307 - 455 swap

[86Sleeper]

If anyone can help me I would appriciate it. I am getting ready to put a 1972 455 into my 1986 cutlass supreme and I could use some advice from anyone thats done it. Mostly Im concerned with the trans,drive shaft,exhaust, etc....

[J-(Chicago)]

What trans are you going to use? Hopefully not your 200c

[86Sleeper]

I have a 400 trans.

[J-(Chicago)]

If you are using the 9'' tail shaft, you may have to move your crossmember, and if you are upgrading to an 8.5'' rear end you will have to get your driveshaft resized. I am doing a similar project this spring. I believe you can use your 307 motor mounts and it will drop in ok. 455 is an inch wider at the intake, but the motors are almost the same size. I'm not sure about A body headers on a G body, but this swap has been done a thousand times, and I'm sure someone else can clarify for you.
The guys on Realoldspower.com probably do this swap weekly. You'll probably find info on everything over there.

[86Sleeper]

Thanks, If you find out anything elese let me know, and I'll do the same.

[joe_padavano]

Originally Posted by J-(Chicago)

If you are using the 9'' tail shaft, you may have to move your crossmember, and if you are upgrading to an 8.5'' rear end you will have to get your driveshaft resized. I am doing a similar project this spring. I believe you can use your 307 motor mounts and it will drop in ok. 455 is an inch wider at the intake, but the motors are almost the same size. I'm not sure about A body headers on a G body, but this swap has been done a thousand times, and I'm sure someone else can clarify for you.
The guys on Realoldspower.com probably do this swap weekly. You'll probably find info on everything over there.

This is pretty much correct. The 455 has a taller deck height, so the engine is both wider and taller than the 307, but the motor mount locations and bellhousings are the same. The 307 accessory brackets will not fit on the 455. Prior to 1980, most Olds brackets were capable of fitting on both big and small blocks, but the 307 brackets are small block only. Note that the brackets, pulleys, and water pump must be a matched set. Olds used different water pump lengths and the pulleys must match.

Be sure to use the 307 motor mounts and frame mounts. DO NOT buy 455 motor mounts, they won't bolt to your frame mounts. As noted above, a TH400 with the short tailshaft will bolt up to the 200-4R crossmember location. Other TH400 tailshafts will require relocation of the crossmember. You'll need a double hump crossmember anyway if you plan to run duals.

[dar83501]

My current project is dropping a 455 into my '87 Supreme, and pretty much everything they said is correct. Unfortunetly I don't have the cash to get started yet...exhaust and rear end build. According to my research the consensus is that the increased deck height on the 455 doesn't allow the air cleaner to clear your hood, so that's one thing you need to take into consideration. Apparently headers/manifolds are a tight squeeze, and the steering shaft gets in the way sometimes. Additionally, the whole rear end needs to be upgraded.


Hooker makes a set of headers specifically designed for this swap, but they cost just shy of $600. If you can find a used set, go for it, otherwise just buy what you want and beat on them until they fit...that's what i'm gonna do anyway

Hopefully I can start working on mine by FALL...

[J-(Chicago)]

Originally Posted by dar83501

Hopefully I can start working on mine by FALL...

1 piece at a time my friend...... 1 piece at a time.
Start with your suspension and work your way up. Each shiny new piece of the puzzle will make you want to go to work the next day.

[dar83501]

Nah, i've already determined the order I want to do things. I should have a good chunk of money by fall, the first thing I'm going to do is build exhaust and actually drop the motor & transmission. I'm building the exhaust by myself, all I need to do it is the money and a chop saw.

Since the 307 is shot, theoretically i should be able to drive the car around, and hopefully i don't turn my diff into metal shavings and snap the axle....as long as i don't stomp on it.

Then, the rear end job. I'm doing gears, diff, axle, and disc brakes in one job.

miscellaneous things along the way include trying to find beefed up front springs, relocating the shifter to the floor, installing a rev limiter, new gauges, and a hundred other things!

[Redog]

Like everything else that has been say about the swap, use the 307 Cutlass mounts, it will bolt up fine.

Get yourself heavy duty springs for the front. The 455 weighs 150 lbs more than the 307

[88 coupe]

Originally Posted by Redog

........ Get yourself heavy duty springs for the front ........

Wait until you see its "stance" before you waste your money.

Originally Posted by Redog

........ The 455 weighs 150 lbs more than the 307

My information is: The actual difference (excluding intake manifolds) is more like 20 pounds.

Norm

[joe_padavano]

Originally Posted by 88 coupe

Wait until you see its "stance" before you waste your money.

