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just a quick question

Posted By: LeadFootedRacer On: 01-03-2008 @ 12:54:03 Reply | Edit

i finally got the rotating assembly installed properly this time... but i was wondering how much tq should be required to turn the crank with all 8 pistons/rods installed with all new rings and bearings... if i toss a torque wrench on the balancer bolt, it takes about 49-50 ft/lbs of torque to turn it... is that too tight?
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1985 Z28 305 5spd...
Fresh 350 rebuild - Summit Cam w/ .488 lift - Edelbrock Intake - Flowtech Headers & Y pipe
Summit Gear Drive - Sealed Power Bearings - ReWorked 58cc 305 Heads (soon) and much more soon

Posted By: 84SEBird On: 03-09-2007 @ 21:55:49 Reply | Top | Edit

It seems really tight. I just rebuilt a 305 for another project. It takes about 25 ft/lbs of torque to turn the entire assembly and the camshaft. Yours seems to be on the tight side. Anyone else out there ever test for the torque required to turn a rebuilt engine?

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Brad
1984 Firebird SE- cream-beige- the prestige color!

1987 Corvette

Posted By: LeadFootedRacer On: 03-10-2007 @ 07:27:56 Reply | Top | Edit

wow... looks like i may have done something wrong. something else i noticed is that the cross-hatch that the machinist put in the cylinders dissapeared once i started rotating the motor and my rings are making a scracthing noise... they are summit steel rings... junk?
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Posted By: 84SEBird On: 03-10-2007 @ 21:45:29 Reply | Top | Edit

Hopefully the rings aren't steel! They should be cast iron or moly coated iron. Steel rings on a iron cylinder wall doesn't sound like a good combo. I am surprised that the cross hatch went away with a few turns of the engine. I've cycled mine a bit and the cross hatch is still there.

Did you check the ring end-gap before installing the pistons? To do this you take each ring, place it in the bore all by itself, use a piston to square it up in the bore and then measure the gap between the ends of the rings. They should be in the .018-.020 inch range (at least .016 minimum) or there abouts, depending on what the ring manufacturer specifies. If there is not enough gap, you need to remove the ring, file one of the ends carefully and put it back in the bore and remeasure. If filing is needed, you need to round off the sharp edges of the ring a bit especially on the outside edges/corner of the ring so it doesnt' dig into the cylinder wall. If the gap is too narrow, it will cause the ends to butt together, especially when the engine heats up and seize a ring into the cylinder wall. Every ring needs to at least be checked in this way to ensure they are not too tight in the bores. Did you swab the bores with oil and work oil into the rings and pistons prior to installing them? If they are in there dry, that could be part of the drag too. Something seems too tight. Keep us posted.
Brad

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Brad
1984 Firebird SE- cream-beige- the prestige color!

1987 Corvette

Posted By: 84SEBird On: 03-10-2007 @ 21:46:21 Reply | Top | Edit

Just another dumb thought... you did put assembly lube on all the bearings and journals on the crank and the cam bearing surfaces right?
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Brad
1984 Firebird SE- cream-beige- the prestige color!

1987 Corvette

Posted By: LeadFootedRacer On: 03-11-2007 @ 02:35:39 Reply | Top | Edit

i did use assembly lube, and the cam isnt in it yet. i didnt check for ring gap... totally forgot about that possibility... my mistake, they are cast iron rings... but rechecked everything today and actually forgot to tq down the rods. now that thats done i'm up to 68ft/lbs to turn it, but it doesnt hang up or anything. i did have to stone the faces of the rods and caps (together) where they meet the other rods and the crank. i put it together before and the damn thing wouldn't even turn with 4 pistons in it. i really appreciate your help.
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Posted By: 84SEBird On: 03-11-2007 @ 12:38:18 Reply | Top | Edit

Hmm.... the most obvious thing seems to be that the rings are oversized/mispackaged from the manufacturer and are too large, or need to have the ring gap checked for possible binding. Unfortunately, that means pulling the pistons out, keeping them in order with their respective cylinders and carefully removing the rings and checking the end gap and reinstalling. Something in there is providing way too much drag.

My reading of 25 ft/lbs is with the crank, all pistons, bearings and the cam and timing chain installed. Did you double check the rod and main bearing clearances with plastigauge? I am wondering if the crank was machined wrong or the tolerances are too tight. The scraping sound you heard really makes me wonder if the ring gap is too tight. The pistons were the correct size for the bore, right? If it was overbored to .030, the pistons should have .030 stamped into the top of each piston.

