Reply With QuoteBradP:
I'll be damned! It does say that!Are we gettin edumacated here or what!!!!!..
I'll be damned! It does say that!
BradP:
I'll be damned! It does say that!Are we gettin edumacated here or what!!!!!..
Umm duh yup! Dats it!
The pistons it is, need to check with the balancer still to see if .060 off the skirts will necessitate a rebalance.
Infomaniac:
BradP This is just my personal preference. Your engine will run fine.
The rod/stroke ratio sucks (1.44). The piston runs away from TDC very fast. The volume of the cyl increases rapidly during combustion. RPM's are limited because the piston can outrun the flame front.
That combination will give a very good vacuum signal because of the piston speed. Just be sure to use components that compliment your combination. You can use larger port heads, open plenum intake and bigger carb. without the normal disadvantages. Keep the RPM's reasonableI definately second that opinion. Consider building rod/stroke ratios with succesfull proven engine combinations like the Small Block Chevy, Chrysler Hemi, and 427 Chevrolet. I personally don't like ratios less than 1.53. One of the reason I run tall deck with .400 long rod and a stock height piston. It also "softens" the low end leave, useful in a flatbottom (less down pedal) or Drag car with high horsepower. Crankshaft pin is at a more "optimum angle".
Can you run the rod length needed for the proper ratio in a standard deck 454 with a 4.25 crank?
Does this affect piston durability in a non race application (longevity)in a mild blower motor? The rod length would be 6.60 does this reduce piston size? I have new Merlin cast iron heads (345's?) worked over by Clay Smith, you said the proper heads will help. How much horsepower is potentially lost with improper ratio? Am I in over my head? Should I just up the boost, grenade the motor and start over? Are Fiat, Info and Gofast trying to make my head explode?
Damn right this an edumacashun!
[ November 19, 2002, 10:51 AM: Message edited by: BradP ]
BradP:
Can you run the rod length needed for the proper ratio in a standard deck 454 with a 4.25 crank?
Does this affect piston durability in a non race application (longevity)in a mild blower motor? The rod length would be 6.60 does this reduce piston size? I have new Merlin cast iron heads (345's?) worked over by Clay Smith, you said the proper heads will help. How much horsepower is potentially lost with improper ratio? Am I in over my head? Should I just up the boost, grenade the motor and start over? Are Fiat, Info and Gofast trying to make my head explode?
Damn right this an edumacashun!I'll try but this stuff can fill a book.
To calculate rod angle divide the rod length (6.135 std Big block length 396/427/454) by the stroke. Your rod angle is 1.44.
With a stock 454 crank, your rod angle would be 1.53.
With a 427 crank (3.76 stroke) rod angle would be a 1.63 which would be the preffered rod angle in my opinion.
Without getting into a book of details, most engine builders consider the 1.53 rod angle to be on the short side. Most would like to get back to a 396/427 type rod angle (1.63)or longer. Most rods all cost the same money no matter what the length (to a point).
The way a longer than stock length (6.135) rod can be used in an engine is to order the piston with the pin hole located up 1/2 of the amount you are stroking the motor. There is a limit to how high the pin hole can be located up into the piston because you are actually starting to bore the pin hole into the oil ring groove.
Example: You are using a stock length rod (6.135) with a 4.250 (.250 stroker) crankshaft. Whoever made your pistons has located the piston pin hole up 1/8" (.125) to compensate for the longer stroke crankshaft you put in. Your rod angle is 1.44.
You could have put in a 6.375 (+.250) long connecting rod, had the piston manufacturer locate the pin hole up another 1/8" (.250 total over stock pin location) and come up with a 1.53 rod angle. As far as a longer rod with a 4.250 stroke, I am not sure what the limitation is on how high the pin can be located.
Visualize the crankshaft rod pin location at just past TDC. You can see the longer rod puts the crank at a more optimum angle. Hope this explains rod angle a little bit and I typed what I should have. If not, everyone can have fun picking it apart! wink A teacher I am not.
I think for what you are doing the 1.44 rod length is o.k. Not what I would have done but remember that much of this is not as critical in a 6500 rpm engine which is what I would expect your red line to be. These are the things you pay your engine builder to know and many times are the subtle differences behind why one motor outruns another.
