Question on connecting rod side clearance
Question on connecting rod side clearance Greetings all. I'm putting my LS1 together and found my connecting rod side clearance is out of tolerance from what GM recommends. They spec it out between .004 - .020. I'm seeing a spread from .020 - .023, measuring between the rods, on each journal, with a feeler gauge.
Setup is:
Stock crank, never turned (nitrided)
Callies Compstar rods
King bearings
Mahle Pistons
Thrust checks out good (.004) along with the mains (.002) and rods (.0015 across the board). I did a search and saw a mention of a few people with this issue with Eagle rods.
Any shops, please chime in. For those individuals who have built their own and recognized this, how are you holding up? Any oil pressure issues? I've got a Katech "modded" LS6 oil pump, will this offset any loss in oil pressure I may see? Thanks in advance!
Ryan
Setup is:
Stock crank, never turned (nitrided)
Callies Compstar rods
King bearings
Mahle Pistons
Thrust checks out good (.004) along with the mains (.002) and rods (.0015 across the board). I did a search and saw a mention of a few people with this issue with Eagle rods.
Any shops, please chime in. For those individuals who have built their own and recognized this, how are you holding up? Any oil pressure issues? I've got a Katech "modded" LS6 oil pump, will this offset any loss in oil pressure I may see? Thanks in advance!
Ryan
The side clearance you have will work just fine, and the bearing oil clearance will ultimately regulate the oil pressure. As a suggestion to verify that your measured side clearance is correct, you may want to use a second feeler gauge of equal thickness on the opposite side of the rods at the same time. This will ensure that the rods are square with each other while checking them.
The Compstar rods should measure .940"-.941" thickness on the big end, which you can verify with a set of calipers, or a micrometer. We check this dimension during QC, so I wouldn't expect that to be out of spec. Within reason, side clearance is your friend.... too little side clearance is asking for trouble in a performance application.
There are some high end applications that control the lateral movement of the rods on the pin end, and the big ends of the rods just float on the crank, with a very generous amount of side clearance. I believe this is done to reduce frictional losses since there is much less rotational movement at the pin end of the rod. This is an extreme example of not having oil pressure issues because of excessive side clearance.
The Compstar rods should measure .940"-.941" thickness on the big end, which you can verify with a set of calipers, or a micrometer. We check this dimension during QC, so I wouldn't expect that to be out of spec. Within reason, side clearance is your friend.... too little side clearance is asking for trouble in a performance application.
There are some high end applications that control the lateral movement of the rods on the pin end, and the big ends of the rods just float on the crank, with a very generous amount of side clearance. I believe this is done to reduce frictional losses since there is much less rotational movement at the pin end of the rod. This is an extreme example of not having oil pressure issues because of excessive side clearance.
Last edited by Joe Racer; May 29, 2005 at 07:18 AM.
Originally Posted by Joe Racer
The side clearance you have will work just fine, and the bearing oil clearance will ultimately regulate the oil pressure. As a suggestion to verify that your measured side clearance is correct, you may want to use a second feeler gauge of equal thickness on the opposite side of the rods at the same time. This will ensure that the rods are square with each other while checking them.
The Compstar rods should measure .940"-.941" thickness on the big end, which you can verify with a set of calipers, or a micrometer. We check this dimension during QC, so I wouldn't expect that to be out of spec. Within reason, side clearance is your friend.... too little side clearance is asking for trouble in a performance application.
There are some high end applications that control the lateral movement of the rods on the pin end, and the big ends of the rods just float on the crank, with a very generous amount of side clearance. I believe this is done to reduce frictional losses since there is much less rotational movement at the pin end of the rod. This is an extreme example of not having oil pressure issues because of excessive side clearance.
The Compstar rods should measure .940"-.941" thickness on the big end, which you can verify with a set of calipers, or a micrometer. We check this dimension during QC, so I wouldn't expect that to be out of spec. Within reason, side clearance is your friend.... too little side clearance is asking for trouble in a performance application.
There are some high end applications that control the lateral movement of the rods on the pin end, and the big ends of the rods just float on the crank, with a very generous amount of side clearance. I believe this is done to reduce frictional losses since there is much less rotational movement at the pin end of the rod. This is an extreme example of not having oil pressure issues because of excessive side clearance.
Ok. That makes me feel better to here it from the "horse's mouth", so to speak. While I got ya here though
.... What kind of rod bolt stretch should I be seeing? I'm seeing .004, pretty consistently, @ 70 ft/lbs. This might be fine, depending on how you spec'd the bolts, ETC. It just doesn't jive with the stretch I have typically seen with ARP hardware in the past (.006 ~.007). The only literature that came in the Compstar box was a recommended torque rating. I tried to call over the last couple of days but I keep missing the one or two individuals who can actually answer this question (that's what I'm told anyway). Thanks a ton.Ryan
I was worried also...mine(eagles) were about .026. The guy from Eagle told me a lot of the circle track racers use their rods and the idea of the extra side clearance is to get more oil flow thru the rod bearings as a cooling measure on sustained high rpm engines. Makes sense but scares you when you first encounter it...seems unecessarily sloppy.
FormerVendor
Joined: Nov 2001
Posts: 3,065
Likes: 6
From: Houston, Tx.
Hey if it makes you feel any better 75 per cent of the aftermarket rods are like this and they never have any problems at all. This is from someone that does this everday so don't worry a bit!
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Verdad Gallardo FormerVendor
Joined: Nov 2001
Posts: 3,065
Likes: 6
From: Houston, Tx.
Originally Posted by ChucksZ06
I was worried also...mine(eagles) were about .026. The guy from Eagle told me a lot of the circle track racers use their rods and the idea of the extra side clearance is to get more oil flow thru the rod bearings as a cooling measure on sustained high rpm engines. Makes sense but scares you when you first encounter it...seems unecessarily sloppy.
