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Discussion Starter · #2 ·
I've been eyeballing this kit for awhile too. Pace had it advertised in a recent issue of GM High-Tech Performance for around the same price. I'd like to here some comments as well.
 
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Discussion Starter · #3 ·
Not at all intending to be rude, but use the search feature as this subject has been brought up before, many times before, many many many times before! ;)
 
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Discussion Starter · #4 ·
We will be doing an LT4 conversion to the wifes wagon next year. Actually she wants to do the work and I get to drink beer and watch.

Look here. http://www.performancess.com/
cheaper than the Super Store. I know some people that have done the switch and love it.
 
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Discussion Starter · #6 ·
To run that kit you will need a 2400+ stall TC and 3.73 gears due to a loss of lowend torque, plus headers and a shift kit. That kit is supposed to be good for 425FWHP if that is a little more than you want and are just looking for a little more pep, the stock heads are quite good and just a cam can wake up an otherwise stock motor.
 
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Discussion Starter · #8 ·
The advertised supposedly "425" hp (and it is at the crank) was under the assumption that you have a Vette with the factory LT1 that was rated at a higher HP to begin with then the Impala, and made the conversion to a Vette.
 
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Discussion Starter · #9 ·
The Corvette engine and the Impala engine are pretty much the same thing. They have a different cam and different heads. BOTH of which get replaced in this kit, so I find the 425hp figure to be pretty standard across the board for ANY LT1 you put the kit on. Now if you want an engine that has a little stronger physical bottom end, get the corvette engine, it had 4 bolt mains. 2 Bolt mains are perfectly fine for this setup. Shoot, most of the 383's out there are 2 bolt mains, so they are plenty strong.

The only engine that may prove to be a LITTLE (and I stress little!) different in hosepower figures is the TRUE LT4 with a HOT CAM. The LT4's revised piston design with reduced valve pocket depth produces a 10.8:1 compression ratio (versus 10.4:1 in LT1). The undercut and rolled fillet cast iron crankshaft improves durability also. The LT4's Dual-mass front torsional damper is tuned for high engine speeds as well. These are the main differences between the LT4 and the LT1... Will they cause big horsepower differences compared to your LT1 with the LT4 buildup? probably not!


Trent Warren - Atlanta, GA - NAISSO #566 - ISSCA #655
 
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Discussion Starter · #10 ·
Do you really think that adding stock LT4 heads, 1.6 RR, and a hot cam will add 165 hp to the stock Impala's 260? Call me a skeptic!
 
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Discussion Starter · #11 ·
For the skeptics.. here's the Chevy High Performance article where they take a LT1 and put the conversion on it. 429HP is for real according to this article.







Sorry for taking up all the bandwidth, but there's the data... take it for what you want. I believe it!


Trent Warren - Atlanta, GA - NAISSO #566 - ISSCA #655
 
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Discussion Starter · #12 ·
And full length headers, and larger TB, and unrestricted intake, and I can't tell for sure from the pics and what little I can read what else, but it took more then just the conversion kit to get those numbers. Back to my statment, the heads, cam, and rr's are not enough to take a 260 hp motor to 425. "still the skeptic"
 
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Discussion Starter · #13 ·
I would assume that anyone looking into buying new heads, a new manifold, and a hot cam would probably have some headers and know they could seriously benefit by porting their 48mm throttle body to 52mm. I guess we should state that with the package, one has the CAPABILITY of hitting 430HP


Our best bet, would be to get some #'s from people who have installed the LT4 conversion kit in the Impala SS.

Trent Warren - Atlanta, GA - NAISSO #566 - ISSCA #655
 
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Discussion Starter · #14 ·
ReeseSS,

I understand your reservations about the power ratings. One thing I think you are over-looking is that the factory rating of 260hp is flywheel net and the 425hp rating is flywheel gross. The stock LT4 was rated at 330hp net. Add the hot cam to that mix and you're probably look at a 90-100 hp increase; which isn't unreasonable.

Don't forget about these hp ratings. The pictures clearly show that the engine was dynoed w/o any accessories or "factory" exhaust system.

I think this gain is a much more realistic way of looking at it then those comparing the 260 to 425.
 
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Discussion Starter · #15 ·
wheres the MAF on that Lt1 on the dyno??

Anyways I struggled and read the fine blurry print.
# one: they added a 52mm TB and headers, for an additional 25hp.
# two: they started with a baseline of 300HP from a VETTE, not an 260hp IMPALA. there is 40hp more off there total.
So, total, take off 65 hp, and you are back to a much more senseable 375 or so flywheel HP... Now THAT makes me less Skeptic.

What about you Resse SS? :D
 
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Discussion Starter · #16 ·
I've also been thinking along those lines of adding the LT4 kit to my 94RMwagon-but what concerns me is driveability and fuel economy and also the size of the stock radiator.Will the stock rad cover the extra power from the kit or should an aftermarket rad be used?I'm new to MPFI and I'm assuming it will idle as smooth as the stock cam?How much less mpg's would we see? Ed
 
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Discussion Starter · #17 ·
Recently saw a lt4 upgrade kit in the new summit catalog for 1800 I don't know how the price stacks up just thought I would mention it.
 
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Discussion Starter · #18 ·
<BLOCKQUOTE>quote:</font><HR>Originally posted by Jons4door:

# one: they added a 52mm TB and headers, for an additional 25hp.
# two: they started with a baseline of 300HP from a VETTE, not an 260hp IMPALA. there is 40hp more off there total.
<HR></BLOCKQUOTE>

#one-Not just headers, but long tubes. A very good hp increase there. Had they used shorties it would not have been as good.

# two-Is not really valid. Most of the hp difference between a vette LT1 and the others is in the the exhaust, and I guess when compared to the Impala there might be some between the aluminum and cast iron heads. With the vette exhaust and cylinder heads gone the hp advantage of the vette LT1 is moot.

Didn't notice a baseline run with it as just a LT1. That would have made for a good comparison of before and after.
 
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Discussion Starter · #19 ·
<BLOCKQUOTE>quote:</font><HR>Originally posted by Jons4door:
wheres the MAF on that Lt1 on the dyno?? <HR></BLOCKQUOTE>

Looks like they were running it with something other than an LT1 PCM...so no MAF needed probably.
 
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Discussion Starter · #20 ·
From a "Been there, done that" perspective, I'm not believin' ANY claims of more than 310 HP at the REAR WHEELS for the conversion. And it's the power at the wheels that count!

BTW, Pace Performance Parts includes all the necessary gaskets with its kit; others do not'

KW
 
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