Valve Guides for Oversized Valves and Lead-Free Gas?

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Walt Jackson

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My 1968 225 is at an engine rebuilder in Phoenix.

I purchased a cam, springs, and oversized valves from Oregon Cam.

The rebuilder says I have a choice: either build the head for lead-fee gas or install the oversized valves. No valve guides exist (to his knowledge) that allow for both.

Is the rebuilder correct?

TIA

–Walt Jackson
 
Guides have nothing to do with lead free gas. Plus, there are many different size guides that are available. Are you talking about valve seats? That might be correct that there are no hardened seats available to be able to install the oversize valves. That I don't know.
 
Thanks, Charlie.

I'll check with the rebuilder. Perhaps I didn't hear him correctly.

I'll call Oregon Cams. Perhaps they have a source.

--Walt jackson
 
What's your thoughts on a newer head? One that would already have unleaded compatible seats?
I know that when I had the head on my truck motor thru the machine shop, a head that I had a set of oversized valves put into, I specifically requested new seats be installed at least the exhaust side. When they called me claiming it was done, I asked again if they cut the head for, and installed new valve seats they tried to tell me they'd be "fine" without, even though they cut them for oversized valves. I'm sure there couldn't have been much if any of the original induction hardened material left after being cut out for those valves. They weren't happy about it when I said id pick up the head after they put the new seats in as I had requested. I got that call about 2 days later. Said he had no problem getting them from his warehouse.
This was a couple of years ago. 3 at very most.
 
Now all that said, I wonder if miles and heat cycling work hardens the seats over the years and "hardens" them like how they talk about "seasoned" blocks .. I am thinking not.
 
volaredon said:
What's your thoughts on a newer head? One that would already have unleaded compatible seats?
I know that when I had the head on my truck motor thru the machine shop, a head that I had a set of oversized valves put into, I specifically requested new seats be installed at least the exhaust side. When they called me claiming it was done, I asked again if they cut the head for, and installed new valve seats they tried to tell me they'd be "fine" without, even though they cut them for oversized valves. I'm sure there couldn't have been much if any of the original induction hardened material left after being cut out for those valves. They weren't happy about it when I said id pick up the head after they put the new seats in as I had requested. I got that call about 2 days later. Said he had no problem getting them from his warehouse.
This was a couple of years ago. 3 at very most.
Click to expand...
Very helpful. Thank you.

--Walt Jackson
 
don't think you need to worry about hardened seats in an iron head if your valves are modern stainless valves.

i'm saying this based on discussions i had when i had my head done. and of course the guy who did my head may be wrong

the gist of it was

modern stainless valves have valve heads made from a material this is so wildly different from the material of the iron head, that they do not microweld to the seat causing ware and what we eventually see as seat recession.

old original valves and iron head would microweld without protective lead compounds and the surfaces would degrade/erode away hence the added lead compounds to the petrol in the 50s 60s to stop that.

you might get seats done on the exhaust side if you are worried or if you need to true up the installed height of all exhaust valves. adding a seat allows you to pick how far into the chamber the valve head sits and ideally they would all be the same

finding seat inserts of any size should not be a problem. they make em for every imaginable size, having enough space in the head to fit some combinations of inlet and exhaust valve sizes may be.

if they can fit new guides to my hemi 6 head i can't see why they can't to a slant head that has more "meat" in it, in every dimension.

if it was a 70 mile per day daily maybe do the exhaust seat. if its a fun car you ain't gonna do the miles to cause the the kind of horror they use in advertisements for valve protection additives.

a shop that does heads should have no problem doing whatever you want within the confines of the chamber

i.e bigger inlet and some guides should be no problem provided the inlet does not interfere with the exhaust and that could include hardened inserts on both if you really feel the need

depends on your valves i guess or at least what they are made from

3000 rpm v8 3000/60seconds then by 8 its either 3 or 6 times a second that those valves hit the seat 4 stroke,... 3 times a second...... i give up..... its a lot just going to the shop and back :)
i think they will work harden the seat in an iron head pretty quick

Dave
 
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Walt Jackson said:
I purchased a cam, springs, and oversized valves from Oregon Cam.

The rebuilder says I have a choice: either build the head for lead-fee gas or install the oversized valves. No valve guides exist (to his knowledge) that allow for both.
Click to expand...
Stock slant sixes usually don't have much valve seat wear issues even with an older head on unleaded gas. Between the relatively low RPM these engines usually run at, the small valve size, and the way the head does a decent job of circulating coolant around the valve seat, there's not too much in the way of hot spots to cause the micro welding that grinds away at valve seats.
 
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