Been reading about the pontiac vs chevy 400s on this site and had a few questions. First, can you bolt a pair of chevy heads on a pontiac 400? I doubt it, but figured it was worth asking. Second, a 400 in a 76 formula firebird, would that be the pontiac or chevy 400 or how can i tell the difference? Tore the "350" that came with my car apart and found out it was a 305. Explains alot. I was planning on building up the 350, but now that I need a new block, why not go 400 if i can get one that'll work with chevy parts.

 

the pontiac 400 is a bbc so just look for that... 400 chevy is a sbc and I believe they have less freeze plugs

 

A Pontiac 400 isn't a BBC, it's a Pontiac 400. There are no interchangeable parts between it and an SBC.

 

As mentioned above, Pontiac and Chev engines have nothing in common. You might as well compare them to Ford and Dodge 400's. Chev hasn't produced a production SBC 400 since 1979.

Yanking out your SBC and installing a Pontiac engine has been done by many third gen owners but it's not that easy of a swap. You'll have to replace the transmission as well since the B-O-P bellhousing is different than the SBC/BBC bolt pattern. There a few older trannys that have a dual bolt pattern but by 1982 when there were no more B-O-P engines, the dual bolt pattern tranny cases were dropped.

Exhaust etc needs to use the factory cast iron manifolds or custom made headers.

There are Pontiac BBC parts but they're specially made, race only parts. Big Chief Pontiac heads are common on ProMod and ProStock BBC engines but have little in common with any production parts.

 

Sorry, i ment it looks like a bbc, I heard those pontiac engines made some outstanding torque, my buddies got one, tho I have never really see it run

 

It just won't go away, will it?

I heard the Earth is flat, too. Somehow I don't think the Earth is impressed though, at least, not enough to change its shape.

They make no more torque, and no less, than any other mfr's motor with similar cubic inches, cam, flow, RPM capability, etc.

Torque = cyl pressure x piston area x stroke x # of cyls

(Note that piston area x stroke = cubic inches)

Nowhere in that equation do I see a correction factor for the plant that the cast iron (or aluminum) came out of. If anyone can point out how that would work, without a bunch of "I heard" or "I read a magazine once", please enlighten us.

 

Well....

You can use your Chevy transmission if you run an adapter. They are usually less than 80 bucks.

Dual bolt pattern transmissions were made from the early 70's up to 1990. The last B-O-P engines were the Buick V6 up to 1988 and the Olds 307 (5.0 liter) which was used up through the 1990 Model year. Both of these engines used multi-bolt pattern TH200c (3 speed) or TH2004R (4 speed) transmissions. Anyway, enough of the GM "JEAOPARDY" knowledge (my specialty) and back to topic...

Last time I was in this predicament, a friend of mine had a 305 and wanted a serious upgrade. We were fighting the smog ***** in CA, so we had to be sly. A day or so later, we saw an ad in the back of a Car Craft magazine that said "get your 82-90 Trans Am into the 12's" and it had a picture of an 84 T/A pulling the wheels off the ground. It had a 400 sbc under the hood.

We used the old adage, "there's no replacement for displacement," and we bought a 76 Caprice with a 400. It was great. We freshened up the bottom end, ran some 350 TPI heads from the wrecking yard, and it was a BIG hit! There are much better heads available now but that was the budget.

Anyway, you need a 1970-1980 400 Chevy if you want to start with 400 cubes on the cheap and easy. The Pontiac is great, and my preference if you ask me, but it's not easy and can't be done cheap.

So, there you go...

 

Distributor cap & rotor interchange. . .

 

Spark plug wires must be close....

Maybe even the oil pan plug?

Sticking with an SBC keeps everything easy, and if this is your first swap, or near to the first, stick with easy.
A 400cid SBC block isn't exactly that common, so finding one might be tricky.
You can however get a 350cid dime a dozen, then get an entry level stroker crank for $200, and have a 383. That's a winning recipe right there.

 

Ok, wow. Thanks for all the responses. And no, if nothing interchanges, then I don't want the hassle of installing a pontiac engine in my Camaro. Was just wondering. What vehicles would likely have a 400 sbc that I can find in a junkyard? If I can't get one, then I'll just go back to looking for a 350, no huge loss at this point.

 

Your chances of finding one are pretty much nil. In the 28 years since the 400 ended production, most of them have been picked clean from the junkyards by now. Your local classifieds and swap meets would be more likely sources.

 

Disappointing though not unexpected. Guess it's 350 hunting time. Are there any 350s I should avoid looking at a lower end strength comparison? I'll be swapping the heads, intake and cam, but the shortblock will be factory stock for the coming season. Limited budget and all.

 

Not really, they're all pretty similar.

 

Chevy pickups from about 76 to 1980 and Caprice/Impala cars from 1970 to about 1976 had available 400 engines. They are out there but you have to look very hard now.

