My Rebuilt 4.3 oil leak running rough thread

[JIMBALLS13]

My first post on here, not the best on forum etiquette, but here goes. My "buddy" rebuilt my 4.3, SN 0F873698 . Gor back 3 years after drop off. Had to get police involved to just get back. He did "finish" the motor before he gave it back. Switched fron 2bbl to 4bbl 1409 edelbrock w/2114 intake. .30 over, 3 angle valve job, hr266 comp cam. Oil filter leaked like a siv, fixed that. First run, lots of hesitation, rejected and changed rods, almost all hesitation gone. Had a high speed high rpm backfire issue. 75% throttle ran fine, getting 52mph on dash speedo. That's about where it ran before, but if you gAve the last 25% it would backfire like hell. Thought it may be timing due to new cam. Checked timing it was at 8.5 btdc in base timing mode. TBV ( I grounded the p/w wire to ground. Advanced it to 10btdc, had more throttle response but same problem at high speed, low load. Did a full tune up on ignition system. Changed cap, pickup, rotor, wires and plugs. Now I'm only hitting 4000 rpm. I was hitting 4700 before ignition tune up. I'm going to time back to 8.5 to see if it helps. Main issue is my "OIL FULL BILGE". I've read a few threads on this, but have a few questions. Do balance shafts and non balance shafts use the same oil pan? OK I'm at the bar and steak just showed up. I'll finish the questions in next post.

 

[JIMBALLS13]

I'm also not sure what year the block is. Will that make a diff. In the oil pan? Timing cover is plastic, is there a better one that is metal? Also is the front seal part of the timing cover? That's all I got for now. Hoping to fix this once. Also, what manual, and where should I get it?

 

[andybuzz2u]

1991 was the last year GM made non-balanced shaft 4.3L V-6, from 1992 onward they were all internal balance shaft engines, the block was modified to allow installation of the balance shaft above the timing gear and it runs through the top of the lifter valley. It appears to me that the issues you are having are from a balance shaft installed 180 out. The oil pan has gone through numerous changes, that engine is still being made today 4.3L LV1 and makes 285HP.
http://gmpowertrain.com/engines/docs/GMQD16CL760_LV1_Product PDF.pdf
When looking from the flywheel forward, all GM V-6/8 blocks have the engine block casting number stamped on the right flywheel mount. If it was a Mercruiser engine, just back from the starter you will see the Mercruiser serial number tag.

 

[achris]

Ok. Your engine serial number tells us all we need to know.
The model # is 443HC00JT
That is 1996, 4.3LXH, for an Alpha drive...

That's a Gen+ engine block (balance shaft, Vortec heads, and makes it the later half of '96), originally supplied with a 4bbl Weber carb (and suitable manifold) on it! So I have no idea why it had a 2 bbl on it...

Your composite timing cover is all you can put on those blocks. None of the pressed tin or cast ali covers will fit. And yes, the front crank seal is in the cover. Due to the alignment dowels in the cover and holes to accept them in the block, the front seal will be lined up. If it wasn't, the cover would be broken. BTW, that cover is a 'one time'. Take it off and toss in the rubbish. And don't buy new ones from Merc, any on-line GM parts supplier will get them to you for about a third the price, and it's the same cover... (ask me how I know. :facepalm. Same with the oil pan, it's a standard GM part... There is definitely a technique to fitting the oil pans. Read my threads on my V6 oil leak... :facepalm: :facepalm: You also need to get your head down there and find out where the oil is coming from. It could be something as simple as a poorly fitted valve cover, or the manifold hasn't been sealed properly at the front or rear... Or an oil pressure switch hasn't been fitted properly and is leaking... Any number of places... Find where it's leaking before you start pulling the engine... (Unless you plan on running it 'on the bench')...

Correct timing for that engine is 10?BTDC in base timing mode.

The only thing that would concern me is the cam. I checked the spec and it requires an adjustable valve train. The votec heads are NOT adjustable, they are a 'screw down and torque to 20ft-lb'... No adjustment.... This could be the source of your high speed backfiring. At higher engine speed, the lifters are pumping up slightly and holding open the valves...








Chris..........

 

[JIMBALLS13]

So I checked the timing this week and it was at about 4 btdc. I didn't check it after I changed the sensor In the dist. Set it to 10 and she runs really good now. I got one backfire after running at 4800 rmp WOT for a few minutes. I was playing with the trim and there wasn't much load on the motor at that time. I wonder if I should change the prop to drop the rpm a hair. I would rather have more power to stay on plane at 20mph for wakeskating, than more top speed though. Not sure how to figure props out, but that's another thread. On to the leak. When I wipe everything down and start the motor, oil starts seeping out right at the top of the curve in the pan on both sides of timing cover.

 

[achris]

Props. The higher the pitch the more the load on the engine. .. if you plan pulling any sort of 'toys', plan on using a SMALLER prop. Ideally you want the prop to be of a pitch to allow the engine at full throttle to achieve the revs in the spec. In your case 4400 to 4800. Preferably aim at the very top of that range. If pulling skiers etc, then (by the engine manufacturers recommendation) drop down (lower pitch/more revs) by at least one size (2"). That should increase the engine revs by about 400. If you're going to err with props, err on the side of smaller.

 

[JIMBALLS13]

I was running 4800 steady and I swear it hit 4900 on one run. Could be the tach, sometimes it's jumpy. I wakeskate and need to stay on plane at 18 mph. That's right on the line Where it wants to come off plane. It's tough to keep it planed unless you've driven it a lot. I have 3 blade 23p laser prop on it now. I'm thinking same pitch 4 blade might help that a little. I was reading that same pitch 4 blade will drop the rpms 50 -150. Also gives better hole shot and acceleration and fuel economy with a little lower top speed. That would be perfect.

 

[achris]

I would get a shop tacho (or the digital tach in an advanced timing light) and check the revs properly. Dash tachos are notoriously inaccurate.

A few option for your 15 knots problem. I'd use a 21" pitch laser, experiment with removing the vent plugs. Another possiblity is a 'High 5', also with vent plugs...

Lowering the revs will make it harder to stay at any given speed, not easier.

Chris......