How can you tell if a SBC has a 1 piece rear main seal or a 2 piece without pulling the pan to see....one guy told me dipstick location is one way...any help here would be appreciated .......thax guys.
The one piece seal is in an aluminum housing that is bolted to the back of the block. I'm at work a few more hours or I'd go out to the shop and take a pic for ya.
LOL! If it's not leaking it is probably a one piece rear main. Dip stick position is not definitive. I have one of each, 1 and 2 pc., in my hot rods. Both dip sticks are on the right. If you take the flywheel cover off, you might be able to see the aluminum seal housing. Probably be able to tell by the casting number.
The dipstick moved from driver side to pass side in 1980, but the rear seal became one piece in 1986. You tell by looking at the back of the engine, from underneath. The aluminum housing should be kind of obvious, as should the lack of the crankshaft flange sticking out past the block. Take a picture of it, and we can tell you.
My one piece block has 880 cast into both sides of the block, near the block drain plug, just above the pan rail. The 880 is upside down in the car (088). It is also roller lifter ready. If that helps.
As far as I know the one piece tear main seal blocks will not have provisions for a mechanical fuel pump. They would have come stock with center bolt heads.
Nope,,,I have two,,,,one has mechanical pump boss machined,,,the other doesn’t. Like Squirrel said,,,look underneath at the rear of the pan. The crank will not have a flange sticking out,,,and you can see the aluminum adapter that holds the seal bolted on back there. Tommy
Nope. My 880 block with 1 piece seal, cam thrust plate, and bosses drilled and tapped for the roller lifter spider is drilled for a mechanical pump. You'd have to ask squirrel about when they stopped that.
Here are some pics from the one that is not drilled for the pump. You can see the adapter bolts to the back of block and the pan seals to the bottom of it. If it is a one piece seal,,,you should see about an half of inch of aluminum from the bottom. The other one that I have is drilled and machined all the way,,,and it was made after this one I just took pics of. I wonder if it depended on the application and maybe what plant they were built at ? I have no way of knowing. Tommy
Its a crap shoot on what block did and did not have a fuel pump provision from 86 up. I have a 2 vortecs one with one without... Some say it depended on what plant they came from. Also 99% of your GM crate engines did have them.
All of them I've owned, had the boss but were not drilled and tapped. Also the z bar stud mounting boss for the clutch was not drilled and tapped. Had to do it myself. I wish I would have had one set up for a mechanical fuel pump. Did the stock cam have the lobe to drive it? Isn't the pan different looking from one piece to 2 piece? If you are like me and dont mind being corrected this place is such a wealth of knowledge. Sorry for the misinformation.
IIRC, it was about '96, when they came out with the MPFI Vortec. Early production may have still had the block off plate installed. It's been awhile... [emoji848]
I've go a 90 model camaro 305 in the shop that has no block off. The fuel pump boss is not drilled and finished. My 88 350 block is also not drilled. I knew the crate engines were though. If you drill one that is not does it have the cam lobe to drive a pump on the stock cam.
You've got me scratching my head now... [emoji848] Not to discount what you are saying but, are you sure those are original blocks and not later replacements? The early TPI and TBI engines had problems with the blocks cracking in the lifter valley and were replaced. Just wondering if that may be the discrepancy. But then again, Christ only knows what was going through the Generals mind at the time of production... As far as the cams and fuel pump lobes, AFAIK, the fuel pump lobes are there.
I have a block from a '95 1500 Suburban here that is drilled and all forna mechanical pump, and it also had the fuel pump lobe on the cam.
I don't know which blocks did or did not have the fuel pump hole drilled. The three 87-95 blocks I've had all have the hole, and the lobe.
The block I have now I know it is the stock factory piece,,,it came from my brothers truck. I got the complete short block from him. Also,,,,the other,,, it came from another truck of his,,, he was in construction at the time and had several trucks in his business. This was from before the big crash,,,eleven years ago ! Man that really hurt,,,,, Tommy
if the two rearmost pan bolts are actually nuts on studs, instead of bolts, then it's a one piece, eh?
1986-1995 are center bolt heads. They are not Vortec heads. Vortec heads have a specific combustion chamber shape, which is not found in 1986-1995 V8s
87 was when the new heads arrived, 86 was when the one piece rear seal arrived. Although I could be wrong.
That is not always true. The early one piece rear main blocks still have the hole drilled for the fuel pump push rod, the engine I built for my daughters car is an early block, had a fuel pump block off plate bolted to it
interesting...I worked on a couple of 86 engines that had the one piece rear seal and perimeter bolt valve covers. All the looking into I've done, suggest that the seal was a 1986 model year change, and the heads were a 1987 model year change.
I am no expert but I used to have an 86 Z28 that had the center bolt valve covers. To my knowledge, it had never been modified before I got it.
1986 Chevy pickup 305 with perimeter bolt valve covers, it also had the computer control Quadrajet 4 barrel
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