Spark Plug Gap for LS-7 454?. - Impala Tech
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post #1 of 12 (permalink) Old 07-04-2009, 08:26 AM Thread Starter
 
 
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Spark Plug Gap for LS-7 454?.

I am currently preparing to start the engine for my 67,I am using the Autolite part# AR-51,with short electriode strap,and copper core.Should I use a stock gap opening?,or other?.
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post #2 of 12 (permalink) Old 07-04-2009, 10:41 AM
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0.032" for a points ignition opened up to 0.045" for a HEI ignition.

You are aware that an LS-7 454 never existed as a production motor (only available as a collection of parts sold across the parts counter). Not only that the LS-7 was a 12.5:1 open chamber motor that will not run on any gasoline you can find at the corner store! If you have a 454 out of a pick-up it will have deep dished ppistons instead of domes to run on pump gas at a whopping 7.4:1 compression ratio. I built three LS-7 motors (one being a back-up) and it would be a toss up as to which I had more fun with; the LS-7 or the L-88.

Big Dave
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post #3 of 12 (permalink) Old 07-04-2009, 10:49 AM Thread Starter
 
 
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Spark Plug Gap?.

Im using the MSD Pro-Billet Distributor,do we consiser that an HEI?,Thank You,Bill.
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post #4 of 12 (permalink) Old 07-04-2009, 02:04 PM
 
 
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Hi Bill and Big Dave

On page 19 of what almost all Chevrolet used parts dealers believe to be the "Bible" of resource publications "Cars and Parts Catalog of Chevy V-8 Engine Casting Numbers 1955-93". it states that LS-7s were, indeed sold "over the counter". I also can vouch for this since I had one since 1974. It was bought through GM as a LS-7 long block, crate motor. It still has never been run ! I just sold it to a close friend and it still sits, waiting to take its first breath of polluted Chicago air. I know of 2 more LS-7s purchased in Chicago, that also came as crate motors from GM at the same time. My LS-7 block was GM # 3999289.The GM number on the block pad was # TO 617 XCH. No other numbers or letters were on the pad. On page # 5 of "Chevrolet Big Block Parts Interchange Manual" under LS-7, it also says that it was available in 1970 as an over the counter crate motor or could be built with over the counter parts. On page # 13 it states that The Mark lV LS-7 long block assembly was GM part # 3965774. What really aggravated me was when GM came out with a small block that they called the LS-7. Did they run out of letters and numbers ?? Badges like Super Sport and LS-6 and LS-7 are HOLY among Gear Heads. I know this has nothing to do with sparkplug gap, but I had to chime in.

Red Light Bandit
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post #5 of 12 (permalink) Old 07-04-2009, 03:44 PM
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Quote:
Originally Posted by Itsamessfrom67 View Post
Im using the MSD Pro-Billet Distributor,do we consiser that an HEI?,Thank You,Bill.
Yes it is. Points are a mechanical switch that opens to break a circuit in the coil causing the magnetic field to collapse and induce electricity to flow out of the coil to the distributor. An HEI uses transistor to amplify an almost non-existent pulse of electricity created by a magnetic trigger inside the HEI distributor.

Big Dave
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post #6 of 12 (permalink) Old 07-04-2009, 11:53 PM Thread Starter
 
 
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LS-7 Motors?.

My motor is not an original LS-7 production motor.I assembled the motor using GM replacemnt parts and after market replacement parts.I started with a 030. 4-bolt block,steel tuftrided LS-6 crank,LS-7/ZL-1 extra heavy duty 7/16 Bolt "Green" Connecting Rod,TRW 12 1/2-1 forged pistons,GM LS-7 Camshaft,Crower "Piddle" Valve type lifters,and GM Signature series rectanguler port aluminum,open chamber heads,I have topped the engine off with the GM aluminum dual-plane hi-rise intake manifold.A local machine shop fitted/balanced and assembled the short block for me,and I completed the build.Well,I guess I will gap my plugs at .045".Thank You,Bill.
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post #7 of 12 (permalink) Old 07-05-2009, 11:10 AM
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Only thing wrong with that is the lifters are supposed to be solid (hot lashed a 0.020"/0.020") not hydraulic tappets. But that is how I built my motors as well.

