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Old 09-14-2009, 10:51 PM   #1
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Default 1975 Pontiac 400 Engine

The casting numbers show its out of a 75 Trans Am 4 speed car. I want to put this into a 68 GTO clone.

Does any one know the factory rated hp for this engine?

Who knows about the heads and porting? Are the head and porting considered high flow? I know 454 Chevy heads came in three types. They used different port diameters to get better flow. I don't know if Pontiac did the same?

I would like to be able to get 360 hp out of this engine by installing a more aggressive cam, bigger carburetor, headers, better distributor and plug wires.

Is this engine a good candidate for modification?

Thanks
BT
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Old 09-15-2009, 06:29 AM   #2
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I would order an Ohio Crank that would make that block a 455. That is the nice thing about Pontiac's, they are all the same external deminsions as each other except the 267 and 301. The 400 uses small mains than the 455. You can bore it .030 and use 455 pistons with the small journal crank with the 4.21 stroke and build the 400 into a 455. The 75 block is still a good one, I wouldn't go with a later year block. Pocket port the heads, put a Bullet cam in it and go have some fun.
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Old 09-15-2009, 11:17 AM   #3
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You can get to your goal with that engine but you will need
1) New Heads
2) New intake manifold
3) New cam
And all the supporting mods, headers, etc....

What is the casting on the head? Should have a number/letter combination
such as 6X or 4H
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Old 09-15-2009, 03:25 PM   #4
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Quote:
Originally Posted by beertracker View Post
The casting numbers show its out of a 75 Trans Am 4 speed car. I want to put this into a 68 GTO clone.

Does any one know the factory rated hp for this engine?

Who knows about the heads and porting? Are the head and porting considered high flow? I know 454 Chevy heads came in three types. They used different port diameters to get better flow. I don't know if Pontiac did the same?

I would like to be able to get 360 hp out of this engine by installing a more aggressive cam, bigger carburetor, headers, better distributor and plug wires.

Is this engine a good candidate for modification?

Thanks
BT
Send me the block and head casting numbers and I will c what I can find out. Also look for the letter codes on the front of the block on passenger side where the head and block meet. Depending on the head # u may not need a large amount of porting.
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Old 09-15-2009, 06:47 PM   #5
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Off the top of my head the HP rating should be about 180 TQ is around 310.
Heads should be 5C castings and the compression will be approx 7.6 to 1
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Old 09-15-2009, 08:58 PM   #6
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You will definatley have to change the heads, the stock heads on later model Pontiac motors had huge combustion chambers and just wernt that great.
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Old 09-15-2009, 11:06 PM   #7
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Quote:
Originally Posted by beertracker View Post
The casting numbers show its out of a 75 Trans Am 4 speed car. I want to put this into a 68 GTO clone.

Does any one know the factory rated hp for this engine?

Who knows about the heads and porting? Are the head and porting considered high flow? I know 454 Chevy heads came in three types. They used different port diameters to get better flow. I don't know if Pontiac did the same?

I would like to be able to get 360 hp out of this engine by installing a more aggressive cam, bigger carburetor, headers, better distributor and plug wires.

Is this engine a good candidate for modification?

Thanks
BT
You may also want to check out the BRE Trans Am. The base Ban 1 has a 455 Pontiac V8 rated at 450hp. From what I remember reading you can buy a turn key motor from the place they get them from if your not wanting to do the engine work yourself. I'm not 100% positive as this was from a few years ago, but if your interested I can find the magazine and article for you because it lists the website to get them. No matter what, good luck with it. I wanna make a 69 GTO clone when i'm older and have the money/experiance to do it. The Judge is one of the sexiest Pontiacs
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Old 09-16-2009, 06:33 AM   #8
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http://www.krepower.com/

http://www.allpontiac.com/

http://www.jbp-pontiac.com/

http://www.highperformancepontiac.co...ild/index.html
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Old 09-16-2009, 01:59 PM   #9
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360hp is easy like falling out of your chair. Should have 5Cs like mentioned earlier, not a bad head just low compression. Still has screw in studs and 2.11 intakes, the 1.66 exhaust valves wont hurt your at all. If you plan to run manifolds you can find some 7K3 heads, they are big valve and have a bit smaller chamber so the compression comes in around 8.8 to 9:1, the problem with them is they are missing the end bolt hols so headers will leak. They did that in 72, not entirely sure why but they are still a good head.

96 heads are from 71, they are identical to the 7K3 but they have the end bolt holes, both of those heads are one year only. 6X is the easiest to find since they came on 350s, 400s, and 455s from 76 to 79. You dont want the heads from a 455, you want 350 or 400 heads, because the 455 head makes for very low CR on a 400. Great for blowers though.

Earlier 72 cc heads will raise your compression too high for pump gas, some people can get away with it due to elevation or ambient temps, but if you are in an area that gets hot and humid, you will need some dishes to run 91-93 octane. Those castings are 670, 13, 12, 48, and 62. If you want to run ethanol those heads will work great, and its easy to set that up.

