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Username Post: LT9 engine        (Topic#58491)
hook 
Member
Posts: 79

Reg: 01-29-04
02-24-04 05:17 AM - Post#397827    

hi all,
Can someone provide me with all the specs of an LT9 engine? I've looked everywhere I can think of(very limited) and all I can come up with are very basic. I would like to know ALL the specs for this engine and what can be done to it for better performance.
Thanks ahead of time for your help
Bill

 
LMC Truck
4.3in84toy 
Senior Member
Posts: 428

Reg: 01-28-03
Re: LT9 engine
02-24-04 02:45 PM - Post#397828    
    In response to hook

If its a propane motor... convert it back to gasoline? not a lot of performance available for a propane motor.

If its a gas motor, do the same things you would do to any other 350.

Chris

 
gchemist 
Senior Chevytalk Moderator
Posts: 22033
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
Re: LT9 engine
02-24-04 04:07 PM - Post#397829    
    In response to hook

Welcome to the board. Can you give a little more information? What year? Model truck? Options on the truck?
'83 Silverardo XST - ZZ4 powered
'96 GMC Jimmy LS Ret. @236651 miles


 
hook 
Member
Posts: 79

Reg: 01-29-04
Re: LT9 engine
02-25-04 06:00 AM - Post#397830    
    In response to gchemist

I have a 1982 1-ton dually, the LT9 to a t-400 to a dana 70 with 4.56 gears. As you can tell it is not built for highway cruising, but that is the way I use it most. I have rebuilt the heads, added a non-stock(but not hot)cam, roller rockers,headers, 2 1/2" dual exhaust and a K&N filter. I intend to make my last mod a new carb and intake, then start on the inside. All I know about this motor is that it has large combustion chambers, small valves and makes its power early. I am not trying to really build this engine but i would like it to respond when I step on the peddle. Any more info you could provide would help.
thanks
Bill

 
bored&stroked 
Senior Member
Posts: 629

Reg: 01-03-03
Re: LT9 engine
02-25-04 11:09 AM - Post#397831    
    In response to hook

big block? small block? what CID? Engines codes don't matter really, at least not with these trucks.
- - - - - - - - -
78 c10: 11:1 388,M20,5/5" drop.-playtoy
98 gmc sierra: 5/6" drop, 17" eagle alloy's, flowmaster 50 series.-daily driver
06 CBR600F4i- freakin rocket ship


 
hook 
Member
Posts: 79

Reg: 01-29-04
Re: LT9 engine
02-26-04 04:49 AM - Post#397832    
    In response to bored&stroked

Sorry, it's a 350 smallblock. One book I have says it makes a whopping 165 hp @3800 rpm. I assume this is due to the 76cc combustion chambers, dished pistons, and small valves? Is changing the heads the only way to get more performance?

 
KShortell 
Senior Member
Posts: 3936
KShortell
Loc: Chesapeake, VA, U.S.A.
Reg: 04-14-01
Re: LT9 engine
02-26-04 05:43 AM - Post#397833    
    In response to hook

The LT9 engine is the 350ci/5.7L Heavy Emissions engine, also referred to as the "M" engine. I forget the cutoff on GVWR, but I think it's 8,500 or something like that.

1/2 and 3/4-ton trucks (C/K 10, 15, 20, and 25) all used the LS9 engine like mine-- the "L" engine.

Note: I only know this because I was looking some stuff about my own truck in my factory service manual last night .
Semper Paratus
FL05-03 Home Page
Stock is not a dirty word...


 
4.3in84toy 
Senior Member
Posts: 428

Reg: 01-28-03
Re: LT9 engine
02-26-04 06:11 AM - Post#397834    
    In response to hook

Quote:

I intend to make my last mod a new carb and intake, then start on the inside. All I know about this motor is that it has large combustion chambers, small valves and makes its power early. I am not trying to really build this engine but i would like it to respond when I step on the peddle. Any more info you could provide would help.
thanks
Bill




Bill why don't you make that new carb and intake a small (142,144,177) blower and 750 cfm carb? With minimal boost, your low compression engine and mild cam will have a bolt on 100 ftlbs of torque or so with little noticeable difference in fuel consumption or driveability.

Chris

 
bored&stroked 
Senior Member
Posts: 629

Reg: 01-03-03
Re: LT9 engine
02-26-04 06:12 AM - Post#397835    
    In response to hook

Quote:

Sorry, it's a 350 smallblock. One book I have says it makes a whopping 165 hp @3800 rpm. I assume this is due to the 76cc combustion chambers, dished pistons, and small valves? Is changing the heads the only way to get more performance?




Ok now we can talk
Things bringing the power down : EMISSIONS equipment, dismanl compression ratio [8.0-8.5:1] horrible heads [bad 76cc chambers, valves are ok at 1.94/1.5, POS ports] and a tiny cam [about 194/196 @.050 and .390/.410" lift] along with the extremley conservative timing curve and stock intake manifold, o yeah and the restrictive exaust manifolds. So basically the entire package is bad

To begin, put a nice set of 1 5/8" headers on with a good exaust to back it up. Also get a edelbrock EPS intake, but keep that Qjet. Get some better heads [vortecs are a great choice, superb flow with 170cc intakes, great torque with the small ports still, but require new intake to match] and a bigger cam [stay at or below 216* duration for a mild motor] and some more compression [going to 64cc combustion chambers gives you about 1 point of compression]. Also, get a crane vacum advance can and put it in and change the timing curve. You'll notice a MASSIVE improvment with these mods.
- - - - - - - - -
78 c10: 11:1 388,M20,5/5" drop.-playtoy
98 gmc sierra: 5/6" drop, 17" eagle alloy's, flowmaster 50 series.-daily driver
06 CBR600F4i- freakin rocket ship


 
hook 
Member
Posts: 79

Reg: 01-29-04
Re: LT9 engine
02-27-04 08:44 AM - Post#397836    
    In response to bored&stroked

Thanks for the info,
I have done all except the intake and carb, the EPS was the exact intake I was going with but now you have me scratching my head on "keep the Qjet", can you elaborate on this? My cam card says that the duration @.5 lift is 204/216. Also can you help on "changing the ignition curve"? I understand the concept but am limited on actually doing it.

 
hook 
Member
Posts: 79

Reg: 01-29-04
Re: LT9 engine
02-29-04 04:44 AM - Post#397837    
    In response to hook

I thought I should re-mention I am still using the original heads(76cc chamber,small valves, dished pistons)

 
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