LS3 Carbed build

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CGT
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Re: LS3 Carbed build

Post by CGT » Thu Jul 05, 2018 10:49 pm

cgarb wrote:
Thu Jul 05, 2018 10:32 pm
Will you be using adjustable valvetrain? Have you given any thought to a solid roller?
Would love to have done a solid roller, but im going to try and get it done with the factory valvetrain, non adjustable, travel limited stock lifters and conical springs.

I wont know how all that jives out until I get there(valvetrain). A solid roller would add thousands of dollars to this project, no cheap way around that but may ultimately be inevitable.

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Re: LS3 Carbed build

Post by cgarb » Fri Jul 06, 2018 12:21 am

My advice to my coworker was to spend as much of his budget he could on valvetrain. Can't go wrong with spending extra there.

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Re: LS3 Carbed build

Post by CGT » Fri Jul 06, 2018 8:51 am

cgarb wrote:
Fri Jul 06, 2018 12:21 am
My advice to my coworker was to spend as much of his budget he could on valvetrain. Can't go wrong with spending extra there.
True. But the factory valvetrain is very well designed. 80 gram valves, beehive springs, light stiff rocker arms, short pushrods. When you change one thing drastically in there it sends you down a slippery slope.

Solid roller= more valve spring pressure, small valve spring pockets=very expensive solid roller springs=very expensive solid roller lifters=stock rockers no longer adequate=very expensive shaft rockers=now questionable stock valves=maybe I should have upgraded crank and rods :lol: . It just doesn't stop.

I will just have to see where this ends up, then go from there. It's creative freedom, like mentioned in the pro vs hobbyist thread here on ST. :lol: It's all just self-imposed limitations on my part.

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Re: LS3 Carbed build

Post by novadude » Fri Jul 06, 2018 8:55 am

cgarb wrote:
Thu Jul 05, 2018 9:52 pm
Why such a large split to the exhaust side? Are the LS heads that bad on the exhaust that you need to crutch them with a big split like on a CJ BBF head?
Does I/E flowz ratio even matter when looking at cam duration split? Seems like the pros are gradually moving away from that school of thought. Does flow at 28" on the bench even relate to what is actually happening in an exhaust port? Just wondering.

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Re: LS3 Carbed build

Post by jet1 » Fri Jul 06, 2018 10:38 am

cgarb wrote:
Thu Jul 05, 2018 9:52 pm
Why such a large split to the exhaust side? Are the LS heads that bad on the exhaust that you need to crutch them with a big split like on a CJ BBF head?
True, the ex side does not flow that bad on the ls heads but the intakes flow really well. We have found that the FI engines like to see more dur on ex by a larger margin than the carbed engines. I have been running a .648 lift 253/259 110 and it run and starts great. stk valve train holds up pretty good with pac1206x springs and stiffer pushrods.

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Re: LS3 Carbed build

Post by A_VAS » Fri Jul 06, 2018 11:12 am

I'm interested to see how the stock rods hold up. Are you planning to loosen up the rod bearing clearance or anything needed to 'help' them last?

also, for the factory rockers....~680 lift...should work out. I've played with the height of the pivot to get a better scrub pattern. I took a stock stand and cut it in sections...milled off the backside in multiples of .050". you can see what lowering the pivot does that way. to raise it I used ford rocker shims for the pedestal mount rockers...they fit the 8mm bolts nice
too lazy to make power w/o boost

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Re: LS3 Carbed build

Post by CGT » Fri Jul 06, 2018 11:43 am

A_VAS wrote:
Fri Jul 06, 2018 11:12 am
I'm interested to see how the stock rods hold up. Are you planning to loosen up the rod bearing clearance or anything needed to 'help' them last?

also, for the factory rockers....~680 lift...should work out. I've played with the height of the pivot to get a better scrub pattern. I took a stock stand and cut it in sections...milled off the backside in multiples of .050". you can see what lowering the pivot does that way. to raise it I used ford rocker shims for the pedestal mount rockers...they fit the 8mm bolts nice
I put arp 2000 bolts in them, but the rods are tough. Their are plenty of them out there in 800rwhp+ boosted stuff, including my own. Gm even now uses them in their forced inducted purpose short block they sell.(I know their are a lot of powdered metal haters out there)

The valve job will be sunk quite a bit, raising the tip height. That alone should keep the rocker scrub looking decent at the point where there is the most valve spring pressure at least. It just depends on how ugly it looks at lower lift. I thought about the possibility of having to cut the stands. Thanks for the info.

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Re: LS3 Carbed build

Post by 3pedals » Fri Jul 06, 2018 12:25 pm

Cutting the stand is definately the right direction to improve ls3 rocker geometry at higher lifts

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Re: LS3 Carbed build

Post by cgarb » Fri Jul 06, 2018 4:53 pm

I always see the LS cams with wide lobe separations, Is this due to shelf cams geared towards EFI or does this engine work better that way? Typical N/A gen 1 sbc with comparable cubic inch, 106 to 108 seem to be the norm.

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Re: LS3 Carbed build

Post by steve316 » Fri Jul 06, 2018 5:18 pm

Like this type of build; it is like the early 70's went all you had was oem parts for your build.

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Re: LS3 Carbed build

Post by CGT » Fri Jul 06, 2018 6:12 pm

A_VAS wrote:
Fri Jul 06, 2018 11:12 am
I'm interested to see how the stock rods hold up. Are you planning to loosen up the rod bearing clearance or anything needed to 'help' them last?
.0025 Rods
cgarb wrote:
Fri Jul 06, 2018 4:53 pm
by cgarb » Fri Jul 06, 2018 3:53 pm

I always see the LS cams with wide lobe separations, Is this due to shelf cams geared towards EFI or does this engine work better that way
A little bit of several things in my opinion. In factory form, idle, driveability and getting a devent IVC and EVO with very short duration.

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Re: LS3 Carbed build

Post by cgarb » Fri Jul 06, 2018 9:43 pm

If this was a strictly bracket engine, and no drivability concerns...would that still be the case? What are all the stock eliminator cars running for camshafts?

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Re: LS3 Carbed build

Post by CGT » Fri Jul 06, 2018 10:11 pm

cgarb wrote:
Fri Jul 06, 2018 9:43 pm
If this was a strictly bracket engine, and no drivability concerns...would that still be the case? What are all the stock eliminator cars running for camshafts?
Its not head limited like an old school typical eliminator car. So thats different than an old sbc or sbf. In order to have enough duration to run a certain rpm and keep the important valve events in check you may end up with a tighter lsa and accept the side effect of too much overlap. Then go to other measures to control reversion. Im not saying my first cam is optimum btw. It just has events that i know wont embarass themselves.......hopefully

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Re: LS3 Carbed build

Post by GARY C » Fri Jul 06, 2018 10:27 pm

cgarb wrote:
Fri Jul 06, 2018 4:53 pm
I always see the LS cams with wide lobe separations, Is this due to shelf cams geared towards EFI or does this engine work better that way? Typical N/A gen 1 sbc with comparable cubic inch, 106 to 108 seem to be the norm.
If I am not mistaken the LS engines ran in a limited dirt class were speced on a 108ish LSA. There would be a lot to take into account depending on which head/valve size and what application.
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Re: LS3 Carbed build

Post by CGT » Thu Jul 12, 2018 10:49 am

Resized_20180711_192435.jpg
Short block flowz! MOO
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