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Old 07-28-2020, 12:00 PM
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Default 389 Small Chamber Heads and Larger 1.92 / 1.66 Valves

I posted this question over in the pre-1960 section but thought more people in this section might have input. I'm exploring options for maintaining my 1959 389 reverse-flow heads that currently have 1.88/1.60 valves, but I'm interested in increasing the valves to later 1.92/1.66 for both the diameter and length. I'm getting conflicting information from online charts regarding valve sizes. According to Wallace Racing, the high-output '59 and '60 heads used a 1.92/1.60 configuration, so it looks like the 1.92 intake valve will work, but will it work alongside a larger 1.66 exhaust valve? But other sources claim the high-output '59/'60 engines used 1.88/1.60 valves. Wallace lists some '61 through '66 heads using the 1.92/1.66 configuration. I know the heads changed in 1961, so I'm not sure if the '57 - '60 heads will accept the larger valves. Question: Can 1957 - 1960 370/389 closed-chamber heads be machined for a 1.92/1.66 valve configuration without getting into trouble with water jackets or cracking the seats/casting?

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Old 07-28-2020, 12:27 PM
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Casting wise yes, no problem, but with the what should be used 3 angle valve job in the chamber for the 1.66" Exh valve, no!

Installing those two bigger valves eats up .050" of the current space between your stock size valves and that's without the expansion of them taking place at running temperature they see.

I would have a shop cut down and reface those 1.66" valves down to 1.60" and back cut them with a 30 degree to leave a .075" wide 45 seat, the new 30 degree seat 1.92" valve should not get a back cut , only the lip should be ground off if it should have such.

Also since your going up to a .060" bigger Intake valve the chamber wall on the spark plug side should get unshrouded by atleast .045" from .030" above the chamber floor on up to the deck.

This all taking place on the Intake valve side of the chamber only.

Also in terms of the Intake valve the chamber needs to be gasket matched on the side of the Intake valve out to the start of the head gaskets fire ring.

After that the head gasket should be placed on the block and a notch ground into the cylinder wall to match what you just did in the chamber.
This notch should stop .020" before where the top ring travel stops.

Failing to do all of this will not buy you much more flow then you would get had you just maxed out the OD of the valve seat from the stock 1.88" Intake valve which if the heads have not had a valve job done to them will likely be some .040" short of the OD they could be .

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Old 07-28-2020, 02:54 PM
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Thanks for the detailed information, Steve. Running the larger valves in the early heads sounds like a lot more labor and thus higher cost of machining than it might be worth. With my build being only mildly hopped up from factory specs for today's standards, I'm not sure I'll gain much that I'd notice on the street that would justify the cost versus running the stock '59 heads and valves with port-matching the intake/exhaust runners. I'm capable of doing any die-grinding and polishing work but not the valve work.

Understanding I would need to covert the stud oiling to pushrod and deal with the reverse-cooling system, would running 1965 - 1967 closed-chamber heads with 1.92/1.66 or 1.92/1.64 valves require the same unshrouding of the cylinder wall on a '59 block?

Keep in mind this isn't a race engine by any means, which I could have clarified from the start. 068 cam, 10.25:1 compression (I'm at 5,400' elevation, so 10.25:1 static acts like 9:1 after calculating dynamic compression and runs fine on 91 octane pump gas), likely dual quads or tripower, 1-1/2" headers, 2-1/4" exhaust, manual transmission, posi rear gears to complement the transmission and engine, all in a 1,800lb 1927 Model T Roadster. I won't get a stock '59 389 to plant all that power on the street to begin with, so I don't want to go overkill on the heads if it only means I'll spend another $400 in machining to roast the tires even more than they already will in every gear

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Old 07-28-2020, 11:18 PM
PontiacJim1959 PontiacJim1959 is offline
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I believe you are over thinking this. Converting to later heads would most likely be more greif than needed - just simply go with a later engine and be done with it.

Nothing wrong with the '59 engine. No need to go with a larger 1.66" exhaust. Keep the 1.60" unless your engine builder tells you the valve seats are worn out and you need to use the 1.66" and have them ground down to work, ie a slight oversize over the 1.60".

If the 1.92" intake can be fitted, then use it. As outlined, going larger in size could shroud the valve and then you gain nothing in performance - might even lose a bit. Depending on lift, knowing you will use the 068, you want to make sure the valve at full lift does not hit the cylinder wall at the top - this is where the scallop/chamfer in the top of the bore comes into play. It can aid in mixture flow, but you are probably fine with the 068. Always check your clearances between valve and top of piston and valve-to-top of cylinder bore when going with more than a factory cam for that year/engine.

Cam selection is where your power will come from. You want more lift/overlap on the exhaust side, but I assume the headers will really help with the exhaust gases, so you don't need to go crazy and the extra duration on the 068 cam will most likely be enough.

Do your port work and get a quality 3-angle valve job, bronze valve guides, Viton valve guide seals, and matching springs/retainers for the 068 cam. Your car won't be heavy, so how much HP do you think you need?