One possibility for drag is the rear main cap and bearings not being aligned. I can't remember right now (been awhile), but I remember that you have to use a rubber or brass hammer to drive the crank shaft forward with the main bearings slightly loose (there is a specification for how tight they should be) and with it nudged to the front, you pry the read main cap (I believe) rearward and tighten the rear main caps and then do a finish torque on the rest of the main caps.

Someone out there jump in and help me on this one as I don't want to steer him wrong. I don't have my rebuild manual on hand right now.

My guess, from the sound you heard may be the ring gap being too tight, but there is always a slight scraping sound (even with well oiled cylinder walls and pistons) when you first turn them. I'm just surprised that the cross hatch is gone so soon.

Keep us posted.
Brad

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Brad
1984 Firebird SE- cream-beige- the prestige color!

1987 Corvette

Posted By: LeadFootedRacer On: 03-11-2007 @ 13:00:46 Reply | Top | Edit

i did not use any plastiguage... the crank wasnt machined to my knowledge, all i had done was the block. i kept the crank in my garage while the block was out and the motor appeared to be VERY stock when i picked it up out of an 89 suburban. it has a 1pc rear main seal, so i dont know if that thrust bearing mumbo-jumbo applies to me... i'll have to look into it.

i'll defintaly look into the psiton ring gaps though, sounds like something obvious i had just skipped over. my dad seems to think if i just put it together and slap a starter on it, it'll loosen up over time... but i don't want to take the chance of putting in the car and what not and have to end up pulling it back out. its my first motor build and i dont want to screw things up... thanks again for the input
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Posted By: LeadFootedRacer On: 03-11-2007 @ 13:05:26 Reply | Top | Edit

oh, and its supposedly .010" over for the hone and what not.. and the pistons are stock 4.000" and the rings are just a set of cheapy summit rings for $19.95
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Posted By: 84SEBird On: 03-11-2007 @ 15:11:01 Reply | Top | Edit

One thing that I've seen before is one of the bearings (rod or main) with the little indexing tip not installed in the slot that's provided in the main cap, block or connecting rod or connecting rod cap. As you know, each one has this small tip/shoulder/slot/index thing sticking out that needs to go into a corresponding slot in the cap/block etc. I've seen them dropped in backwards and torqued into place where they deform due to the torque pressure and actually allow the thing to half-way seat... but it makes it incredibly tight. It's easy to do this as there are quite a few bearing halves to install and keep track of.

I don't think you have the rear main bearing thing to contend with, but I must admit that right now I'm not sure. Best to check it out in your manual.
Brad

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Brad
1984 Firebird SE- cream-beige- the prestige color!

1987 Corvette

Posted By: 84SEBird On: 03-28-2007 @ 21:27:12 Reply | Top | Edit

Any update on the cause of the extra drag on the engine?

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Brad
1984 Firebird SE- cream-beige- the prestige color!

1987 Corvette

Posted By: LeadFootedRacer On: 03-29-2007 @ 07:39:16 Reply | Top | Edit

no... i haven't had the time... i just recently started working 3rd shift and i'm having a hell of a time conforming to a sleep schedual so i never find a free minute to pull it apart. i think i'm going to ditch the project, throw in a running motor and build a more hi-po motor for it. i just want to drive the car for now, and being set back with the issues of the 1pc rear main seal is killing me. i cannot for the life of me find a 153 tooth flywheel for 1pc rear main seals that i can afford. i can get one for a 2pc for less than $100... boggles the mind. my 79 station wagon has a 305 with 117k on it and i'm thinking of just tossing that in with a new set of bearings. it has a mild case of a knock. that has a mild cam, intake, and i'll use my new headers/y pipe, and set it up for the new motor. i want something like a 406c.i.d. with aluminum heads and something like 10.5:1 compression. a buddy of mine has one... but his has a mini blower, and i'm not looking to go that route.
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Posted By: Shift On: 03-29-2007 @ 14:25:58 Reply | Top | Edit

Mine took 24 ft/lbs. I put the old bearings in the wrong way once as 84sebird was saying, and it wouldn't turn over at all.
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Posted By: LeadFootedRacer On: 03-29-2007 @ 15:13:50 Reply | Top | Edit

ouch... that sucks... i double checked everything except for the ring gap... but i'm not bothering looking at untill i either find a flywheel or a new short block with 2pc rear main seal
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