any destroked builds out there
11-12-2008, 06:34 AM
#21
Just my thought on this, based on the poster's original question, he needs to promote RPM, to get the car up there and have it live at that level of power, the Turbo will do all the talking here. It will make up for the under power band hp/tq. For those who run a snail know what they need to do to get boost built.
I would agree to try to get the most cubic inches with in the class rules to help you but at the same time, you do not want to fight physics if he needs to be a HIGH rpm car.
At the same time, making a motor w/ alumnium rods will help promote that RPM needed to make power.
I would agree to try to get the most cubic inches with in the class rules to help you but at the same time, you do not want to fight physics if he needs to be a HIGH rpm car.
At the same time, making a motor w/ alumnium rods will help promote that RPM needed to make power.
11-12-2008, 08:50 AM
#22
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I thought it was already clear we were discussing stroke independent of bore size.
I'm sure you'll agree, increasing the stroke to 4" from 3.75 in the 383 would make more power than the original 4"x3.75" configuration (ignoring rod/cam complications). Similarly, a 4" crank swapped in the 377 would also make more power. Conversely, a 3.25" stroke crank would cost both motors power, even though you might be able to spin them to the moon (assuming the valve train is up to the task).
In any racing class where displacement is free or only lightly penalized, the front runners will not be leaving any displacement on the table. In any racing class where short-stroke motors are favored over much bigger motors, it's only because displacement is heavily penalized, usually by vehicle weight or intake restrictors.
I'm sure you'll agree, increasing the stroke to 4" from 3.75 in the 383 would make more power than the original 4"x3.75" configuration (ignoring rod/cam complications). Similarly, a 4" crank swapped in the 377 would also make more power. Conversely, a 3.25" stroke crank would cost both motors power, even though you might be able to spin them to the moon (assuming the valve train is up to the task).
In any racing class where displacement is free or only lightly penalized, the front runners will not be leaving any displacement on the table. In any racing class where short-stroke motors are favored over much bigger motors, it's only because displacement is heavily penalized, usually by vehicle weight or intake restrictors.
Last edited by novaflash2002; 11-12-2008 at 08:56 AM.
11-12-2008, 10:14 AM
#23
A good comparison of cubic inches pushing displacement in relation to turbo size is something like a 4 cylinder- a DSM- the 4G63, is 2.0L in displacement, however, they are able to make 700 rwhp with a single GT35R, and over 1100 with a GT42R.
With an LS1, you would push a single GT35R out of its efficiency range quickly, and a single 42R on Kyles ( Na$ty TA) TA was done really early and only went a 10.0@ 14x.
With an LS1, you would push a single GT35R out of its efficiency range quickly, and a single 42R on Kyles ( Na$ty TA) TA was done really early and only went a 10.0@ 14x.
11-12-2008, 08:33 PM
#25
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Smokey Yunick liked longer rods but never recommended a smaller engine over a larger one just to have a better rod ratio. We all asked him at PRI and he even got mad that people thought you could make more power with less inches but a longer rod. He just liked longer rods but even said that with today's heads that wasn't even any firm rule of his any longer.
Smoky also noted to the guy that asked him about destroking for power that they had all cheated by building larger engines than were allowed including Roush and many in NASCAR but no one ever cheated by building a really small motor !!!!!!!! (with super long rods) .........enough said.
Smoky also noted to the guy that asked him about destroking for power that they had all cheated by building larger engines than were allowed including Roush and many in NASCAR but no one ever cheated by building a really small motor !!!!!!!! (with super long rods) .........enough said.
11-13-2008, 10:42 AM
#26
FormerVendor
It was at the same time Jack Roush and many others were joking about cheating in the old days in the beginnings of the NHRA and then Grumpy even said "some people" ran bigger stuff except at Nationals and everyone was laughing. Linda Vaughn then tried to take over and kept talking about keeping the performance industry in America and buying Hurst parts. Could have been roundtable too but I think it was breakfast.
Someone even asked about running stuff under the CID limit and everyone up there was confused. We ate a snack/lunch with him at the snack bar and that's when he got PO'd about the long rods vs inches and said people were trying to misquote him. It was the snack bar by the bathrooms in the middle of the show. You have to realize how long ago that first book was written too and what has happened since then.
A NASCAR head flowed 250 at that time if they were lucky on a Chevy.
Someone even asked about running stuff under the CID limit and everyone up there was confused. We ate a snack/lunch with him at the snack bar and that's when he got PO'd about the long rods vs inches and said people were trying to misquote him. It was the snack bar by the bathrooms in the middle of the show. You have to realize how long ago that first book was written too and what has happened since then.
A NASCAR head flowed 250 at that time if they were lucky on a Chevy.
11-15-2008, 07:17 PM
#28
FormerVendor
11-16-2008, 12:46 PM
#29
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In your opinion is the 3.62" stroke crankshaft even capable of reaching the speeds needed to accomplish what he is trying to do here? Shy of the super expencive after market I mean. Or are you talking about only LARGER than stock cranks?
11-16-2008, 07:05 PM
#30
FormerVendor
If you want to stay inexpensive then yes just use the 5.7 or 6.0 3.622 crank.
11-16-2008, 07:28 PM
#31
If no rules are guiding your choice, you would be best served with the largest engine that is of sound mechanical design.
That being said, I have built class engines that used a shorter than stock stroke and ran very well and if the guy that made the original post wants a smaller engine I say have at it!!
Kurt
That being said, I have built class engines that used a shorter than stock stroke and ran very well and if the guy that made the original post wants a smaller engine I say have at it!!
Kurt
I think they key to the original poster's thought was that a 72mm turbo will be the most efficiant on the smaller cube engine, and that's the biggest his class allows. The bigger bore will allow bigger valves and more headflow thus more power. Do the valvetrain right, and have at it.
11-16-2008, 08:38 PM
#32
FormerVendor
The turbo doesn't know if you have a bigger engine at lower rpm or a smaller one at higher rpm. The bigger engine will spool the turbo faster though for sure. The larger engine with the smaller turbo will just have a lower rpm band and can use a tighter converter and taller gears.