The LS-7 also used round port exhaust heads (only other engine to use them was the ZL-1 427) instead of the usual square port used on every other BBC.

Big Dave
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post #8 of 12 (permalink) Old 07-06-2009, 03:10 PM
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Suggested plug gaps from MSD based on compression:

Compression Spark Plug Gap
Up to 10.5:1= .050-.060
10.5:1 – 13.0:1= .040-.050
Above 13.0:1= .035-.045

Also- stay away from the newer platinum type plugs if running an MSD unit.
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post #9 of 12 (permalink) Old 07-06-2009, 11:53 PM
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Hey Big Dave, Bill, and John,

I'm NOT trying to be argumentive here, just going to try to relay some previous experiences in regards to statements made here. Every Big Block Racer(S/S-Pro Stock-Funny car) that I knew "Back in the day", WOULD have NEVER used anything other than solid lifters, and the heads of choice were Rectangular/ Square port,Open chambered. Although, A LOT less compression with nitro. As for the existence of a complete LS-7 motor from Chevrolet....Yes, THEY did come from over the parts counter in a crate. All one needed to do was mount a carb and drop in a distributor. Now if my memory serves me correctly (I can't find my receipts,that far back and several moves,one involving a tornado) the price was $1,395. plus tax. Also available were Open Chambered Aluminum heads bare or complete.In 1973,I had 5, LS-7's come through the shop and 10 boxes with AL.OC heads. As everyone knows, IF we had the technology then as we do now,oval port heads would not of been used as boat anchors. Today,we get so much more out of them with less compression,better rotating assemblies, and add EFI...."The possiblities are endless"!!!!! As for your last statement Big Dave, I saw one ZL-1 in Illinois in a Camaro and it too had Rec/square port heads. I know anything could of been put together.... I'm just stating the things I have seen/been part of over the years. I hope this has not "Muddy the Waters"
Gary
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post #10 of 12 (permalink) Old 07-07-2009, 11:55 AM
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Quote:
Originally Posted by Red Light Bandit View Post
Hi Bill and Big Dave

...What really aggravated me was when GM came out with a small block that they called the LS-7. Did they run out of letters and numbers ?? Badges like Super Sport and LS-6 and LS-7 are HOLY among Gear Heads. I know this has nothing to do with sparkplug gap, but I had to chime in.

Red Light Bandit
The older LS7 was never a production engine. The newer LS7 is. GM was going for the "heritage" thing bringing back that name and putting into production this time. LS7 has always meant big power.

What about the LT-1? And Dodge rehashed the Hemi, right?
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post #11 of 12 (permalink) Old 07-07-2009, 05:33 PM
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You could buy the fully assembled engine minus carb and water pump and distributor back in 1970; but only if you wanted to pay shipping. If you wanted all of the parts to build one the costs was the same (generally a collection of parts cost more than the whole), but the dealer ate the shipping. So it was faster in terms of getting one in your hands (I could assemble one in hours after getting the machine work done in a day or two), as opposed to waiting for the truck to arrive with your new toy. Since I didn't run the stock cam I needed the pistons fly cut for valve to piston clearance anyway, and I had to set up the heads for my springs.

If you lived in Detroit then I imagine buying a crate motor was the way to go. I did eventually buy one assembled motor, and I had already purchased five L-88's already screwed together as the sum of the parts definitely exceeded the whole for the L-88.

Big Dave
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post #12 of 12 (permalink) Old 07-07-2009, 07:53 PM Thread Starter
 
 
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Spark Plug Gap?.

Thanks 1968 Caprice,I recieved a informative/straightforward answer from you,Bill.
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