350/350H.P. Rebuild
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Drifting
Joined: Jan 2002
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From: Dandridge TN
350/350H.P. Rebuild
I am going to rebuild my engine and need a little help. I have a set of 11.5/1 pistons and always had a spark knock. These were stock in my car new. Do you guy think it would be better to go with a smaller piston like a 9/1 compression ratio. I was thinking of the cheap gas now a days was the reason I have a spark knock because I ran a tank of 103 octane and the knock went away. I can't afford to keep running $5.00 a gallon gas in my car!!! A little help on your all's expertise would be appreciated.
Le Mans Master
Joined: Jun 1999
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From: Newport Michigan
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Re: 350/350H.P. Rebuild (Steve Adkins)
Never found octane boost to do any good on my L46 - the only thing that has worked is a 50/50 mix of 92 octane premium and 110 octane racing gas (at $3.69/gallon :eek: )
I think lower compression and a good set of aluminum heads is the way to go if you're not too concerned about originality.
[Modified by 70L46, 11:35 PM 2/16/2002]
I think lower compression and a good set of aluminum heads is the way to go if you're not too concerned about originality.
[Modified by 70L46, 11:35 PM 2/16/2002]
Pro
Joined: Aug 2000
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From: Montrose CA
Re: 350/350H.P. Rebuild (Steve Adkins)
My only follow up is a story about how a coworker with a 96 TA goes over to the hot rod store every few weeks to stick a few gallons of super high octaine gas in the tank to blend with the stuff he gets from the pump... Likely overkill as his LT-1 engine has knock sensors to retard the timing when using lousy gas or really loading the engine.
My engine rebuilder suggested holding my 383 to about 9.2-1 for the sake of running pump gas... I am running 91 octaine from the pump... I have yet to try regular! No clatter so far.
I hope you can find a solution while keeping the monster pistons in the car!
My engine rebuilder suggested holding my 383 to about 9.2-1 for the sake of running pump gas... I am running 91 octaine from the pump... I have yet to try regular! No clatter so far.
I hope you can find a solution while keeping the monster pistons in the car!
Drifting
Joined: Oct 2001
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From: Westampton NJ
Re: 350/350H.P. Rebuild (Steve Adkins)
If the domes on the pistons are not hollow, you can mill them down to lower the compression to 10.5:1 or if you mill them flat, to about 10.25:1.
Or buy lower compression pistons. I'm pretty sure my internals are original, and I use 91 + one thing of octane boost per tank...no knocking...
Or buy lower compression pistons. I'm pretty sure my internals are original, and I use 91 + one thing of octane boost per tank...no knocking...
Melting Slicks
Joined: Oct 2001
Posts: 2,065
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From: Halifax, Nova Scotia, Canada
Re: 350/350H.P. Rebuild (Steve Adkins)
Hi Steve..
Here's what worked for me.
I rebuilt my engine in '96. I retained everything stock, including the 11:1 CR.
Remove any sharp edges from the heads (combustion chamber), and the same with the pistons. Smooth/round the edges on the piston dome.
Assemble with a thicker head gasket. GM 10105117
I now use pump gas with no additives with no problems.
It worked for me.
Barry
Here's what worked for me.
I rebuilt my engine in '96. I retained everything stock, including the 11:1 CR.
Remove any sharp edges from the heads (combustion chamber), and the same with the pistons. Smooth/round the edges on the piston dome.
Assemble with a thicker head gasket. GM 10105117
I now use pump gas with no additives with no problems.
It worked for me.
Barry
Drifting
Joined: May 2000
Posts: 1,573
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From: Ga.
Re: 350/350H.P. Rebuild (Steve Adkins)
Here is what I did when rebuilding my 350/350hp. I decided to run 9.5 cr Keith Black pistons and incrase the engine's stroke by dropping in a 400
crank making it a 383. I still have the same power, more torque at lower rpm where I wanted it and a lower cr to run regular unleaded gas. The engine still looks the same but is more streetable on today's gas...... :smash: :smash:
crank making it a 383. I still have the same power, more torque at lower rpm where I wanted it and a lower cr to run regular unleaded gas. The engine still looks the same but is more streetable on today's gas...... :smash: :smash:
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Burning Brakes
Joined: Jan 2001
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From: Gainesville, Florida
Re: 350/350H.P. Rebuild (Steve Adkins)
I have basically a stock L46 short block (exc. Comp XE274 cam). A set of aluminum heads & a longer duration cam will help alot. The heads diffuse heat much faster than irons and the cam duration will bleed off cylinder pressure which are both prime contributors to detonation & pinging. I have the TFS 23Ds (64cc) with the factory 11.0-1 pistons. I run 36D full timing advance w/15 initial with no pinging on 93 octane pump gas. And the car runs like a beast! :D
Mark
Mark
Thread Starter
Drifting
Joined: Jan 2002
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From: Dandridge TN
Re: 350/350H.P. Rebuild (mdsmith)
Thanks guys for all your input. I guess I am going to go with a smaller CR piston and try to make up the difference of power somewhere else. Maybe you guys can help me out in this area also. Recommendations on what type of cam, head, intake, carb etc... Thanks for all of your advice. :confused:
Safety Car
Joined: Feb 1999
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From: Fountain Hills AZ
Re: 350/350H.P. Rebuild (Steve Adkins)
Definitely drop the cr while you have it apart. As already posted, aluminum heads and more overlap will allow for higher cr's. 10:1 should work fine with premium pump gas even with iron heads if all else is right. A little more cam or better heads will more than compensate for the small amount of power you give up by dropping the cr a point or so.
As far as recommendations, what are your goals and how do you use the car? Some of us are willing to give up drivability in exchange for the most power and some of us aren't. Makes more sense to do it the way YOU want it the first time rather than have to redo part of it or live with something you're not happy with.
As far as recommendations, what are your goals and how do you use the car? Some of us are willing to give up drivability in exchange for the most power and some of us aren't. Makes more sense to do it the way YOU want it the first time rather than have to redo part of it or live with something you're not happy with.
Thread Starter
Drifting
Joined: Jan 2002
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From: Dandridge TN
Re: 350/350H.P. Rebuild (Vetterodder)
I am really not looking for a whole lot of power. I would like to keep the car at least 350 hp. Maybe a little more. I will probably drive the car 2 to 3 times a week on pretty days. I am right in the middle of a frame off restoration and you are right I don't want to go back a redo something I am not happy with. I would like to have a strong running dependable car when I am finished if there is such a thing.