LS3 Carbed build

General engine tech -- Drag Racing to Circle Track

Moderator: Team

Post Reply
CGT
Guru
Guru
Posts: 2063
Joined: Sun May 10, 2009 12:29 pm
Location:

Re: LS3 Carbed build

Post by CGT »

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.
cgarb
Guru
Guru
Posts: 2006
Joined: Wed Jul 09, 2014 11:50 am
Location: Maryland

Re: LS3 Carbed build

Post by cgarb »

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.
CGT
Guru
Guru
Posts: 2063
Joined: Sun May 10, 2009 12:29 pm
Location:

Re: LS3 Carbed build

Post by CGT »

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.
novadude
Guru
Guru
Posts: 1500
Joined: Thu Oct 11, 2007 3:24 pm
Location: Shippensburg, PA

Re: LS3 Carbed build

Post by novadude »

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.
jet1
Pro
Pro
Posts: 449
Joined: Tue May 22, 2012 1:11 pm
Location: Alberta

Re: LS3 Carbed build

Post by jet1 »

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.
A_VAS
Pro
Pro
Posts: 208
Joined: Thu Dec 03, 2009 1:52 pm
Location: Harrisburg, PA

Re: LS3 Carbed build

Post by A_VAS »

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
CGT
Guru
Guru
Posts: 2063
Joined: Sun May 10, 2009 12:29 pm
Location:

Re: LS3 Carbed build

Post by CGT »

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.
3pedals
Member
Member
Posts: 151
Joined: Tue Nov 13, 2007 7:15 pm
Location: WPG. Manitoba

Re: LS3 Carbed build

Post by 3pedals »

Cutting the stand is definately the right direction to improve ls3 rocker geometry at higher lifts
cgarb
Guru
Guru
Posts: 2006
Joined: Wed Jul 09, 2014 11:50 am
Location: Maryland

Re: LS3 Carbed build

Post by cgarb »

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.
steve316
Expert
Expert
Posts: 630
Joined: Fri Apr 13, 2007 10:06 pm
Location: St.Joseph,mo.

Re: LS3 Carbed build

Post by steve316 »

Like this type of build; it is like the early 70's went all you had was oem parts for your build.
CGT
Guru
Guru
Posts: 2063
Joined: Sun May 10, 2009 12:29 pm
Location:

Re: LS3 Carbed build

Post by CGT »

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.
cgarb
Guru
Guru
Posts: 2006
Joined: Wed Jul 09, 2014 11:50 am
Location: Maryland

Re: LS3 Carbed build

Post by cgarb »

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?
CGT
Guru
Guru
Posts: 2063
Joined: Sun May 10, 2009 12:29 pm
Location:

Re: LS3 Carbed build

Post by CGT »

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
GARY C
HotPass
HotPass
Posts: 6301
Joined: Tue May 14, 2013 10:58 pm
Location:

Re: LS3 Carbed build

Post by GARY C »

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.
Please Note!
THE ABOVE POST IN NO WAY REFLECTS THE VIEWS OF SPEED TALK OR IT'S MEMBERS AND SHOULD BE VIEWED AS ENTERTAINMENT ONLY...Thanks, The Management!
CGT
Guru
Guru
Posts: 2063
Joined: Sun May 10, 2009 12:29 pm
Location:

Re: LS3 Carbed build

Post by CGT »

Resized_20180711_192435.jpg
Short block flowz! MOO
You do not have the required permissions to view the files attached to this post.
Post Reply