[ November 19, 2002, 07:23 PM: Message edited by: Fiat48 ]
Fiat48:
BradP:
Can you run the rod length needed for the proper ratio in a standard deck 454 with a 4.25 crank?
Does this affect piston durability in a non race application (longevity)in a mild blower motor? The rod length would be 6.60 does this reduce piston size? I have new Merlin cast iron heads (345's?) worked over by Clay Smith, you said the proper heads will help. How much horsepower is potentially lost with improper ratio? Am I in over my head? Should I just up the boost, grenade the motor and start over? Are Fiat, Info and Gofast trying to make my head explode?
Damn right this an edumacashun!I'll try but this stuff can fill a book.
To calculate rod angle divide the rod length (6.135 std Big block length 396/427/454) by the stroke. Your rod angle is 1.44.
With a stock 454 crank, your rod angle would be 1.53.
With a 427 crank (3.76 stroke) rod angle would be a 1.63 which would be the preffered rod angle in my opinion.
Without getting into a book of details, most engine builders consider the 1.53 rod angle to be on the short side. Most would like to get back to a 396/427 type rod angle (1.63)or longer. Most rods all cost the same money no matter what the length (to a point).
The way a longer than stock length (6.135) rod can be used in an engine is to order the piston with the pin hole located up 1/2 of the amount you are stroking the motor. There is a limit to how high the pin hole can be located up into the piston because you are actually starting to bore the pin hole into the oil ring groove.
Example: You are using a stock length rod (6.135) with a 4.250 (.250 stroker) crankshaft. Whoever made your pistons has located the piston pin hole up 1/8" (.125) to compensate for the longer stroke crankshaft you put in. Your rod angle is 1.44.
You could have put in a 6.375 (+.250) long connecting rod, had the piston manufacturer locate the pin hole up another 1/8" (.250 total over stock pin location) and come up with a 1.53 rod angle. As far as a longer rod with a 4.250 stroke, I am not sure what the limitation is on how high the pin can be located.
Visualize the crankshaft rod pin location at just past TDC. You can see the longer rod puts the carnk at a more optimum angle. Hope this explains rod angle a little bit and I typed what I should have. If not, everyone can have fun picking it apart! wink A teacher I am not.
I think for what you are doing the 1.44 rod length is o.k. Not what I would have done but remember that much of this is not as critical in a 6500 rpm engine which is what I would expect your red line to be. These are the things you pay your engine builder to know and many times are the subtle differences behind why one motor outruns another.Well, guess that covers the first half of page one!!.....
Yeah, My fingers are numb! Now it is your turn!
Fiat48:
Yeah, My fingers are numb! Now it is your turn!
BradP:
Can you run the rod length needed for the proper ratio in a standard deck 454 with a 4.25 crank?
Does this affect piston durability in a non race application (longevity)in a mild blower motor? The rod length would be 6.60 does this reduce piston size? I have new Merlin cast iron heads (345's?) worked over by Clay Smith, you said the proper heads will help. How much horsepower is potentially lost with improper ratio? Am I in over my head? Should I just up the boost, grenade the motor and start over? Are Fiat, Info and Gofast trying to make my head explode?
Damn right this an edumacashun!Do not fret man. Your engine will run OK.
Potential loss of HP if much will probably be in the form of power range. Short rod deals will tend to be more "Peaky" so to speak. Not have a wide power curve.
Those heads will work well with a blower.
There is a bit more side pressure on the piston with short rods. They will wear faster, but will not wear out instantly.
Remember hind sight is 20/20. Get your clearance thing fixed, finish putting it together, put it in the boat and enjoy it.
Oh Yea: I am building a tall deck 540 with a very good rod/stroke ratio for a guy with a stern drive 23' tunnel. It will be 10-71 blown and intercooled on pump gas. He has the very best of everything brand new in it. He will have approx. 10.5 K in the long block ready for blower. It should make some serious pump gas power and push the boat in the 120's
[ November 19, 2002, 08:28 PM: Message edited by: Infomaniac ]
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