4.5" stroker RPM & durability?
02-23-2002, 03:55 PM
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4.5" stroker RPM & durability?
What RPM's can my engine reliably sustain at cruise and WOT? 3400 to 3600 RPM seems safe but what about 4100 RPM cruise and what is my upper RPM limit? How long can I run WOT 5200 to 5400 RPM and what do you think my engines max upper limit is?
My engine is a 572" tall deck (10.2"), 4.5" Lunati 4340 crank in a 4.5" bore Merlin block, 6.7" Lunati billet rods, JE pistons and a very small cam .575"/.595" lift hydraulic roller. The naturally asprated 572" dyno's at 620hp between 5200 to 5400 RPM.
I see lots of folks claiming they turn 5600 and up on these longer stroke motors but no mention as to how long they sustain these RPMs nor sustain cruise RPM's.
Chuck W
28' Scarab, 572", single Bravo 1,
My engine is a 572" tall deck (10.2"), 4.5" Lunati 4340 crank in a 4.5" bore Merlin block, 6.7" Lunati billet rods, JE pistons and a very small cam .575"/.595" lift hydraulic roller. The naturally asprated 572" dyno's at 620hp between 5200 to 5400 RPM.
I see lots of folks claiming they turn 5600 and up on these longer stroke motors but no mention as to how long they sustain these RPMs nor sustain cruise RPM's.
Chuck W
28' Scarab, 572", single Bravo 1,
Last edited by skunknet; 02-24-2002 at 03:10 AM.
02-23-2002, 09:12 PM
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I have a callies 4340 4 3/4 stroker in merlin 10.20 4.60 bore, oliver 6.70 rods with JE flat tops. I turn 6100 natural and 6700 on nitrous. The cam is a SOLID roller, my engine builder claims the motor is good for 8200 and he would have no problem turning 5900 ALL DAY. I typically cruise between 4000 and 4500. Don't think the bravo would appreciate 5900 r's continuous.
02-24-2002, 09:21 AM
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Rpm reliability is calculated using, as you said stroke length and pistion diameter, weight etc.
If balanced properly you could spin 8k. The top fuel guys do. But, they rebuild every time or two down the track, for other reasons besides just rpm limits.
The reason behind the limits is when you spin things that fast, no matter how well balanced they stretch.
Long story short, if balanced properly and cam/valve springs can handle it, you can spin 5200 and more with no problem.
DAVE
If balanced properly you could spin 8k. The top fuel guys do. But, they rebuild every time or two down the track, for other reasons besides just rpm limits.
The reason behind the limits is when you spin things that fast, no matter how well balanced they stretch.
Long story short, if balanced properly and cam/valve springs can handle it, you can spin 5200 and more with no problem.
DAVE
02-24-2002, 06:06 PM
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you should be able to spin 5200-5400 for a long period of time with all that hardware i spim my 600 sc's 5000+ for as long as i want and they have been great
merlin540 has hydraulic rollers in his motors and spins them 5900 all day long with no problems
merlin540 has hydraulic rollers in his motors and spins them 5900 all day long with no problems
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