Besides the lack of a kit for swapping a Pontiac V8 into a Fiero, why aren't there any transversely mounted Pontiac V8's? The only swaps I have seen are longitudinal in both normal and reverse rotation. Is the problem that the dimensions of the Pontiac block are such that the engine bay lacks adequate space?

I have a Pontiac 400 block that I'd like to use but I want to retain the manual transmission(as much as I enjoy the longitudinal/reverse rotation idea).

One last question, has anyone measured the weight difference between a Chevy and Pontiac V8?

Thanks!
Larry S.

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The Pontiac block is much larger and heavier than a Small Block Chevy. That's why. I may be possible, but not adviseable.

The Pontiac V8 is a pig. It would be cheaper to build a small block Chevy. Poncho V8 parts are available, but they aren't cheap. You can build all the power you need with a SBC. Put that 400 in an early Trans Am or GTO.

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1986 SE 350 V8

The 400 would lunch transverse transaxles left and right too. That's a big reason for the TH425.

GL

455 Poncho in a Fiero

Rob

Trunk? We don't need no stinkin' trunk!

Yes, I've seen that. Guess what? NOT TRANSVERSE.

Larry S.

You're up against two problems: the length of the crank vs. available space, and tranny strength. If you can whip those, you've got it.

GL

[This message has been edited by Tugboat (edited 03-18-2004).]

Your going to need a hell of a welding gun and some extra scrap metal

Does anyone have the numbers showing the differences in dimension between the SBC and Pontiac? How about weight?

I've never built a V8 before but here are some ideas to address the excessive torque generated by the Pontiac V8.

* Use a lightweight crank
* Use a light weight flywheel
* Build a highly free-flowing exhaust

My hope is that if I can keep the tq. between 300 - 400 ft. lbs. that I won't be trashing manual trannys as often. Now I know that there are SBC's out there running with this amount of tq. reliably. For example, the ZZ4 crate engine(400 ft. lbs. tq.) which is so popular.

I want to reduce torque and increase hp. and revability. I know that Pontiac V8 are relatively low rev'ing, but I think that I'll be happy rev'ing to 6500 rpm. I'd like at least 400 rwhp. My thought is that I will be able to accomplish this by going with a full roller conversion and increasing the compression ration to 9.5:1. Stock CR is anywhere between 7.7:1 to 8.2:1).

To further reduce the weight of the engine, in addition to the lightweight components described above, I plan on installing aluminum heads and intake manifold.

No, it's not going to be the most cost effective way to increase my cars performance. And I haven't spoken with any engine builders yet to verify the feasibility of my ideas. Admittedly, I'm usually way off!. But, this is a long term project and I just like the idea of having a Pontiac V8 in my car. 'Nuff said.

Thanks all,
Larry S.

[This message has been edited by swanthog (edited 03-18-2004).]

According to this site, the SBC is 26" wide x 28" tall x 27" long and weighs 575 lbs.

The Pontiac 400 is 25-1/2" wide x 32" tall x 30" long and weighs 640 lbs.

While you can lower the weight of the Poncho with aluminum heads and such, you can do the same to the SBC and make it even lighter. What you have to also consider is the aftermarket for the Pontiac V8 is MUCH smaller than for the SBC, so parts will be very expensive and hard to find. You could build an all aluminum SBC with as much HP as the Pontiac for thousands of dollars less. The Pontiac will be able to produce more torque, but you can break any transaxle out there with the SBC, so the extra torque doesn't help you at all.

You will also have to work out all of the oil filter and starter issues. Those have already been figured out on the SBC swap.

quote Originally posted by swanthog: Does anyone have the numbers showing the differences in dimension between the SBC and Pontiac? How about weight? I've never built a V8 before but here are some ideas to address the excessive torque generated by the Pontiac V8. * Use a lightweight crank * Use a light weight flywheel * Build a highly free-flowing exhaust My hope is that if I can keep the tq. between 300 - 400 ft. lbs. that I won't be trashing manual trannys as often. Now I know that there are SBC's out there running with this amount of tq. reliably. For example, the ZZ4 crate engine(400 ft. lbs. tq.) which is so popular. I want to reduce torque and increase hp. and revability. I know that Pontiac V8 are relatively low rev'ing, but I think that I'll be happy rev'ing to 6500 rpm. I'd like at least 400 rwhp. My thought is that I will be able to accomplish this by going with a full roller conversion and increasing the compression ration to 9.5:1. Stock CR is anywhere between 7.7:1 to 8.2:1). To further reduce the weight of the engine, in addition to the lightweight components described above, I plan on installing aluminum heads and intake manifold. No, it's not going to be the most cost effective way to increase my cars performance. And I haven't spoken with any engine builders yet to verify the feasibility of my ideas. Admittedly, I'm usually way off!. But, this is a long term project and I just like the idea of having a Pontiac V8 in my car. 'Nuff said. Thanks all, Larry S.