On the other hand, this site routinely has 400's for sale. Some are bare blocks and some are complete, and some are anywhere in between.

If you want one, post in the parts wanted section; it can't hurt to try.

 

don,t think a PONTIAC can,t be made to run VERY effectively in the car, the pontiac engine while totally differant than the chevy has a good deal of potential. I build LOTs of pontiacs, they will cost more to build than a sbc but there are some advantages

http://www.carcraft.com/techarticles...50s/index.html

http://www.classicfirebird.com/hand/hand.html

http://members.tripod.com/futom/id59.htm

http://www.krepower.com/Heads.htm

http://www.boyleworks.com/ta400/psp/blockID.html

http://fiedlerh.home.att.net/PontiacCams.htm

http://www.teufert.net/pontiac/cranks.htm

http://www.pontiacpower.com/

http://www.edelbrock.com/automotive_...erformer.shtml

http://www.wallaceracing.com/techarticles.htm

 

The problem w/ poncho motors is that there are very, very few performance heads available. For that reason alone I can't afford to build one. And the stock poncho heads for the 400 give under 8:1 compression unless you use 350 poncho heads (terrible flowing) or early ram air closed chamber heads (671 comes to mind?) which cost a fortune nowadays. I'll take my sbc where you can throw some $800 new iron heads on there and be done w/ it.

 

The only good thing about a pontiac 400 is the fact that it can be punched out to be a 455.

The pontiac 302-455 uses the same block. Only difference is piston bore and stroke. Some came 4 bolt some 2.

Pontiac parts are very expensive. Heads over $2k, intakes are expensive. Etc.

 

I don't think that is actually true. All pontiac motors do use the same block. However, when the core was cast for a 400 vs 455 vs 326, whatever, the cylinder liners were cast appropriately thinner for the smaller bore motors. Otherwise they would be wasting tons and tons of metal making cylinder walls like an inch thick, plus that would make the smaller displacement motors actually weight more than the larger displacement motors. That would not make any sense from a manufaturing standpoint. If you tried to bore a 400 to a 455 you would go way through water, from my understanding.

 

You are mistaken. a pontiac 400 can be bored to a 455. It is the same block. You will hit no water jackets.

 

If that really is the case then I have some boring to do. I thought it wasn't though.

 

http://en.wikipedia.org/wiki/Pontiac_V8_engine

encylopedia of the pontiac motor

from the encylopedia :


[edit] 455
For 1970, the 428 bore was expanded to 4.152 inches, combined with a 4.21 inch stroke (105.5 mm by 106.9 mm), yielding a total displacement of 455 in³ (7.5 L). The engine became available for the first time in Pontiac Firebirds and the Pontiac GTO, as GM lifted its restrictions on the use of engines larger than 400 cubic inches (401 in some Buicks) in mid-sized cars. The Pontiac V8 design differs from other manufacturer's designs in that the external dimensions of each engine, from 326 - 455 in³ displacement, is identical. The displacement is determined internally with changes to the bore and stroke; therefore, there is no "big block" Pontiac engine. The 455 was used through 1976.

 

Understood, but just because the block layout is the same does not mean they cast the cylinder liners the same thickness regardless of bore. I just did a quick search on boring a 400 out to a 455 and found one of the magazines bored to 440 something, because they said the cylinder walls were getting thin, but that you could "reputedly" go to 455. I'd want to see the sonic test reports from a 400 bored to 455, vs a real factory 455. I'd bet the real factory 455 would end up w/ thicker liners.

"The displacement is determined internally with changes to the bore and stroke;" means they probably adjusted the liner thickness when they cast, based on what the target bore would be.

 

Provide proof. Watching powerblock two weeks ago when they did a pontiac motor they said exactly what I said. So if I am wrong please show proof. I do not want to spread false information. However the wikipedia article explains it best.

The 400 has a different crank than a pontiac 455.

So you put a 455 crank in a 400 and bore it you get a 455. Plain and simple. The blocks are identical in every which way expect 455's came with 4 bolt mains.

 

I don't know about "every which way". The 455 has larger journals than a 400. To make a 455 crank even fit in a 400 block the journals have to be ground undersized.

sourced from:

http://www.pontiacpower.com/FreeEngine3.htm

It does look like there is enough meat to bore it though. Interesting. There would basically be no reason to rebuild a 400 at 400 ci then.

The pontiac motors are very gigantic. My friend has a 400 and it is large and in charge. I can't imagine wanting that in a 3rd gen engine bay, for a street car.

 

Doesn't matter.

You still can't bolt a set of Chevy heads on a Pontiac 400.

Seems like every time Pontiac, Buick, or Olds motors get brought up, we get the same stupid wrangling over the same stupid things with the same stupid "torque monster" type of urban legends.

