454 rod big end and bearing clearance question - Chevelle Tech
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Old Sep 28th, 05, 6:57 PM
BarefootDave BarefootDave is offline
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Question 454 rod big end and bearing clearance question

I've got a small issue and I'd like some educated advice please. The motor I'm building is a total street 9 to 1, VooDoo hydraulic cam .0040 over 454 that will be driven daily and I usually run 20/50w with a high volume pump.

I bought some reconditioned 454 rods with Pioneer rod bolts from a guy with a machine shop in VA Beach. The rods look great and are balanced and I have the specs. I take them to a machine shop closer to home (BillK was a little too far away) and they happen to check one of the rods prior to balancing my assembly. They tell me the big end is @ 2.367 and that the "midpoint" is 2.350 so it is actually .0017 too big. They also tell me it is tapered .0015. with my .010 cut crank it looks like I'm looking at .0040 oil clearance or possibly more depending on how close to tolerance the crank was cut.

I call the guy in VA Beach and he says he purposely cuts them a little big for .0030 to .0040 clearance and that he cuts the cap on a taper on purpose to make the parting line smaller and have less chance of a rod failure. He will gladly resize the rods smaller if I want and will do whatever it takes to make them right.

Both folks have been in the business for 30+ yrs and have great reputations it just appears they have different standards and do things a little different.

My questions are...is .004 too much clearance on the rods? is .0045? Is tapering the big end a common procedure? What would you do?

Thanks for any input!
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  #2  
Old Sep 28th, 05, 9:11 PM
BillK BillK is online now
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Default Re: 454 rod big end and bearing clearance question

Dave,
Taper, if the term is used correctly, is not ok. It means that the rod bore is bigger on one side compared to the other. This is not good and will cause bearings to wear unevenly. I do know that some guys still seem to stick to the old idea that if you cut the caps on an angle, the rod will be perfectly round under high rpm conditions ... I have never done it.
The rod bores need to be the correct size in order to hold the bearing in place. Making them big is really taking a chance on spinning a bearing in my opinion. The "crush" of the rod is what keeps the bearing in place and it has to be correct. I always size rods to the tight end of the spec. If you want more clearance, you can grind the crank accordingly.
I think you may have misstated the sizes. The range for rat rods is from 2.3247 to 2.3252 I always put them at 2.3252"
I think that .004" is way too much clearance. I would either have the guy give you your money back, or ask him to make the rods the correct size and round and straight. If not have the guys at Kenson resize them and figure it a lesson learned. I would not leave them like they are.
By the way, I cannot think of very many engines that should be running 20w50 oil in this day and age. 10w40 maybe, usually 10w30.
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Old Sep 29th, 05, 8:42 AM
BarefootDave BarefootDave is offline
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Default Re: 454 rod big end and bearing clearance question

Quote:
Originally Posted by BillK
Dave,
Taper, if the term is used correctly, is not ok.
Thats what I thought...must be an "old timer" kinda thing. I remember hearing about that 29 yrs ago when I used to build engines.

Quote:
I think you may have misstated the sizes. The range for rat rods is from 2.3247 to 2.3252 I always put them at 2.3252"
You're right Bill......I found my note and they measure 2.3267 but what Kenson suggests is 3.252. Do I need to rebuild the big end of the rods to get that # correct? If so I guess I got what I paid for ($100 for the rods with new Pioneer bolts, balanced/weighed and sized). They charge $120 just to size the rods....sound about right?

Thanks for any other input from any knowledgeable BB builders!
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Old Sep 29th, 05, 2:38 PM
Wolfplace Wolfplace is offline
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Default Re: 454 rod big end and bearing clearance question

Quote:
Originally Posted by BarefootDave
Thats what I thought...must be an "old timer" kinda thing. I remember hearing about that 29 yrs ago when I used to build engines.



You're right Bill......I found my note and they measure 2.3267 but what Kenson suggests is 3.252. Do I need to rebuild the big end of the rods to get that # correct? If so I guess I got what I paid for ($100 for the rods with new Pioneer bolts, balanced/weighed and sized). They charge $120 just to size the rods....sound about right?

Thanks for any other input from any knowledgeable BB builders!
=
Yes you need to have them redone. That is way too damn big.
The only thing that holds the bearing in the rod is the crush & with a thou & a half extra bore you will have about none,,, not good.

On the "taper" I am assuming he is talking about cutting the cap at an angle to pull the parting line in & this is an old production rebuilder trick so the rod will clean up at the parting line & look pretty.
I don't believe in it but it is done & it does work.

Back when we used the stock GM rods we actually ground the cap at a slight angle the other way to add more clearance at the parting line for hi RPM deals so the bearing would not "grab" the crank at the parting line when the rod distorted.
This was part of the way I got bearings to stay where they belonged in L88 rods with TRW pistons at 8500+,,,
I am not recommending doing this today with the better rods & lighter pistons available,,,

But,, back to your deal,, you need to either start with a fresh set of rods (my choice) or have yours redone but be advised they are going to get shorter every time you resize them. Not a huge deal in a stock grocery getter but not the best plan in a performance build.
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Old Sep 29th, 05, 2:59 PM
cody cody is offline
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Default Re: 454 rod big end and bearing clearance question

damn 20/50 and a high volume pump?????
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Old Sep 29th, 05, 5:18 PM
BarefootDave BarefootDave is offline
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Default Re: 454 rod big end and bearing clearance question

I guess the oil and the HV pump wouldn't be the way to fix it??

Seriously...thanks for the input and advice! I am returning the rods to the guy in VA Beach for a full refund and I bought a set of rods from a guy at the machine shop that are already the correct size and length with ARP bolts for the same price.......problem solved!

Thanks so much for being here. We are very lucky to have some of the most knowledgeable folks in the performance business!
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