Lightweight parts don't reduce torque, they only help acceleration ability. Less torque is used accelerating heavy parts, more to the wheels. You'd have to use a radical camshaft to limit torque.

GL

Theres a lot of cars I'd put a 400-455 in, the Fiero isnt one of them

Its just not practical for the application. It weighs way too much and makes way more torque than is good for it. All pontiac engines are torque monsters, they make torque down low then fall on their faces at high RPMs. They're really not meant to be revved high. A 5500 RPM redline is what you'll be seeing with stock rods, 6000 will reduce the life of the engine a good amount, 6500 you'll find pistons in the oil pan pretty quickly. Getting aftermaket H or I beam rods will bring it up a little but then you have to worry about the valve train and head flow. If you want a high revving engine a SBC is much more suited. A 327 will rev to the moon and keep its low end torque in a managable range (I'd hate to try to launch a Fiero with 500+ ft-lbs of torque)!

As for size, a Pontiac engine is a lot bigger than a SBC, and a bit smaller than a BBC. When I was rebuilding my 455 I had it on an engine stand, and my friends SBC for his circle track car was on another stand near it, the Poncho made the SBC look like a toy engine.

You're going to have a REALLY hard time keeping a P400 in the 300-400 ft-lbs range. Even the late 70s engines that were rated at 170-200 HP still made over 350 ft-lbs of torque. As was stated before, a lightweight crank and flywheel wont reduce your torque at all, a free-flowing exhaust will SLIGHTLY but only if you tune it to do so. If you use aluminum heads such as the KRE Dports or Edelbrock heads you'll be saving a good amount of weight, but your power output will go through the roof.

Like Tugboat said, a HUGE cam will be the only way to get the low end torque down, but then you'll move all the power up into the high RPM band (6000+) where you cant use it.

EDIT: Also something to think about is part availibility. You can find SO many more parts for a SBC/BBC than a pontiac. Look though a summit cataloge and everything in it is for a SBC/BBC, hardly anything is listed for a pontiac. Now there are some GREAT part suppliers (PAW engine parts) but its nothing compared to whats available for chevys. If you want cheap HP, go for a chevy, just dont put it in a firebird!

[This message has been edited by PontiacMan (edited 03-18-2004).]

Okay, I can see that I was confused a little about what torque is. I was misinterpreting the "rotating mass" idea. So, it seems that I'd want a heavier flywheel and crankshaft in order to reduce torque being output. Here's a decent article:

http://www.circletrack.com/techarticles/84199/

Larry S.

[This message has been edited by swanthog (edited 03-18-2004).]

You're not going to find many cranks for a pontiac heavier than a one out of a 400 or 455.

Those puppies weigh a LOT!

I don't think it would be advisable to add weight to the bottom end to reduce torque. a better way would be to reduce the piston diameter and change the rod length to stroke ratio. But to do this you might as well go SBC because it won't be a 400 anymore.

quote Originally posted by PontiacMan: You're not going to find many cranks for a pontiac heavier than a one out of a 400 or 455. Those puppies weigh a LOT!

No kidding! I tore down my 400 over the weekend and held a 400 crank in my hands for the first time. The thing is monsterous!

I agree that adding weight to the crank is a bad idea. Especially where main bearings are concerned. I'm just searching for ways to reduce torque without de-stroking. I don't know enough about engine building yet to answer this question....just throwing out random ideas.

Larry S.

Hehe, yah they're huge hah? You should see a 455 crank, even bigger!

You dont have many options with destrokeing a 400 because you're stuck with the 3.75" stroke. Both the 350 and 400 used the same crank with a different bore size. Then the 428 used a 4" stroke and 455 used a 4.21" stroke and both had 3.25" mains.

I admit a 400 in a Fiero would be REALLY cool, but the practicality is limited. Im sure the weight would effect your handeling a good amount.

If you're really serious about doing the swap though, I'll be happy to help you with the build up of the engine, I've helped out friends on a couple poncho rebuilds and just recently finished my own engine for my firebird myself.

