# 65 GTO: help me choose an engine



## torpedo51 (Sep 8, 2009)

I've got a basket case that is progressing nicely. The car is a true GTO. I'm normally a purist, but its time to have a little fun. I definitely want to stick with pontiac stuff. Seems a little too easy to go right for the 455. I'd rather get a smaller displacement engine and try to squeeze power out of it. I've been fascinated with strokers, etc. I'm limited by budget, so I can't get too nuts.

I know the pontiac blocks are generally the same. I'm trying to pick a number between 389 and 428. Maybe you guys can shed some light on things to watch for and things to watch out for. I'd like to increase the performance slowly over time with some budget conscious add-ons.


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## Thumpin455 (Feb 17, 2010)

See what block you can find if you dont have one already. 400s are easy to find and they can be stroked easily. It doesnt take much to drop a 4.5" crank in a 400, 428, or 455 if you want big inches. If you want to keep the 3.75" crank of the 400 you can still build a very healthy engine with it. The 65 I am working on is getting a 400 with ported 5C heads and a Summit 2802 cam, it should be lots of fun to drive with plenty of power from idle to 5500. 

How much power do you want? Have an idea of how fast you want it to be? Big strokes are the easy way, but not the only way. A 400 is still pretty big inches, its easy enough to make them run, the only difference is they need a little more gear than a 455 or larger does. I have been thinking of the 4" crank in a 400 block for 434ci or so, just because its something different from what I have been building.

Do you wnt a highway cruiser, a drag toy, or something that will embarrass people at stop lights?


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## wwhozhot (Jun 11, 2010)

*heres an idea for you*

LS2 05 06 ????????? there not hard too find and there light wieght & i got a friend that just put one in a 55 chevy great ride lots of power and very reliable anyways just a idea.....:cheers


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## torpedo51 (Sep 8, 2009)

I'd like to have enough power so that its easy to tell that I'm not driving a rental car. I'm not taking it to the strip or trying to draw the attention of the local law enforcement. That being said, I want the car to perform like it can and should - detroit muscle. It needs a lumpy cam, a torquey whine, and a noxious smell that will offend the neighbors. As I drift by, it must cause them to pause from their morning driveway gatherings of sipping white wine and chatting about headlines in the morning paper... to tense up in anticipatory fear.

I like your idea of the 4" crank in the 400 to get to a 428. I was thinking of building a poor man's 421 by going with a 389 block... that would require a stroke of 4.0625. Does anyone sell such a thing? Is it a bad idea to have the bore and stroke identical at 4.0625?

I remember a CarCraft article where they took a ford 302 and added 100hp strictly by changing the heads and headers (not the cam). Whats the holy grail of pontiac heads between 65 and 68?


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## geeteeohguy (Feb 2, 2008)

Torpedo, have you ever driven a '65 GTO? Even a bone stock 389 4 bbl '65 will piss off the neighbors!!!! These are crude, visceral, thumping cast iron detroit V8'S! No need to put in a later engine like an LS2....it has LESS torque than the original 389 and a LOT more manners! A 389 or 400 with a tripower and a mild cam is all you need to get the car sideways and to put it into a power pole the first time out. Be careful, and have fun. My suggestion would be to locate other GTO owners in your area and go for a ride or two. Then decide! Good luck.


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## likethat (Oct 5, 2007)

400 HP is 400 HP new or old. I have owned a 1999 ws6 TA with a STS turbo kit that dyno'd at 408 HP at the wheel and I own a 560+ Hp 427 67 camaro and a 1978 Trans Am SE 400 w72 with a little over 375 rwhp. They're all fast. The 78 on the highway was close to the 99 and the 67 is crazy with 225/60r14s. I can walk out sideways in fist gear at any speed from 0 to 40 mph. My best friend about crapped when I dropped it down and S'ed it down the street at 35 mph. If I leave it in 1st I can poop the throttle as many times in a row as I want and it will burn the tires. Like geetee said the 389 is a very stout engine.

LS2 is cool but by the time you speed all the money and time to make it work in the car you can build what you have and get more stuff done to the car. LS2 is a cool project and with a 6speed it is well worth it. It is just up to how much real time and money you have and want to spend.


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## torpedo51 (Sep 8, 2009)

geeteeohguy said:


> Torpedo, have you ever driven a '65 GTO? Even a bone stock 389 4 bbl '65 will piss off the neighbors!!!!


Haha - yes! My fleet includes:
65 GTO hardtop: 389, tripower, M20
65 Tempest hardtop: Olds 455, TH400
66 LeMans convertible: Pontiac 455, AED, Powerglide

I purchased these drivers in all in solid running condition, so I haven't learned much yet... so this basket case that I'm restoring is an educational project... and I'd like to put something in it thats different than what I already have. Thats why I like the idea of a stroker. I hear the 421 was the racer's choice back in the day?


