1964 Lemans - 389 or 400? - Pontiac GTO Forum
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post #1 of 6 (permalink) Old 06-12-2019, 08:15 AM Thread Starter
 
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1964 Lemans - 389 or 400?

So I'll start off by saying that none of my Pontiacs are original nor worth terribly much. I build them as I like. Have a 98 Trans Am (not TECHNICALLY Pontiac) that has nothing stock left on it. Also have a 56 Chieftain that we're building into a gasser, along with a couple Catalinas and Lemans.

I am in the process of cleaning house a little bit and thinking of just keeping the TA, 56 Cat and 64 Lemans. The Lemans needs a lot of work but is a pretty straight car.

It is an original manual trans car, although the trans is gone. It currently has a Poncho 350 in it of unknown condition. Now, I have a 63 Grand Prix here that has the 389/303hp engine in it. I don't know the condition of it, but it supposedly ran and it isn't locked up. I've been trying to sell the GP (it is parts/big project) and no one is buying, so thinking of taking the 389 out of it and cleaning it up for the 64.

I also have a few 400s here, but thinking maybe I'll do the 389 for now. I honestly don't know much about the 389 as far as upgrades, I mostly only deal with 400s. I like to keep my 400s for stroker/performance builds so I'd debating on some upgrades on the 389 and using it.

What says the forum?
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post #2 of 6 (permalink) Old 06-12-2019, 04:52 PM
 
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I'd go with 400 stuff. Parts are much easier to find. Going with a '63 & older 389, you might run into some problems which could be avoided by going with 400 stuff. One problem that I've read about is that '63 & older engines did not have provisions for a block mounted starter. I think those blocks came along in '64.

"...All Pontiac blocks from 1964 and up have the same provisions for mounting the...starter...Prior blocks had the starter mounted to the transmission bellhousing, and large-body cars, like Bonnevilles and Catalinas, continued to have the starter mounted in the transmission bellhousing until 1965 (despite having the provision for starters on the block in 1964)..."

IMO all the advantages go to the 400, as long as you don't use a "557" block. Use a 481988 or older 400 block, & you have lots of stroke/head/intake/carb options---Anything from a mild low CR, low power 400, to a 500hp + torque monster.

Last edited by bigD; 06-12-2019 at 05:41 PM.
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post #3 of 6 (permalink) Old 06-12-2019, 06:50 PM
 
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bigD is correct in that the 400CI would be easier with regards to part sourcing, but with all thw aftermarket availability of custom pieces, you could do a nice rebuild on the 389CI.

Reading your post, I assume you have fabrication skills, and may like a challenge.

Your first hurtle will be that the starter bolts to the bellhousing, and not the engine block. So you would have to use a matching bell. However, you can purchase an adapter that would solve this problem. It allows for a later 1965 Chevy/BOP and up bolt pattern bell transmission. Has provisions for a starter mount as well. It is for an automatic trans, but my guess is if you were to contact the company, they may be able to let you know if they offer a kit for a manual transmission. Wilcap Pontiac Engine Adapter Page

Engine mounts are most likely different, so a little fabrication may be at hand. Possibly grafting the cradle mounts from the GP over to the '64?

Transmission crossmember might need some attention, but with all the aftermarket tube style trans mounts, this would be easy enough to get to work if you could not modify what you already have.

The 389CI would be more "period" correct and you don't see these used as much anymore with the 400CI or a stroker slapped in in its place. Butler has stroker kits which I am sure you are aware of.

Heads can be used if no cracks, but I believe you will find that the oiling for the rockers goes through the engine/rocker arm studs. They are also 3/8". The SD engines used a 7/16" stud and it was pinned, not a screw-in affair. There is a replacement 7/16" stud that is offered on Ebay designed for the early heads. As he states, insert these and then go with pushrods that have the oil hole in them to oil the rocker arms. He has sold a number of sets and has a 100% positive rating. Check this option out: https://www.ebay.com/itm/Pontiac-GTO...UAAOxy7MtRuncH

I assume the valves are the smaller 1.88" Intake/1.60" Ex.. The HP 1964 and up 389CI was 1.92"/1.66" and the SD head used 2.02"/1.76" valves. You can size the smaller valves up. One trick is to use the Chevy 283" 1.94 Intake. Same length and dia as the Pontiac. It has a double groove keeper, so this is where I don't know if you can use the Pontiac spring retainer/keepers or have to go with a Chevy match. The thing that will limit the Intake size is the closeness of the Int/Ex valves in the center. Another former member did this and I cannot recall what intakes size he went up to, but did say you were limited as to how big you could go in diameter. It may have even been the 1.94/1.66 combo.

A good gasket port match and blending in the bowl area if going with the larger valves will help. I like bronze valve guides & Viton valve seals if you can use them. Keep the 1.5 rocker arm ratio.

Intake for me would have to be a tripower. You will have to get one to match your intake pattern on the heads. The 1964 GTO and 1965 & up Pontiac uses a different pattern. The intakes can sometimes be cheaper as they are not in big demand. Check this out: https://winstonsalem.craigslist.org/...879896408.html

You can go from there on cam choice and other goodies. You will use all the pulleys/water pump cover, balancer, etc. from the '63 engine.

I am no expert on the earlier engines, so I may be missing a few things. You will have to do the research. I don't know if it'll cost any more to rebuild the 389 vs a 400 as I don't see a lot of difference when it comes to same machine shop needs and parts. But, would look nice with the 389 valve covers and tripower under the hood if you can make it work.
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post #4 of 6 (permalink) Old 06-13-2019, 08:52 AM Thread Starter
 
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Kind of my thought. Making mounts and a crossmember isn't really a huge deal. Trans mounted starter on the 63 isn't a big deal either. I think I have a bellhousing around here for one.

I was just thinking a cleaned up 389 with a tri-power would be pretty cool. I am putting a 462 into my 56 Chief gasser while I build a destroked 400 (316 crank with crank spacers, end up around 326cid) and once we finish that engine I'll probably put the 462 into the Lemans.

This engine does have the smaller valves with the closed chamber heads. I know the valve angle on these early heads is not great too so wouldn't want to drop too much money in them. Probably would just do a simple valve job, bigger cam and just bearing slap and rering it if the cylinders spec out. Would definitely have to have a tri-power.

I have two sons - 12 and almost 9. I wanted to rebuild an engine with them to show how to do it, I thought this 389 might be better stockish build than letting them help me with a high performance stroker 400. LOL
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post #5 of 6 (permalink) Old 06-13-2019, 06:30 PM
 
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OK, sounds like a plan. My first car at 16 was a 1956 Pontiac 4-Dr HT Chieftan. One owner car, 316CI/Dual Range Hydramatic. Learned autobody repair and turning wrenches on that car. I still have an original 1956 factory Developmental (the early manifolds) 2 x 4 cast iron intake. I think I paid $20 for it and never installed it on the '56, but did mount it on the 347CI in my '57 just for looks. Only thing I have left from the car, plus the pictures.
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post #6 of 6 (permalink) Old Today, 09:33 AM Thread Starter
 
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Very cool. I think I might do the 389. I'm getting into the 56 kinda deep now so that will be getting the big motor first.

My biggest hold up is the heads, the 10.25 CR isn't exactly conducive to making good power.
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, LeMans & GTO Engine Tuning and High Performance

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