I feel your pain, man. I too wanted to put a Pontiac engien into a Fiero. But, alas, it was not meant to be.
I am under the assumption that you are going with the 400 because you already have one??
If that is the case then you are better off going with a SBC swap, because even after you get
the engine, build it up, and install it, you're still gonna be getting out of it cheaper than the
pontiac will let you. Plus, you can get a 4 bolt main block Chevy and it will hold up better to the revs.
Just one fellow Pontiac lover to another.

I say go with the Pontiac power.
I don't think you can squeeze one in transverse, but longitudinal well......

Yesterday I purchased a recently rebuilt 428 from a friends wrecked Firebird. This will be going in an 87 notchie, mounted long.
I will start putting it in as soon as I get my wifes 3.4 TDC installed (hopefully next weekend) and replace the 4.9 in my Fiero with a new 4.9 I am building with a custom cam and head work along with an Allante intake.

The 428 will not handle like my car which I AutoX, but at the drags and Saturday night downtown, it will shine. It will also have the WOW factor (just scroll back up the the picture near the top) which I like. I am considering topping it off with a Tri-power intake, even though the modern carbs are probably easier to set and maintain.

It is cheaper to build a SBC, but you still have a Chevy powerplant in a Pontiac.

Gene

Maybe convert the tri power intake to FI, use the carbs for TBs.

GL

I did that once with a tunnel ram and a pair of 600 holleys. I even ran fake fuel lines to the carbs just for looks.
I may just build a Megasquirt and do that.

Gene

You want to decrease torque, increase revability to about 6500rpm, but don't want to go with a small block Chevy?
Well, there's a few problems there.
Pontiacs don't rev well. I love Pontiacs. I'm a die-hard Pontiac man, but 6500rpm would be considered a VERY high redline for a non-race Pontiac engine. To make that useful, you'd need a lot of custom parts, like forged rods, pistons, not to mention Edelbrock Aluminum heads to hope to get any power at that rpm.
Pontiacs are heavy (compared to a SBC).
Pontiacs are low rpm torque engine. Even the 455 H.O. in my '72 Trans Am redlined at about 5500rpm, IIRC. I think the Ram Air IV redlined at under 6000rpm, too.

Your plan keeps everything bad about a Pontiac and gets rid of everything good about them.
Can you do it? Hey, you can do anything you want with enough time, money, and expertise. I'm just trying to warn you that you're really banging your head against a wall doing it this way. I grew up abhoring Chevy. But if I were going to put a V8 in a Fiero, it would be a SBC. (4.9 and N* are other good choices).

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[This message has been edited by Formula88 (edited 03-18-2004).]

One thing about the Pontiac engines is that they are torque monsters for sure and you can get incredible HP from them, but as big a fan as I am of the 389, 421, 428, 455, they are ancient technology. There are many other ways to HP and torque now thru recent technology and fuel injected, blown or turbocharged engines that I just couldn't see the cost of putting one of these beasts in a Fiero. I toyed with the idea, but as cool as it may be, your money is better spent putting a late model engine of your choice........LOL.

Phil

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87 FIERO GT 2.8 5spd

GM auto tech for 27 years. Specializing in electrical and computer problems. Now on workers comp. and it looks like I will be unable to return to work as a tech.

quote Originally posted by swanthog: No, it's not going to be the most cost effective way to increase my cars performance. And I haven't spoken with any engine builders yet to verify the feasibility of my ideas. Admittedly, I'm usually way off!. But, this is a long term project and I just like the idea of having a Pontiac V8 in my car. 'Nuff said. Thanks all, Larry S.

I originally made the above quote in order to snub non-technical discussions about the folly of my idea such as, "don't use that engine". I guess what it boils down to is I like the "cool" factor of this idea. And now, more to the point....

I plan on buying an Archie Centerforce clutch and stock Pontiac V8 flywheel as a starting point. I am thinking of cutting a section out of one of my old transmission's bell housing so that I can see and measure to ensure that clutch engagement/disengagement will work properly. From there, I can determine how thick my transmission to engine adapter should be. I need to make sure that the throwout bearing isn't riding on the pressure plate when in it's resting position. I also need to make sure that it's position relavtive to the pressure plate is such that the Fiero's measely 1 3/4"(?) throw is enough to disengage the clutch.

Does anyone know if a SBC clutch will bolt to a Pontiac V8 flywheel?

Thanks,
Larry S.

