View Full Version : Pontiac 400.....tell me what you know about it


BeefTip
12-18-2008, 11:01 PM
I just posted this in another section on here but, I have found a 78 trans am with a pontiac 400 in it(not the olds 403).

I know absolutly nothing about these motors. Does anyone know anything about it...good or bad or whatever.
Do they take to mods well?

01ssreda4
12-18-2008, 11:37 PM
i know it takes more to build them up then say a SBC.

BeefTip
12-19-2008, 12:13 AM
yeah i was figuring that....however, im not sure how many things dont cost more to build than an sbc

2c5s
12-19-2008, 12:23 AM
yeah i was figuring that....however, im not sure how many things dont cost more to build than an sbc

What exactly do you want to know? $ for $ an LSx will make more power and be more efficient.

BeefTip
12-19-2008, 12:27 AM
What exactly do you want to know? $ for $ an LSx will make more power and be more efficient.


I know all about ls1's. Im looking at getting a 78 trans am that has the original pontiac 400 in it that has been "built". I dont know to what extent yet, but im going to check it out in a few days. I was basically curious about any high/low points about this motor.

87silverbullet
12-19-2008, 07:48 AM
Take a look at butler performance. All they deal with is pontiac motors. The heads on them are very similar to an ls1 with symmetrical intake ports. The factory heads are crap. The cheapest head you can get for it would be the edelbrock heads. Butler Performance has some other heads but I cant remember what they are.

BeefTip
12-19-2008, 08:16 AM
Take a look at butler performance. All they deal with is pontiac motors. The heads on them are very similar to an ls1 with symmetrical intake ports. The factory heads are crap. The cheapest head you can get for it would be the edelbrock heads. Butler Performance has some other heads but I cant remember what they are.

thanks ill check that out.

BAN-LS1
12-19-2008, 07:47 PM
Yup stock heads suck. Very low compression.

2c5s
12-19-2008, 07:50 PM
I know all about ls1's. Im looking at getting a 78 trans am that has the original pontiac 400 in it that has been "built". I dont know to what extent yet, but im going to check it out in a few days. I was basically curious about any high/low points about this motor.

They are great low speed tq. motors.

Z51C6
12-19-2008, 08:25 PM
If for some reason you loose interest in the T/A, let me know.:secret2:

ws6ed
12-19-2008, 09:26 PM
Look at the casting numbers. On the heads, they're on top of the center exh ports. Then find the engine block code, facing the front of the engine, just above and to the left of the water pump, should be two letters (YJ etc). If you want to know if the engine is original to the car the vin is stamped on a pad on the lower left of engine beside the front cover just above the oil pan but is very hard to see in the car. With these numbers you can get an idea of what you're dealing with. Stock heads can be good or bad, you just want the right ones for the combo. Later smog heads had really large chambers for low compression. Generally, earlier 400 blocks were considered better because they are "beefier" and less likely to distort in high hp use. Stock intakes will work perfectly well on mild to mid hp combos, and can be made to out perform even aftermarket stuff with an afternoon worth of grinding. A Pontiac motor will cost more to build than a SBC, but how many do you see any more? Besides its what the car is supposed to have in it... Good luck !

Z51C6
12-20-2008, 12:06 AM
I had a black/gold 78. Blew the motor and found a SD 455 with a nice size cam. Sold it to a guy in Opelika in 82. This one wouldn't black/gold would it?

RaggedRides
12-20-2008, 01:49 AM
They're interesting engines, to say the least. There were so many variables in head castings throughout the years, you just have to decode them to see what you've got. I used Google to find out everything I wanted to know about my old 400. The heads are lower compression #16's out of a '69 Grand Prix casted on October 9th of 1969. the short block is '73 vintage with flat-tops. It's torn apart at the moment, but will be up and running again soon. Being that it's a late '70s car, I'd bet it's got a set of 6X heads.

Seriously, Google "Pontiac Head Casting Numbers" and shit of that sort. There's a few good websites out there that tell you where to look and what it means. If you can find any of his publishings, Jim Hand is the business when it comes to Pontiacs.


They're physically large engines and weren't differentiated by big and small blocks. From 326 to 455 cubes, they all look the same externally. The displacement casting was on the front passenger side of my block. In my opinion, they're built more like a big block than anything. They make great torque, but don't rev too high. The rotating assembly is heavy, especially the crank.

Parts are expensive, but that comes with the territory when messing with anything other than Chevy or Ford iron. Buicks, Ponchos, Oldmobiles, AMCs and Mopars always cost a pretty penny. They're interesting engines, but not common knowledge like three-fittys and five-ohs. It'll piss you off when you're looking at intakes or something and the Pontiac stuff costs twice as much.