They're all perfectly good designs, with both strong and weak points compared to each other and to Chevy big and small blocks. They all don't fit one of these cars without a CONSIDERABLE amount of money and effort, usually better spent some other way (in raw, simple, easy-to-understand terms of HP/$$$). Even if the motor core is FREE, it will cost MORE to rebuild and install it than it will cost to BUY OUTRIGHT a fresh Chevy motor. Leave the foreign motor swaps to the people that know them well, have the parts at hand or know where to get them, know what fits and what doesn't and why, what combos of heads and intakes and pistons work well and which are just another gas-guzzling smogger slug with lots of tractor-motor type low-end grunt, and so on. Some old wore-out 70s 200 HP smogger turd out of grandpa's 74 4-door sedan isn't going to put your car onto an even footing with the Pro Stocks, you can believe that. That's one of the main reasons it's been laying in the mud by the creek out at the far end of the back 40 since about 1995 when they took his license away because he couldn't see any more, and you're getting it for free (or whatever the details of the particular instance of this repetitive post might be).

We'd do alot better to stick to PROVABLE, MEASURABLE facts; and answer legitimate questions, rather than arguing over stupid stuff like whether you can bore a 400 out to a 455; which you CAN'T, but you can bore it a little bit and then with a little effort put a 455 crank into it, and end up with a 455.

Did I say "stupid" enough times?

All Pontiac V8s have the same bore spacing, even the lowly 301 and 2whatever it was. Which of course includes that hideous asinine 151 4-cyl that got put in a few of these cars; it's just half of a 301. : puke : Take the WORST motor Pontiac ever made, cut it in half so it's REALLY gutless, then put it in a car that's slow even with twice as much motor.

 

The 455 bore is about .030" larger than a 400, which is reasonable to expect from a standard rebore, regardless of whether you were planning on changing the stroke or not. The stroke has to be changed though, or else you're building a .030"-over 400 instead of a 455.

 

There was some rocket scientist on this board who put I think an olds engine in a 3rd gen. He had the oil pan hanging down like 3" below the engine cradle, almost touching the road, and I think it would have needed like a 6" cowl for the hood to shut. It was quite the piece of work

 

That would be a 265...

Just in case someone cares...

 

I always thought that the earth was flat too naw I was not talking about numbers, to me, stock numbers is pretty good... (talking about the motor)

Thanks on the torque eq. it helps How would you figure horsepower then? if its possible

 

Isn't HP just TQxRPM/5252? Such that TQ=HP at 5252 RPM, always?

Anyway, kinda a moot point...
Cubes build power. Pontiac/Olds/Buick V8's are known to be 455 cubes, since those are pretty common in that world (relatively common). So when my brother would say "yea that 455 olds I used to have had tons of TORQUE", i'd agree, because it was being compared to his other V8 cars (302 ford granada, 265 chev malibu etc). Still, the "oldsmobile" was the fastest.

 

It's not an equation, it's a proportionality. Sofa just didn't know how to make the ∝ sign.

 

I gave a Poncho 400 away. It was a complete engine. Parts are expensive and to mode a engine bay for it to work is a lot of work. For the price of building up of a poncho 400, you could build a killer BBC. A lot less work, cheaper and parts availability for the BBC is way better.

 

No, it's very much an equation. Oversimplified in some ways, but the truth just the same.

Cyl pressure is in lbs/sq in. Piston (bore) area is in sq in. Multpily the 2, you get the force applied to the piston, in lbs. Multiply that by the stroke, you get in-lbs; divide by 12, you get ft-lbs. Multiply that by the # of cyls firing per revolution, that's how much torque the engine makes (minus pumping and compression and friction losses and such); and of course, taking into account that the cyl pressure isn't a constant, continuous value, but rather, changes during the stroke.

Pretty simple really. Not alot of mystery there. Just physics.

Notice, as described above, that if you regroup the terms, it comes out to CID x cyl pressure x # of cyls. In other words, the torque an engine produces is INDEPENDENT of the bore/stroke ratio, as well as the brand of cast iron; all that the ratio does, is change the RPM at which max cyl fill (peak torque) occurs, if all else (cam profile especially) is held constant. NOT its absolute value.

Also notice that there's no correction factor that I've ever seen for the company that poured the castings. The fuel and air molecules do not come to life somehow during their process of releasing their energy, and look around at the brand name on the castings, and gauge the emotional preference of the owner, and produce energy accordingly. Not in THIS universe, anyway.

Now, like I said, that's a bit oversimplified; for instance, different head designs or camshaft profiles can lead to different cylinder fill at different RPMs, which in turn affects the cyl pressure, and different bore/stroke ratios and rod/stroke ratios affect the shape of the torque output curve during the stroke. But, the basic principles ALWAYS apply: pressure, times area, times lever arm, equals torque.

 

Brings back memories, I used to work for a company that must have had 10 of those 2.5 Iron Dukes with TBI, wrapped in an Astro Van shell. I think they could hit 70 with a tail wind and a long down grade. Pathetic.