Buying Short Block

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1973_Scamp

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Hello Folks
I'll be buying this 318 short block. The seller said it's a 1985
He stated "This was a new factory warranty replacement but never installed by owner"
- What should I inspect for?

This plan is just a daily driver for 1973 Plymouth Scamp with A/C, P/S, 904 transmission, and 7.25 rear. I already have the following:
- Camshaft XE268H
- Seat harden ported 302 Engine heads. 1.88 x 1.60 Stainless valves 67-70 CC open chamber design. .509" lift springs (purchase from Aerohead)
- Gasket match 2167 Edelbrock Performance
- Edelbrock 1406 Carburetor
- 273 Adjustable Rocker and push rod
- ProComp distributor with PC-91 ignition coil.
- Hedman “block Hunger” exhaust 78506
- JEGS Performance Products 30500 Header-Back Dual 2-1/2" Exhaust Kit

Any advice would be greatly appreciated, since this will be my first attempt:

Thanks
Scamp
 

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I'd do some math on what CR you are going to have with those heads on a 1985 engine out of the 8:1 smog era... not that you need to have a 11:1 screamer, but if those are truly 70cc chamber heads you may be pretty low. 62cc would probably yield much better. I will admit i have no clue how far in the hole, or what the dish on a oem 1985 318 piston would be. but i can't imagine it's going to yield much for CR.

don't forget those are internal balance, and have a unique balancer, and oil pan that does not interchange with a 360.

as far as inspection. make sure it turns over, no rust in the cylinder walls.

and lastly...i bought a fresh rebuild, running, carb to pan 318 that was fairly moderate for $750 a few years back. I hope you're getting this 1985 short block for a song...
 
I am getting just 7.9:1 static CR with 71 cc heads and a thinner than average head gasket and pistons .08" down in the hole, which may be on the optimistic side. If it is truly a new, unused short block, and is cheap, then I would buy it but put in new pistons to bring the SCR up to in the low-mid 9 range.

Did you mean Edelbrock 2176 intake? The 1406 carb is a square bore and the 2176 manifold is a spreadbore. Otherwise, the parts seem to be a reasonable street setup. Can't find info on the valve springs to see if they are rated properly for that cam and to see if they clear the 273 rockers well.

Inspect the lifter bores for excess rust.
 
nm9stheham said:
I am getting just 7.9:1 static CR with 71 cc heads and a thinner than average head gasket and pistons .08" down in the hole, which may be on the optimistic side. If it is truly a new, unused short block, and is cheap, then I would buy it but put in new pistons to bring the SCR up to in the low-mid 9 range.

Did you mean Edelbrock 2176 intake? The 1406 carb is a square bore and the 2176 manifold is a spreadbore. Otherwise, the parts seem to be a reasonable street setup. Can't find info on the valve springs to see if they are rated properly for that cam and to see if they clear the 273 rockers well.

Inspect the lifter bores for excess rust.
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My CR numbers were pretty similar to yours for what i figured he has. So a moderate cam, no compression, and an incorrect carb flange...we're not looking too hot.lol

Scamp, you either need to rethink the purchase of that shortblock, put pistons in it, or go find a better suited used engine to start with. I can't imagine what price you'd have to get on that short block to make putting pistons in it worth it.

the ONE benefit to this short block is the roller cam...and you're putting a flat tappet in it.

my 2 cents.
 
Honestly - it sounds great. No concerns with the compression ratio. it might have a little lope to it, that's all. I'd pull one rod cap and look at the bearings and inspect the lifter bores for any rust. Any rust in there MUST be removed before you use it - and don't use scotchbrite to do it. use emery paper if needed. Rotate the shortblock to make sure the rings are not rusted in place. Give the rings a good few squits of transmission oil, then put it togeher with your parts. Degree the cam. Make sure to preoil it with a priming shaft not the starter, and rotate the engine by hand while you do so. Verify the oil gets up top, and then go through the cam break in process. Looks like a nice driver package overall. You'll basically have a 340 under the hood.
 
krazykuda said:
A 72 c head with a 10.5 compression 318 piston will end up at 9.2.