The good thing is there are plenty production-based combinations that were strong runners back in the day and still make stout street cars.


http://www.pontiacpower.net/castnum01.html

http://www.yearone.org/updatedsinglepages/Id_info/pontiacengineid/pontengid3.asp

http://www.angelfire.com/fl4/pontiacdude428/HeadID.html


There's shitloads of details that vary from one to the next. You just have to do your research.

87silverbullet
12-20-2008, 02:26 PM
There is a guy locally around here that has a 489 pontiac motor that is 15:1 compression and has edelbrock heads and a solid roller setup that got butler performance to spec out for him. Its in a 67 firebird that has full interior and a cage. He was street racing with it and was beating everybody with it. Then one day me and my buddies saw him at the track and he had N/T on the windows and the track goofed and still showed his time it was 9.70 and that was on the motor.

lt1taracing
12-20-2008, 11:54 PM
edlebrock aswell as kauffman make good heads for the pontiac motors. BTW, i believe all pontiac 350,400,455s have flat top pistons. the difference in compression is made in the heads. like said they have the engine size stamped on the drivers side of the block. checkout the new pop.hotrodding mag. one of the engine masters challenge guys built a pump gas (10.4 comp.) 400 (407ci) engine. with a flat tappet cam and kauffman heads, it made 628hp and 578 ft.lbs. trq. n/a.

87silverbullet
12-21-2008, 09:06 AM
I think horsepower tv did a build awhile back on a 400 pontiac and they put in a mild cam edelbrock heads and intake and it dynoed somewhere north of 500 hp

N2RACINGLS1's
12-21-2008, 05:15 PM
Some of the statements in this thread are way off.

1st, If you are looking at this car and it does have the original engine in it and the code is X7 it is 220 HP. The X7 is the best block for 1978. In building this engine you can get 400 HP pretty easy and the 6X heads can be milled down to get a pump gas compression of 10.5 to 1.

2nd, There are many good after market heads but you do not need them. Many of the factory heads are big valve and high compression. Some said the stock heads suck not true at all. You need only a set of 1971 #96 heads and a pre 1973 400 block and you are good to go!

3rd, Not all pontiacs engines had flat top pistons and compression was not based on head cc's alone. It had a lot to do with bore and stroke.

4th, You have 326, 350, 389, 400, 428 and 455 CI Pontiac engines.

5th, The vin number is not always stamped on the block.

I would say go for it and have some fun with an great American classic!

N2

2c5s
12-21-2008, 11:41 PM
Some of the statements in this thread are way off.

1st, If you are looking at this car and it does have the original engine in it and the code is X7 it is 220 HP. The X7 is the best block for 1978. In building this engine you can get 400 HP pretty easy and the 6X heads can be milled down to get a pump gas compression of 10.5 to 1.

2nd, There are many good after market heads but you do not need them. Many of the factory heads are big valve and high compression. Some said the stock heads suck not true at all. You need only a set of 1971 #96 heads and a pre 1973 400 block and you are good to go!

3rd, Not all pontiacs engines had flat top pistons and compression was not based on head cc's alone. It had a lot to do with bore and stroke.

4th, You have 326, 350, 389, 400, 428 and 455 CI Pontiac engines.

5th, The vin number is not always stamped on the block.

I would say go for it and have some fun with an great American classic!

N2

1. x7, why is it the best?

2. stock ports?

3. bore and stroke, how so?

4. what about 421?

5.It was after 1968.

red83
12-22-2008, 10:28 AM
the infamous 301?
show some love for the crank breaker

~JOSHUA
12-22-2008, 05:42 PM
I read an article in Pontiac Enthusiast that got 100hp from heads alone!

They added 1.6 roller rockers and got another 20hp (crank hp on an engine dyno)

They tried two different types of headers (shorty and mid) and neigther made power on the stock motor...

The aftermarket intake only gained 4hp... so the stock intakes are fine (even the post '76 with the smaller barrels on the inlet are good without grinding, the test proved it)

So If I had that car/engine (I wish) I'd add some nice heads, a cam with stock 1.5 ratio -roller rockers, ignition upgrades, some headers and a full tune up...

Save up for a fresh paint job, and a 5/6 speed tranny swap...

Time to pimp. :secret2:

N2RACINGLS1's
12-22-2008, 08:01 PM
1. x7, why is it the best?

2. stock ports?

3. bore and stroke, how so?

4. what about 421?

5.It was after 1968.


