455 Main & Rod tolerance question
January 24th, 2011, 01:21 PM
#1
Ben
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Join Date: Mar 2009
Location: Snohomish, WA
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455 Main & Rod tolerance question
had this going in another off topic thread, wanted to give it its own place...
My question is below about the rod & main tolerances gene mentions below.
Applogies if this is a stupid question, i'm still trying to get my head wrapped arouund some of these machining concepts before i pass that point in the project so i don't make mistakes. My crank is out for grinding now, so if i need to have them change stuff, now is the time.
Do i just provide those specs to the crank grinder instead of him using stock specs?
My plan up till now was to simply rebuild the bottom end as the factory did it. No restrictors, maybe restricted pushrods, Stock specs. I have a 5qt toropan & scraper setup to use, will get a high volume pump.
I don't plan to rev the engine beyond 5500, just looking for 425-450hp range.
Are the stock machining specs really that bad that a motor like that would not survive Street and very occasional strip blasts?
Thanks for any input.. like i said i'm learning.
Ben
My question is below about the rod & main tolerances gene mentions below.
Applogies if this is a stupid question, i'm still trying to get my head wrapped arouund some of these machining concepts before i pass that point in the project so i don't make mistakes. My crank is out for grinding now, so if i need to have them change stuff, now is the time.
Do i just provide those specs to the crank grinder instead of him using stock specs?
My plan up till now was to simply rebuild the bottom end as the factory did it. No restrictors, maybe restricted pushrods, Stock specs. I have a 5qt toropan & scraper setup to use, will get a high volume pump.
I don't plan to rev the engine beyond 5500, just looking for 425-450hp range.
Are the stock machining specs really that bad that a motor like that would not survive Street and very occasional strip blasts?
Thanks for any input.. like i said i'm learning.
Ben
Just curious (not trying to debate) how those specs compare to stock. These clearances are looser than stock, correct?
I'm learning as i go (which is expensive)... If a crank is ground under 10 or under 20... thats from the stock spec... and the replacement bearings are for -10 or -20 under stock specs. so can you also get different bearings that will give you slightly different tolerances within that -10 or -20 or do you have to specify to the crank grinder exactly what you want the grind to be (beyond the stock spec?), or is that last little bit done by polishing?
i probably should just post this as its own question instead of hijacking, huh...
I'm learning as i go (which is expensive)... If a crank is ground under 10 or under 20... thats from the stock spec... and the replacement bearings are for -10 or -20 under stock specs. so can you also get different bearings that will give you slightly different tolerances within that -10 or -20 or do you have to specify to the crank grinder exactly what you want the grind to be (beyond the stock spec?), or is that last little bit done by polishing?
i probably should just post this as its own question instead of hijacking, huh...
I am learning as I go as well and it does get expensive, but hopefully this site will help with that. I have been through 5 motors for various reasons since I've had my car. You are correct on both points. If you grind your crank 10 or 20 under then you get 10 or 20 oversize bearings. The final clearance is determined by the amount left from grinding or polishing to get the desired tolerances.
I understand how to check the tolerances... i was just curious if the wider tolerances are desired for rebuilding- Most shops that grind a crank are simply going to grind it to factory specs plus whatever they need to clean it (.010 under or .020 under).
If a WIDER than stock toerance is desired, does it have to be specified to the guy grinding the crank, or can that extra clearance be POLISHED later later after you've checked the initial tolerances, or are bearings available that will give you slightly more than stock -10 -20 bearings?
That is why i was asking how those numbers compared to the stock main & rod bearing tolerance specs. Because -10 or -20 is just off the stock size. If custom size is desired, i want to know when & to who that gets specified during the build.
My crank is still at the machine shop now... so thats why i want to know if i should be feeding him info other than the stock specs he's using.
If a WIDER than stock toerance is desired, does it have to be specified to the guy grinding the crank, or can that extra clearance be POLISHED later later after you've checked the initial tolerances, or are bearings available that will give you slightly more than stock -10 -20 bearings?
