Will this piston/stroke/rod length work?

Posted By: Von

Will this piston/stroke/rod length work? - 02/25/09 04:41 AM

Mathematically this should work, but will the rod length be ok and not pull too much of the piston ABDC?

4.375 stroke
6.9 rod
1.621 comp height
10.725 deck height

What do you think?

Posted By: Sport440

Re: Will this piston/stroke/rod length work? - 02/25/09 05:31 AM

That will depend on the diameter of the crank counterweights and the contour of the piston skirts and thickness at the wristpin.

To the Deck the math is fine. So is my quick math to BDC. with a 7.25" crank. If things get close get the Makita, out. mike

Posted By: Von

Re: Will this piston/stroke/rod length work? - 02/25/09 04:39 PM

Quote:

That will depend on the diameter of the crank counterweights and the contour of the piston skirts and thickness at the wristpin.

To the Deck the math is fine. So is my quick math to BDC. with a 7.25" crank. If things get close get the Makita, out. mike

Mike,

Thanks for your reply.

If I do have clearance issues, can I turn the counterweights down and rebalance?

Seems like this combo uses 7.1 rods usually, but I already have the pistons and started

Posted By: JohnRR

Re: Will this piston/stroke/rod length work? - 02/25/09 04:54 PM

Quote:

Quote:

That will depend on the diameter of the crank counterweights and the contour of the piston skirts and thickness at the wristpin.

To the Deck the math is fine. So is my quick math to BDC. with a 7.25" crank. If things get close get the Makita, out. mike

Mike,

Thanks for your reply. If I do have clearance issues, can I turn the counterweights down and rebalance?

Seems like this combo uses 7.1 rods usually, but I already have the pistons and started

One thing you need to be concerned about is how far the pistons pulls out the bottom of the bore with the shorter rod .

Posted By: B1MAXX

Re: Will this piston/stroke/rod length work? - 02/25/09 05:09 PM

I run a 4.3 stroke with a 6.7 rod. If that helps

Posted By: Von

Re: Will this piston/stroke/rod length work? - 02/25/09 05:13 PM

Quote:

I run a 4.3 stroke with a 6.7 rod. If that helps

Do you know what the diameter is of your counterweights?

Posted By: B1MAXX

Re: Will this piston/stroke/rod length work? - 02/25/09 05:14 PM

Not off the top of my head but it is an out of the box Ohio crank.

Posted By: Von

Re: Will this piston/stroke/rod length work? - 02/25/09 05:16 PM

Quote:

Not off the top of my head but it is an out of the box Ohio crank.

Thanks!! I'll look it up.

Posted By: DemonDust

Re: Will this piston/stroke/rod length work? - 02/25/09 05:21 PM

Just mock it up. You can't make mistakes that way.

Posted By: JohnRR

Re: Will this piston/stroke/rod length work? - 02/25/09 05:35 PM

Quote:

I run a 4.3 stroke with a 6.7 rod. If that helps

B or RB ???

Posted By: AndyF

Re: Will this piston/stroke/rod length work? - 02/25/09 05:43 PM

You'll be fine, where did you find a 6.90 long rod? The popular rods are 6.70, 6.80 and 7.10. I've seen a couple of other lengths but never 6.90.

Posted By: Von

Re: Will this piston/stroke/rod length work? - 02/25/09 05:45 PM

Quote:

You'll be fine, where did you find a 6.90 long rod? The popular rods are 6.70, 6.80 and 7.10. I've seen a couple of other lengths but never 6.90.

I was thinking I had seen a 6.9. But, I went back and looked and I was wrong. Back to the figuring.

What about 4.5 stroke with a 6.8 rod? It figures to be .054 down in the hole. Will that combo pull too much out at BDC?

Posted By: B1MAXX

Re: Will this piston/stroke/rod length work? - 02/26/09 03:03 AM

Quote:

Quote:

I run a 4.3 stroke with a 6.7 rod. If that helps

B or RB ???

Posted By: n_bogie1984

Re: Will this piston/stroke/rod length work? - 02/26/09 03:27 AM

http://store.summitracing.com/partdetail.asp?part=ESP%2D6860C3D&autoview=sku

how about a 6.86 hemi rod will leave ya about .056 in the hole

Posted By: Von

Re: Will this piston/stroke/rod length work? - 02/26/09 03:40 AM

I checked and the compression height is 1.633

So would 4.5 stroke, 6.8 rod, work? I come with .042 in the hole.

Would it be ok with a 7.48 counter weight? What about bdc?

Thanks

Posted By: Von

Re: Will this piston/stroke/rod length work? - 02/26/09 03:41 AM

Quote:

http://store.summitracing.com/partdetail.asp?part=ESP%2D6860C3D&autoview=sku

how about a 6.86 hemi rod will leave ya about .056 in the hole

Good idea 'cept I need a bbc width rod.

Posted By: n_bogie1984

Re: Will this piston/stroke/rod length work? - 02/26/09 03:51 AM

well you cant exspect me to get everything right

Posted By: RemCharger

Re: Will this piston/stroke/rod length work? - 02/26/09 03:55 AM

Quote:

Quote:

http://store.summitracing.com/partdetail.asp?part=ESP%2D6860C3D&autoview=sku

how about a 6.86 hemi rod will leave ya about .056 in the hole

Good idea 'cept I need a bbc width rod.

Why, are you using a bbc crank?

Posted By: Von

Re: Will this piston/stroke/rod length work? - 02/26/09 02:06 PM

[quoteWhy, are you using a bbc crank?

Some if not most of the aftermarket cranks are set up for a BBC rod.

Posted By: B1MAXX

Re: Will this piston/stroke/rod length work? - 02/26/09 05:14 PM

Why not just use 7.1 rod 1.313 piston (3.75 stroke 400 shelf piston) and 4.5 stroke rb and deck the block for desired comp ratio?

Posted By: Von

Re: Will this piston/stroke/rod length work? - 02/26/09 09:37 PM

Quote:

Why not just use 7.1 rod 1.313 piston (3.75 stroke 400 shelf piston) and 4.5 stroke rb and deck the block for desired comp ratio?

Cuz I already have the pistons.

Posted By: B1MAXX

Re: Will this piston/stroke/rod length work? - 02/27/09 03:05 AM

6.8 rod 4.5 stroke deck for comp. ratio.

Or do you have the crank too?

Posted By: Von

Re: Will this piston/stroke/rod length work? - 02/27/09 03:30 AM

Quote:

6.8 rod 4.5 stroke deck for comp. ratio. Or do you have the crank too?

Dont have the crank. But, if I decide to do the 4.5 stroke, I'll do like you say. Shouldnt be a big deal.