what is the rear main seal and what is the difference between a one piece rear main seal and a two piece rear main seal?

 

The rear main seal is what keeps the oil from seeping past the crankshaft.

The two piece is just that. It forms a full circle seal that surrounds the last (back) journal on the crank. You put the upper half in the block, and the lower half on the rear main cap. Once you install the cap, the lower seal sits against the upper part in the block. This adds two more spots for the oil to get out.

The one piece slips onto the rear of the crank in one complete circle. There's a housing you press it into, then slide it over the back of the crank, then bolt the housing to the block. It's a better seal because there are less spots for oil to get out.

Either are a PITA to change. The two piece requires removing the oil pan, the oil pump, then the rear cap, then 'pushing' the upper part out from one end so it slides out the other. Kinda like a snake slithering through a hole. Then you have to 'push' the new upper part into the slim groove going up and around the crank. The bottom's easy. Pull the old one out of the cap, and plop the new one in.

The 1 piece is easier to change 'per say'. You remove 4 bolts (actually 3 bolts and 1 nut), slide the housing off, replace the seal, and slide it back on. The problem with it though is you HAVE to drop the tranny and the flexplate/flywheel.

 

so why do engine manufactureers still make engines with two piece rear main seals. basically will it matter if i buy an engine with a two piece or one piece?

 

"Engine manufacturers" still make motors with 2-piece seals, because there are an enormous number of existing racing crankshafts and flywheels and so forth in the world already. The people who own all of those couldn't care less what GM has taken to putting in grocery carts. They just want their 45 years of existing investment in parts to still fit and work.

The difference in sealing effectiveness is really quite small, between a properly installed 2-piece seal and a 1-piece. The factory did it more as an assembly-cost thing than for its effectiveness. It's alot quicker on an assembly line to just jam a metal-clad lip seal into a little housing and bolt it on, than it is to futz around with the older design.

 

After all that, no one has mentioned that the two-piece desing was originally a graphite impregnated rope seal (basically like valve or pump packing), while the one-piece is a contact lip seal. Either works fine, but the packing tends to wear and leak after time. Rubber is used as a replacement for the two-piece seals, and can seal as well and last as long as a one-piece design. The key is proper installation and trimming, as RB pointed out.

The different design of the one-piece with its carrier required a different design crankshaft rear flange/hub, thereby requiring a different design flywheel. One-piece rear seal SBCs have been the passenger car standard since the 1986 model year. Just be careful about what you're getting into so you don't have issues you didn't plan for.

 

ok im looking at engines and i need one for my car. it seems the ones with two piece rear main seals and about 250 hp (nothing fancy) are the cheapest and it has goodwrenchs warrenty.

basically im thinking of sticking this engine in my car with my 700r4. will it work?

http://www.sdpc2000.com/cart.asp?act...id=128&pid=110

 

Yes it will work. How much for the engine?

 

click on the link. the reason my parents said they would put the money up is because it is nmot overpowered and has a warrenty. My parents think my foot is a little to heavy.

 

Ask SCPC about the 91-93 B-body motor. It has a warrenty An comes the same way the other motor does but with lots of extras.

 

give me a link please. also how much is it?

 

I paid just under $1500.00 for mine. Check out www.paceperformace.com

 

learn to spell performance

 

can you copy/paste the direct link to the engine that you bought. I think the one for the b body is made for tbi. im running 4bbl carb.

 

also what extras come with the b body motor. could i possibbly use it with a carb?

 

demonchild... Bite me on the spelling. No I can not post a direct link. Big deal, you are running a carb. The motor was designed to run a tbi setup. Just about the same, just not computer controlled.
For a senior member you sure don't know to much.

 

Jeeze..... he was just joking.

demonchild....... go to www.paceparts.com or www.goautocenter.com to find the good deals

BTW jeffbluez, just because I've been golfing for 10 yrs doesn't mean I'm good at it.

 

hmmmm...considering i turned 16 three months ago your damn straight i dont know nothing about cars. AND I WAS JOKING ABOUT YOUR SPELLING. will the manifold i have on the carbed engine line up with the tbi engine?

 

its doesnt matter, i have a 355 right now, 350 .30 over, and i could throw on TPI or TBI or what ever else was made for a chevy small block it doesnt matter, they werent and arent ever made differently, excapt i think the vortec heads which you would just have to drill the holes in the head at a different angle ro something of that sort, but they will still fit. good luck.

oh and where can i find one of those rubber seals for a 2-peace rear main, min's leaking right now and i have the heads in the shop so its a lil easier to do now since she is on blocks. thanks

 

http://www.paceparts.com/subcatmfgpr...3&1=360&2=1112

Part# 12513151. That 's the engine I used. I have since swapped the cam & heads. That engine has the standard (non Vortec) 87 & up heads type on it. It's got a 1 piece rear main seal & 2 bolt mains. Most any intake will fit on it, some older ones will need the 4 center holes elongated.

 

I think you'll find that most replacement seal kits are now Viton or EPDM rubber compounds, not a rope seal packing.

http://www.federal-mogul.com/felpro/...ets/pg_54.html

 

i wasnt asking about the seal because mine went. i asked about it because i threw a rod and need a new engine. Thanks for all the information. Also there is not a discription on the b body motor. From what you people said im guessing the extras are the one piece rear main seal and 87 and up heads. Does anyone have a hp rating?

 

Demonchild
sorry for the blow-up last night. Just had a fight with the girl friend. The internals go like this. LT1 hypereutectic pistons, 1053 forged steel crank, powder metal rods in a two bolt roller block. The cam is from an 88 IROC-Z. The bottom end even has a windage tray. The heads that come with the motor have the 87 and up intake bolt pattern. They have 1.94" in and 1.50" ex valves. The motor will even have a 12 mo 12,000 mile warrenty! All this for around $1,500.00

 

Check here:

http://www.paceparts.com/page.asp?id=293

Or here:

http://www.sdpc2000.com/cart.asp?act...id=128&pid=105

Or here:

http://www.sdpc2000.com/cart.asp?act...id=128&pid=110

 

thx vader and jeff. I think im going with the b body motor because of the one piece rear main seal. Does anyone know the hp rating. i looked all the way through paceperformance website and did not find anything.

 

I'm Think it was in the 190 hp range with the stock tbi. You should do much better with the carb setup.

 

i see. however i dont think that a carb will give me 60 more horepower. i could also be a complete idiot.

 

It should be close to an 88' 350 IROC. The 190 hp is for the stock caprice motor with the original cam. The new b-body motor comes with the 88' IROC cam. Sorry for the confusion.

 

im not familiar with the hp capabilities of the iroc cam. What hp would the engine put out?