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UNLIMITED 427 power

This is a discussion on UNLIMITED 427 power within the General Help forums, part of the LSx Technical Help Section category; I want to know about the maximum hp I can get out of this engine? I would like to know ...

  1. #1

    Question UNLIMITED 427 power

    I want to know about the maximum hp I can get out of this engine? I would like to know about 1/2, 3/4 and full race applications. I have seen 402s and 408s making all this power but what about my engine, is there anything I can do engine wise to pull more hp w/out power adders right now?

  2. #2
    oh and just think of baseline parts on the engine right now that way I can go from there

  3. #3
    Grand Imperial Wizard Sarge's Avatar
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    I'll take a shot .....
    Performance modifications seem to have gone crazy these days with the Internet and a catalog coming in the mail often folks just "start modding" with no specific goal or purpose in mind...and end up with an unreliable/drag/auto RX "thing" sitting in there garage worth $80K
    I would sit down and determine what my goal is/ I want a 1/4 miler...street beast.....drifter...road racer....what? Do you want to keep it streetable? Drivable? Don't care? Focus on what you envision your ultimate Hot Rod to be first and foremost before you twist a single wrench....
    With that said......the 427 has been modded out the wazoo...lots and lots of aftermarket parts for her.....some basic truths I have found to be consistent over the years....
    The Basics in generic form......
    1. Let her breathe....Cold air restrictions out. That usually means some brand/type of Cold Air Intake....Exhaust....Flow baby Headers....Y Pipes...Performance mufflers etc.
    2. Dyno Tune or hand held tune (second choice)....Your baby got ponies just waiting to be let out.....let 'em out man! Some of the biggest performance gains I have seen have come from a dyno tune.....Check out some shops in Waco and Austin....get references....should be around $400.....A dyno tune will adjust timing and Air Fuel amongst other things....well worth it....
    3. Suspension....Frame Bushings....Anti Sway Bars...Frame/Strut Braces....etc. Put the power your making now to the ground. Drag Radials/Performance Tires etc coupled with some inexpensive frame adjustments make a huge difference....

    Now your focused...know what you want to the basics.....get the basics done first....then you can go crazy from there with Heads/Cams Forced Induction/ Nitrous etc....but you have a clearly defined goal at least you will know when you achieve it
    Hope this helps man.....good luck...I know many great shops here in Central Texas.....feel free to ask lots of questions...many great gearheads/sponsors we have here who can save you a helluva lot of frustration/money/time....

  4. #4
    Quote Originally Posted by deception05
    I want to know about the maximum hp I can get out of this engine?
    What engine: you mentioned 427 but don't mentioned which 427.

    If you have the old big block 427 then you can get about 450-460 RWHp out of it on the street but fuel economy will be really bad.

    If you mean a CM Gen III or Gen IV 427, that is a C5R or LS7. Little differences in them but they are basically the same engine.

    The C5R in full race tune with racing heads put out about 670 HP at LeMans in 2003, when it placed 1-2-3 in GTS. It was hardly a streetable car, however, and it was running on race gas, too.

    Two tuner/aftermarket suppliers that set good benchmarks for street strip are Lingenfleter and MTI. Lingenfelter is always a bit conservative in their ratings and they advertise their C5R 427 street tune at 550 flywheel, about 480 RWHP. The admit they can get more from it but Lingenfelter goes heavy into turbos to get more power than about 550, so . . .

    MTI (Motorsports Technology Inc.) in Houston sells parts as well as engines and the entire "ZO7" kit which is the most extreme street normally aspirated 427 I know. Theirmost extreme street cars use a 427 and put down about 540 on the dyno - say equivalent of 600HP flywheel. They are streetable but have a nasty idle and not a lot of low or mid range.

    You could call both places and talk to the folks there: my experience is that they are very happy to advise you what parts to buy.

    One piece of advice is don't use a sleeved block if you are going for max power. Pay the money and get a C5R or LS7 block (they are basically the same-no big difference except the C5R is set up for wet sump, LS7 for dry sump).

    I have a C5R based engine with just about every trick. Built and tuned for low end torque rather than max top end. I put a lot of money into th heads. Patriot IIIs with a lot of porting and poshing and cc'ing after they came from Patrio. Flowing 342 in bench test.
    Only 10.25:1 compression so I could SC it later. We tried a number of different cams and it made 507 RWHP with a good streetable cam (225/232/113 .594 lift -- this is a big cam but not that big for a 427).

    With a D1SC and only 5 lbs of boost, it delivers 595 RWHP and 544 RWT, with 500 RWT available from 2000 RPM up.

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