Need HELP with Accelerator Cable.....

**Joe L.** · June 7, 2008, 04:12 AM

Re: Need HELP with Accelerator Cable.....

Originally posted by Greg Euston (49104)

Hi Every One

My name is Greg Euston, i live in Australia. I have only just joined NCRS and this is my first visit to the Tech.Dis.Brd. I hope the information i give you all is adeqaute to answer my questions!! if not let me know!! I thought i knew a lot about Corvette's, but since i started the restoration of my dream Corvette to NCRS standard i have discovered i know very little!!!! So i will be asking you all many, many questions!!!!!!!!!!

I'm 52 yrs old, i have dreamt of owning a 1970-72, 4-Sp, Big Block Corvette since i first seen one when i was 16 yrs old.

I own a 1971, LS5, 454ci, 365hp, 4-Sp Vette. The engine has Service Replacement LS6 Heads, Intake Manifold with the snow flake & Holley Carby 4803 List #.

MY QUESTIONS ARE...

(1) What type of Accelerator Cable was used on LS6 4-Sp Vette's??. The original one being used looks to long??

(2) If the LS6 Holley Accel / Cable is different to the LS5 Rochester type, can
the LS6 Holley Cable still be purchased??

(3) What are the advantages & disadantages to the horse power rating, compression rating and the all over running of the engine now with the LS6 combination.

Any other information you can supply me about my questions will be GREATLY APPRECIATED!!!!!!!!

Kind Regards...

Greg...
Australia.

Greg-----

Great to have you aboard! I think you'll find folks here will be very helpful to you, especially since you're from out-of-the-USA. Most of us understand how difficult it can be for folks with Corvettes in foreign countries to obtain information, parts, etc.

Anyway, here's what I can offer relative to your questions:

1) The accelerator cable for all 1968-73 Corvettes, except 68-69 with 3 X 2, are FUNCTIONALLY the same. Your car was originally fitted with cable GM #3990560. The exact same cable would have been used with 1971 LS-6. The GM #3990560 cable is no longer available but its replacement, GM #336977, is available. So, if you were to require a cable, you can get one through GM or any of the Corvette parts vendors like Dr. Rebuild. However, if your cable is in good shape, you can be assured it's the same one that was used with LS-6.

While the accelerator cables are the same for LS-5 and LS-6 (or, any other 1971 engine option), the carb-mounted cable BRACKET is different between Q-Jet applications (like your original LS-5) and Holley applications (like LS-6 or LT-1). Holley-equipped engines require bracket GM #3972627. This bracket is GM-discontinued but available in reproduction. The clamp (the small, C-shaped piece that clamps the cable to the bracket) is the same for either Q-Jet or Holley brackets.

2) As far as the combination you have now, from what I can tell, you have an LS-5 bottom end (i.e. block, rods, pistons, crank, and, possibly, camshaft) with LS-6 heads and LS-6 (or other Holley flange) intake manifold and Holley carb. If so, I don't think this is a good combination. Keep in mind that your original LS-5 heads and pistons produced an advertised compression ratio of 8.5:1. The LS-5 heads had a combustion chamber volume of 113 cc, nominal.

1971 LS-6 used different pistons and 118 cc, nominal, cylinder heads to produce an advertised compression ratio of 9.0:1.

So, if you use LS-6 cylinder heads, either aluminum as originally used on 1971 Corvette LS-6 or cast iron as used on 1970 Chevelle LS-6, on a bottom end with LS-5 pistons, you are going to drop your compression ratio well below the original LS-5 rating of 8.5:1. You'll probably be down in the 7.9:1 range. That's too low of compression (unless you're using a supercharger or turbocharger).

Of course, if pistons have been changed, that could bring you back up to higher compression depending on what pistons were used.

For the most part, to convert an LS-5 to LS-6, you really need to make a LOT of changes to the engine. You just can't add-on a set of LS-6 heads, manifold, and Holley carb and have an LS-6. In fact, as I mentioned, if one does just that, one will end up with something that's not as good as the LS-5 one started with.

If you provide more specifics on just what changes have been made to the engine, we might be able to provide further information.

Need HELP with Accelerator Cable.....

Need HELP with Accelerator Cable.....

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