Get it and put a set of 10.5 318 pistons in it...


There are plenty of reasonably priced piston assy's for the 3.91" bore...
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Need to look at the compression height carefully or he'll be right back where he started...!!
 
nm9stheham said:
Curious as to the reasoning......??
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Double that question....7.9 compression and too big of a cam on a smog piston short block? ...also never realised low compression yielded "lope" ... this thing would need two turbo's on it to warrant that low of compression. someone needs a lesson in quench, static CR, and valve shrouding....
 
nm9stheham said:
Need to look at the compression height carefully or he'll be right back where he started...!!
Click to expand...

I ran that "recipie" on a 72 318 that my brother gave me with 10.5 forged pistons...

With 318 heads my compression was too high and I was getting detonation.

Installed a set of 77 360 heads and it was fine with pump gas.... No milling needed...
 
The 268 cam is too large for a 318 of this nature, IMO. I honestly don't know why it's everybody's "go to" cam. It's mediocre at best.
 
krazykuda said:
I ran that "recipie" on a 72 318 that my brother gave me with 10.5 forged pistons...

With 318 heads my compression was too high and I was getting detonation.

Installed a set of 77 360 heads and it was fine with pump gas.... No milling needed...
Click to expand...

Would not be surprised. Fortunately, no one is advising the OP to go to 10.5 CR, just move from 7.9 up to the low 9 range to get better low end torque. For daily driving, good torque makes for a good response. The OP is going to need all he can get with the 268 cam, as that is going to degrade the already low CR to an even lower one and that will be felt as 'bogginess' at low RPM's.
 
RustyRatRod said:
The 268 cam is too large for a 318 of this nature, IMO. I honestly don't know why it's everybody's "go to" cam. It's mediocre at best.
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Agree! I would at least go one size smaller, I wouldn't want anything more than about 218 at .050 for the intake duration
 
IMO, I don't think the combo to bad. The 302 heads are for certain a closed chambered head. While I think they can certainly benefit from a set of larger valves and porting. The overall comp ratio should be OK with a .028 thick gasket.

Reading the chamber cc of the OP's head, and the possible depth of the cylinders, perhaps milling the head before installation (?) as an easy fix for the combo. A set of Rhoades lifters could also be a soulution.

The slugs deck height is a unknown. And a problem to this mathematical equation.

I also like to yield @ [email protected] for a low compression 318.
 
Thanks for all ideas and feedback.
Sorry for upside down pictures
I Picked up the block today for (4.25 bills)
It's a standard bore
Block number 4323330318-2 Date code 84
Crank number 4751841 (cast or steel) - Could it be 340 Crank?

Inspected
-No rust in any of the lifter hole or anywhere that's critical
-Crank turn freely.
-Cylinder wall look good.

By the Way.
What Harmonic balance I will need for this block? Would any 318 internal harmonic will do?
http://www.summitracing.com/parts/sum-163273/overview/year/1973/make/plymouth/model/scamp


The tag has a serial number that I need to call Detroit Michigan to get what has put in the block.
Scamp
 

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betting lettering on pistons denotes different bore sizes.... no big deal, but something to note.
 
OP, rotate the crank 'til one of the pistons is as high in the bore as it will go, and measure how for down from the block deck that it is. It'll probably be .080" to .100" down.
 
....and the tag does not mean "call someone at Chrysler". It merely notes that for any internal parts the parts guy should reference the tag number. For any external parts reference the vin ID of the vehicle it's going in.
 
nm9stheham said:
OP, rotate the crank 'til one of the pistons is as high in the bore as it will go, and measure how for down from the block deck that it is. It'll probably be .080" to .100" down.
Click to expand...

for real! without any valve reliefs, I bet those things are Burried!
 
A body said:
betting lettering on pistons denotes different bore sizes.... no big deal, but something to note.
Click to expand...

Or the letters could mean a weight rating for the rod/piston assy or it could designate which bearing to use for proper clearance... (They did that on the 3.5 L with A, B, and AB piston/rod assemblies in the factory)...
 
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