1970 LS5 454 Pistons - some guidance, please? - Chevelle Tech
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post #1 of 16 (permalink) Old Sep 2nd, 19, 10:40 PM Thread Starter
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1970 LS5 454 Pistons - some guidance, please?

I have a 1970 LS5 that I am redoing and it was all stock when I tore it down. I have had the cylinders bored and honed 0.030 over. Now what pistons do I run. I was going to run Forged pistons and was looking at Speed Pro. Do I run the flat top and if so how much would that lower the compression and if I go with the next size bigger it is a little bigger than stock. I'm running the factory heads and intake. I haven't decided on the cam yet until I figure out the pistons, I'm also going to run a good set of headers and exhaust. I'll keep the stock carb also. I'm only buying good parts and will spend the money since I don't plan on selling it. Also what rings would you recommend to go along with the pistons. I've had small blocks for years now I have moved up to Big Blocks and I'm learning everything I can on this engine. I also plan to drive this thing and have fun with it.

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post #2 of 16 (permalink) Old Sep 3rd, 19, 1:47 AM
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Re: 1970 LS5 454 Pistons

Moving to an appropriate forum.

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post #3 of 16 (permalink) Old Sep 3rd, 19, 2:09 AM
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Re: 1970 LS5 454 Pistons - some guidance, please?

With flattops you will have around 8.5 in comp or with the speed pro 2399 9.5-10.
Have you ccd the heads? Are the block decked?

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post #4 of 16 (permalink) Old Sep 3rd, 19, 6:46 AM
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Re: 1970 LS5 454 Pistons - some guidance, please?

Just my 2 cents worth,if it were me I would contact Mike "Wolfplace" Lewis and ask about the Autotec line of pistons.
https://www.lewisracingengines.com/
They are lighter and built in the USA and they can supply custom pin height,domes etc. for off the shelf pricing,IIRC
Mike could probably point you in the right direction for dome size and could also recommend a nice Bullet camshaft
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post #5 of 16 (permalink) Old Sep 3rd, 19, 6:54 PM
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Re: 1970 LS5 454 Pistons - some guidance, please?

I would run some Icon or SRP pistons, much nicer and lighter than the Speed Pro slugs.
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post #6 of 16 (permalink) Old Sep 3rd, 19, 8:46 PM Thread Starter
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Re: 1970 LS5 454 Pistons - some guidance, please?

Thanks David for moving it to the correct spot!
I'm using the stock heads and here is the info for them. 3964290 1969-72 454 2.06 1.72 Closed Chamber 100.9.
The block is not decked and the heads I ran on the lapper for 30 seconds and there nice and flat.

Lewis race engines has some cool stuff He is showing on His site. Very impressive!

I'll look into the other choices you mentioned 68Chevele
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post #7 of 16 (permalink) Old Sep 5th, 19, 3:35 AM
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Re: 1970 LS5 454 Pistons - some guidance, please?

".... heads I ran on the lapper for 30 seconds and there nice and flat."

what is this lapper you speak of? got a pic? is it like a big belt sander?
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post #8 of 16 (permalink) Old Sep 5th, 19, 10:35 AM
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Re: 1970 LS5 454 Pistons - some guidance, please?

You know, I'm not bustin' anyone's chops, but I couldn't picture it either Tom. My 3 yrs of shop experience was back in 1977-80, and the bugger was always strapping that head down to the table properly to mill the decks clean. We did VW cores on a three head mill, but all the V8 and exotic ( Cosworth mostly) stuff was "manual". Once the horizontal boring mill showed up, I think the boss a jig to make it much easier. Dang I cut and ground so much cast iron back then.

Jay, I cant comment on 454 slugs other than to say I just an engine pro built ( my garage built 427 done good for the last 20 yrs!) and Mark Jones prefers the Mahle slugs for that app. For the 427 I used an SRP medium dome slug I bought from Competition Products. BTW, the ring pack typically comes with the pistons, well, it did with the SRPs.

