[57GMC-347]

Hello,

with a good reference from - the safari - i found my way here

I've just started 347 teardown low compression model 210hp

out of a 1957 GMC 100 survivor. CA truck right out of Oakland

good summer swap meeting - I've got date coded tri-power intake , and the fresh carbs came on a SBC intake tri-power set up to be used

reading some stuff on 347 vs 370 i get a bit confused inter changeable not interchangeable

exhaust manifolds are in bad shape,

main engine platform being the 347 tri-power intake and 347 engine block

is or will the 370 heads work for this build and does the 370 heads have a header exhaust option?

from the looks of the 347 heads - i'd call them odd ball

sorry for the long thread - heads are off and delivered to a shop for inspection

it was a rusty of all rusty - and i'm new at this haha

[steve25]

Here’s some general info.

The oil pump is the same from 55 thru 58.

The flywheel from 55 thru 57 are the same.

55 thru 62 the balancers are the same.

56 thru 60 the heads will swap if the correct intake and exh manifolds are used.

56 thru 60 the valve sizes where the same.

55 thru 60 the rocker arms are the same.

Note that there where two different tri power set up’s used on these motors, and the difference is the center carb used between the auto or manual trans cars.

If your using carbs off a Chevy motor then they are likely not jetted right for the 347 and you stand a good chance of harming a newly rebuilt motor.

Just note that in my opinion if the motor needs a top to bottom rebuild you need to be prepared to spend at least 600 Dollars more then if you needed to do such on a 1965 and newer motor.

[Bill Hanlon]

The rocker arms to rocker arm ball and rocker arm to valve tip interfaces on these heads get their oil through a path that is metered by the #2 cam bearing (passenger's side head) and #4 cam bearing (driver's side head). The oil coming up the pushrods only lubricates the pushrod to rocker arm interface. There are no "spurt holes" in the rocker arms. Make sure that a shop doing head work takes the plugs out of the ends of the heads and cleans the oil gallery well. They also need to confirm that the rocker arm studs oil passages are open.

Now that I've done a "thousand words", here is a picture that explains it.
https://chevy.oldcarmanualproject.co...5559mm435.html

[Bill Hanlon]

GMC Master Parts Book shows the same intake manifold to head gasket for 347 (1957) and 336 (1958-based on Pontiac 370), so I'm betting that any combination of the 57 or 58 intake manifold would bolt to the 57 heads. The Pontiac Master Parts Catalog shows the same part number (534501) for all '57 and '58 engines (except Fuel Injection).

[pfilean]

57 Pontiac tri power should have the same size bore and venture diameter for all three carbs. That changed in 59 when secondary got larger carbs. However, there are Chevy carbs that look about the same as Pontic (still 2gG.2GC) but have smaller bore and venturi than Pontiac. Not saying that Chevy can't be made to work but check it out and see where you are and get proper jetting. Check Dick Boneske and/or PontiacTriPower.

Exhaust manifold for 57 are RH523537 (exc FI) and LH 523539.. Thats in a Pontiac. Maybe GMC used different to get different outlet location. Also, other year Pontiac may bolt to the heads but are different for alternate outlet location.

Your heads will be for the reverse flow gusher cooling. That change I think in 60. The later used a different water pump and cooling routing when that change was made.

I sure like to see the old GMC with Pontiac. Neat find.

[Bill Hanlon]

Originally Posted by pfilean

Exhaust manifold for 57 are RH523537 (exc FI) and LH 523539.. Thats in a Pontiac. Maybe GMC used different to get different outlet location. Also, other year Pontiac may bolt to the heads but are different for alternate outlet location.

'57 GMC V8 used the same part numbers.

[57GMC-347]

let the journey begin - haha - looking forward to it

i've noticed on teardown rod #'s dont correspond to the cylinder not all that important but odd -

[57GMC-347]

good point on the carb front - i will check porting and confirm proper jetting for the 347 - might have a dinner table center piece if it doesnt work haha

[steve25]

I don’t know what your experience is with Pontiacs, but unlike Chevy and some other motors cylinder # 2 is ahead of number 1 with the way the block is cast.

This then means that rod number 2 on the 1 and 2 journal is closest to the front bulk head of the motor.

Does this explain what you noticed?

[694.1]

Welcome!
And thanks for not putting a Chebby in it!.
If we don't have the answer here, nobody does.
Where you located?

[Bill Hanlon]

What transmission is in your truck?

Are you missing the small grille that goes in the hood?

This was my '57.

[Bill Hanlon]

... and when you get past the engine and need to talk truck I'd recommend https://oldgmctrucks.infopop.cc/eve

[Bill Hanlon]

Another thing to tell the people working on the heads is to be VERY careful when removing the cylinder head water tubes. They are fragile and made of UnObtainium.

[Bill Hanlon]

Also, keep track of which tube was in which head.

Some of the tubes were brass (more fragile) and some stainless (not quite so bad).

[Bill Hanlon]

Also, keep track of which tube was in which head.

Some of the tubes were brass (more fragile) and some stainless (not quite so bad).

[57GMC-347]

its has the hydramatic transmission

[57GMC-347]

this is will be my first pontiac - i coded the connecting rods to the cylinder/crank journal location

interesting code - no ryhme or reason - not sure if i will even be using the same connecting rods - definetlly not the same pistons

[57GMC-347]

Originally Posted by Bill Hanlon

What transmission is in your truck?

Are you missing the small grille that goes in the hood?

This was my '57.

i do have a couple of front grilles - one is the black and other is the red

[Bill Hanlon]

Originally Posted by 57GMC-347

its has the hydramatic transmission

So did mine. and I loved it. If it needs work plan on spending a lot of time finding someone competent to work on it and a lot of $$$ getting the work done.

[57GMC-347]

not only is this my first pontiac - to learn

this is my first "BLOG" world figuring how to navigate haha

always with the pedal down... lol