Someone posted on LS1 tech about offset grinding the crank to use a SB chevy rod and bearing. The difference in offset grinding and going to the new bearing would net .212 more stroke. Any engine tech experts yeild any advice? A stock crank and iron block would yeild roughly 400 cubic inches. :crazy:
http://www.ls1tech.com/ubb/ultimateb...c;f=1;t=008409
Phillip

 

I did not read all the posts following this subject, but the guy does not know what he is talking about... You can offset grind an LS1 crank from 2.100 diameter down to the early SBC diameter of 2.000 and the result is a .100 increase in stroke... In most cases, you must also grind another .010 to allow for tollerance variations... In other words, to get the full .100 stroke increase, you must grind the journal .110 under and use a .010 under sized bearing... On a stock LS1 that increase in stroke would result in a displacement of 356 cid... To get this you would also need custom pistons... The offset grind technique is only beneficial if you are also going to a lorger bore that requires the custom pistons anyway and you can pick up an additional 10 cid from the offset grind... This is also true if you offset grind a stroker crank... .100 is the maximum stroke increase possible from this combination of parts...
Shirl Dickey
SD Racing Enterprises

 

Actually the stroke gain is .200 inches: you would gain .100 at the top of the stroke and .100 at the bottom.

The increase of about 8 cu. in. you stated is correct for a .200" increase in stroke.


[Modified by SoCal C5, 10:52 PM 10/23/2002]

 

Right, maybe he was talking about offset gringing a 400 pontiac crank from the older cars or something.

 

That was me. And before you say I don't know what I am talking about maybe you should read the thread.

I SUGGESTED using SBC rods with 1.888 Acura rod bearings. This is a cmmon practice in NASCAR. The rods are avaliable right now from ost aftermarket rod suppliers. Since Top Fuel is only using a 2.100 journal for their motors it stand to reaon that a cast crank should be able to handle around 500 - 650 HP at that size, more if using a Lunati crank. This is what is done to get 360in motors. Offset grind the crank from 2.100 to 2.000. I am only suggesting another logical jump.

 

Actually the stroke gain is .100 inches. By grinding .100 off the "inside of the journal and .000 off the "outside" you move the crankpin C/L by .050. This at the top & bottom of the stroke gives .100.

 

A machinest that I used as a kid used to make welded stroker cranks. He would add material (welded) to one side of the crank throw and then put it in the lath and machine it to the proper diameter.

When I rebuilt the 327 cid engine in my 66 Vette I had him do my machine work and engine balancing before I reassembled it. That was one very smooth running engine.

Mark

 

Well I guess we are both right. You are right if the crank is offset ground to 2.0. The original post, however, was proposing an offset grind to a 1.888 pin dia. (about 0.2" smaller and 0.1" offset). That would yield the .2" increase in stroke that I indicated.

 

J-Rod,
Perhaps we can learn from each other here... I am not aware of any rod manufacturer that produces a SBC rod that accomodates the stock Accura bearing. Please provide the manufacturer and part number so that I can check out the specs... On the other hand, it would not surprise me to learn that a bearing manufacturer would produce a thick shell bearing that fits the small journal SBC rod with the Accura bearing journal diameter... Is that the combination you were refering to? If so please provide the bearing manufacturer and part number of the thick shell bearing... Please educate me here.
At the other end of your post, I think you need to do some more research on what can be achieved with an LS1 regarding long stroke cranks. The combination you suggested (4.125 crank, offset ground to 4.337") is not practical... This is because the reluctor wheel and the counter weights limit rod length to 6.125" (and longer with the combination you suggest). The 4.337" stroke and 6.125" rod results in a piston compression height of only .947", and with a SBC wrist pin diameter of .927", leaves only .483" (to zero deck) for the ring pack and top ring spacing etc... There may be an engine builder out there that would specify such a piston, but I am not one of them... There is no custom piston manufacturer that would make such a piston either... I know that Ross will not build a piston with less that about 1.035" compression height and that requires a support ring under the oil ring... So until someone comes up with a tall deck LS1 case, I think your 480 cid LS1 engine is just a pipe dream... No flames intended, Your comments please...
Shirl
SD Racing Enterprises

 

Now that´s too much tech for me.....I quit :lol: :lol: :lol:

Michael

 

No problem. My original post was to put this out there for comment, and the reason I did so was to invite comments both positive and negative to see if such a combination was possible.

As for rods, most of the aftermarket major rod MFG's produce them. Check with Crower to start. I know the MaxiLite 93s are avaliable.

I did a quick look in their recent Catalog and found references. If you look at any of their currents sheets they talk about producing rods in the "popular Accura and Quad 4 sizes for SBC".

As for the ringpack, you bring up a very valid point there. Obviously that produces a problem that cannot be overcome going with a stoke that large. However, taking the approach of offset grinding a stock crank for an inexpensive stroker is still a workable option.

