What main bearing clearances are you guys running with aluminum Shelby blocks?
 

nm .

Clearances should be NO LESS THAN .0025. I am running between .0027 and .003 on the mains and rod bearings. Anything less can cause problems (I know first hand).


Clois

Keep in mind that these are what I recommend for racing engines, but the oil clearance you use depends on oil viscosity. With that said, main-bearing oil clearance should be about 0.0026 in. However, if a low-viscosity oil such as 0-20W is used to reduce pumping losses--not recommended for the street or long engine life--oil clearance should be on the tight side, or about 0.0018 in. But don’t be surprised with low oil pressures at speed. Ten 10 psi is typical on the high banks. Likewise, zero oil pressure has been observed in the lights with drag cars. In both cases, coated bearings allow the crankshafts and bearings to survive.

clearance
 

nm .

Byots: You can either purchase coated bearings or send them to a coater such as Calico in Denver, NC. Buildup from the coating is 0.0002 to 0.0004 in.

No I don't have an aluminium block. Dean Lampe and I had our 427's built by a builder that set both our tolerances at .001-.0015 on mine and between .0012 and .0018 on Deans. Dean spun #1 rod bearing w/in an hour after getting it back from the builder. My oil pressure dropped and my oil temp went up 30 deg (210)before I shut mine down. Both engines had been ran in for 1 1/2 to 2 hours before they were given to us. Both our engines were running 20-50w Valvoline. Both engines are having their cranks re-turned to .0020 under to accomodate .0027-.003 clearances and mine is getting the correct oil pump (MHV 57). We are not real happy campers.

Clois

If it had not been for George at Gessford I would have assembled my 427 with the bearings in the .0015 to .002 range thinking that was perfectly "normal". No doubt George saved my butt!!! Once again making a strong case for finding a builder that KNOWS FE's!

I understand the greater clearance is required because of the larger journal size of the crank than most of other engines? I don't know why the clearance specs would change with an alloy vs iron block? Or if it would.

CI v. Aluminum main clearances shouldn't be any different. The caps are steel regardless of block material. And when cross-bolted, the top half of the bore, be it ci or aluminum, should stay put.

clearance
 

nm .

I would work with the low end of the standard oil-clearance spec with an aluminum block. But don't forget oil viscosity and application. More engines have been killed with high-viscosity oil and tight clearances and vice versa. Starting a cold engine with tight clearances and cold oil will cause scuffing. Cold oil will have a hard time squeezing into those tight clearances. And there's nothing like experience. Go with what works.

When checking clearances, do it with the block at about 72 degrees with the bearings in place and the main caps torqued to spec. Otherwise there's nothing to it. :LOL:

For a good idea of clearances check out Childs & Alberts web site: http://www.childs-albert.com/catalog...gs.pdf#search='aluminum%20block%20oil%20clearance'

On the Gessford website under "Blocks" there is a picture of the spec sheet that comes with the shelby aluminum blocks. It says "allow a moderate bearing clearance. .0022-.0028 is a good choice".

Hope this helps.

Clois. Who built yours and Deans motors?

Michael, formally of Brookside. Infact grew up behind the new Harley Dealer on Peoria.

Gotta love the Cramalot Inn! Viva Tulsa...(smiles)

I had rather not say at this time but I may be talking soon. None of the good guys we all know around here and it wasn't my former builder Carbone'. One of those deals where another builder has an engine and in order for you to buy it he has to do the build.


Clois

.00225 rod and main,,and thats "word" Tim

Hey Buzz, I went bye the old Camelot about 3 years ago , it was all borded up and looked more like the Munsters house than the quality motel it was when it was 1st built. Peoria Ave was the place to be on Fri, Sat nites. Places like Pentingtons Drive Inn made Arnolds look pale by comparison. It truely was American Grafitti every weekend. It was a great place to grow up and now that I'm nearing retirement its getting time to go home. Plus you cant beat the exchange rates on Calif/Tulsa Real Estate.

clearance
 

n m .

Would the coated bearing make a difference on the clearances?

Chris

Michael:

Yeah, peoria was quite a place in the past. It is making a comeback now again. Property prices on brookside are climbing. Can you believe 180-200K for those houses down there? I grew up next to Zink park on 31st right off of peoria and my dad sold his house ..got over 600K and it was about 2/3rds of an acre. They tore down the house, they just wanted the land. Just going nuts there.

Camalot in is FULL of asbestos..that is why it is still standing. No one wants to pay to have the thing taken down the proper way, would cost more than the property is worth. So it has turned into the biggest eye sore on the planet. Penningtons moved to 81st and Lewis and then went under. Danged if I can't taste a slice of that black bottom pie right now! The restless ribbon. I remember going down there in the 60s with the folks who went down there just to "watch the hiipies" and their chevy vans all painted with murals and everything. Cars jacked up to the moon. Bell bottoms. One time, I was about 9 or 10...wandered into Zink park and found myself right in the middle of an orgy...no kidding. I just sat and watched! Dad did not have to tell me NOTHING about the birds and the bees after that.

LOL....yeah, those were the good ole days! Now I am back in town, live 81st and harvard...right up the hill from God's place (or Oral Roberts Univ to some). The town sure has changed in some ways and other ways, nothing changes.

Sorry for my digression and of topic comments, just walked through yesterday a little.

Buzz

Buzz,
No kidding. I grew up on S. Evanston right off 81. We were the poor saps with the fence between us and OR. Not sure if it was to protect us or them.

I nearly fell over a couple years back visiting on business. Saw the new OR medical center on the other side of 81. They took away all those pretty pumps for OR????

Chris