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## geeteeohguy (Feb 2, 2008)

A 421 would be my choice for a modded '64, '65, or '66 GTO. But they're hard to find and pricey. Still, just the way "421" sounds rolling off the tongue is impressive. go with what you want, and have fun.


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## torpedo51 (Sep 8, 2009)

Great... poor man's 421 it is. 

Does anyone make an off the shelf crank with a 4.0625 stroke and a journal of 3.00" to fit the 389?

And what is the best choice of pontiac heads for this application?


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## 66tempestGT (Nov 28, 2009)

when you get done pricing parts you might have to find another name for it.


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## geeteeohguy (Feb 2, 2008)

Torpedo, I've heard good things about guys putting 455 cranks in 400 blocks....they end up with a 455 that screams. Also, 440 CID Pontiacs seem to run really hard. There is all kinds of info on this topic on the "other" forum: performance years. Go to the "street" or "Race" sections and have at it. I warn you, though....it's addictive!!! Eric sold his cherry stocker '67 and is now building a blown '67 street basher. It could happen to anybody.....


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## 66tempestGT (Nov 28, 2009)

torpedo51 said:


> Great... poor man's 421 it is.
> 
> Does anyone make an off the shelf crank with a 4.0625 stroke and a journal of 3.00" to fit the 389?
> 
> And what is the best choice of pontiac heads for this application?


ok, i learned a little about pontiac engines and i see what you are getting at. if 421 is your magic # you wont need a 4.0625 crank unless you have a standard bore 389. if you have a standard 389 then you can take a 421 crankshaft (with its large journals) and have it offset ground to fit the 389 block and get your custom stroke at the same time.


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## 66tempestGT (Nov 28, 2009)

so a 400 is a .060 over 389 at 4.1225. the bore of a 428 is 4.125 (.0025 larger). so for all practical purposes a .060 over 389 with a 4.00 inch crank is a 428. (actually 427).


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## 66tempestGT (Nov 28, 2009)

so if you bore the 389 .030 over to 4.0925 (4.09375 is standard 421 bore) and use a 4.00 crank (just like a 421) you will get 420.723733 or 421.


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## 66tempestGT (Nov 28, 2009)

or you can bore it .03125 and use 421 pistons and turn down a 421 crank or buy an aftermarket 4.00 crank and have the real deal.


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## 66tempestGT (Nov 28, 2009)

it makes my head hurt. i would find a 400 block (they seem more common) bore it till it cleans up and stick a 4.00" crank in it. if it ended up 427, 434 whatever doesnt seem to be much difference.


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## 68greengoat (Sep 15, 2005)

Your head hurts???!!!!


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## torpedo51 (Sep 8, 2009)

So... as I was saying, where can I get a 4.0625 crank with the smaller journal for the 389? And, is it a good idea to have the bore and stroke both be 4.0625? And finally... how do I choose the best heads for this project?


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## jetstang (Nov 5, 2008)

Get Jim Hands Hi perf Pontiac book, or go on the PY forum and ask him, he is the master. I've priced standard pistons for a Pontiac, I can't imagine the price of custom pistons, good luck with that..
Shane, WTF is all that, lol- you have too much time. You can edit, and add info and keep it one post, but that's funny stuff.:cheers


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## 66tempestGT (Nov 28, 2009)

a crank like that will have to be a custom grind. any racing crank manufacturer can make it for you. all it takes is money. unless you have a standard bore 389 using that crank will give you more than 421 cubes. i dont see any reason not to use the readily available 4.00" crank. whats the big deal about 1/16th".

having the bore and stroke the same is fine. it is refered to as being "square"


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## Thumpin455 (Feb 17, 2010)

torpedo51 said:


> So... as I was saying, where can I get a 4.0625 crank with the smaller journal for the 389? And, is it a good idea to have the bore and stroke both be 4.0625? And finally... how do I choose the best heads for this project?


Do yourself a favor and get a 4" crank and a 400 block. You can run the old style heads if you can afford some from a 421 with the early valve reliefs, or you can go with the post 67 heads with the bigger valves. Dress it to look like a 421 and nobody will know the difference. 

You can get the 4" crank with 3" mains from any of the Pontiac vendors/builders. You can get a balanced assembly, pistons, rings, rods, bearings, and crank that drops right in for about $1400. Call it a 421 even if it actually displaces 434, its pretty much the same as if you found all the stuff and rebuilt it after boring the block. No need to get hung up on a crank that has .06 more stroke..


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## Eric Animal (Oct 28, 2007)

jetstang said:


> Get Jim Hands Hi perf Pontiac book, or go on the PY forum and ask him, he is the master. I've priced standard pistons for a Pontiac, I can't imagine the price of custom pistons, good luck with that..
> Shane, WTF is all that, lol- you have too much time. You can edit, and add info and keep it one post, but that's funny stuff.:cheers


Around $1000 for custom pistons.......