That is why i was asking how those numbers compared to the stock main & rod bearing tolerance specs. Because -10 or -20 is just off the stock size. If custom size is desired, i want to know when & to who that gets specified during the build.
My crank is still at the machine shop now... so thats why i want to know if i should be feeding him info other than the stock specs he's using.
Last edited by RAMBOW; January 24th, 2011 at 01:33 PM.
January 24th, 2011, 01:48 PM
#2
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Location: Rogues Island, USA
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Basically the specs they are giving you are for blue-printing the engine. Although the factory specs are probably very close to this now I think the intention is that if you have the engine apart already and need the crank cut now would be the time to do it right. To answer your question: No I don't think the factory specs will hurt anything but you also don't know what they are until they've been measured. Since you have it apart now why not do it right the first time. You might want to think about dropping off the block too since the main saddle bores aren't perfect either. Your machinist will need something to measure off of.
January 25th, 2011, 10:13 AM
#3
Registered car nut
Join Date: Apr 2008
Location: Puyallup
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I'm still getting use to the logic of the Olds engine needs also.
My machinist agree's with the "loose" if you'll be running above stock HP or RPM's.
If I have this right the crank moves around a bit at higher RPM's and needs more space to do so. Sounds odd the way I explain it. Bill Trovato
did a much better job in his book.
My machinist agree's with the "loose" if you'll be running above stock HP or RPM's.
If I have this right the crank moves around a bit at higher RPM's and needs more space to do so. Sounds odd the way I explain it. Bill Trovato
did a much better job in his book.
January 25th, 2011, 03:53 PM
#4
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Join Date: Nov 2008
Location: Central Fl
Posts: 7,827
To clarify the reason you need more clearance is because as hp and/or rpm increase so does the potential for more flexing of the stock parts i.e. block and rods. Plus as I've mentioned many times before a good machinist knows the larger journal diameters of an Olds or anything for that matter, require more clearance.
The right way to do it? Have the mains checked and align honed if needed, same with the rods. Then use a dial bore to get the inner dimensions with the bearings installed, then grind the crank to achieve the desired clearance. Make sure your machinist uses a dial bore with very little tension as one with more will give a false reading by digging into the bearing surface.
If needed try to have everything done in the order that is best, align hone, square deck, bore with Bor-Tru, then hone with torque plate. I still believe this is not only good for longevity but can also add a few hp.
The right way to do it? Have the mains checked and align honed if needed, same with the rods. Then use a dial bore to get the inner dimensions with the bearings installed, then grind the crank to achieve the desired clearance. Make sure your machinist uses a dial bore with very little tension as one with more will give a false reading by digging into the bearing surface.
If needed try to have everything done in the order that is best, align hone, square deck, bore with Bor-Tru, then hone with torque plate. I still believe this is not only good for longevity but can also add a few hp.
Last edited by cutlassefi; January 25th, 2011 at 04:03 PM.
January 25th, 2011, 04:32 PM
#5
Ben
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Join Date: Mar 2009
Location: Snohomish, WA
Posts: 1,825
Doh... So i guess I'm doing this out of order then?
Have the crank being ground & polished & rods resized now at one shop- Block will be measured & aligned honed (and all the rest of the blocks machine work) done at another place at a later time. (once i have my pistons) and after i have the rotating assembly balanced.
So it sounds like i should have waited to have the block align honed before having the crank ground?
Have the crank being ground & polished & rods resized now at one shop- Block will be measured & aligned honed (and all the rest of the blocks machine work) done at another place at a later time. (once i have my pistons) and after i have the rotating assembly balanced.
So it sounds like i should have waited to have the block align honed before having the crank ground?
January 25th, 2011, 04:57 PM
#6
Rambow, That is how I do it. I align hone the mains to the middle spec. Insert all the main brgs, install the main caps, torque the bolts to spec. Use a dial bore guage and take a measurement. Machine the crank to the size you need for the clearence you want.
Stock spec's are good for a daily driver that see's very little RPM. if you are going to use and abuse it, you need more clearence. With the big journols and mains, the brgs speed is to much, you need a little more clearence to give the crank room to flex at high RPM. HV pump with at least a 7 qt pan. I redrill the spring hole in the oil pump and move it over .250. It gives a little more pressure, you mainly need voluume.
