383 or 396
12-01-2008, 09:34 AM
#2
There is no substitute for cubic inches. You need some big heads to have a fast 396". 225 cc or bigger intake ports. With the 7200 RPM limit, assuming you use the factory PCM, a 396" would be easier to make fast. Slow 396"s usually have one thing in common, small ports. I would at least use least ported LT4 castings.
12-01-2008, 10:16 AM
#5
Just understand that the increased stroke means more clearancing into the block,
welding/filling to seal the water jacket and take into consideration that the rotating
assembly may come much closet to the cam than it would in a 383 and may require
machining (depending on the rods and bolts you choose).
The extra stroke is going to make for a nice increase in torque though.
In retrospect, I regret not looking into it more when I built my 383.
Like Ed said, make sure you select heads than will flow enough to make proper use of that displacement.
Talk to your favorite head porter or aftermarket casting provider to see what best fits your needs.
welding/filling to seal the water jacket and take into consideration that the rotating
assembly may come much closet to the cam than it would in a 383 and may require
machining (depending on the rods and bolts you choose).
The extra stroke is going to make for a nice increase in torque though.
In retrospect, I regret not looking into it more when I built my 383.
Like Ed said, make sure you select heads than will flow enough to make proper use of that displacement.
Talk to your favorite head porter or aftermarket casting provider to see what best fits your needs.
12-01-2008, 10:54 AM
#6
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As long as the correct rod profile is used like a Compstar H-beam rod (Eagles should be out of the question) and a skilled machinist then there will be no worries breaking into a water jacket. A small base circle cam can also be used for further clearance.
12-01-2008, 11:49 AM
#7
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12-01-2008, 12:15 PM
#8
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ok well i have an extra lt1 block, so would you suggest using it and getting crank rods and pistons seperate, or buying a short block from a manufacturer?
12-01-2008, 12:41 PM
#9
I opted to use my spare block and order the parts myself to avoid the shop markup.
Having a local shop do the work gave me more control over what went into the motor
and how it was assembled. It worked out well overall in my case.
I saved money, got exactly what I asked for and was able to visit and discuss options with the machinists 1 on 1.
If you go this route, make sure you understand what components you need and which work for your combo.
Don't just start throwing things together because the prices are right, or the individual part gets good reviews.
And there's nothing wrong with copying off someone who's combination has served them well over the years.
Ordering it from a shop that specializes in (or at least does a lot of) LTx motors would be nice advantage.
They generally sell proven combos and have a good track record of producing quality motors. (which comes at a price)
Then there's shipping .... Shortblocks are not light .... longblocks even less so.
I don't think anyone warranties racing engines anymore though. I think Golen used to.
A good shop will help you out if the failure was obviously due to their parts or installation.
(I find this easier to do with a shop that is local to you)
Keep in mind that any shop, no matter how reputable, could close it's doors
any day, and your motor could end up stuck in a legal battle.
(Ask people who got screwed by NRT, Raging Motorsports or NuTek)
Call around, see who gives you the warm and fuzzy and discuss with people who've been though similar projects (local and otherwise).
Remember, you don't want to be building a new bottom end again anytime soon, have it done right the first time.
12-01-2008, 01:44 PM
#10
You need to figure out what you budget can handle and what your capability is for building, if you have been there and done that then save yourself the money and build it yourself and just have a machine shop do the block work and balance the rotating assy. The scat I beam rods are what i used with my last 383 and i think would work fine for the 396. I pieced my last 383 together for 900$ for the crank, rods and pistons, but that was a cast crank, a forged piece will run 3 or 4 hundred more if you find a cheaper brand, so pistons and crank are the special pieces.