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## jetstang (Nov 5, 2008)

So, if you run a bored/stroked 455 and call it a 421, who will know? Unless someone decodes your block, you can call it whatever you want. If they see your block numbers, then you can just tell them it's stroked. I'm not into telling tales, I would build the best motor I can afford regardless of hitting a certain number. i won't overbore and chance overheating or lose the chance to rebuild the motor again for a certain number.


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## torpedo51 (Sep 8, 2009)

Yeah, I'm not at all stuck on the number 421, and there's certainly no need to be deceptive - the engine will be fun whatever it is. I'm just trying to do something a little different... 

I thought it might be interesting to keep a standard bore of a 389 at 4.06250, and increase the stroke up from 3.750. The resulting displacements are:
4.06250 x 4.000 = 414 (this is the same stroke as a stock 421 and 428)
4.06250 x 4.063 = 421 (this is a custom stroke)
4.06250 x 4.210 = 437 (this is the same stroke as a stock 455)

The 400, 421, 428, and 455 all use a bore greater than 4.09375. So if I started with a 389 and tried one of the combinations above, I'm getting a pure stroker.


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## 66tempestGT (Nov 28, 2009)

my question is where do you get a standard bore 389 that doesnt need at least .020 to freshen up the cylinders.


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## torpedo51 (Sep 8, 2009)

Damn, you're right. 
That gives 414, 425, 440 respectively. 

Maybe I need a different approach: what's the longest stroke that I can put into a 389 or 400 block?

By the way, I'm visiting Denver where I see a few cheap 389, 400, 428, and 455 blocks.


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## DukeB-120th (Oct 19, 2009)

66tempestGT said:


> my question is where do you get a standard bore 389 that doesnt need at least .020 to freshen up the cylinders.


Does this mean there are no brand new 389s on the market?


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## jetstang (Nov 5, 2008)

torpedo51 said:


> Maybe I need a different approach: what's the *longest stroke that I can put into a 389 or 400 block*?
> By the way, I'm visiting Denver where I see a few cheap 389, 400, 428, and 455 blocks.


EXACTLY what I was thinking!! I was wondering the hang up on the number, when it's all about performance.
I have a standard bore 66 389/325HP non GTO motor sitting in the corner, needs bored, but ran great, just smoked like a freightrain when you got on it.


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## Rukee (Feb 8, 2007)

DukeB-120th said:


> Does this mean there are no brand new 389s on the market?


Not that I'm aware of.


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## Thumpin455 (Feb 17, 2010)

torpedo51 said:


> Damn, you're right.
> That gives 414, 425, 440 respectively.
> 
> Maybe I need a different approach: what's the longest stroke that I can put into a 389 or 400 block?
> ...


You can stuff a 4.5" crank in a 400 with little trouble. A 4.25" crank is a bolt in deal. You can find pretty much anything you want here. There are others, but these are the people I have bought from, talked to on the phone, or have conversed online for advice.

Butler Performance
SD Performance
Pacific Perfomance
Coast High Performance
Kaufman Racing
Kens Speed and Machine
Paul Spotts


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## DukeB-120th (Oct 19, 2009)

Rukee said:


> Not that I'm aware of.


There are so many crate motors out there, why no 389s?
What about 400s?


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## Rukee (Feb 8, 2007)

Aftermarket maybe, no NOS engines, that I know of anyway.


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## Eric Animal (Oct 28, 2007)

Not enough demand probably......


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## DukeB-120th (Oct 19, 2009)

Oh ok, I didn't expect there to be any N.O.S. examples out there... I would probably want to get an aftermarket 389 block to throw parts at as it would be a fresh engine without boring the cylinders!


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## 66tempestGT (Nov 28, 2009)

when you buy an aftermarket block it comes unfinished and you bore it to be whatever you want. :seeya:


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## Rukee (Feb 8, 2007)

If you're going aftermarket, why not go as big as possible?? Why a 389? Why not a 455 block to start out with? They are the same outside dimensions.


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## Eric Animal (Oct 28, 2007)

Check out ALL PONTIAC IAII block!!! Call Frank G. and tell him Eric Aull/Richie Hoffman sent ya'..............:cheerswww.allpontiac.com


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## Rukee (Feb 8, 2007)

I just had an engingasm.  :cheers


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## DukeB-120th (Oct 19, 2009)

Shane, Ah, good to know. You learn something new every day.

Haha, wonderful suggestion Eric!

Rukee, I suppose I am a bit of a purist - for what it's worth, I can tell you without a doubt, that purist or not, I am _definitely_ a perfectionist.


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## geeteeohguy (Feb 2, 2008)

"Enginegasm"......I love this thread!


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## likethat (Oct 5, 2007)

Is that the same guy that had been running adds in HIpro Pontiac and the National Dragster about making a better Pontiac block?


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