Whats the deal with destroked engines?

[GsxrMike]

I want to build an engine eventually and I would like to build something that will be able to turn high rpm and produce high HP (for mud races) but still be torquey enough to mess around on trails etc. My buddy is slapping together an engine and we were going threw a bunch of old parts and found a 327 crank. We started talking about destroking a motor and I started doing a little research and I can't seem to get a straight answer. I found this article http://www.purplesagetradingpost.com/sumner/techinfo/350 chevy engine.html
and I think this motor would be SWEET for what I want but everybody says that destroking a motor kills the torque for higher rev limits. I don't get it. In the article they produced more than 400ft/lbs of torque over a very wide rpm range and I'm sure with a little better set of heads and a larger cam they could have made the HP jump quite a bit. What does everyone think of destroked motors?

 

[dyeager535]

I *think* that the article is old enough that it's lost some of it's validity. That's right when the "fast burn" (Vortec, etc) combustion chamber came out, I suspect you can do just as well, if not better, with more modern stuff, in more than just the heads.

Put an LS1 motor up to those numbers and see what they look like. Bore/stroke ratio, etc.

 

[BILTIT]

Yes, less stroke will reduce torque and increase rev limit. We do it all the time with pontiac engines. Our 455P usually have too much torque to put to good use in a street car so we destroke them to a 440 and they have a nice combination of revability and usable torque. 400P have just enough torque (with the right gear ratio) but you need to scream them for the HP.

Remember heads and cam is where the power is for any combo. Cubes add power across the range though.

 

[Roxie78]

Forget about the 327 and build a 383........ you can get as much RPMS and way more torque. my buddy HAD a 327 in a mud truck for the last half of mudding this year until it ate it's puppies, I have a 383 in my truck and it wants whatever you can through at it.

 

[smalltruckbigcid]

I want to build it to turn high rpm's...how high? The right rotating assembly can turn 10,000rpm all day, its just not cheap.

But if you say 6500rpm is fine then build a 383 with a forged crank and figure out the heads and cam because they are going to be the key to your happiness on both ends. Remember the cam that does what you want at 2000 is going to run out of steam around 5800.

 

[dyeager535]

Yep...you aren't going to build a high RPM screamer that is going to be any fun at all to drive at low RPM's. Solid lifters, massive cam, stout springs, beefy rockers, etc. With completely redesigned (read modern) engines you can make lots of power on a curve that is more of a horiztontal line, but that is where different bore/stroke combinations, head design, and the like come into play, such as the LS series of motors.

I do have to say that if they are truthful, and were running 11:1 compression on 87 Octane back then, with no problems, I'm impressed. Even with aluminum heads that's roughly equivalent to 10:1, which this very second is about the max on 87 octane that any major manufacturer I'm aware of, can get away with.

 

[1979jimmy350]

i would look into the LS style engines, they cna be had way cheaper than it costs to build a 383 and in stock trim they have tons of power and torque, plus they rev well and have injection

 

[toomany]

If the truck were built only to mud race, with steep gears and a high stall converter, it could work out decent. But you said you wanted to do some trails too, how much time do you really spend at high rpm on the trail (where the power would be)?

If I were to destroke an engine, or build a small displacement one, I wouldn't put it in a truck. Maybe a 377 (350 crank in a 400 block), but it would be just as easy to build a 406.

Bigger motors make more power, and do it easier. A 302 making 450hp is going to be working allot harder than a 400 making 450hp at the same rpm. If you're gonna build a motor stick with 350 or bigger.

 

[BILTIT]

FWIW, i rev my 462 pontiac (4.21 stroke) to 6500 no problem. Not sure what you are looking at for high rpms.

 

[Roxie78]

If the truck were built only to mud race, with steep gears and a high stall converter, it could work out decent. But you said you wanted to do some trails too, how much time do you really spend at high rpm on the trail (where the power would be)?

If I were to destroke an engine, or build a small displacement one, I wouldn't put it in a truck. Maybe a 377 (350 crank in a 400 block), but it would be just as easy to build a 406.

Bigger motors make more power, and do it easier. A 302 making 450hp is going to be working allot harder than a 400 making 450hp at the same rpm. If you're gonna build a motor stick with 350 or bigger.

Agree totally I had a decently built 350 in my truck and then built a nice 383 and it is night and day difference... the power is in cubes!!!

 

[ryoken]

perfect destroked motor = chevy 302..

cinderblock the pedal and watch it scream all day..

truck, eh, prolly not the best idea...

 

[GsxrMike]

Ok so the destroke is out. Whats with the torque curve in the motor they built in the article? It looked good to me. I have heard alot of "rumors" the 383 are "popper" motors because they don't last long. I have an LS1 sitting in a wrecked Camaro I have sitting in my backyard that I am trying to sell. Maybe I will just part it out and keep the motor. Thanks for the help guys!

 

[Roxie78]

Poppers i would say not as long as they are built right. I have a good friend that race dirt track and has had the same 383 for 3 yrs turning it 7k every night. But really if you don't cut ANY corners on the build of any motor you should get along fine................

 

[dyeager535]

LS1 is pretty hard to beat. Should last about forever, as flat a curve as you are likely to get, good economy, good power, injected.

 

[GsxrMike]

I don't know a whole lot about LS1 motors. How hard is it to start squeezing more power out of one and still keep the computer.

 

[dyeager535]

I don't know much beyond what I posted above unfortunately. I think you have to flash the prom for any changes, but it's probably quite common nowadays.

You would probably be best off trying it out as-is first, and seeing what you think.

I believe enginemasters did a bit on the LS1, but I'm not certain of that.

 

[Stomis]

Cheap RPMS would be the only advantage. Even then with how far technology has come along the concept really doesnt hold water quite to well.

 

[Hogback Fabrication]

I don't know a whole lot about LS1 motors. How hard is it to start squeezing more power out of one and still keep the computer.

Most LS1's were rated for ~315 hp but put the F-bodies they came in usually put more than 300 hp to the ground, meaning that GM underrated those motors (they are probably more like 350 hp at the motor).

As for getting more power out of them, the computers are very tolerant. They can handle changes much better than the old TBI computers.

 

[sandawgk5]

Alot of the new buggys being built by guys are running the LS series motors so that should tell you something about the tune-ability of them.

If I had the funds or could find one cheap I would put a 6.0 in my K5.

Dik

 

[uao85]

i would look into the LS style engines, they cna be had way cheaper than it costs to build a 383 and in stock trim they have tons of power and torque, plus they rev well and have injection

x2... Carcraft magazine has been doing periodic 5.3 engine builds while testing parts along the way and how much power they pick up from stock parts. With very little money they have been pulling 500+hp from a stock bottom end 5.3...enough said. time for a 5.3 swap.

Remington