1. The X7 has a high nickel content in the block and extra webbing!

2. Many stock heads flow very good and have nice big valves, intake 2.06" exhaust 1.72" in them to move a lot of fuel and air and have low cc's like 68!

3. If you take a 1969 350 HO with #48 heads on it the compression ratio is 10.5 and a 1969 RAIII 400 with #48 heads on it has a compression ratio of 10.75. The only difference is the bore. A 400 engine with a cut down 428 crank gives you a 440 CI and if it is bored out to install a 455 piston your up to 450+ CI. Take a 455 block and bore it 30 over and get 469 CI's. Some of the late pontiac engines even had dished pistons in them.

4. I forgot all about the 421 and the 301! My dad actually had a 1962 GP with a 421 tri power 4 spd he bought brand new.

5. That is not 100% true. I have had plenty of 1969 & 1970 models and later without the correct vin number on engines I knew were original. Now by the late 70's GM may have marked all their engines. I have a close friend that has a 78 he bought new so I will check with him and see what he saids.

I hope this helps some! I am no expert, but I have been blessed with owning several Pontiacs over the years! Like I stated before to the original thread starter buy the TA and have fun with it!

N2

BeefTip
12-22-2008, 10:43 PM
Well i went up to north GA to visit some of the family this weekend and i was supposed to go see the guy about the TA. I was about to take the exit off of 85 to go to his house when he called me and said that he had just discovered that the heater core had gone out and the passenger side floor was soaked. Needless to say I decided to pass on the car. If it was closer I would have still looked at it but with no other way to get it home then by driving it, it would have been a waste of time.

BlueBird346
12-23-2008, 01:52 AM
I thought the 400s are SBCs? Like interchangeable parts with a 350, 327, 302, ect.

N2RACINGLS1's
12-23-2008, 06:51 AM
Well i went up to north GA to visit some of the family this weekend and i was supposed to go see the guy about the TA. I was about to take the exit off of 85 to go to his house when he called me and said that he had just discovered that the heater core had gone out and the passenger side floor was soaked. Needless to say I decided to pass on the car. If it was closer I would have still looked at it but with no other way to get it home then by driving it, it would have been a waste of time.

You could have just cut the heater hose going into the heater core and connected it to the head and bypassed the heater core all together pulled the carpet up and cleaned up the floorboard. Then got the car home wearing a coat and gloves and had a big smile on your face all the way home.

N2

N2RACINGLS1's
12-23-2008, 06:55 AM
I thought the 400s are SBCs? Like interchangeable parts with a 350, 327, 302, ect.


I guess you meant to say the 400s are like SBC. regarding changing parts out.

The Pontiac engine is nothing like a SBC as stated early they are mostly considered Big Blocks. The great thing is for example you can put a set of 428 heads on a 350 block and so on.

N2

BeefTip
12-23-2008, 08:10 AM
You could have just cut the heater hose going into the heater core and connected it to the head and bypassed the heater core all together pulled the carpet up and cleaned up the floorboard. Then got the car home wearing a coat and gloves and had a big smile on your face all the way home.

N2

lol, more than likely I would have just been mad that i had to fix a car before i bought it..........especially since it was in "perfect mechanical condition" lol

red83
12-23-2008, 08:13 AM
pm me a number for the seller or a link....i may go get it. its supposed to be almost 70 this weekend. i think i can have the heater bypassed in say.....................2 minutes

~JOSHUA
12-23-2008, 09:12 AM
Seriously, If you're passing on the car, can you send us the details on this car...

(I want to buy it.)

red83
12-23-2008, 09:20 AM
step in line sucka!

~JOSHUA
12-23-2008, 03:03 PM
step in line sucka!

What's the matter?

You tired of sloppy seconds and thirds? :lol:

BeefTip
12-23-2008, 10:04 PM
here you go guys...its probably a great deal, im just passing. Its supposed to have all ac equipment hooked up, just needs recharging....also, it has brand new autometer gauges and a new interior. Only needs one rust spot patched. Its located in Jefferson GA, the guy had it listed for 3800, no listed for 3000 OBO

http://atlanta.craigslist.org/cto/965225047.html

RaggedRides
12-23-2008, 11:15 PM
Not a bad deal. With some paint and body work, it'd be an awesome ride. I paid $3,800 for my 400/TH400'd '80 and drove it daily for almost two years before getting my Camaro.

http://i63.photobucket.com/albums/h124/rakestraw666/HarveyBird.jpg

If anyone snatches it up, I'm parting out the Pontiac drive train and have a few new parts, like the intake, cap, rotor, harmonic balancer and other junk up for grabs.