392 exhaust valve guides

Jesse B.

Jesse B.

Member
I have a detailed question I was hoping to get some informed advice on. As some of my previous posts indicate, I am in the process of rebuilding a 392 ic. I am very close to completing the project but have run into a problem with the exhaust valve guides. The IH manual states that the exhaust valve stem diameter is supposed to be between .414 and .415. I purchased new sealed power exhaust valves (at $25 a piece). The new valve stems measure .4145.

The old guides were bell-mouthed so I had them replaced. The IH manual states that the valve to guide clearance should be between .0015 and .004, with a maximum of .4181 inside diameter. I picked everything up from the machine shop and started to check everything. The new guides, after installation, have an inside diameter of .419. Troubled by this, I took the heads back to the machine shop and asked why. They explained, which I later confirmed with my own research, is that no one makes valve guides with the correct id. .419 is the closest you can get. (I did find that sealed power advertises their id as .418, but I am skeptical. It seems all of these parts are made by one or two companies and everyone just pays to put their name on them.) the IH manual states unequivocally that guides that are out of spec, must be replaced. (IH emphasis, not mine.)

so, what should I do with this? Is everyone with a rebuilt 392 running around with loose exhaust valve guides, and burning oil, or do they know something I don't? The machine shop gave me several options. (1) leave it alone and run it; (2) they could install intake valve guides with an id of .375 and then ream and hone them to the correct id diameter (at a fairly high expense); (3) they could install a set of Ford exhaust valves that have nearly the same head diameter, but have a stem diameter of .375, (the Ford valves are slightly longer, but they can face the stem to get the correct stem height). Choice (3) means buying new Ford valves at $20 a piece, but I would gain the benefit of proper clearance as well as gaining the benefit of having a viton valve seal installed, since valve seals are not made for .414 stems. It also means I will have 8 IH exhaust valves that I cannot return. Choice 3 is the most expensive, followed closely by 2, followed by 1.

Bronze guide inserts are apparently not an option because they are not made in .414. They could install a .375 guide insert, but they believe by the time they are done reaming and honing, there won't be enough of the guide insert left to stay in place.

I have, as is true with any IH project done correctly, dumped a lot of money into this engine, and I am not thrilled with the idea of a newly rebuilt engine burning oil or puffing blue smoke becuase I cheaped out on the exhaust valve guides. I understand that most problems with the puff of blue involve the intakes (because only the intake valve and guide operate under a vacumn), but I just don't have enough experience to know if these few thousandths in the exhaust are going to make a difference.

Any help would be appreciated. Thanks,
 
Jesse,
you are right about wanting it right. I setup valve stem to guide clearance at .0015-.002. And prefer the .0015. Certainly not .0045.:icon_eek: the rocking motion will wallow the seats and end up leaking soon.

No easy fix really. What ever you do don't knurl the guides.

Sleeving the guide is preferred to knurling but not the best option.

I would buy under sized bronze guides (.375?) and have them sized to your preferred clearance. The guide id needs to be honed to size not simply reamed.

Let me see what is available and I'll post back.


Robert
 
Jesse,
sealed power #vg646 guides for the 392 list at .418 id 2.906 oal. Still leaves you at .0035 s/g clearance. :(

one of my contacts has a listing for a 392 bronze guide at .415 id .688 od and 2.920 oal. This will give the shop a thou. To hone.

The company only sells to machine shops so your shop will need to call to order for you.if you are interested send me a pm.

Robert
 
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My take on this scruuball IH valve guide-to-stem deal...

Back in the day when the 152/266 were placed on line, no one cared about oil sukkage past the guides. Neither was "emissions" a consideration. Old timers thought that the "puff of smoke" at cold/hot startup, along with smoke on the "over-run" (high manifold vacuum) was a sign of "good top-end oiling"!

But then those motors never have had decent valve guide sealing, the "o" rings are not seals, but only "deflectors". Same for the umbrellas sometimes used, another makeshift deal. And another reason these motors tend to "use oil". It's sukked past the intake guides and burned! That kinda oem stem-to-guide clearance is considered majorly wore-out for most "normal" engines!

