l48 vs 290 hp GM crate engine?
Thread Starter
Intermediate
Joined: Feb 2008
Posts: 39
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From: Foley Alabama
l48 vs 290 hp GM crate engine?
OK, just a newbie trying to learn all this stuff and looking to make more hp engine out of my L48.... lots of good info found on this topic in the searches on this site and on the internet.
But something isn't making much sense to me... the 290hp GM crate engine looks to have basically equivalent components to the L48 with the exception of the cam: dish pistons, 8.5:1 compression, same valve sizes, etc. The cam in it appears to be the same specs as the L82 cam, but the L82 is 9:1 compression and only 215 at the wheels. I understand the 290 is rated at the flywheel and the L48/L82 is rated at the rear wheels, but something here doesn't seem to add up to me....
what I am missing or misunderstanding here????
thanks,
Michael
But something isn't making much sense to me... the 290hp GM crate engine looks to have basically equivalent components to the L48 with the exception of the cam: dish pistons, 8.5:1 compression, same valve sizes, etc. The cam in it appears to be the same specs as the L82 cam, but the L82 is 9:1 compression and only 215 at the wheels. I understand the 290 is rated at the flywheel and the L48/L82 is rated at the rear wheels, but something here doesn't seem to add up to me....
what I am missing or misunderstanding here????
thanks,
Michael
Le Mans Master
Joined: Apr 2001
Posts: 5,000
Likes: 1
From: Minneapolis, Mn USA
There is the parasitic loss of the accessories for the SAE net rating. -fixed!
IMHO, go LS1. WAYY more power out of the box, less weight, and no BS about flat tappet cam oil ZDDP crap!
IMHO, go LS1. WAYY more power out of the box, less weight, and no BS about flat tappet cam oil ZDDP crap!
Last edited by MN-Brent; Nov 18, 2010 at 05:15 PM.
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
GM never rated any of its engines at the rear wheels. It is with all the accessories attached. The is the net HP. Gross HP is just the motor by itself with no accessories. Rear wheel HP is totally different.
Race Director
Joined: Apr 2000
Posts: 17,676
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
OK, just a newbie trying to learn all this stuff and looking to make more hp engine out of my L48.... lots of good info found on this topic in the searches on this site and on the internet.
But something isn't making much sense to me... the 290hp GM crate engine looks to have basically equivalent components to the L48 with the exception of the cam: dish pistons, 8.5:1 compression, same valve sizes, etc. The cam in it appears to be the same specs as the L82 cam, but the L82 is 9:1 compression and only 215 at the wheels. I understand the 290 is rated at the flywheel and the L48/L82 is rated at the rear wheels, but something here doesn't seem to add up to me....
what I am missing or misunderstanding here????
thanks,
Michael
But something isn't making much sense to me... the 290hp GM crate engine looks to have basically equivalent components to the L48 with the exception of the cam: dish pistons, 8.5:1 compression, same valve sizes, etc. The cam in it appears to be the same specs as the L82 cam, but the L82 is 9:1 compression and only 215 at the wheels. I understand the 290 is rated at the flywheel and the L48/L82 is rated at the rear wheels, but something here doesn't seem to add up to me....
what I am missing or misunderstanding here????
thanks,
Michael
I must the run-on sentence king
Le Mans Master
Joined: Sep 2004
Posts: 5,116
Likes: 5
From: Livonia MI
Not sure where you ever heard of a RWHP rated factory car, but a new one for me. Since 72' all engine's were rated actual SAE flywheel HP as installed in the car driving the water pump, alternator, ext through the sometime's very restrictive smog exhaust system. Crate motor's are also flywheel HP on a stand, usually water pump, alt, but probably free flowing longtube's and minimal exhaust. The modern head's probably flow much better, and the cam while seemingly similar, is surely computer optimized.
Drifting
Joined: Sep 2006
Posts: 1,986
Likes: 21
From: Columbus MN
I have the GM crate a step up from the 290 hp one: 350 HO. I've never had it on an engine dyno, but it's been on a chassis dyno a few times. The last run in May got 293 rwhp and 327 torque. GM advertises the engine at 330 hp and 380 torque.
Estimated crank-rw loss ranges from 15-20% for manual transmission on the CF. With 293 rwhp after a 15% drive train loss, then my GM 350 HO is an over-achiever. Granted, I've tweaked and fiddled with the ignition and 600 cfm carb on my HO, but the GM ratings are realistic and achievable.
If you can scratch up the difference between the 290 hp and 330 hp engines, I highly recommend the HO. Vortec heads flow pretty well, and GM sells a cam kit that will get you just over 400 hp.
Estimated crank-rw loss ranges from 15-20% for manual transmission on the CF. With 293 rwhp after a 15% drive train loss, then my GM 350 HO is an over-achiever. Granted, I've tweaked and fiddled with the ignition and 600 cfm carb on my HO, but the GM ratings are realistic and achievable.
If you can scratch up the difference between the 290 hp and 330 hp engines, I highly recommend the HO. Vortec heads flow pretty well, and GM sells a cam kit that will get you just over 400 hp.
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