I have had JBP, now Butler Performance Group do a few sets of heads for me, they do outstanding work but yes you pay for that work. Kaufman does good work and there is a guy in Canada that does excellent porting as well. You can either send in your heads or buy a set from them already ported and set up with springs. Iron heads usually run about $1200-$1400 fully ported and assembled. You cant get into a Edelbrock or KRE aluminum head for less than $2k. KRE does make a D port that will work with inexpensive headers, round ports require at least a $500 set of headers.

To hit your 360hp number, you could go with a set of ported 6X-4 (350 heads) a Bullet 280-288 cam, call them they will know what you are talking about its an older UltraDyne cam. A little bigger one that works great is a 288/296 UD cam. A stock intake, a built Qjet, some headers, and an HEI. You could go with an RPM intake on the ported heads if you want to run a Holley carb. The Performer isnt any better than a stock intake, even the EGR intakes like your engine should have. The only thing it will do the stock ones wont is allow a Holley to be bolted up. Whatever you do dont go with a single plane intake.

A higher budget would be an Eagle stroker kit making it a 462 like mentioned above, no need to go forged on the crank at your power level. KRE D port aluminum heads, and a cam with 228 intake duration and 230-234 exhaust duration @.050 lift. It would idle like a stocker and make well over 400hp, and get decent mileage if you can tune a carb.

I have a 455 in the 70 GTO with ported 5C heads from a 400, RPM intake, Qjet, and the 280/288 cam, its at 4100lb with 2.93 gears and a stock converter it ran consistent 13.50s. 275 65 15 street tires were a smoke show even at 35mph and a Th400. Its a silly amount of grunt from that combination, and a stock intake would work just as well. I ran the same heads and cam in a 400 in the GTO and while I never made it to the track it was very similar in performance.
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Old 09-16-2009, 02:06 PM   #10
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When I had my 80 T/A I had a cammed 400 out of a 68 GTO with #48 heads, pump gas in WV about 3000FT.

As stated above butler performance is good, also look into Edelbrock heads they are very good for Pontiac motors.
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Old 09-16-2009, 02:41 PM   #11
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Quote:
Originally Posted by Thumpin455 View Post
360hp is easy like falling out of your chair. Should have 5Cs like mentioned earlier, not a bad head just low compression. Still has screw in studs and 2.11 intakes, the 1.66 exhaust valves wont hurt your at all. If you plan to run manifolds you can find some 7K3 heads, they are big valve and have a bit smaller chamber so the compression comes in around 8.8 to 9:1, the problem with them is they are missing the end bolt hols so headers will leak. They did that in 72, not entirely sure why but they are still a good head.

96 heads are from 71, they are identical to the 7K3 but they have the end bolt holes, both of those heads are one year only. 6X is the easiest to find since they came on 350s, 400s, and 455s from 76 to 79. You dont want the heads from a 455, you want 350 or 400 heads, because the 455 head makes for very low CR on a 400. Great for blowers though.

Earlier 72 cc heads will raise your compression too high for pump gas, some people can get away with it due to elevation or ambient temps, but if you are in an area that gets hot and humid, you will need some dishes to run 91-93 octane. Those castings are 670, 13, 12, 48, and 62. If you want to run ethanol those heads will work great, and its easy to set that up.

I have had JBP, now Butler Performance Group do a few sets of heads for me, they do outstanding work but yes you pay for that work. Kaufman does good work and there is a guy in Canada that does excellent porting as well. You can either send in your heads or buy a set from them already ported and set up with springs. Iron heads usually run about $1200-$1400 fully ported and assembled. You cant get into a Edelbrock or KRE aluminum head for less than $2k. KRE does make a D port that will work with inexpensive headers, round ports require at least a $500 set of headers.

To hit your 360hp number, you could go with a set of ported 6X-4 (350 heads) a Bullet 280-288 cam, call them they will know what you are talking about its an older UltraDyne cam. A little bigger one that works great is a 288/296 UD cam. A stock intake, a built Qjet, some headers, and an HEI. You could go with an RPM intake on the ported heads if you want to run a Holley carb. The Performer isnt any better than a stock intake, even the EGR intakes like your engine should have. The only thing it will do the stock ones wont is allow a Holley to be bolted up. Whatever you do dont go with a single plane intake.

A higher budget would be an Eagle stroker kit making it a 462 like mentioned above, no need to go forged on the crank at your power level. KRE D port aluminum heads, and a cam with 228 intake duration and 230-234 exhaust duration @.050 lift. It would idle like a stocker and make well over 400hp, and get decent mileage if you can tune a carb.

I have a 455 in the 70 GTO with ported 5C heads from a 400, RPM intake, Qjet, and the 280/288 cam, its at 4100lb with 2.93 gears and a stock converter it ran consistent 13.50s. 275 65 15 street tires were a smoke show even at 35mph and a Th400. Its a silly amount of grunt from that combination, and a stock intake would work just as well. I ran the same heads and cam in a 400 in the GTO and while I never made it to the track it was very similar in performance.

