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Thread: Unknown Internals 477 RWHP SBC Advice?

  1. #11

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    There's more to Octane requirements than just compression ratio. Pistons and chamber design affect it, and even more so the camshaft.
    And even running temps. Intake air temp etc

    And Compression alone doesn’t make power, air flow is the most important factor in doing so. You can safely run 12:1 on pump gas with the right combination of parts. So you would have no problem running a base tune at low throttle opening even at 13:1.

    Why would you pull the engine to check the cam? No reason it can’t be checked or changed with the engine in the car. If it has decent chambers 28° is all it will need for max power.
    Last edited by Mad Cadder; 09-17-2019 at 12:51 PM.

  2. #12

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    Quote Originally Posted by djh61187 View Post
    I'd want to know too. Especially for extended WOT like the Silver State Classic. Compression, Cam Timing and fuel octane are most important. And besides, it not like it's hard to pull a engine on a '69 Camaro. I can pull the engine on my '69 Chevelle in less than a hour. Maybe a little longer now with all the extra wiring for the 1250 Super Sniper and all the extra sensors and wiring I added.
    Quote Originally Posted by djh61187 View Post
    What if it's 13.5:1 and setup for C16. How long do you think it would last on 91 octane and a Bottle of Octane Booster running mile after mile wide open?
    To be clear, I'm not racing the car, and certainly not Silver State Classic. That's just what the car was built for back in the early 2000s.

    It ran fine on a Demon carb with both 100oct and 91 + booster. We pulled a bit of timing when I bought it, in the blind, to be safe on 91.

    I just use it for playing in the Santa Cruz mountains, $100 hamburger runs, chasing my buddies in GT3s, NSXes, Speciales, etc. Most of the time I'm driving it in anger it's 2nd and 3rd gear hill climbs and mostly traction limited (still on leafs at the moment).

    Quote Originally Posted by JF74CHEVELLE View Post
    Pull the engine and actually degree the cam to find out the specs, and CC the heads to figure out compression ratio.
    I'm trying to get an idea of how the car works on the street with EFI before deciding to freshen the engine or go to an LSx.

    Quote Originally Posted by RPnova View Post
    1) You don't need race gas for this. I don't even know why compression ratio matters so much to anyone anyways. Put the race tune in the ECU if you wish and run the car. I'd use the 91 octane with Amsoil octane booster if you're worried. I'm a Amsoil dealer if you need some. The engine has 477 horsepower out of a 406 Dart Iron Block. It's not like it has 1000 horsepower naturally aspirated out of a 400 cubic inch engine. How high can the compression ratio be anyways.
    2) Check for oil and oil pressure.
    3) Set the initial timing for 20°.
    4) Since your doing the full HyperSpark setup, why not install it per the instructions and be done with it.
    Quote Originally Posted by RPnova View Post
    He said he runs 91 on the street plus octane booster and 100 octane for his races. Based on what he said, his engine will not blow up with 91, plus booster is safe for the street, and initial Learning.
    He can always tune the engine by what the engine wants not what you think it needs. I still would not pull the engine. I'd limit my total timing to 28° to be a safe starting point. You'll just have to go slow, and not go full blast from the beginning.
    Thanks for the timing advice. You're exactly right, I'm hoping the Sniper can determine what the engine wants, and slowly work my way into the timing with a trusted tuner (who's tuned my stock short block LSA to a very reliable 702 RWHP) without the weekend of R&R the engine.

    I'm an Amsoil 'dealer' too, as I buy enough per year that I come out ahead. For #4) the tach works fine off the MSD 6AL, so unless there's a big lag from the Sniper RPM signal to the MSD 6AL to the tach out (unlikely), it's one less wire to run under the dash.

  3. #13

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    If you've been running this engine with a carb for a while like it sounds like you have, just use the same setup you did with the carb initially. How much timing were you running with the Demon? Maybe back off a degree or two if you're worried, but that'll be a good starting point.
    69 Camaro
    400 SBC, ProCharger D1SC

  4. #14

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    Greg- Neophyte carb/distributor question as I'm not knowledgeable about either. Is there any way to know what the timing was if I have removed the carb and fuel system, but not the distributor? I've yet to unbolt and remove my distributor, but I was going to this week to spin the oil pump with my drill.

    I've already flushed my fuel cell and changed from an in-line low pressure pump to an in-tank high pressure pump (and changed a few AN fittings), so I can't throw the carb back on, fire her up, and check timing with a timing light.

    Sorry for the basic question, but I'm a younger guy and a LS1 swapped RX7 was my first performance vehicle, and I've never adjusted a carb or distributor in my life (hence the move to the Sniper and HyperSpark). Thanks, Jason
    Last edited by Widebody 69; 09-17-2019 at 05:14 PM.

  5. #15
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    Quote Originally Posted by RPnova View Post
    He said he runs 91 on the street plus octane booster and 100 octane for his races. Based on what he said, his engine will not blow up with 91, plus booster is safe for the street, and initial Learning.
    He can always tune the engine by what the engine wants not what you think it needs. I still would not pull the engine. I'd limit my total timing to 28° to be a safe starting point. You'll just have to go slow, and not go full blast from the beginning.
    True. And the Sniper should compensate for the compression and octane or lack of. I agree with not pulling an engine just because cam spec and compression is not known. He can degree the cam with the engine still in the car and the heads on the engine. Obviously, he can run 93 octane pump gas and check for spark knock. That would shed a little light on compression as long as he knows the engine timing.
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