I need to replace my tired old L48 engine with something with a little more oomph. I have new heads, cam ,intake, carb etc. and I want to replace the old two bolt main block with a new four bolt main GM shortblock with two piece rear seal. I have found a new shortblock on gmpartsdirect.com but it has -12 cc dished pistons and that will lower my compression ratio more than I want. Does anyone know if GM sells a 350 shortblock with four bolt mains, two piece rear seal and flat top pistons? A part number would be great. I don't want to go with a ZZ4 shortblock with the one piece rear seal unless someone knows what oil pan for the one piece rear seal will fit in a '79.

 

The oil pan that comes with the zz4 works in vettes
I am using a zz4 short block with aftermarket heads drops right in

 

Thanks for the reply. Are you absolutely 100% positive that the oil pan that comes with the zz4 shortblock will work on my '79. I don't want to buy one and find out that it won't fit and have to go through the hassle of returning it or searching for a pan that will work

 

I just went to gmpartsdirect and their description of the zz4 states that it does NOT come with an oil pan. Now I'm confused. Please provide more information on your purchase of the zz4 shortblock if you would.

 

I believe the complete zz4 comes with an oil pan, however the zz4 shortblock does not

 

oil pan will work with no problems thats whats on my 75

 

it is not an issue it bolts in

 

No the zz4 short block doesnt come with a oil pan all you need to do is get the part number for a zz4 oil pan its a nice pan it has baffles and order it.
You also are going to need oil pump,timing chain and cover and cam retaining plate and GM lifters.dog bones and a spider gaskets and a balancer..
with the zz4 short block you get a forged steel crank forged powdered metal rods good for 500 hp and flat top AL pistons.

 

Does the ZZ4 block have the casting for the Clutch Z bar? I also thought this was an externally ballanced engine. Am I correct or not? If it is, the OP will need a new flywheel or flexplate. I also thought these were set up for roller lifters if you wanted to. Al

 

Flywheel / Flexplate:
Like all small block V-8 engines produced since 1986, the ZZ4 engine has a 3.00” diameter flywheel flange bolt
pattern. Small block V-8 engines produced from 1958 through 1985 had a 3.58” diameter flywheel flange bolt
pattern. This change in bolt circle diameter was made to accommodate a leak-resistant one-piece rear main
seal. Due to revisions in the crankshaft design, a ZZ4 engine must have a counterweighted flywheel (or
flexplate) for proper balance. The ZZ4 engine includes a flexplate Part number 14088765.

 

The GM 290 hp version should be a direct drop in long block:
The 350/290 HP engine incorporates modern technology in a package that can be installed in most applications
where 265-400ci small block Chevrolet V-8’s were originally used. This complete engine is assembled using brand
new, premium quality components. Due to the wide variety of vehicles in which a 350/290 HP engine can be
installed, some procedures and recommendations may not apply to specific applications.
The 350/290 HP engine is internally balanced and requires no balance weights on either the flywheel/flexplate or
the harmonic balancer. A non-Vortech design intake manifold must also be used. When using the 350/290 HP
engine as a replacement for an original equipment engine, the performance intent of this engine should be
considered. The torque curve is higher and consequently may require a torque converter with a higher stall speed
on automatic transmission equipped vehicles. Consult with a reputable torque converter manufacturer for
assistance in selecting the correct torque converter for your application.
The 350/290 HP engine is manufactured on current production tooling; consequently you may encounter
dissimilarities between the 350/290 HP engine assembly and previous versions of the small block V-8. In general,
items such as motor mounts, accessory drives, exhaust manifolds, etc. can be transferred to a 350/290 HP when
it is installed in a vehicle originally equipped with a small block V-8 engine.

 

Yes the zz4 short block has the threaded hole for the z bar ball stud.
also it has everything for a mech fuel pump and the stock vette motor mounts work with the zz4 block..

 

This answers a lot of questions about the zz4 but the 350/290 shortblock is what my original question was mostly about. This shortblock is the one that comes with -.12cc dished pistons which will lower my compression ratio verus flat top pistons. As I stated in the original post, I already have alum. heads, intake ,cam, lifters, carb, headers, etc. which should put the horsepower in the 350 -375 range. Does GM sell a 350 4 bolt main shortblock with a 2 piece rear main seal and with flat top pistons. If they don't sell one then I may have to go with the zz4 which is a lot more money but of course it's a killer engine.

 

Any reason you are looking for a 2 piece rear main.

 

The only reason is that I can use my original oil pan, flexplate and balancer from my L48 plus the shortblock assembly should be about half the price of a zz4 assembly. I won't be running the engine hard at high rpm's so I really don't need the steel crank etc that the zz4 has.

 

http://www.ohiocrank.com/shortbpage1.html
I know you said you already bought parts but check this out.
that 388 doesnt look to bad.

 

http://www.blueprintengines.com/inde...ons-shortblock

http://www.jegs.com/i/Blueprint-Engi...oductId=761058

 

That's a lot of motor for a real good price. If I lived closer I'd be more interested. Just concerned about warranty issues should I have any, hence my interest in new Gm shortblocks

 

If you believe you can achieve 350 to 375 hp utilizing the 350/290 block assy, that is a bit more than a ZZ4 anyway. Here are the peak HP of the ZZ4 assy.
The ZZ4 comes to you with a full 355 horsepower and 405 lb.-ft. of torque. With its high level of performance and durability, it could very well be the perfect crate engine – able to meet the needs of car builders from all phases of the motorsports world.

 

Not to turn you off on any of the GM pp crate engines but youneed to read the GM warranty very carefully and check with your local GM dealer and see if they will honor that warranty.