LetsGetThisDone

iTrader: (1)

You can hone bearing tunnels for clearance. As with the crank journal having a range for diameter, the bearing bores also have a range.

I suppose you could also polish the crank to remove some material, but not everyone has access to a machine shop that can properly micro polish a crank.

RightSaid fred

Offset grinding has been done for years and years and years.

You're NOT going to do it to a 4G63 because the big ends are only 45 mm.

It was commonly done 40 odd years ago to the Cleveland V8 where the 2.311 big end was offset ground and reduced to 2.1 inch in order to use narrowed SBC conrods. That increases the stroke from 3.5 to 3.7 inch. That takes a 351 to about 370......I've got one of those too.
With a ( free from the junkyard) 6G74 crank you can increase the stroke from 85.8 mm to 91 mm by reducing the BE size from 55 mm to just under 50 mm.
That will give an increase from 3.5 to between 3.7 and 3.9 litres depending on bore size.
You can still go 3 sizes below that in case of a spun bearing.
The only downside is that the crank needs nitriding and balancing afterwards and certainly beats paying $3500+ for a billet one.


...just to correct matters.


Plus polishing is only done to take off the roughness left by the stone.
If you try to use a polisher for reducing diameter, the surface will become uneven.
It's the wrong tool for the job.

2winscroll

Give it a break Fred...yada yada yada. Off Topic AGAIN.

Ayoustin just ignore Fred for obvious reasons. What bearing clearance would you recommend for a 9500 rpm 4g63, stock crankshaft, GRP aluminum rods, 50 psi boost, 1000~1100 horsepower, running E85 with a healthy shot of methanol?

Oh yea oil recommendation?

Ayoustin

iTrader: (2)

Hahaha he lost me after he started talking about small blocks.

I would take my recommendation with a grain of salt as I have no experience with aluminum rod engines but I would say right around .003". I set my rod clearances to .0025" on my engine but it's never going to see much more than 500whp or higher than 9k rpm. If I were in your shoes I would consult whoever is building the engine. If you're building the engine then I would contact the bearing manufacturer and tell them that same info and see what they recommend. A third source you could ask would GRP, like I said I've not dealt with Al rods before but it wouldn't hurt to call them and ask if Al rods require larger clearances.

As for oil, something thick. I'm running 15-50 dominator oil but that's mostly because I wanted something with a high HTHS viscosity that would keep the engine safe during short starvation periods. For a drag application (assuming that's what you'll be using it for) I would probably run Brad Penn 15-50 as it's a pretty well proven oil that protects well and isn't crazy expensive. Another oil I would consider would be 15-50 VR1. The Brad Penn stuff isn't rated for E85 use so you would want to keep your OCI pretty short. The VR1 is better rated for alcohol use I think (don't quote me on that) but it's also a good amount more expensive.

2winscroll

Hey Thankyou for the reply. I do all my own engine assembly and have a very good machine shop that does only racing work, so they are usually my "go to" for clearance questions. It's always nice to hear others educated opinions on this type of stuff. I was using Brad penn but im switching to redline. We will see how it performs.