Reply With QuoteInstead of wearing my fingers out, read this!..
You might want to download the Excel spreadsheet too!..
Rod Ratio! (http://e30m3performance.com/tech_art...atio/index.htm)
Is there anything to look for when building a big inch motor? Short rod= faster acceleration but what about rod ratio?
Instead of wearing my fingers out, read this!..
You might want to download the Excel spreadsheet too!..
Rod Ratio! (http://e30m3performance.com/tech_art...atio/index.htm)
Hinted at this in your other thread, but here are the details. I had a 598 built on a 4.5" crank with 6.8" rods - really short pistons, pins way up in the oil ring, very short ring stack. My buddy Greg has a similar motor but with 6.7" rods. Both motors were built with good parts by reputable builders and made great power when fresh. By the end of the first season, mine was using some oil, maybe 1/2 quart per weekend. After the third season it was going through 1-2 a weekend depending on how much and hard we ran it. Greg's is now at the end of its third season and is starting to use some, maybe 1/2 - 1 quart or so per weekend. So, his is doing better than mine did but still is showing signs of needing some attention. Mine definitely had more hours on it per season, but still I think his oil consumption is better. When I reconfigured for the blower, I went to a 4.25 crank and 6.535 rods to keep the pin out of the oil ring and plenty of room for the rings. I hope this one lasts longer. With your light jet boat, I would trade a little torque for the better longevity. The power will still be there if you use good heads, cam and intake. Just my unedumacated opinion of course...
:boxed:
get an eagle or scat stroker kit 396, it sure takes out alot of the guess work.i've been runnin bbf's so long now that havin to remember all the bbc rod lengths now is drivin me crazy :220v:
Instead of wearing my fingers out, read this!..
You might want to download the Excel spreadsheet too!..
Rod Ratio! (http://e30m3performance.com/tech_art...atio/index.htm)
Nice info artSo they are saying that the piston speed is increased when used on a shorter rod @ TDC BUT can also slow down @ BTDC. Also, faster piston speeds are harder on pins,rods,and bgs. Thats what i got out of them pages..
get an eagle or scat stroker kit 396, it sure takes out alot of the guess work.i've been runnin bbf's so long now that havin to remember all the bbc rod lengths now is drivin me crazy :220v:
Thats what i am thinking but I am still learning so this is all great info for me and everyone else thats reading
Hinted at this in your other thread, but here are the details. I had a 598 built on a 4.5" crank with 6.8" rods - really short pistons, pins way up in the oil ring, very short ring stack. My buddy Greg has a similar motor but with 6.7" rods. Both motors were built with good parts by reputable builders and made great power when fresh. By the end of the first season, mine was using some oil, maybe 1/2 quart per weekend. After the third season it was going through 1-2 a weekend depending on how much and hard we ran it. Greg's is now at the end of its third season and is starting to use some, maybe 1/2 - 1 quart or so per weekend. So, his is doing better than mine did but still is showing signs of needing some attention. Mine definitely had more hours on it per season, but still I think his oil consumption is better. When I reconfigured for the blower, I went to a 4.25 crank and 6.535 rods to keep the pin out of the oil ring and plenty of room for the rings. I hope this one lasts longer. With your light jet boat, I would trade a little torque for the better longevity. The power will still be there if you use good heads, cam and intake. Just my unedumacated opinion of course...
:boxed:
Thanks brian, thats some good info there. I will definately keep this post in mind :idea:
Nice info art
Here's some more info for ya!..
Rod Ratio Dynamics! (http://e30m3performance.com/tech_art...mics/index.htm)
here's my two cents... as far as a boat motor goes they are running at higher rpm for longer periods of time.. if you want it to live at high rpm put long rods in it. long as you can get. you will lose a little tourque but the reliability will be worth it.. your piston skirts will thank you for it.. :rollside:
For a standard, and off the top of my head deal, here goes.
Higher piston pin height means lighter piston. But do not go higher than about 1.12 on standard ring deal, or 1.08 on dual .043s' or you will start to have ring and stacking issues.
Longer rod is easier on the sideloading of pistons, cylinder walls, piston rocking, and ring stuff. But the difference in 1" longer or shorter rod will not make any difference in power. Lots of BIG dollar tests taught us that many moons ago.
I like to run longer rods for wearing properties, and to make a lighter piston. Oil support rings are a standard around this shop. Just don't get greedy and stack them too tight.
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