# Heads on 389 help



## Billoney (Mar 14, 2011)

Hey guys newbie here. I have a 64 tempest custom and have a 66 389 that I just tore down to check it out. it has a fresh 030 rebuild on it with flat top pistons with 4 relief cuts on them. Everything looks good so far and getting ready to put it back together. I have a 71 donor motor that has 96 heads on it and was wondering what heads to use. Also while its apart should I do a cam change and if so what would be a good combo for what I have to work with. Also I have a Edlebrock Performer dual plane manifold with 1407 750 carb and an HEI that Im going to use. Going to take the heads (which ones not sure yet) to the machine shop to have them checked out as soon as I know what ones to use. I plan on making it pretty much a streetable car but would like it to get out of its own way. Oh yea plan on running a 200-4r trans.
Thanks All:seeya


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## jetstang (Nov 5, 2008)

The 389 heads valve location is different than the later 400, so the valve reliefs in the pistons are in a different location. The 400 heads can't be used on a 389. I had the same issue, and wanted to use 6X heads on mine. You could overbore it and use 400 pistons, but yours is a fresh bottom end, I would have the 389 heads done and have hardened seats installed for unleaded gas. But, you also have to find/fix the compression ratio as the 389s are high compression. What are the heads #, and is there a part number on the pistons? I'm sure the guru's can figure out your CR with those numbers.


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## geeteeohguy (Feb 2, 2008)

Billoney,all of this information is available here on various threads and sticky threads. You will find all your answers by searching these threads. This subject has come up a lot, and has been gone over many times. Good luck.


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## Mr. P-Body (Jan 20, 2011)

Jetstang is correct to a point. The valve angles are different. However, if max lift is under .500, you're probably fine either way. 

The 389 heads are either 092 or 093 (center exhaust ports) if true '66. 092s on "big cars", 093s on GTO. IMO, the 96s aren't a good choice, as static compression will be in the toilet (around 7.8:1). Not enough can be milled off to make a significant difference, and fitment becomes a real challenge when too much IS taken off. 

Consider having a small "dish" machined into the heads of the pistons. A 3" diameter, .100" deep "simple dish" (turned on a lathe) will get the compression "down" to a manageable level for 93 octane. .125" would give more "room". 

For a relatively "stock" sound, and a good power band with the lower compression, Comp XE262H is the cam of choice. It will make MORE power than a 10.5:1 389 with 068.

FWIW

Jim


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## Billoney (Mar 14, 2011)

Thanks Jetstang and Mr. P-Body The heads I have are 092 and have to check out the piston part number. From the info I had from the previous owner was that he had the motor rebuilt 3 years ago but only had 3000 miles on it before the tranny went out. He said that he ran 89 octane fuel and had no problems with it supposedly. After Tearing it down the motor,heads and gaskets show that it was a low mileage rebuild. Now could this be true that he is running this on 89 octane fuel and what would happen if I put it back together and tried to run it as is. Thanks again for all your help 

P.S. Has anyone ever ran the 200 -4r BOP OD Trans? I have Turbo 400 but I would like to have an OD for Mileage.


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## jetstang (Nov 5, 2008)

He may have put dished pistons in it on the rebuild. If it is running good on 89 octane, the compression is reduced or he took all the timing out of it. You could put it back together as is and probably be good. Post up picks of the short block and we'll see what's up.


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## Billoney (Mar 14, 2011)

Will do Jetstang, Im out of town for the weekend but can have picks up tomorrow night. When I looked at it before I believe that they were flat top sealed pro pistons with 4 relief cuts in them. But Ill double check and post pics of the build. Thanks


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## snakeyes (Apr 2, 2013)

Confirming if what Mr.P-Body stated will work in my case: 65 389 333hp big car block, #77 heads, headers, 66 tripower, keeping below .500 lift by using XE262H cam. 
Would like to lower CR to use 95 octain and use #77 heads
Dish pistons as stated 3" dia .100-.125? or I do have access to 6X heads but will heads fit all above components. Have done alot of looking but have not seen a pic of 389 flat top dished


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## 67GTO4SPD (Oct 4, 2012)

snakeyes said:


> Confirming if what Mr.P-Body stated will work in my case: 65 389 333hp big car block, #77 heads, headers, 66 tripower, keeping below .500 lift by using XE262H cam.
> Would like to lower CR to use 95 octain and use #77 heads
> Dish pistons as stated 3" dia .100-.125? or I do have access to 6X heads but will heads fit all above components. Have done alot of looking but have not seen a pic of 389 flat top dished


You most likely need to find a machine shop that can machine dishes into flattops. (one that builds race engines can usually do this). Butler Performance, Jim (Mr P Body) at Central Virginia Machine, SD Performance, and others could do this for you. Even the smallest chamber 6X's are going to produce a low CR.


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## geeteeohguy (Feb 2, 2008)

Did one this way and the pistons were Ross custom made ones. No such thing as a 'flat top dish". If it's dished, it's no longer a flat top. The dished pistons with the 389 heads work very well.


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