

How is this honing done?

What clearance values can you run when you do the better job in fitting the guides?

Post by **SchmidtMotorWorks** » Sun Jul 17, 2005 9:03 pm

One other thing comes to mind, I have visted a lot of foundries that cast cylinder heads and noticed that the OEM chevy small block heads all have two piece sand cores that make a water passage over the exhaust port.

The only ones I ever saw that didn't were aftermarket heads for cost savings reasons. Next time you have the heads off maybe you can look and see if the water passage goes over the exhaust ports. I also know that even when there is supposed to be a water passage over the exhaust ports that sometimes the sand core gets a crack in it or isn't put in right and the opening gets sealed-off. This would be hard to see from the water jacket holes but you might be able to put the head on its end and squirt water in with a solvent bottle in one opening and look to see where the water runs out.

SStrokerAce · Post by **SStrokerAce** » Mon Jul 18, 2005 2:30 am

Mike Rogers wrote:You run a coolant line between the to center ex. ports.I will try to find the diagram for it and how to drill it.Maybe Don has it or one of the other guys on here.

Chevrolet Power The Official Factory Performance Guide HPBooks-1087 Seventh Edition Page 62

The Diagram for this is right there.

Bret