New to the forum. A friend has a 71 442 with a 350 and he wants me to put in a 455 for him. Never done one of these before I usually do Chevy and Fords so any in put from you guys would be really helpful, like tranny bolt up, exhaust, pan clearance etc. Thanks Mike

 

A 71 442 did not come with a 350 from the factory. It was possible in 72 but all 71 442's came with the 455. I haven't done one but it is an easy swap since the engines are so similar. Use the search function and you will find lost of threads on here relating to this swap. Be sure and read about which motor mounts to use. Determine if he has a turbo 350 or 400. The 455 will bolt up to the 350 but with hard driving the 350 may not last.

 

This is a very easy and straight forward swap. Motor mounts from 350 work but suggest using new ones. they are cheap and you are there. Trans bolts up fine. Exhaust is a little different but can be made to work. All the engine brackets will work but the belts will need to be longer. the hoses all work. all the sensors and hook ups are the same. Very easy and very beneficial swap.

 

The belts don't need to be longer if you use the ones from the 455.

Everything should bolt up fine.
You'll need an appropriately sized radiator and the fan and clutch from the 455.
Exhaust bolts up in essentially the same place, and if he's already got an aftermarket system, should be big enough (a stock 350 single exhaust, less so).
You'll need (or at least want) a pair of notched valve covers, to make access to items around the engine, and valve cover removal, a bit easier.

The 455 and the 350 are essentially the same engine with different deck heights and main bearing sizes.

- Eric

 

it's a 72 442 not a 71. will that make any difference?

 

Nope.

- Eric

 

Will a 455 hook up to a stock duel exhaust from a 350? The 455 I have has a 400trans. Will it take the existing drive shaft?

 

The exhaust should work using the small block manifolds. There is a small difference in deck height to deal with though.

The drive shaft would have to be shortened. Big cars use the long tail shaft trans. Or just use the trans you have.

If you are swapping a 350cid/th350 to a 455cid/th400, you'll have to shorten the drive shaft.

If you do the 455cid/th350 swap you don't have to shorten the drive shaft.

Remember,the big cars used a long tail trans. The equal short shaft 400 used in abodys is shorter, but still longer by 3/4" than a th350.

And please, use the small block engine mounts on your block, not the big block ones.

If this isn't clear as mud keep asking questions.

 

Thanks for the reply. Got some ahead of me

 

TH400 and TH350 use different output yokes, as well as needing different driveshaft lengths and different emergency brake cables.

- Eric

 

Which will cause the 350 pipes to hit the underside of the floor.

More to the point, why go through all the trouble to swap to a larger motor then restrict it with crappy 350 exhaust manifolds?

 

On the other hand, allowing for manufacturing variations among different exhaust pipe benders, if you mean will the exhaust PIPES bolt up to the big block manifolds, yes, they should, but possibly with a bit of "persuasion."

- Eric

 

"And please, use the small block engine mounts on your block, not the big block ones."

NOT TRUE -- its only mixing years of the mounts that causes trouble. but if
have them, use the same ones that were on the motor you are removing -- you cant go wrong.

 

Im in the middle of a 350 to 455 swap. I checked the other day my dual exhaust pipes that bolted to the 350 thru manifolds, will work w the WZ BBO manifolds w only slight adjustments.

I used the stock 350 motor mounts on the 455.

 

If going from a Turbo 350 to a 400 you'll need to switch from a kick down cable to a switch mounted on the gas pedal. Wiring should already be there.

 

You also need to either swap to a non-TH350 gas pedal or cut off the tab that the TH350 kickdown cable attaches to. This tab hits the TH400 switch otherwise.

 

Thanks. It's the small stuff like that will make me question my sanity

 

You are fine with a turbo 350 tranny!

 

Hey guys. I'm beginning this swap myself and after reading this thread i'm thoroughly confused in regards to the mounts. I am installing a 455 and keeping my th350 trans. My plan was to replace the frame mounts with 455 mounts and use the 455 motor mounts as well. Is this incorrect if I'm keeping the th350 trans? Will the 350 mounts affect the deck height? I am ruining full factory OAI.

 

Welcome. Read this thread.

 

Thanks Joe. If either combination puts you in the same location, why did the factory use two different setups rather than standardized big and small block cars?

 

The factory DID use the same mounts for BBO and SBO for model years 1965-1968 and 1973-up. In addition, the full size cars ALWAYS used the same mounts for BBO and SBO. The issue on the A-body cars came about due to a major recall for broken motor mounts on GM cars in the mid-1960s. Originally, the factory mounts were simply two metal brackets with rubber molded between them. Once the rubber deteriorated and cracked, the mounts would separate, usually on the driver's side. The solid rod throttle controls of that vintage would jam at wide open throttle when this happened.

Olds came up with redesigned mounts that had an interlocking feature imbedded in the rubber such that even if the rubber failed, the two metal parts could not separate. The first design for this was fairly large, and Olds prioritized the insertion of these mounts on the big block A-body cars - since these were most likely to be driven, ah, "aggressively".

The first design for this interlock resulted in a physically larger mount, which required a matching frame mount to fit in the same space. These were used first on BBO A-body cars in the 1969 model year, then with all engines in the redesigned full size cars in the 1971 model year, and finally with all engines in the A-body cars with the redesigned 1973 cars. This larger mount is the commonly available 2328 mount.

The smaller mount has also now been designed to have the interlock feature and retrofits into those applications. This is the 2261 mount.

 

Wow. Mind blown. Thanks!!!!

 

This is why I don't call them "big block" or "small block" mounts.

Be aware that there is a LOT of bad info out there on Olds motor mounts, and nearly every vendor has the listings wrong. Most show the 2328 mount as 1968-72, when they are 69-72, for example. RockAuto doesn't even show motor mounts available for the A-body cars, but sells 2261s if you search by part number instead of application.

 

JOE -- I have found that to be true about a lot of parts at Rock Auto -- they will appear in a part number search but dont appear in the vehicle catalog listing. I found heavy-duty un-drilled U-joints that way just last week. I also found several Dorman parts that way too. Saved some bux in the process!! It "pays to shop around"!!