And then there was/is the issue regarding the rocker shaft lubrication deal (or lack thereof!). Obviously the excessive stem-to-guide clearance that IH spec'd did nothing to prevent valve's sticking in guides due to lack of lubrication so that point doesn't hold water!

The oem guides were plain old cast iron alloy, sure nothing upscale about that. The system "works" but most certainly was cheep to manufacture.

When emissions regs kicked in, I find it hard to believe that no attention was ever paid to "oil control". But obviously not, as nothing in the design of the valve train ever changed except the "cost reduction" involving eliminating four rocker stands and the changeover to the throwaway stamped rocker arms. That has nothing to do with oil control past the valve stems.

So the aftermarket installation of bronze guides, or the use of the spiral bronze inserts (a repair system), along with positive valve stem seals (involving machining the tops of the oem guides to accept the seals) is a definite upgrade. Most especially inna performance motor build so we can keep oil out of the combustion process!

As for the availability of parts for doing this, keep in mind that in the last 15 years or so, the market for professionally-rebuilt IH sv motors has been exactly zero! Therefore the folks to manufacture/supply these kinds of parts in bulk to pro rebuilders have dropped the stuff from their lines, there is just no demand! But with enough research of the folks who specialize in this kind of parts supply (not the typical neighborhood auto parts emporium), stuff like this can still be sourced, just takes alotta effort to find it, and a machine shop willing to do the leg work and go the extra mile.
 
You're pretty much correct with your statement Jesse. There are a lot of IH engine being rebuilt with sloppy valve guides. And honestly it's not just IH engines, it's a good many others. Main reason (most) people are cheap. Second reason, machine shops know (most) people are cheap, so they don't bother informing the owner they need new guides. Third reason is sad, but honestly, you'd be surprised at how many "reputable" machine shops just don't give a damn to even check the condition of the valve guides.
Mr mayben is absolutely correct about the o-rings on the valves. They don't seal anything as far as the guide is concerned. When these engine are "tight" and all the clearances are in spec they don't puff at startup. But they don't stay "tight" for ever. Chevy had this same craptastic system till the 80's. And they have the same puff at startup after they get some use.
As mr m. Also suggested a positive style seal is the only true solution.
Perhaps purchase one of the questionable seal power guides, make some measurements, and see if they are usable.
A little late for this I know, and not ment to be a jab at anyone. But something I've been doing with IH sv's I've been playing around with has been to scrap the stock valves, and install new ones with 11/32" stems (manley makes them for me, last set of 16 was about $350). Unless it's for a big truck, you're not going to hurt the smaller stem.
Also, if you're planning on boring out a 3/8" guide, keep in mind that the 392 intake is the same guide as a 304/345 exhaust. If you have some old intake guides, you could just use them and save some money.
 
71 thanks you your input right-on on the stem seal deal at least on the intake and usually on the exhaust. Unless the app' is a very high duty cycle application then I leave the exhaust guide open to the added lubrication and better heat transfer.

Actualy I found a source for .415 id si bronze guides a week ago at a supplier I use that only sells to builders. I gave Jeff and Jesse the info bc and I believe all is figured out.

The smaller stemed (3/8) valve was an option from the get-go but as you know you need more than a guide diameter change you will also need spring retainers and locks + all of the mockup time costs $$$. 11/32 on a big street truck engine? Even GM used 3/8 exhaust valves on there hipo motors like the dz-302 and big valve fuelie heads.

Imho they are too small here. A must for very high rpm apps though.

Rk
 
I think you misread Robert.
I stated to use 11/32" stems, unless it was in a big truck application.
Also the stock retainers, springs, keepers from the 392 exhaust will work perfectly fine on a 3/8" stem. If you look at the 392 exhaust valve it's 3/8" where the retainer and keepers are.
 
You think I misread? :gringrin:....................................................................................................................................................
"I" think I misread. :frown2: :icon_eek:
 
As far as seals go, I had the intake guides machined to accept viton positive lock seals. From what I have read, and according to the builder, this type is compatible with iron guides since they do allow some oil past the seal. Earlier teflon positive lock seals did not. I do not know what I am going to do with the exhaust, but I am probably going to leave them alone and use the factory o-ring seal. Due to the rotator, I am running out of room to use any other type. I'll know better upon final assembly. Thanks for all the input.
 
