two unrelated questions:

can a 455 Pontiac mount to the TH125C with an adapter plate?

Does the reverse rotation option on the TH325/TH425 resolve the handling problems, or does this setup still handle less well than a stock fiero?

thanks in advance.

Poncho 455 uses a BOP (Buick/Olds/Pontiac) bellhousing pattern, and I've never seen anyone make a plate for it.

The 455's are also incredibly heavy (got one in my '77 T/A), and don't rev that high unless REALLY masaged. They also have enough torque to turn the best tranny into a pretzel (been there, done that twice now!), let alone a lil' 125C.

Stick to an SBC that'll turn 7G's (or a 3800, or, or, or....)

You can mount anything, ct, if you have the right adapter made, but the 455 would fry the 125c the first time you took off. I'd use a 440T if I was gonna go to the trouble and I'd have a manual switch on the TCC so that it wouldn't burn out the clutch the first time you had it at almost full throttle in 3rd or 4th gear. Or have a switch to cut it off at past 1/2 throttle or tie it into the TPS so that it wouldn't come on past 2v at a MAP sensor reading of more than 3v or something to that effect.

Phil

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87 FIERO GT 2.8 5spd
0-60 in 6.8 seconds!

I think if you use the Toronado tranny or the tranny from an early 70's cadillac eldorado they will bolt up with any BOP.... I believe they are both TH425's... and the one from the caddy can handle massive amounts of torque considering its from a car with a 500 cid engine with over 500ft/lbs of torque and i do believe the toronado tranny is about the same thing as the one from the caddy... Cardealer and a few other guys prolly know a lot more about the subject than myself... Look up "A Monster Powered Fiero" in Tech... you might get some info there...

-DRye

The longtitudinal mounted V8s from old Toronados and Eldorados would put the engine almost exactly over the axle centreline. If there is any difference mounting it backwards (which is what I assume you mean when you mentioned reverse rotation) it is probably only minimal. The point is that these were very heavy engines and the weight distribution would be shifted significantly to the rear.

Also, from the standpoint of polar moment of inertia, SBC kits like Archie's are still mid engine cars (the engine is entirely within the wheelbase), the weight distribution is changed but the mass is still within the wheelbase. The early Toronado setup would really make it more of a rear engine car since half of the engines mass would be behind the rear axle centreline.

It would make a great drag racer but on the street it would have typical muscle car handling, in other words stay away from turns. Most of the articles I have seen about people doing this conversion has been to produce a drag racer.

Ira

[This message has been edited by Monza76 (edited 03-08-2003).]

I pulled a toronado engine/tranny out for a guy that needed just the engine and he let me keep the tranny for my labor.
The assembly is huge, the axles exit exactly in the center of the engine block, which puts the bell housing and what looks like a chain drive cover at the very back of the trunk (on the inside). Reversing it would put more weight inside the axles, but the assembly is so long the chain cover would probably be in the passenger compartment just a little.
Don't know what to do with it now, not much drag racing up here. One of those situations where I had to look, now I know.

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I do know that if you want to mount the engine with the pulleys at the back it'll put about a 100lbs or so more in front of the axles instead of behind them... From what I have heard its a ***** to do the reverse mounting... you have to flip the dif on the tranny and machine your own adapter plate... I have also heard that it only works with certain trannys so you'll have to search for the right one... And with those toronado and eldorado trannys you'll prolly want to get them re-geared (especially the eldorado) 'cuz they only have like 3.07 gears in 'em...

-DRye

Held Motorsports had a cradle that place the TH425 ahead of the engine next to the firewall. When using a SBC engine they said most of the power tran was ahead of the rear axle's.

quote Originally posted by watts: Poncho 455 uses a BOP (Buick/Olds/Pontiac) bellhousing pattern, and I've never seen anyone make a plate for it. The 455's are also incredibly heavy (got one in my '77 T/A), and don't rev that high unless REALLY masaged. They also have enough torque to turn the best tranny into a pretzel (been there, done that twice now!), let alone a lil' 125C. Stick to an SBC that'll turn 7G's (or a 3800, or, or, or....)