Thats pretty much how I do it. My engine has been in there for 8 years, and I race a lot.
Check "Amazon" for Bill at "BTR racing for his book. Makes for great reading.
Check out, Bill @ Olds performance, -- John @ Rocket racing, Smitty @ M & J proformance, -- Andy @ Olds performance products
Gene
Stock spec's are good for a daily driver that see's very little RPM. if you are going to use and abuse it, you need more clearence. With the big journols and mains, the brgs speed is to much, you need a little more clearence to give the crank room to flex at high RPM. HV pump with at least a 7 qt pan. I redrill the spring hole in the oil pump and move it over .250. It gives a little more pressure, you mainly need voluume.
Thats pretty much how I do it. My engine has been in there for 8 years, and I race a lot.
Check "Amazon" for Bill at "BTR racing for his book. Makes for great reading.
Check out, Bill @ Olds performance, -- John @ Rocket racing, Smitty @ M & J proformance, -- Andy @ Olds performance products
Gene
January 25th, 2011, 08:31 PM
#8
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Join Date: Jan 2011
Location: Machesney Park, IL.
Posts: 253
I am in the process of rebuilding my 2,500 mile engine because I ASSUMED my set up was good enough to keep my engine alive.
In the fall of 09 I took my engine to Rocket Racing and had the short block rebuilt including full machine work and balancing.
The motor was great on the street but once I took it to the strip I found out my fuel system was not big ehoung and even through I upgraded my oiling system my stock pan was too small for the track.
My motor is at Rocket Racing again and after talking with John for over an hour I have a plan to upgrade my fuel system and oil pan and pick up tube.
If I would have asked more questions the first time I would not be here a second time. A reputable builder will help you with your complete set up not just the engine portion.
January 25th, 2011, 09:00 PM
#9
Ben
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Join Date: Mar 2009
Location: Snohomish, WA
Posts: 1,825
Thanks for the info guys. I know this stuff seems obvious to you, but i'm still learning as i go.
I guess I didn't explain properly... My crank is already at the grinders- it has already been ground & polished 10/10. I'm still waiting on them to drill it out for the m/t pilot bearing & resize the rods before i get it back.
The block is still here waiting to go to my buddies shop that will do the block work...
I assumed I would not need to take it to him until after I had the roatating assembly balanced- So I guess I have already goofed by started out of order.
When i get the crank back, i will speak to my guy about doing the align hone on the mains and figure out what my clearances are before i take the crank for balancing in case i have to have it ground more.
When i bought this block/crank/pistons/rods setup, it was at this particular machine shop already. Since "my" guy does not have the stuff to do crank work, i figured i'd have this place go ahead and do the crank grind & polish & rod resize, then have my guy do the block work.... Turned out to be kind of a hassle due to their location and I really should have just taken everything to my guy when i bought it and let him have his own crank specialist do that part. Would have made life simpler.
Anyway, Thanks again for explaining. I really appreciate it.
I guess I didn't explain properly... My crank is already at the grinders- it has already been ground & polished 10/10. I'm still waiting on them to drill it out for the m/t pilot bearing & resize the rods before i get it back.
The block is still here waiting to go to my buddies shop that will do the block work...
I assumed I would not need to take it to him until after I had the roatating assembly balanced- So I guess I have already goofed by started out of order.
When i get the crank back, i will speak to my guy about doing the align hone on the mains and figure out what my clearances are before i take the crank for balancing in case i have to have it ground more.
When i bought this block/crank/pistons/rods setup, it was at this particular machine shop already. Since "my" guy does not have the stuff to do crank work, i figured i'd have this place go ahead and do the crank grind & polish & rod resize, then have my guy do the block work.... Turned out to be kind of a hassle due to their location and I really should have just taken everything to my guy when i bought it and let him have his own crank specialist do that part. Would have made life simpler.
Anyway, Thanks again for explaining. I really appreciate it.
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