I'm in the process of rebuilding a '58 371 for my '56.
I need two things, first what is the outside diameter of the bushing to accept the Hydra Matic transmission? The 371 crankshaft needs to be bored for the bushing.
Second, I need the torque on the head bolts for the 371, the 324 is 60 to 70 lb, ft. but I don't have '58 service manual.

Thanks,
Wally

 

1958 Shop manual show cylinder head to block bolts 60-70 Ft. Lbs


Bob

 

Thanks, so it didn't change from the 324..
Wally

 

Here is the bushing you will need;
Pilot Bushing Dorman/AutoGrade 690-014 | eBay
Just take it with you when you take the crank to the machine shop.
Ask them to bore the crank for a "press fit ", and then have them press the bushing in for you.
Make sure they bore it deep enough that you can put a gob of grease behind the bushing.

Also be aware that the 58 engine is "offset balanced ' so you will need to weld a weight on the flywheel and have the engine re-balanced.

 

Thanks Charlie,
I'm going to pick one up tomorrow and send the crankshaft to get it polished and bored for the bushing.

Wally

 

Don't you have the original flywheel off the 371,or did miss something? It should be balanced for the 371, will need to be balanced if used on the 324, or at least the weights removed from the flex plate...Tedd

 

Along with the change in the engine, I am staying with the Hydra Matic transmission. The flywheel is part of that transmission. The 371 has a flex plate that connects to the Jetaway transmission so no flywheel.

 

When Olds upped their engine to 371 in 1957 they didn't have room for the larger counterweights in the crankcase that the longer stroke required.
They resorted to "offset balancing".
That is, balance weights were added to one side of the vibration damper and the flywheel (or flex plate) to make up for the weight they couldn't add to the crankshaft.
To assure that the balance weight would be installed in the correct location in relationship to the crank, one of the six bolts that hold the flywheel (or flex plate) to the crank was offset slightly.

In order to mate a "slant pan" hydra-matic to a 371 or 394 the flywheel must be modified.
Weight must be added to one side of the flywheel in proportion to the additional weight on the 371 flex plate.
In addition, one of the flywheel bolt holes must be elongated so that the bolt hole lines up.
The weight must be clocked correctly in relationship to this offset hole.
The engine must be re-balanced after this.

Do you have the '58 flex plate?

 

Charlie,
Thanks for the information. I have more work to do before I can get this swap ready.
Yes, I have the flex plate for the engine/transmission of this combination.
I'll be looking for someone to balance the engine before assembly.
Thanks again Charlie!
Wally

 

My machinist got the 371 block hot tanked and we've decided to go 0.060 over in order to ensure good cleanup. At 0.060 over that gives me a displacement of 382 cu. in. I've ordered pistons. The heads will be the next thing on the list. Hardened seat for the exhaust valves and I have the rocker arm assemblies already cleaned up and ready to install.
Progress....

 

Is he going to deck the block ? What are piston pin to crown dimensions (compression height) on the pistons you ordered ?

Does your manual list the stock Piston pin to crown dimension (compression height) ? How deep in the block do the pistons sit ?

 

On the advice of my machinist, I'm going 0.060 over on the pistons, The compression height is correct.
No plans to deck the block unless necessary. The compression ratio is already high enough that I'll probably need to run 93 octane.
The heads will get hardened seats for the exhaust valves.
The crankshaft has been sent out to get polished or ground as necessary and machined to accept the bushing for Hydra Matic.
I cleaned up the rocker arm assemblies and they are ready to go back on the heads.
The distributor is disassembled, cleaned and ready to go back together with a Pertronics electronic conversion.
I still need to source a new water pump, machine a phenolic carb spacer, clean and paint the oil pan, and decide what I'm going to do for a cam.
Progress continues...

 

Try Camcraft cams;
Automotive Performance Camshaft Production Manufacturer | Camcraft Cams

Fusick Automotive has water pumps;
Water Pumps-Fusick Automotive Products, Inc.

 

Thanks, I sent them an email to see what they have. I'll post again when they get back to me.

 

Has your machinist cc'd the heads as a reference ? There are people that can rebuild your water pump. I am not sure if anyone locally does it. You're making progress.

 

That thick carburetor spacer is still viable, I bought one a few months ago, I think made by Mr. Gasket. If you do a search for it under 4GC rather than Oldsmobile specific. It will be cheaper than having one built..Tedd

 

Thanks for the reply Tedd but I make my own spacer. I bought 1/2" thick phenolic material and machine it to match both the carb and manifold.

 

Update on the build, took the cam to be ground and the lifters to be rebuilt. This will mean I'll need either adjustable rocker arms or longer pushrods.
The stock pushrods appear to be 9" and a set out a 324 appear to be 9.25".
So does anyone make adjustable rocker arms?
If none are available, there appear to be a few Melling pushrods of various lengths between 9.00" and 9.25" and hopefully one of these will work. Won't know until he finishes the regrind.
Any help on adjustable rocker arms will be appreciated.

 

Some major cam suppliers such as Crane etc. will make pushrods to any length you specify.
Adjustable pushrods are also available.
Adjustable rocker arms have been made in the past, and are sporadically available on the used speed equipment market.

 

I bought a set of 16 adjustable push rods from Smith Bros.in Oregon for my 324, i sent one of my old ones to them and they made it adjustable +.030", so far so good. Definitely more expensive than a standard set but as things wear and get noisy there is some adjustment to quiet things down. Personally, i would rather have the adjustment in the rocker arm but very hard to find those parts.

 

An update on the 371. It is finally in process, bored 0.060 over and in the process of honing. The short block should be ready soon.
New though, bought three cams, an Engle, a Crane, and an Isky. Couldn't pass up the deal for all three. Now all I have to do is identify them and the specs. Found a page on the Engle but if anyone has some old Crane or Isky catalogs any help would be really appreciated!

 

Walt. post the Engle catalog when you have time.

 

Here ya go Ralph