According to muscle car chronicles A stock 455 HO could rev right into 6k

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1986 Fiero SE
www.2m6performance.tk
Don't hate the player,Hate the game!

quote Originally posted by GTDude: Watts......Buick, Olds, and Pontiac all used 455 engines, but none of them were the same engines........not even close.

I was just stating that they all used a common bellhousing - not that they were the same engine. You can actually toss Caddy (early stuff) into the mess too.

quote Originally posted by bamman: Held Motorsports had a cradle that place the TH425 ahead of the engine next to the firewall. When using a SBC engine they said most of the power tran was ahead of the rear axle's.

Unfortunately, Held Motorsports has discontinued its engine cradles for the TH425.

Discontinued?

You mean they actually made and sold one?

Or did they just run an advertisement that made you think they did?

Just curious.

quote Originally posted by D-Ri2k4: I do know that if you want to mount the engine with the pulleys at the back it'll put about a 100lbs or so more in front of the axles instead of behind them... From what I have heard its a ***** to do the reverse mounting... you have to flip the dif on the tranny and machine your own adapter plate... I have also heard that it only works with certain trannys so you'll have to search for the right one... And with those toronado and eldorado trannys you'll prolly want to get them re-geared (especially the eldorado) 'cuz they only have like 3.07 gears in 'em... -DRye

Yes, it is a b**** to do and it does get most of the engine in front of the rear wheels. Probably 75% of the engine/trans combo is ahead of the front wheels in this arrangement. There is alot more to it than flipping the differential 180 degrees and making an adapter plate though. After the diff is rotataed, nothing, and I mean nothing from the eldo axle setup fits anymore and more adapters are needed. And that is just for starters, next you need some very creative chassis work because the tranny mounts are about 1/2" from the firewall. The bulkhead brace against the firewall is in the way and needs to be cut and pushed back a bit. The crossmember you will need to fabricate fopr the tranny motor mounts wants to be located abouit the same place as the front cradle bolts and this creates more problems. Alss, when you rotate the diff, you actually change the distance between the axle shafts, making them further apart which causes the engine to shift over towards the drivers side of the car by about 2" more off the centerline than if you placed the tranny in the forward direction. A small block Chevy barely fits, I doubt seriously if a Pontiac engine would fit, I think the driver side head would hit the strut tower.
I am working this combo now, it's taking longer than I anticipated and I don't get to work on it that much so I can't say when it will be done but that's what you are up against if you want to try it.

Hugh, on this Forum, used to have a SBC mounted to a 425 transaxle, in his 88 GT.
IIRC, he said it did *not* handle well. I believe he disassembled the whole thing, and replaced it with a 3800, mounted in the "conventional" way.
Hugh has got a great deal of experience. You should see his twin 455 (not a typo) '70 Chevelle.
If anyone could have made the 455 work properly in a Fiero, it probably would have been Hugh.

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Raydar

88 coupe.
Fiero Factory/Grooms 3.4.
Fierotech ECM programming.
19 lb. injectors.
Darrell Morse TB.
Sprint manifolds.
Konig Absolutes.
IRM spoiler.

quote Originally posted by Raydar: Hugh, on this Forum, used to have a SBC mounted to a 425 transaxle, in his 88 GT. IIRC, he said it did *not* handle well. I believe he disassembled the whole thing, and replaced it with a 3800, mounted in the "conventional" way. Hugh has got a great deal of experience. You should see his twin 455 (not a typo) '70 Chevelle. If anyone could have made the 455 work properly in a Fiero, it probably would have been Hugh.

if i can recall correctly, i think hugh purchased the fiero already set-up with the sbc/425. i know he told me that it was not done very well. i think rockcrawl put in the 3800. although i one thing is for sure, hugh is the man!!!!

