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Topic Review (Newest First)
09-05-2011 11:00 PM
Steveon91 I may have found the answer. I will post this encase anyone is interested in what Mercruiser thought was right.

Mercruiser 5.7l engine specs
350 CID / 5.7L Gen + Engine Specifications


Main Journal Diameter

No. 1
2.4484-2.4493(62.189-62.212)

No. 2, 3, 4
2.4481-2.4490(62.182-62.205)

No. 5
2.4479-2.4488(62.177-62.199)

Taper
Production
.0002(0.005) Max

Service
.001(0.025) Max

Out of Round
Production
.0002(0.005) Max

Service
.001(0.005) Max

Main Bearing Clearance
Production
No. 1
.0007-.0021(0.018-0.053)

No. 2, 3, 4
.0022-.00610(0.0009-0.0024)

No. 5
.00250-.00690(0.0010-0.0027)

Service
No. 1
.0010-.0020(0.250-0.510)

No. 2, 3, 4
.0010-.0025(0.0250-0.0640)

No. 5
.0025-.0035(0.0760-0.0380)

Crankshaft End Play
.002-.008(0.0500-0.2000)

Connecting Rod Journal
Diameter
2.0978-2.0998(53.2840-53.3340)

Taper
Production
.0003(0.007) Max

Service
.001(0.025) Max

Out of Round
Production
.0003(0.007) Max

Service
.001(0.025) Max

Rod Bearing Clearance
Production
.0006-.0014(0.16-0.35)

Service
.0010-.0030(0.025-0.076)

Rod Side Clearance
.006-.014(0.15-0.35)
09-05-2011 08:44 PM
Steveon91
Quote:
Originally Posted by ssmonty
If the rod is damaged and you think you need to replace it you may be able to take it to a local machine shop for comparison. They probably have an extra lying around that you could get re-worked(magnafluxed,big end re-sized and new bolts) and weighed. You would have to take it to the shop anyway to get the piston pressed on & off if I'm not mistaken.
ssmonty
Yeah I got it pressed off with no damage to the piston shwooo I also found a STD STD GM Crankshaft used but ready for assembly today for 125.00.

Here is my question I bought fed mogul STD rod bearing, then cleaned the Crank Journals/Rod journals real good with alcohol, installed new bearings and double checked that they were clean, I then torqued them down to 45ft pounds with 1 strand of green plastigage and I get .0015. The person I got the crank from told me I should try for .001 Clearance Since the engine will be at around 150 to 160 degrees F. He is an old school Top fuel Machinist - engine Builder - Driver and was even in Hot rod magazines Didnt get the last name but First was Randy in midlothian, TX really nice guy.

Clevite recommends to have .001 clearance per 1 inch journal diameter in most applications. So that is about .0021 Also Clevite recommends if the application is a truck pulling a camper all the time go up to .003. I asked Randy about that and he Said it could be because of the high heat that a street engine will have. Marine engines run alot cooler.

