Aluminum rod bearing clearance
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Aluminum rod bearing clearance
What would be optimal bearing clearance on an 1.88 rod journal with GRP aluminum rod on an all out race motor turning max RPM of 8500
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Re: Aluminum rod bearing clearance
AF2 : I have GRP rods as well in at .002" or a shade less.I was trying to help the thread.
I have not seen my bearings yet.
I have not seen my bearings yet.
"I promise you Sheriff, I won't throw one more rock... Didn't say nothin' 'bout no brick!" --Ernest T Bass
Re: Aluminum rod bearing clearance
Michael Giannone who owns MGP rods and used to own GRP rods recommends .003 to .0035 for aluminum rods...period. Personally since I run his rods I always shoot for that clearance and the bearings always seem happy.
Blessings......Ron.
Blessings......Ron.
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Ron Clevenger
CSU Gas Dominator ProCharger nonintercooled
Top Eliminator West http://www.topeliminatorwest.net
Steve Morris http://www.stevemorrisengines.com
6.49@219mph (still tunning)
John 14:6
Ron Clevenger
CSU Gas Dominator ProCharger nonintercooled
Top Eliminator West http://www.topeliminatorwest.net
Steve Morris http://www.stevemorrisengines.com
6.49@219mph (still tunning)
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Re: Aluminum rod bearing clearance
We just dis assembled our motor with MGP rods, .0035" clearance....bearings were coated, 160 passes and a ton of dyno pulls several weeks ago to work on carbs....... The bearings look perfect !! best we have ever had....... Wished I hadn't taken it apart....... Wanted to change rods........Motor was making 1220hp........ Reher Morrison likes the wider specs. also
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Re: Aluminum rod bearing clearance
Thanks for the info just mocking motor up and had .0037 i thought it was a .0005 on the fat side but talked to some eperts and they said .003-.004 with my combo .
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Re: Aluminum rod bearing clearance
I always like that "little extra" that seems to be too much on any Alum. rod because they always settle a little between the cap and rod in the serrations. That chaffing action between the cap and rod will close up the clearance just a little after they are run. If you are setting it up to run with REAL thin oil you might want to tighten up the clearances some. I've seen engines with loose bearing clearances loose hp on the dyno when real thin oil is tested. It has to do with the film strength of the oil and the crank contacting the rod bearing causing a little drag.
Adger Smith
Adger Smith Performance Engines
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Adger Smith Performance Engines
903 794 7223 shop
903 824 4924 cell
adgersperf@aol.com e-mail
Re: Aluminum rod bearing clearance
How do you know that the HP loss was not from increased leakage and windage? Was there visible evidence on the bearings?
"I promise you Sheriff, I won't throw one more rock... Didn't say nothin' 'bout no brick!" --Ernest T Bass
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Re: Aluminum rod bearing clearance
I still say WOW.
What all out race motor are we talking about?
Blown Alky likes a different rod clearance than a n/a gas deal.
How can you know? Not knowing what motor is being talked about.
What all out race motor are we talking about?
Blown Alky likes a different rod clearance than a n/a gas deal.
How can you know? Not knowing what motor is being talked about.
GURU is only a name.
Adam
Adam
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Re: Aluminum rod bearing clearance
No loss of Vac... so not extra blow by... Take the thin oil out and the power came back. I made a few more pulls checking a few other things and quit the session. I've done that test several times with customer engines and seen the same thing a time or two. Esp with big inchers... one of My own little SS/Comp V-6 engines did it too. I took it apart after I took it off my Dyno and the bearings did show signs of bumping the crank. I also called one of my buddies that works in an engine shop for a cup team and he said all their engines that use thin oil are set up with tighter bearing clearances than the engines using heavier oil. He said they had seen exactly what I had noticed. I have also had a non coated cam bearing stick with thin oil. I think Too much load with the heavy roller springs pushed the thin oil film out. I think a tight Jesel belt contributed to te load. Thats the only explanation. I polished the cam and put coated bearings in, ran the 00 oil and had no more problems. I'm pretty sure just puttimg thin oil in an engine doesn't mandate an automatic HP increase. I'm sure you should build the engine esp. for thin oil to get the most benefits fom it.
Adger Smith
Adger Smith Performance Engines
903 794 7223 shop
903 824 4924 cell
adgersperf@aol.com e-mail
Adger Smith Performance Engines
903 794 7223 shop
903 824 4924 cell
adgersperf@aol.com e-mail
Re: Aluminum rod bearing clearance
Thanks for the reply.
BTW I think Super Stock rules. I love those cars.
BTW I think Super Stock rules. I love those cars.
"I promise you Sheriff, I won't throw one more rock... Didn't say nothin' 'bout no brick!" --Ernest T Bass
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Re: Aluminum rod bearing clearance
I have not seen to date any engine lose hp from wider clearances as opposed to tighter ones. I do see in some occasions slight hp loses from lighter viscosity oils when using dry sump pumps due to the inability to create the vacuum that a heavy oil creates when going through the scavange sections.I've seen engines with loose bearing clearances loose hp on the dyno when real thin oil is tested. It has to do with the film strength of the oil and the crank contacting the rod bearing causing a little drag.
strangemagicperformance.com
Strange Magic Camshaft Technologies
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Strange Magic Camshaft Technologies
Decisions on parts and advise should not be based on how much money a company can pour into marketing. This is a common mis-conception in the industry.