I'll second that. I've done a number of big-block-in-place-of-small-block swaps and never had to swap springs. In fact, I usually end up cutting a coil off the fronts to lower the front end even more. If you want a good indication of how the car will sit after the swap, sit on the front fender and see if the stance is acceptable.

Note to Norm: While your ~20 lb number is probably correct for a 60s vintage BBO and SBO, the thinwall, windowed 307 is probably somewhat lighter. I have bare 455 and windowed 403 blocks in the shop right now. My precision Wal-Mart bathroom scale (built with only the finest Chinese steel and lead paint) says the 403 is 170 lbs and the 455 is 200 lbs. I'm guessing that the 307 is a little lighter still. Factor in the lighter crank, shorter rods, and smaller pistons, and the difference is more than 20 lbs. Having said that, your original point about waiting is correct.

[J-(Chicago)]

Originally Posted by joe_padavano

sit on the front fender and see if the stance is acceptable.

Note: This is not a good idea if you are
obese,
have wet paint,
or have a chain on your wallet or pocket watch.

[Oldsguy]

Originally Posted by joe_padavano

(built with only the finest Chinese steel and lead paint)

Ahhh, as my son would refer to it as "Chinese-ium". The best steel on the market.

[88 coupe]

Originally Posted by joe_padavano

........ 403 is 170 lbs and the 455 is 200 lbs ........

Assuming A/C on the 403, we are looking at a 36 lb difference between it, and the A/C '70 455. Close enough to your 30.

........ I'm guessing that the 307 is a little lighter still ........

Common knowledge.

........ Factor in the lighter crank, shorter rods, and smaller pistons ........

And lighter heads. About twenty pounds lighter, for a total of 56? Lets call it 60 lb. Still a heluvalot closer to 20 than 150, which was my point.

It doesn't, however, excuse my failure to catch the A/C error.

Norm

[joe_padavano]

Originally Posted by 88 coupe

I've seen similar numbers for Olds motors, but I'm curious as to the source of the chart. Some of the items just don't make sense. For example, 69 W-31s and 69 455s don't have aluminum intakes, so are these really 70 numbers or aftermarket intakes? Also, if you believe a big block aluminum intake is worth 35 lbs per the chart, why would a windowed 79 350 with iron intake be 46 lbs more than a 69 350 with aluminum intake? Since the difference in the block weight is in the 25 lb range for an SBO, the aluminum intake on the 69 should make the weights a wash. I guess we don't really know what "dressed" means - full accessories?

[88 coupe]

I though you'd never ask.



Norm

[joe_padavano]

Originally Posted by 88 coupe

I though you'd never ask.

Norm

That wouldn't be the same Mondello who propagated the "offset engine" in the Supreme myth,, would it?

[J-(Chicago)]

Step 2: With your left hand and the biggest effen screwdriver you can find, carefully gouge your connecting rod journals. Making sure to spell your initials in a grafitti-like fashion.

That #9piston is as big as the drag slick.

Drawing not to scale?

[joe_padavano]

Originally Posted by J-(Chicago)

Step 2: With your left hand and the biggest effen screwdriver you can find, carefully gouge your connecting rod journals. Making sure to spell your initials in a grafitti-like fashion.

In fairness to Mondello, the drawing shows someone checking the thrust bearing clearance. Note the dial indicator on the crank flange. Note also that the main caps are NOT in place...

[J-(Chicago)]

Aw dang.....
BUSTED!

I apologize for my mistake all

[88 coupe]

Originally Posted by joe_padavano

That wouldn't be the same Mondello who ........

I don't know that Joe was responsible for it. Would have cost him a lot of sales revenue.

For what it's worth: His '97 catalog showed both Hooker and Thorley headers with the notation "will not fit convertibles".

Norm

[Chaney3000]

I am looking to do the same thing with my 86 Cutlass. I want to swap the 307 for a 455.

[rccktmn2]

I've got a 455 in an 87 supreme. I used the hooker super comp headers and fab'd my own frame mounts for the engine and the air cleaner does clear the hood with a torquer intake. I also put in an aftermarket double hump crossmember so I could run true duals. You can bolt in a chevy 12 bolt, easier to find and with the right aftermarket control arms they work very well. I also have moroso trick front springs and the stance is about 1/2 below stock. The only downfall with the hooker headers is that you won't be able to turn the wheels from lock to lock without rubbing, I went to the 3 1/2 weld pro stars but I think you can go to a 5 or 6 inch wide wheel and tire and it won't rub. With the stock 307 springs you should be ok with the ride heighth. let me know if you need any help.