Am I ok at .0015? I have not checked the others but is there a ballpark I need to stay in Say .001 - .002 on Rods Same on the Mains? and a little more for number 5 main
09-03-2011 10:37 PM
SDLuck My question is a cast steel crank better than cast iron,I have looked up both types.I believe your buck knife to be forged steel and that is different
09-03-2011 06:35 PM
ssmonty If the rod is damaged and you think you need to replace it you may be able to take it to a local machine shop for comparison. They probably have an extra lying around that you could get re-worked(magnafluxed,big end re-sized and new bolts) and weighed. You would have to take it to the shop anyway to get the piston pressed on & off if I'm not mistaken.
ssmonty
09-03-2011 06:23 PM
Steveon91 is it ok to replace the 1 rod stock for stock should I make sure they weight the same>?
09-03-2011 06:16 PM
ssmonty If you were to ask a salesman, I wouldn't ask for an externally balanced crank, I'd ask for a one piece rear main seal crank for a small block Chevy.
If you ask for an external balanced crank, most would think your referring to a stroker I believe.
ssmonty
09-03-2011 06:07 PM
Steveon91
Quote:
Originally Posted by ssmonty
Sorry Steveon91, I missed your heading "1998 Vortec 355". It would be a one piece rear main seal engine needing an externally balanced crank. (use your same flywheel) Just specify one piece rear main seal and external balance is implied I believe.
You would be better off talking to the Scat salesman as far as the type of bearings, and if balancing is required, that is if you decide to buy a Scat crank. I'm sure they would be happy to help and give you the best info. Might even get a better deal than if you ordered from summit?
FWIW
ssmonty
Ok thanks that is very helpful! So I need an externally balanced Crank.
09-03-2011 04:05 PM
ssmonty Sorry Steveon91, I missed your heading "1998 Vortec 355". It would be a one piece rear main seal engine needing an externally balanced crank. (use your same flywheel) Just specify one piece rear main seal and external balance is implied I believe.
You would be better off talking to the Scat salesman as far as the type of bearings, and if balancing is required, that is if you decide to buy a Scat crank. I'm sure they would be happy to help and give you the best info. Might even get a better deal than if you ordered from summit?
FWIW
ssmonty
09-03-2011 03:14 PM
ssmonty As far as internal or external balance, if your block uses a 2 piece rear main seal then it is an internal/neutral balanced crank, meaning that you don't need an external counterweight on the torsional dampner/harmonic balancer or on the flywheel to balance the rotating assy.
If the block is a one piece rear main seal type it will need a flywheel made for one piece seal engines as they have a counterweight built in that replaces the weight removed from the crank to make it a one piece seal type making it an external balanced assy.
Most all small blocks were internally balanced until the advent of the one piece rear main seal design with the exception of the 400 that used a counter-weighted balancer and flywheel because there wasn't enough room to add the weight to the longer stroke crankshaft economically for internal balancing. Sorry for being so long-winded.
If your rods and pistons are stock the Scat crank should be close enough for mild rpms as far as balancing goes. You need to call Scat and ask one of their salesmen for yourself. If it were mine I'd probably get it checked, but then again I'm picky and go overboard too often.
As far as noting that it was steel vs. cast iron I didn't even know that there was a jury out on the subject. I ***umed that for one if they were making it out of a more expensive base material that it was because it was to make a higher quality product. At least I thought steel was more expensive than iron. I know that it has more torsional and tensional strength before failure. How many bolts do you see made out of iron? All of my wrenches, screwdrivers, hammers, jacks, toolboxes are made of steel. I can see that perhaps iron is harder and may wear longer if dirt were to get into the oil, but isn't that what the oil filter and the bearings are supposed to take care of? I've carried my 112 Buck knife for 30 years and have yet to see one with a cast iron blade. Forgive me if I ***umed steel was a better material for a crank.
FWIW
ssmonty
09-03-2011 02:23 PM
Steveon91 Well I just tore it down and all the bearings were good but #1? probably bad assembly is the only thing I can figure.

How do I know if I need a external or internal balance Crank. and should I have it balanced or is that just for high RPM engines?
09-03-2011 01:49 PM
SDLuck
Quote:
Originally Posted by ssmonty
In response to SDLuck's ?

http://www.summitracing.com/parts/SCA-935060L/

I didn't say it was forged steel. I said it was steel instead of cast iron.

I'm not saying this is what Steveon91 needs as the link is for a stroker crank.
I know you didn't say it was forged steel,the jury is out on whether cast steel and cast iron,which is better?Don't get me wrong the scat is a very good product and I have a chevy cast steel crank in my 383.
09-03-2011 01:12 PM
Steveon91
Quote:
Originally Posted by ssmonty
I personally have a Scat 9000 crank for a 383 in the works, and every journal measured good as far as being concentric and no taper. I haven't checked the stroke yet, but from what I've seen so far I don't expect any surprises. I haven't got the rotating assy. balanced yet either, but if it needs balancing work thats not Scats fault because I didn't get the pistons from them.
I bought the Scat after doing a lot of research and getting various recommendations as well as hearing a lot of negative things about others.
FWIW
PS The Scat is steel where the 305 is cast iron.
Hey my Friend,



Sounds like the Scat Crank is the way to go!
09-03-2011 11:37 AM
ssmonty In response to SDLuck's ?

http://www.summitracing.com/parts/SCA-935060L/

I didn't say it was forged steel. I said it was steel instead of cast iron.

I'm not saying this is what Steveon91 needs as the link is for a stroker crank.
09-03-2011 11:11 AM
SDLuck Why do you say the scat is steel?
09-03-2011 10:31 AM
ssmonty I personally have a Scat 9000 crank for a 383 in the works, and every journal measured good as far as being concentric and no taper. I haven't checked the stroke yet, but from what I've seen so far I don't expect any surprises. I haven't got the rotating assy. balanced yet either, but if it needs balancing work thats not Scats fault because I didn't get the pistons from them.
I bought the Scat after doing a lot of research and getting various recommendations as well as hearing a lot of negative things about others.
FWIW
PS The Scat is steel where the 305 is cast iron.
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