Archie's plate should work, except you will only be able to use 4 of the 6 bolts to fasten it to the block. The top and bottom 2 holes are the same on BOP and SBC. It's the middle 2 that are different, and you could easily modify the plate to pick those up as well.

As far as the clutch goes, you will have to either find or make a 12.75" dia flywheel that will bolt to the Pontiac motor and then drill it to accept the stock Fiero 9-1/8" clutch. Use the SPEC Stage III clutch. It is good to 450 ft/lbs. I have that clutch in my V8. It will hold .

The starter and oil filter bypass are the next issues, as well as mounting and exhaust.

After you mount the adapter plate to the block and install the flywheel you should have 7/8" from the friction surface of the flywheel to the transaxle mating surface of the adapter plate. Since All of the old GM V8's share the same dimensions back there, you should have no trouble. Back in my hot rodding past, it was very common practice to use BOP trannys on Chevy engines (and vice-versa) because we were poor and the junkyards were littered with low mileage "mom and pop" type Buicks and Oldsmobiles.

Hope you find this information useful.

Yes, I find your suggestions extremely usefull. Now I'm getting excited. The engine->transaxle adapter will be easier than originally anticipated. Thanks!

I was planning on installing a high torque mini starter. Other than Archie's adapter, I can't visualize what it is that the starter will be interfereing with. Can you shed some light on this? For those who don't know, the starter is on the opposite side compared to the SBC. As for Archies's adapter, I wonder if I can flip it 180 degrees on it's horizontal axis? What do you think?

Thanks!
Larry S.

quote Originally posted by tesmith66: Archie's plate should work, except you will only be able to use 4 of the 6 bolts to fasten it to the block. The top and bottom 2 holes are the same on BOP and SBC. It's the middle 2 that are different, and you could easily modify the plate to pick those up as well. As far as the clutch goes, you will have to either find or make a 12.75" dia flywheel that will bolt to the Pontiac motor and then drill it to accept the stock Fiero 9-1/8" clutch. Use the SPEC Stage III clutch. It is good to 450 ft/lbs. I have that clutch in my V8. It will hold .

Will a 12.75" diameter flywheel fit in the bellhousing of a Fiero transmission? I don't think so.
You might have a better starting point by getting Archie's adapter plate and re-drilling it as needed. If the plate is totally unuseable, I'm sure you could sell it (if you haven't drilled it yet). Then you might consider Archie's flywheel, since it takes into consideration the thickness of the adapter plate and redrill it to fit the Pontiac (if that's possible - I don't know).

Here's the main thing to consider. The Pontiac V8 is 3" longer than the Chevy V8. You will have to move the transmission to the left, and notch the frame rails on the driver's side. You may still have to notch the passenger side as well, and even then it might not fit. That needs to be evaluated first.

Yes....it may be wise to start with Archie's flywheel as well. I'll check it out.

Oh, no! The dreaded notching of the frames rails! That has always disturbed me. I'm going to find a free Fiero junker to test engine position. I have a couple of places to check.

The Pontiac starter is on the driver's side of the engine if observed from the front of the engine mounted in the donor vehicle. The SBC starter is on the passenger's side of the engine. When installed in a Fiero, the SBC starter is on the axle side, not the Pontiac's.

What else?

Larry S.

The 153 tooth flywheel is 12.75" in dia. I have one on my V8 Fiero right now. I did not use Archie's kit- I made my own starting with an adapter plate and mounts from a now-defunct V8 Fiero business. I found out later the plate is an exact copy of Archie's. The Chevy 153 tooth flywheel fit like a glove and gave me the correct depth into the bell housing- the magic 7/8". I know what I am talking about because I have done this swap. The car runs and drives just fine. I have pictures am willing to answer any questions you may have.

Notching the frame rails:

*** A little background here *** I have been building cars for aver 20 years. I have also been a mechanical design engineer for over 15 of those years. I have put a lot of thought into this swap and have relied heavily on my knowledge and experience to work through the problems inherent with such an endeavor. I am providing this information in order to inspire, assist or otherwise inform the Fiero community.

There has been A LOT of passion and fear about this. Don't sweat it. Whatever you remove from the "frame" in the inside, you can weld back on to the outside. I notched mine a bunch, then welded in 1/2" square tubing to reinforce it. No problems at all. As a matter of fact, Chester notched his, Archie has notched a few, California Kid's car is notched (Zumalt kit), etc. It doesn't hurt a thing- as long as you put some material back.

