Connecting Rod Side Clearance Question
Thread Starter
Racer
Joined: Aug 2005
Posts: 355
Likes: 1
From: Ephrata PA
Connecting Rod Side Clearance Question
What should the side clearance be on the connecting rod crank journal on a small journal 327? I currently have .020 and am wondering if that large of a clearance needs a high volume pump. Anybody have any experience with this?
Drifting
Joined: Jan 2006
Posts: 1,944
Likes: 22
From: Yooperville MI
Should be between .008 & .012 for stock Chevy rods. Wider for aftermarket rods, but use the mfr. spec. If your rods are used Chevy pieces, sounds like someone ground them before. I assume you checked the clearance between each pair? Are all of the rods .020 apart? I would replace the rods that are bad, the oil pump idea is a band-aid. The wide gap will wear the bearings faster at the load points.
Drifting
Joined: Jan 2006
Posts: 1,944
Likes: 22
From: Yooperville MI
Originally Posted by dmentzer
Rods are new Scats and all are a consistant .019-.020.
Race Director
Joined: Jan 2000
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From: Corsicana, Tx
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You'll be OK. It's a little wider than necessary on a small block..but it's no issue. It will *slightly* increase oil flow through bearings, but nothing you would notice. Many new engines use clearances MUCH larger than that on side clearances.
Just use a normal std volume pump with a HP spring. Basically the "Z-28" pump. I like the increased pressure with the stouter spring.
JIM
Just use a normal std volume pump with a HP spring. Basically the "Z-28" pump. I like the increased pressure with the stouter spring.
JIM
Thread Starter
Racer
Joined: Aug 2005
Posts: 355
Likes: 1
From: Ephrata PA
My friend who is allowing me to do all of the mechanical work at his speed shop told me it's not out of the ordinary and I would need to use a standard pump with a higher rate spring. I just wanted to verify it with a few other opinions. I am constantly hearing about never using anything other than a standard pressure pump that I wasn't sure. Thanks.
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Racer
Joined: Jan 2004
Posts: 398
Likes: 0
From: Eastern Shore Maryland
Sound like the same rods i used in my 383, did you decide on which cam? I thought earlier you had the XS274 comp in mind. If so i can give you some results. And my rods also had .018-.020 side clearance.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
Most high volume pumps have a 25% volume increase ... some folks either don't need or don't want all that.
Melling makes a pump that has a 10% v increase and uses a bolt on pickup-screen that can be adjusted up or down about 3/16". This pump's shafts extend into the pump cover ... stronger pump & nice piece ... cost 2-3 times what a plain jane M-55 or M-55HV does.
+10% sbc pump P/N 10552
centered pickup for 7" deep pan P/N 12557
for 7 1/2" P/N 12558
for 8" P/N 12559
Melling makes a pump that has a 10% v increase and uses a bolt on pickup-screen that can be adjusted up or down about 3/16". This pump's shafts extend into the pump cover ... stronger pump & nice piece ... cost 2-3 times what a plain jane M-55 or M-55HV does.
+10% sbc pump P/N 10552
centered pickup for 7" deep pan P/N 12557
for 7 1/2" P/N 12558
for 8" P/N 12559