You could convert to pushrod oiling, but I don't see any advantage. If you had a broken stud and could not get a replacement, then I would go for it. Right now save a few bucks and keep what you have.

Focus on a good intake set-up, ignition, head work on what you have, cam, and exhaust. Then use what you have as it came from the factory. Otherwise it would be more cost effective to simply go with a 1965 or later engine, but then having a nostalgia build would not be the same, right?

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Old 07-29-2020, 02:49 AM
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Quote:
Originally Posted by PontiacJim1959 View Post
I believe you are over thinking this.
I'm here to learn, and overthinking and underthinking are part of my process in finding the sweet spot. Outside of most of the machine work, I'm building the engine, so I don't have an engine builder's experience specifically with 389s to rely on aside from the kind people on this forum and a factory service manual. The popular 389 engine books out there don't cover these types of questions.

Quote:
Originally Posted by PontiacJim1959 View Post
Otherwise it would be more cost effective to simply go with a 1965 or later engine, but then having a nostalgia build would not be the same, right?
And there's the rub. I have set myself the task of building as nostalgic an early 60's hot rod as possible within reason. The two issues I'm having with the '59 heads are (1) new correct shorter valves aside from the full-on racing variety are alluding me and (2) Jack Gifford on this forum has explained that '59 rocker arms are a different shape/geometry than '61+ rocker arms. New stamped '59 rocker arms don't appear to be available.

Obsolete parts are driving my questions about retrofitting the '59 heads far more than performance. If I had a definitive answer that I can pop 1965 1.88/1.60 valves and rocker arms into '59 heads without having geometry issues, I'm there and my concerns are addressed since I can source those parts new. Or If I had a solid line on new correct '59 valves and usable stamped rocker arms, I'd have no issue running the stock '59 heads.

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Old 07-29-2020, 07:28 PM
PontiacJim1959 PontiacJim1959 is offline
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Quote:
Originally Posted by Roycroft View Post
I'm here to learn, and overthinking and underthinking are part of my process in finding the sweet spot. Outside of most of the machine work, I'm building the engine, so I don't have an engine builder's experience specifically with 389s to rely on aside from the kind people on this forum and a factory service manual. The popular 389 engine books out there don't cover these types of questions.



And there's the rub. I have set myself the task of building as nostalgic an early 60's hot rod as possible within reason. The two issues I'm having with the '59 heads are (1) new correct shorter valves aside from the full-on racing variety are alluding me and (2) Jack Gifford on this forum has explained that '59 rocker arms are a different shape/geometry than '61+ rocker arms. New stamped '59 rocker arms don't appear to be available.

Obsolete parts are driving my questions about retrofitting the '59 heads far more than performance. If I had a definitive answer that I can pop 1965 1.88/1.60 valves and rocker arms into '59 heads without having geometry issues, I'm there and my concerns are addressed since I can source those parts new. Or If I had a solid line on new correct '59 valves and usable stamped rocker arms, I'd have no issue running the stock '59 heads.
First, check out this forum 1959 Pontiac engine tear down over at the H.A.M.B. These are the guys who can answer your questions. https://www.jalopyjournal.com/forum/...ac-389.996461/

I assume you have a Service Manual for 1959? That will have all your specs and give you info on the valve length/size, diameter, etc.. This guy on Ebay seems to offer both intake and exhaust valves for your engine. With his selection, I am sure he can get whatever you need. https://www.ebay.com/i/192507438329?...DefaultOrganic

Here is another nice debate on rocker arms, screw-in studs, and head oiling: https://www.hotrodders.com/forum/389-build-248282.html

Read post #14. You may have to physically purchase a SBC Intake Valve, and see what you have with the 1.60". Then perhaps drop in a 1.66" exhaust and see how that looks, but I think I recall another build that used the larger SBC valve and the 1.60" exhaust had to be used as the 1.66" was too large and hit: https://www.hotrodders.com/forum/can...ck-419482.html

Ferrea can also supply valves, stock and custom, so valves should not be an issue.

Kanter can be a good source for parts. Here they offer rocker arms: https://www.kanter.com/productdetail...Cat=32&Prc=368

Have any/all parts hat tanked and magnafluxed before you do any work or purchase any parts. Make sure nothing is cracked.

I would also suggest getting a membership to the Pontiac Oakland Club International (POCI) as they have tech people for various years and could probably answer your questions. I used to be a member many years ago and they were helpful on a few questions on a 1956 Pontiac I had in my younger days. Assume they can still provide help.

Again, should not be that difficult to get the nostalgia out of your engine. You can see all of what I just pulled up for you. You will have to be the one to do a lot of leg work, and perhaps measuring parts/pieces as you go and what you cannot find, you have to make work with some kind of substitute. That's why it is called Hot Rodding. You may also want to look at Ebay in the magazine section as they sell the old Hot Rod, Popular Hot Rodding, Car Craft, etc. magazines and you may find one having the build you are looking for. Many drag racers used them, so you may find a good article that'll provide some info/specs.

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