You won't be able to rotate the adapter plate, but you can simply cut it off in order to mount the starter. You may have to modify the engine cradle to clear the starter. I am assuming the oil filter is on the opposite side? You may be able to simply bolt a bypass up and run the lines away from the axle.

[This message has been edited by tesmith66 (edited 03-19-2004).]

I'll tell you, it feels good to be backed by a veteran mechanical design engineer. Cool.

I was just looking at Archie's V8 installation illustrations. He moves the starter to the opposite side on the SBC so that it won't interfere with the axles. This is where the Pontiac starter resides in stock form. Very interesting....

Larry S.

Thanks! I love stuff like this, and I'm having a good time digging this information up.

This site has oil filter bypass adapters, electric water pumps and high torque starters for Pontiac V8's

It appears that the oil filter adapter is situated on the right side of the block, so that will clear the axle. The availability of an electric water pump makes things easier.

****** The following bellhousing information has been revised due to the discovery of an error on my part. Thanks, Tugboat for pointing that out. ******

The above pictures show a "corporate" bellhousing (Chevy and BOP) and a Chevy only bellhousing. You can see that the 2 bottom holes and the dowel pin holes are the same, but material will need to be added to the top of Archie's plate to pick up the top 2 holes, and the middle 2 can probably be drilled and tapped into the plate.

I'm having a bit of trouble finding good flywheel info. You will need one 12.75" dia or smaller to avoid having to machine the adapter plate. You may be able to have a Chevy flywheel re drilled. I don't have a Pontiac V8 at my disposal or I would take some measurements. You can got to a parts store and have them pull a flywheel for a 1985 305 Camaro (that's what I used) and a few Pontiac V8 flywheels (maybe 1975 Firebird with a V8) and compare. I do not know if the Poncho 400 is internally or externally balanced. That is important. The 85 and older (2 piece rear main) SBC are internally balanced (except the 400), so the flywheel is neutrally balanced.

The above pictures are from this page.

[This message has been edited by tesmith66 (edited 03-20-2004).]

(edited - no longer applies)

Glad to help. Kinda looked like a dead end road, no point in letting you go all the way down it.

BTW, if the oil filter mount or the filter itself is in the way of the tri-pot or axle, you can get a remote adapter plate from Trans Dapt. I might even have one kicking around.

GL

[This message has been edited by Tugboat (edited 03-20-2004).]

Thanks, Tugboat, for pointing that out. I have edited the post to show the correct information.

I have a GM Oil filter relocation kit. Will that work with the Pontiac? It's just the standard kit. I originally ordered it for my 3800 conversion from summit racing. Either way, I'll unbury it and try it out.

What I'm talking about replaces the elbow that bolts to the block and holds the filter. It's a cast plate with two bosses tapped for hoses. You would probably want to use some elbows for better clearance.

GL

Last weekend I picked up the car that will be donating its rear cradle, engine bay, and frame rails. It's in really poor shape but it only cost $50 and has everything I need to test fit the Pontiac 400. I arrived with a borrowed car trailer to pick the donor up on a Friday evening after work. The car had only one wheel leaving 3 of the cornerns sitting in the dirt. I brought 3 of my wheels and some spare lug nuts. I thought I would roll the Fiero up onto the trailer. Wrong. Two of the wheels were seized.

It was raining hard and getting late. Muddy and rain soaked, we decided to lift the poor Fiero with a backhoe. The front and rear glass were already busted out so we ran a chain through the openings where the glass once resided and lifted the entire car by its roof. I then rolled the car trailer under the car. I really hated doing this but like I said the car was really rough to begin with.

How about some pics?

The car that will be receiving the swap is the one seen in my signature. It's an '86 GT with a 5-speed.

Larry S.

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Here are some "before" photos of the Pontiac 400 engine:

Only 2 bolt mains...sigh.

6X heads. These will not find their way onto the rebuilt engine. They are HEAVY and LOW flowing.

Flex plate. Judging by the lack of symmetry in the flex plate, I'd say this engine is externally balanced.

Notice how jagged the interior of the block is between the cylinder banks. I will have it deburred and lightened.

The crank. Monstrous indeed. The engine had a spun rod bearing that gouged the crank. Needless to say, it won't be re-used.

First step is to get the block hot tanked and sonic tested. This will be done in the next week or two. Next, it will be hot honed. Who says Pontiac blocks are heavy?

Cheers!
Larry S.