i wouldnt recommend the 425 tranny for a dailey driver but if your are considering building a v8 fiero with more than 450hp, i wouldnt use anything else other than the 425 tranny. generally most of the comments you get relating to this conversion on this forum are unfounded and coming from people that have no "real" knowledge of doing this type of conversion. if someone is considering this type of conversion, try waiting a few more months. i will be outlining a clean, dependable, streetable version of this swap with a 525hp destroked oldsmobile 455 with a th425 trans. i have figures on weight comparisons on a sbc/4t60 vs. the 455/425 i am doing. it will suprise you! just on a side note, the reveresed rotation isnt really worth doing, there are other ways to deal with the weight issues.
more to come soon!

Hugh's car had other problems that severely affected the handling. For starters, it had original rubber bushings in the rear suspension. And most importantly, the long bolt that holds the two parallel links to the upright was very loose, this is a common problem on the '88s. The rear swaybar had also been removed due to clearance problems, and never reinstalled. I probably could have made the car handle well enough to suit him, but at this point he had already made his decision. The conversion was a mess anyway. Upon disassembly I found that the car originally had a transverse mounted SBC, it had all the telltale signs of a V8 Archie conversion. I suspect the previous owner was having trouble keeping a trans behind it so it got the 425. He has a much nicer car now with the 3800SC.

I really didn't have any problems with the 350/TH325-4L that I built. It was no road racer, but it was no worse handling than the average Camaro or Mustang. I would (and probably will) build another one. It's just different.

bump

just a little more info on the reversed rotation setup-

i found out that the reversed rotation will not work for me in performance conditions. it seems that under very hard acceleration (i.e drag racing) that trans fluid will have a hard time getting pumped out of the converter from sitting backwards in the car. kinda like if you take a hard turn in a fiero with an automatic, they some times tend to slip untill the fluid returns to its normal flow pattern. after months of research a 10 minute chat with my tranny guy confirmed the results.
oh well... back to the standard position for me.

quote Originally posted by cardealer: just a little more info on the reversed rotation setup- i found out that the reversed rotation will not work for me in performance conditions. it seems that under very hard acceleration (i.e drag racing) that trans fluid will have a hard time getting pumped out of the converter from sitting backwards in the car. kinda like if you take a hard turn in a fiero with an automatic, they some times tend to slip untill the fluid returns to its normal flow pattern. after months of research a 10 minute chat with my tranny guy confirmed the results. oh well... back to the standard position for me.

Cardealer, I think that cannot possibly be true. Isnt the fluid in an auto tranny already under pressure? the pump pressurizes the fluid between 60-150 psi on a TH425, i can't imagine the g forces encountered during a launch will offset it that much.

A guy in my former club had a longitudinal installation which used an LT1 with the Toronado 325 tranny. The installation ran perfectly,looked nice and the car was very fast and reliable. However, the down side of this swap seems to be the complete loss of the trunk and LOTS of added weight. This swap requires a specially built cradle, a modified oil pan and much cutting, fabrication and welding.

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87GT 3.4 Turbo Best 0-60 5.2 seconds
http://turbofiero.fierojoe.com/turbo.htm

BUMP

quote Originally posted by GTDude: Watts......Buick, Olds, and Pontiac all used 455 engines, but none of them were the same engines........not even close. Each was as individual as a 454 Chevy engine is. Just thought I'd clear up this misconception. Thanks Phil

One more tid bit of info. Yes, Buick, Olds, and Pontiac all had their own 455 engines, but they ALL used the same bellhousing bolt pattern. Chevy used a different one. So while a Pontiac and Buick 455 are totally different, they'll both bolt up to the same transmission. So you've got 2 basic bolt patterns for RWD GM: Chevy and BOP (Buick/Olds/Pontiac). (I'm not sure, but I think Caddy uses the BOP pattern, too)

quote I'm not sure, but I think Caddy uses the BOP pattern, too

It depends which Caddy you're talking about. They've used Chevy 90*V, 60*V and BOP patterns. All of the Cadillac TH324 and TH425 were BOP.