Has anyone ever used one of the 106mm Brian Crower cranks in a 4g64? I was wondering if anything needed to be done to the block for clearance? Also wondering what the max RPM range with aluminum rods and 1g ported polishes oversize valve head would be?

jrloarr said:

Has anyone ever used one of the 106mm Brian Crower cranks in a 4g64? I was wondering if anything needed to be done to the block for clearance? Also wondering what the max RPM range with aluminum rods and 1g ported polishes oversize valve head would be?

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I am not sure if you can still order it. I thought it's already discontinued many years ago. They now have 102mm crank instead. I have never used the BC 106mm crank in a 4g64 block but if you are thinking to use it with aluminum rods, then for sure you will have to grind the block/main cap to keep the rod/block clearance within safe range and may also need to modify oil passage. How much you will need to grind would depend on the rod length and dimension.
I am speaking is based on a 4g63 6 bolt block and the BC 106mm/102mm crank is only for 7 bolt. so something could be different between on a 6 bolt block and on a 7 bolt block, on a 4g63 and on a 4g64. but I think what you have to do would basically be the same.

Not many have been used in a 7 bolt DSM, but I believe there was a certain tuning shop that went through a few of those in an Evo 8. Same part number.

IIRC, they had a lot of trouble keeping it together. Ruined multiple 2.4 blocks for different reasons, at least 1 was from rapid wear and egging out the cylinders.

There are better options, that much stroke really limits max rotational speed the assembly can handle.

Well the rotating assembly is together. CP Carrillo custom H beam rods

Keep in mind this is a NA build do to racing rules. 2g head ported and polished with 288 cams. The engineer that came up with the rod and piston numbers is telling me 300 HP on the conservative side. Valve reliefs are milled so it’s now non interference as well. Cost? Well I got the crank new old stock for $800. The pistons, rods, pins, rings, and King bearings were $2,700. Like new used cams were $200. The porting was free. Polishing I did my self. The add new water pump, oil pump, gaskets, timing components machining block, aluminum flywheel, all ARP studs and critical bolts and DSM Link I’d guess the total is at something north of $7k with everything including what I’m forgetting Big price tag for 300HP.

Is the spec sheet on those pistons mostly correct? 87mm bore and 160mm rods?

CR = 4.0:1, yeah right

So, that means those pistons have a compression height of about 22mm? (Center of pin bore to crown)

And you're over 2500cc for displacement, with a decent rod ratio of 1.50.

I’m sure that’s a misprint. It actually calculates out to be exactly 18.63486:1 CR. Insane! But I was told once I went over 12.5:1 I may as well go all the way because any fuel that will run over that will run at any CR. Guess I will find out. The guy that designed it should know what he is talking about because he was John Forces engineer way back.

jrloarr said:

I’m sure that’s a misprint. It actually calculates out to be exactly 18.63486:1 CR. Insane! But I was told once I went over 12.5:1 I may as well go all the way because any fuel that will run over that will run at any CR. Guess I will find out. The guy that designed it should know what he is talking about because he was John Forces engineer way back.

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The compression ratio of this setup would be around 14 with the .030 head gasket that is specified in the spec sheet. With a standard .051 cometic MLS would be around 13.25.

You are exactly correct. Just got of the phone with CP. they said the same thing

How accurate are these displayed figures?

You can use injector duty cycle (for a known flow rate injector) and afr to estimate the airflow, but it's still a guess as to how much power that airflow actually creates. The generally accepted guess is about 10whp per each lbs/min of airflow.

I'm sorry but I would need better proof to believe you're making 449hp naturally aspirated on a 2.5L engine.

Not saying I am. Seems awful high to me. That’s why I asked.