So is there an easy fix for the puff of smoke? Mine will sometimes puff enough to look like the Scout is on fire:icon_eek: I can let it sit 15 minutes and get a huge cloud other times just a puff. It's like only some of the valves have the issue and maybe related to there position. I.e. Open to the cylinder. I was hoping I could just pop on some Ford caps that bill has used in the passed.
 
Robert,
I brought this guide issue up with a rebuilder I've been using the last year or so. He's been in the biz 30 or so years, works on any thang with a piston in it hi pro, stock, ag, commercial, you name it. According to the catalogs he uses, only the .419" or .418" are available. Sbi's cat# for a .418 was 140-7680. Probably the same all over with other shops.
He said egge machine in la would be a good place to check if I really wanted a tighter spec. They only do "older" engines, not much past 1965. You heard of them?
 
Greg,
I know egge machine very well. They are the only place to get some rare engine parts. I don't really know if they have IH stuff mainly because I have other sources. To be honest they are not the right part to use in any kind high performance application which is where I would play. For a rare basically stock street car they are perfect and I would not hesitate to use them in that case. Many people I know have and with good outcomes.

I have a supplier for 392 exhaust guides in Nevada that I gave to Jeff. They have full bronze guides that are supplied at .415 id. Great for a light hone to finish at .4165 or what ever you prefer.

Robert
 
I wanted to add a bit to the egge machine. When I say that I would not use them for performance I am referring to their large assortment of pistons which for the most part are cast and have been known to fail but not valve guides. If they are made from the correct phosphor or silicone bronze and of the correct heat treat they would be fine.

I heard through the grapevine that they have begun to offer a limited selection of forged pistons but I have no personal knowledge of this.

They have a long history in the vintage car world that is as good as it gets for the proper application.

The above was a personal opinion that I have and one that I have heard from others in the industry. I am sure others opinions will differ.:gringrin:

Robert
 
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Fyi,

I had my builder purchase and install the bronze guides that Robert spoke of above. No problems, although they turned out to be about .4165 id from the supplier, so the builder did not need to hone anything out of them.
 
Thanks for the update Jesse! This topic is definitely one we need to pay much attention to for many reasons! Either an oem-type engine rebuild or a hi-per motor freshen.

Egge is certainly a supplier of record for many nla items for antique/special interest stuff and has been for nearly half a century. But they are not a goto for many of the ultra-performance components that some folks wanna source, some stuff they actually manufacture, some is outsourced also.

So what is the final verdict on the guide issue. Were the bronze guides machined for positive seals? Did your guy machine the guides for positive seals? Are you using positive seals or not?
 
Michael,
the parts Jesse is refering to are "not" egge maching parts.
I am pretty sure you know that but I was just making sure. I can't remember if we spoke on that point.

The guides are designed as direct replacement and I would expect them to be like the oem guide/boss designe and not be machined for a seal. It is an easy machining job to accomplish after installation should one chose to use seals. Like written earlier some guide seals are not going to let enough lubrication into the guide for heavy duty use so be carfull and use the black rubber type seal that felpro offers if any not the nylon/teflon lipped ones. You can tell from my tone that I don't believe a valve seal is needed on this type of vehicle but to each his own. Do however consider intake valve stem seals.

Rk
 
Yes, I knew they were not egge parts, I researched that maybe seven or eight years ago when I first approached this subject for my own benefit. I was responding to both points from the previous posts!

And egge was the first source I thought about regarding those stroker pistons we've been jawing about, but once we kinda homed in on the extremely available variations of the 307 chev pistons, I gave that idea up.

The way I see it...the properly clearanced bronze guides fitted with positive stems seals will cure the "oil past the guides" issue same as on any similar engine, thus the startup smoke will be a thing of the past.
 
Robert/michael: thanks for your input. So as it stands now, I take it that ihonjeff is the go to guy should I elect "factory" spec'd guides as opposed to catalog guides. I've been planning a rebuild for the 800's power plant for some years now. Actually in all modesty I should say dream vs. Plan. I intend a stock motor.
 
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