Engine suggestions

[Jeffyboy]

Hey guys,



I\'m having a helluva time with my motor leaking oil like a sieve and have already replaced the rear main seal once, which only worked for a few hundred miles. It\'s good that I don\'t drive it all that much because I lost 1/4 of a quart of oil on the last drive I took - about 60 miles total. I\'ve decided that if I pull the motor again, I want to do heads and cam. Here\'s my question:



Do I use my newy rebuilt-but-leaking 2-bolt main shortblock with domed pistons (10.5:1 with a 76cc head) and just change heads, cam, and rear main seal (again) . . .



or



Should I try to find a 4-bolt Vortec 350 motor and have the heads machined to take a high-lift cam and just get a carbed manifold for those heads. That\'ll give me a 1 piece rear main seal, too. If the motor was in good shape, I probably wouldn\'t have any machining done to it - just new bearings.



Also, if I just use my existing block, any ideas on how to get the rear main to seal up? We already put the seal in cockeyed, but kinda forgot to silicone the ends of the seals. Could that one oversight be causing that massive of an oil loss? If I get new heads, would I be better off getting bare castings and having them assembled, or just buying assembled heads?



Thanks for the help.



Jeff

[insomniacshotrods]

Id use the motor you already have and maybe get the vortec heads or an after market heads or just keep the heads you have ,depends on what you want the truck to do....as for the rear main seal leaking ,try rotating the seal so about a 1/4 inch or so is sticking up from the block,it keeps all the joining surfaces from lining up....that should take care of that problem...also use some silcone on the edges.... have a good one

[spacecadet]

I 2nd the advice on the rear main seal issue that insomniacshotrods stated.

I would also check the back of the intake and the oil pressure switch spot at the top of the block at the intake.

My PU had a nasty oil leak when I got it. About 2 weeks later, the flywheel broke. So when I changed the flywheel, I bought the rear main seal kit. My rear main wasn\'t leaking but the retainer was. THere was 2 broke bolt 1 on each side. Clean the backside of the motor really good. Made all the repairs, thought it was fixed. A couple days later I noticed I still had big oil under my truck. further investigation foung that the back off the intake gasket blew out. It was dumping alot of oil. Well fixed that seal and its not had a problem since then.



Space..

[insomniacshotrods]

Oh thanks Space that reminds me ,I did have my oil sending line loosened up on me after a couple months of driving....leaked like a #$%$%&*&(*)^&#$%@#$! at least it was easy to find with the truck running....might check that as well

[DMONOTJR]

i also agree. keep the bottom end that you have, for what you would pay for a new 4 bolt and fresh internals- isn\'t worth it. you have a good bottom end now. just before you reinstall another seal, you might want to check to see if you have any base pressure that might be blowing out your seals. more than likly you shouldn\'t have any, but you never know what may happen to an engine. if it is just a mis installed seal, just take you time and CLEAN all areas that the seal contacts, offset the seams on the seal from the cap seams ( i was able to offset mine almost 90 degrees-ALMOST) as for heads, those vortec heads are hard to beat for the price, a good cam of your choice and- you know the rest.

[Jeffyboy]

OK - thanks for the advice. I\'m just really frustrated by the puddle of oil that\'s constantly showing up on my garage floor - not to mention my blacktop driveway that\'s all stained now.



I already offset the seal last time I changed it, but forgot to seal the ends. My cousin/mechanic suggested using a dye to find exactly where the leaks coming from. It doesn\'t seem to be the pressure fitting, though, and we used rtv on the ends of the intake. What is \"base pressure\" that you\'re talking about? I\'m not familar with that term . . .



Regarding the heads, I\'ve got junk 624 castings right now. I can\'t really go with vortecs unless I change pistons - something I don\'t want to do. My compression would be off the charts with a 64cc head. I\'m leaning toward World S/R Torquers. And for the cam, a Comp XE 274. I think that should compliment the heads and 2400-2600 stall in my TH350 pretty well. I\'ve got a Crane 302H and the powerband is so high, I don\'t even use everything it can offer since I want to keep it under 6000 rpms. And my current heads can\'t flow enough to take advantage of it either.



So, any advice on whether to get bare castings and build them up or buy the pre-assembled heads?



Thanks guys,



Jeff

[DMONOTJR]

base pressure is the pressure that suppose to be in the cumbustion chamber but, somehow finds it way below the piston. ie bad/ broken ring,hole in piston, distorted/cracked cylinder wall. i see this happen all the time on deisel engines at my work. the pressure would blow oil out of the filler neck about a foot, and blow out the front and rear seals nearly ever time. all you have to do is check you combustion pressure at the plugs and see if leaks down. now if it leaks down check to see if the valves are closed fully. hope this explains it for you.

[Scotty_S-15]

So base pressure is Blow-by? The quick check for excessive blow-by is to check your crankcase air intake (usually your filler) for either vacuum or positive pressure with the palm of your hand. This is of course, presuming you\'ve got a PCV thing going on.

........... If manifold vacuum cannot overcome the blowby at idle, there\'s a big problem.



Getting back to the rear seal, not likely the crank is messed up at the seal area, but you never know. Be sure to check that.

[Jeffyboy]

I do have a PCV, so if I pull my breather off and put my hand over it, I should feel vacuum, right? I have very minimal vacuum at idle right now due to the cam I naively chose - would that cause issues? Wouldn\'t these types of problems cause driveability issues? The truck runs and drives well . . . If the crank was messed up at the sealing surface, is there any way to fix it or does the crank have to be replaced?



I\'m planning on driving it the rest of the summer while it\'s still leaking and maybe pulling the motor this winter - unless I find that I have a couple of free weekends somehow. Just thinking about what parts to gather up.

[Scotty_S-15]

If you\'ve got poor vacuum at idle, the main thing is that you don\'t have a lot of pressure escaping. As you might guess, that wouldn\'t be good. A sign of bad rings, or even a cracked piston.

....... Regarding the oil leak, I\'ve had success over the years by making \"Kotex\" pads for my cars & trucks. What works well is some absorbent pads used for chemical spills, maybe they even have them at Auto Parts places? dunno.

...... My \'94 1500 has leaky oil hoses going to the radiator. I spirally wrap them with that material, ty-rap them, and change them once a year. Keeps oil off the driveway. http://www.s10v8.com/images/smilies/icon_wink.gif Not good for \"concourse\" open-hood shows howver.... http://www.s10v8.com/images/smilies/icon_razz.gif

[Jeffyboy]

I don\'t think I have too little or abnormally low vacuum - just what\'s natural for my camshaft. I also don\'t have leaks anywhere except at the back of the motor.



I\'ve thought about the maxi-pad idea actually, but didn\'t want to go that route. Especially since I\'d have to change it pretty regularly. I did make one for the garage floor though out of a bunch of old t-shirts rolled up and stapled to some plywood. I think the new version will be a plastic tub like you get to set your washing machine in in case it leaks or overflows - it\'s only about an inch tall - and then fill it with oil dry. That\'ll get me through the summer driving season anyway.



Well, I\'ll keep you guys posted after we do the dye trick - it\'d be nice if it wasn\'t the rear main at all. The * of it is that I found out I had a torn valve cover gasket a while back and hoped that it was my problem. Replaced the gasket and it still leaks like crazy. Oh well. Thanks for all the help.



Jeff