As you stated, going to all the way to 4.337 may not be practical. But I would suspect that some stroke could be picked up. Now, how much will be limited as you point out by the ring pack and the counterweights.

I guess I need to sit down with my engine math stuff and come up with another maximum limit...

Anyway, thanks for posting the info, keep it coming...


http://www.hotrod.com/editorial/arti...=text&id=84819


[Modified by J-Rod, 1:42 PM 10/24/2002]


[Modified by J-Rod, 1:46 PM 10/24/2002]


[Modified by J-Rod, 1:52 PM 10/24/2002]

 

You've raised a very interesting possibility for stock cranks... Now, I'd like to know if any major tuners have actually done this with an LS1 engine, and what is their experience and success/failure rate... What is the price of a set of these rods? Anything not strictly SBC can be VERY expensive.
The top fuel and NASCAR guys are doing this, but they are using the best forged steel cranks that money can buy... You seem to be suggesting that this experience is transferable to a production cast crank... A cast crank has great fatigue properties, but is not so great with ultimate strength... To offset grind a cast crank to such a small diameter further reduces its strength... Who'se going to try it first? How about it Phill... :D
Shirl
SDRE

 

the problem of offset grinding a LS-1 crank is it is a cast crank that requires that a rolled fillet be used in the corners of the bearing journals for added strength. if you offset grind a LS-1 crank you will loose that rolled fillet and the strength of the crank. the older SB chevy cranks are forged and you can do this and there are over the counter rods out there for the 1.88 bearings. :chevy

 

First off, thanks for the replies. I do want to hear both positive and negative in regards to this.


Now, as for crankpin strength. My example about T/F using a 2.100 crankpin size was to illustrate the 2.100 is probably a bit of overkill (not that that is a bad thing) on the LS1. I understand that when comparing a cast crank to one made out of EN30B there are strength differences to take into effect. No doubt.


My point was that when using a 4340 stroker such as the Lunati, you could increase the stoke by decreasing the crankpin diameter. Obviously the 4340 Lunati is sufficaently similar to the material in a NASCAR crank that this could be considered a fairly close comparison.

Now, as for using it with a stock crank. While I have no empiric data on what the fatigue strength of the stock crank is, there is empiric data to suggest that it is good to around 600HP in its stock form. Which correlates to what I have see out of other stock cast cranks in the past.

So, for a stock motor, or heck even a 6.0L iron block this may be the ticket to picking up extra cubes. I don't know but I guess we'll see.

Oh, One other qustion.

Is the LS1/LS6 a hydraulically rolled fillet? I know my GN cranks are hydraulically rolled, but I was not aware that the LS1 was. The reason that I ask this, is that many folks out there are already offset grinding from 2.100 to 2.000. If they are doing so, they are cutting out the fillet in this process.

Obviously a generous fillet in a crank like this is important, I was just wondering if you were sure the stocker was hydraulically rolled?

 

all cast cranks from GM have hyd. rolled fillets even the 4 cylinder cavalier engines we raced. with the LS-1/6 engines it is more cost effective to buy forged a stroker kit because you will need custom made rods and pistons if you try to do a offset grind and you will still not have the strength of a froged setup.:chevy

 

I'll have to look at a crank. I wonder what ARE and the folks are doing. Obviously they aren't hydralically rolling new fillets intot he crank. My guess is thay must be just putting a generous fillet back in its place.

As for the cost. A stroker kit is the same thing custom rods and pistons, plus a $2600 crank. I was just offering the possibilty of some cost savings. Plus on the stroker cmbos picking up extra inches with the same crank.

 

This wayy to high tech for me.. but I can reliably say..

STAY AWAY FROM CROWER PRODUCTS!!

(you don't wanna know...) :eek:

 

In case anyone was wondering who makes 1.888 rods, Carillo has a nice selection. Sets used by NASCAR teams for one race, or one dyno pull can be purchased from jrmotorsports for $550.
http://www.jrmotorsports.net/

look under products then select connecting rods. There are about 100 sets for sale...

Also Shirl. One of the members of LS1tech disagreed with your comments about the Ross Pistons. Here are his comments. I don't have any other details other than what he posted. Just passing this along...


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LS171Malibu

Launching!
Member # 1609

posted October 25, 2002 01:19 PM
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quote:
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... I know that Ross will not build a piston with less that about 1.035" compression height and that requires a support ring under the oil ring...

Shirl
SD Racing Enterprises
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You can relay to Shirl that is B/S, I have a set of custom Ross pistons in my hands that have a comp height of .975"

Blake Arnold
71 Chevelle
previous set up
1998 ls1 heads and hot cam, M6, bolt-ons applicable with a swapp.
Pictures HERE


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THANK YOU!!!
I was wondering about the "experts" in these forums

 

I agree...especially those from 10 years ago.
IBTL