Great post...

I've seen the stroker option mentioned a few times.. and if the OP was looking for 500hp I'd be on the bandwagon, but the kind of horses he's looking for can be done on a budget ( Pontiac budget... not Chevy budget).

The 400 set up in my sig makes the kind of power he's looking for and it was done fairly cheap.
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Old 09-17-2009, 02:12 AM   #12
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It costs me around $2000 to build either a 400 or a 455, add about $700 for porting. Plenty cheap power if you know how to do some of the work and pick the right cam and tune it right. No need for deep gears or high stall converters, and a build like the OP wants can be done easily with stock rods and cast or forged Speed pro pistons. Get your rings, bearings, oil pump, gaskets, and pistons from Summit or Jegs, no need to buy the kit, but you can go that way too.

Next week I'll be dropping a 400 like he wants in one of the Trans Ams, ported 670 heads, .040 over block, balanced, stock rods, forged slugs, and a 288/296 cam. Its going to be an ethanol engine so I wanted more compression. It should easily make 360hp and a bunch of torque.
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Old 09-24-2009, 01:18 PM   #13
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Guys:

The deal with the 68 LeMans & 400 5C heads fell through. I now have a 70 LeMans with 400 engine and 6x heads. The boss to left of the 6X is either a 6 or 8 I can't tell which. This number is the combustion chamber head size and should be 4 or 8. Did Pontiac make a 6 size?

The head date code is XE317. This came from the passenger side head front. When were these head made?

The block number is 50055. This came from passenger side rear below distributor where the head and block meet. When was the engine made?

It has a Rochester Q jet 4 barrel but where do I find numbers?

It has a Pontiac intake manifold number F207 near top radiator hose bracket.

I would like to get 360 hp out of it since that is what the 70 GTO was rated at.

Is the 6X head better than the 5C head?

I was told the engine came out of a 72 Grand Prix however I don't know if the engine is original to the Grand Prix.

I need to check the spark plug wiring back to the distributor. Is there a mark on the distributor that identifies #1 and does the numbering increase clockwise or counter clockwise?

Thanks,
BT
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Old 09-24-2009, 03:26 PM   #14
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No 6X-6, it's either a four or a eight head ( sounds like you have an 8).
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Old 09-24-2009, 03:35 PM   #15
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I believe my 6x-8 heads are D port. What's the difference between D port and O port? Is one better than the other?

Thanks,
BT
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Old 09-24-2009, 05:13 PM   #16
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Quote:
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I believe my 6x-8 heads are D port. What's the difference between D port and O port? Is one better than the other?

Thanks,
BT
The Oval port heads came in the high performance heads, the D ports were the regular design.
The 6X's actually had decent flow numbers ( for stock heads of the era )...
BUT... you're probably at 7.6:1 compression
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Old 09-24-2009, 10:31 PM   #17
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The only thing that has changed from my original post is I am using 6x-8 heads which have a CR of 7.6:1. So is a 366hp goal from a Pontiac 400cid with aftermarket cam, aftermarket distributor, aftermarket intake, headers, and aftermarket carb reasonable? Is there any reason to go with an aftermarket carb as opposed to staying with the Q-jet?

What is the CR of the 5C heads? Is it similar to the 6X-8 head? If I find 6X-4 heads would this require higher octane fuel or can I stay with 87 octane?

Thanks,
BT
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Old 09-25-2009, 10:31 AM   #18
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Quote:
Originally Posted by beertracker View Post
I believe my 6x-8 heads are D port. What's the difference between D port and O port? Is one better than the other?

Thanks,
BT


the O ports only came on the Ram Air IV and Super Duty's. All the rest are D ports. Most aftermarket aluminum heads are O ports. The headers won't interchange between D and O.
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Old 09-25-2009, 03:32 PM   #19
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Quote:
Originally Posted by beertracker View Post
The only thing that has changed from my original post is I am using 6x-8 heads which have a CR of 7.6:1. So is a 366hp goal from a Pontiac 400cid with aftermarket cam, aftermarket distributor, aftermarket intake, headers, and aftermarket carb reasonable? Is there any reason to go with an aftermarket carb as opposed to staying with the Q-jet?

What is the CR of the 5C heads? Is it similar to the 6X-8 head? If I find 6X-4 heads would this require higher octane fuel or can I stay with 87 octane?

Thanks,
BT
The 360+HP you are looking for is going to be a stretch with those heads...my 400 is very close to your goal and I have ported/milled 6X-4's.
You're gona need better heads.
My 6X-4's work awesome on 87 still.
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Old 09-26-2009, 04:26 PM   #20
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What kind of budget do you have for the engine? Figure out how much you can spend on it and I will give you links to parts to get what you want, or close to it.
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Old 09-26-2009, 04:26 PM
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