I hope these are the same "models" as was used in my new 454, yet I dont see any that come in at the 9.8:1 comp ratio the new engine sports. ? MAHLE North America | PowerPak pistons

As recommended earlier, I would call a builder, Mike, Carl, Mark, etc and get the right parts. Summit is my go-to ( 1 day shipping to BUff), but somethings they may not carry OR have the technical expertise to recommend.
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post #9 of 16 (permalink) Old Sep 5th, 19, 2:13 PM
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Re: 1970 LS5 454 Pistons - some guidance, please?

Quote:
Originally Posted by Tom Mobley View Post
".... heads I ran on the lapper for 30 seconds and there nice and flat."

what is this lapper you speak of? got a pic? is it like a big belt sander?
I thought everyone had a "lapper" hiding in the corner...............
And before you ask,,, no I don't do heads on it............
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post #10 of 16 (permalink) Old Sep 6th, 19, 7:54 PM Thread Starter
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Re: 1970 LS5 454 Pistons - some guidance, please?

Quote:
Originally Posted by 427L88 View Post
You know, I'm not bustin' anyone's chops, but I couldn't picture it either Tom. My 3 yrs of shop experience was back in 1977-80, and the bugger was always strapping that head down to the table properly to mill the decks clean. We did VW cores on a three head mill, but all the V8 and exotic ( Cosworth mostly) stuff was "manual". Once the horizontal boring mill showed up, I think the boss a jig to make it much easier. Dang I cut and ground so much cast iron back then.

Jay, I cant comment on 454 slugs other than to say I just an engine pro built ( my garage built 427 done good for the last 20 yrs!) and Mark Jones prefers the Mahle slugs for that app. For the 427 I used an SRP medium dome slug I bought from Competition Products. BTW, the ring pack typically comes with the pistons, well, it did with the SRPs.

I hope these are the same "models" as was used in my new 454, yet I dont see any that come in at the 9.8:1 comp ratio the new engine sports. ? MAHLE North America | PowerPak pistons

As recommended earlier, I would call a builder, Mike, Carl, Mark, etc and get the right parts. Summit is my go-to ( 1 day shipping to BUff), but somethings they may not carry OR have the technical expertise to recommend.
Thanks for the info. Summit is in my area of the state and next day shipping. I stopped in and talked to a guy there that builds engines and He gave me his input but mostly builds small blocks.

Jay
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post #11 of 16 (permalink) Old Sep 6th, 19, 7:55 PM Thread Starter
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Re: 1970 LS5 454 Pistons - some guidance, please?

Quote:
Originally Posted by Wolfplace View Post
I thought everyone had a "lapper" hiding in the corner...............
And before you ask,,, no I don't do heads on it............
We have a power lapper at work that is kept in nice shape and checked for flatness constantly.

Jay
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post #12 of 16 (permalink) Old Sep 6th, 19, 8:04 PM Thread Starter
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Re: 1970 LS5 454 Pistons - some guidance, please?

Quote:
Originally Posted by Tom Mobley View Post
".... heads I ran on the lapper for 30 seconds and there nice and flat."

what is this lapper you speak of? got a pic? is it like a big belt sander?
We have a Lapmaster at work and it is a lot bigger than this one and a lot older. Looks like the rings on this one are to big. Take the rings off and put the heads. Then we have a hand lapper for a real nice smooth finish but heads are to big and heavy!


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post #13 of 16 (permalink) Old Sep 12th, 19, 3:02 AM
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Re: 1970 LS5 454 Pistons - some guidance, please?

Mike, is that a chainsaw under the machine? What, you use that for roughing in used heads? or what?





Quote:
Originally Posted by Wolfplace View Post
I thought everyone had a "lapper" hiding in the corner...............
And before you ask,,, no I don't do heads on it............

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post #14 of 16 (permalink) Old Sep 12th, 19, 12:18 PM
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Re: 1970 LS5 454 Pistons - some guidance, please?

Quote:
Originally Posted by Tom Mobley View Post
Mike, is that a chainsaw under the machine? What, you use that for roughing in used heads? or what?

That's a multi-task tool...... cuts trees, trims the wolves toenails, riffraff dismemberment.... normally kept in the customer complaint department area,,,
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post #15 of 16 (permalink) Old Sep 12th, 19, 4:49 PM
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Re: 1970 LS5 454 Pistons - some guidance, please?

food preparation tool for wolves....
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