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Re: Gen 5 LT1 L83 L86 heads

Posted: Fri Jul 21, 2017 10:33 am
by A_VAS
In February I built a Gen5 short block with stock crank, forged rods, and forged Wiseco piston.
numbers work out same as earlier stuff...6.125 rod, 3.622 stroke, 1.304 CH
pistons were ~.004-.006 out of the hole using this new GM, undecked Gen5 block
so yes the 9.240 nominal is correct

I also just put a set of Diamond pistons in a LT1, reusing the stock rods and crank.
stock rod length in the Gen5 is 6.125 btw, just use a weird pin dia.

Re: Gen 5 LT1 L83 L86 heads

Posted: Sun Jul 23, 2017 2:34 am
by In-Tech
Thanks A_VAS,
I wasn't sure which head I have here but it does appear it is a L83 and not a L86. It appears the L83 has a 1.928" In valve and 1.556" ex valve. The L86 is 2.13" and 1.59" respectively. I haven't measured it completely yet but it looks like a 2" valve is all the L83 will handle in stock form. The casting does appear to have enough meat for me to install a larger seat so as time allows I will do that.

A_VAS, besides the 8 bolt flexplate/flywheel, is the Gen5 the same crank otherwise as a Gen3/4? Thanks again for all the feedback.

Re: Gen 5 LT1 L83 L86 heads

Posted: Mon Jul 24, 2017 10:19 am
by A_VAS
on the crank, yes as far as I could tell it is the same as say a LS9 crank.
journal sizes and width are same as previous...it is a forging..I did not measure the snout length to see if it was the same as earlier versions.

the main line is a bit different in that they use the same #3 cap as the rest 1/2/4/5. There is no machined surface on the cap for a thrust bearing...they only put a flange bearing in the block side of #3 and not the cap. The cap uses the same bearing as the other positions.
so it has a 1/2 thrust bearing so to speak, with flange only on 180*

Re: Gen 5 LT1 L83 L86 heads

Posted: Mon Sep 11, 2017 1:49 am
by In-Tech
midnightbluS10 wrote:
tt 383 wrote:L83 has a 248cc intake and 107cc exhaust 57/58 combustion chamber. That's from LPE. Can't find the L86 port volumes but supposedly they are about 50cfm better than the L83 head... I feel like the L86 was 26x cc volume in some literature I read.

According to a post on their forum from Tim@Lingenfelter,
L86 LT1 General Motors Cylinder Head Runner Volumes and Chamber Volumes

The factory L86 LT1 cylinder heads runner volumes and chamber sizes are as follows.

Stock L86 LT1 cylinder heads -

297 CC intake runner volume / 107 cc exhaust , 56.5 cc chambers


Lingenfelter CNC ported L86 LT1 cylinder heads -

308 CC intake runner volume / 110 cc exhaust . 61 cc chambers before surfacing.

With a camshaft change you would require better valve springs.

We offer the following camshafts for the LT1 engine & the related spring kits are included on the item pages

http://www.lingenfelter.com/mm5/merc...gory_Code=C606

I would suggest checking the pushrod length during assembly. In most cases the stock pushrods can be reused (LT1)
And the LT1/L86's flow somewhere around 320/210 estimating from a quick glance at the graphs

http://www.lingenfelter.com/forum_linge ... -flow-data
Hello Folks,
I apologize for the delay, I've had some health issues and this all got back burner'd :| Somehow I missed that the L86 had such a larger port(noted in above quote), to me that means it must be a different casting so I'll be on the hunt for one and if anyone knows the casting number I should be looking for, it would be appreciated. I might even put a new blade on the band saw for this one. :mrgreen:

A-VAS, thanks for the half thrust bearing knowledge. Maybe I missed it in one of your posts, do these all have piston oilers like the LSA and LS9?

Re: Gen 5 LT1 L83 L86 heads

Posted: Mon Sep 11, 2017 11:02 am
by A_VAS
the car engines LT series have the squirters yes.
I have not personally seen a LT truck engine to verify if the squirters are in all of them.

Re: Gen 5 LT1 L83 L86 heads

Posted: Mon Sep 11, 2017 11:18 am
by cuisinartvette
nothing technical to add just gotta admire what gm has done
back in the 80s or 90s guys woulda cut their toes off for something similar
Todays stock engines are the "race" engines of those days in a sense.

Re: Gen 5 LT1 L83 L86 heads

Posted: Mon Nov 06, 2017 6:00 am
by In-Tech
A_VAS wrote:
Fri Jul 21, 2017 10:33 am
In February I built a Gen5 short block with stock crank, forged rods, and forged Wiseco piston.
numbers work out same as earlier stuff...6.125 rod, 3.622 stroke, 1.304 CH
pistons were ~.004-.006 out of the hole using this new GM, undecked Gen5 block
so yes the 9.240 nominal is correct

I also just put a set of Diamond pistons in a LT1, reusing the stock rods and crank.
stock rod length in the Gen5 is 6.125 btw, just use a weird pin dia.
Hi A_VAS, Was it the standard .945" LS pin size or weirder?

Re: Gen 5 LT1 L83 L86 heads

Posted: Mon Nov 06, 2017 7:00 am
by Newold1
ALL the GM manufacturing data is now designed and built in metric dimensions. Could it be that the new pin diameters are done in newer even metric dimensions and those now convert to odd inch dimensions? A lot of us guys are going kicking screaming and befuddled when it comes to using metric dimensions that the whole industrial world has been using now for about 20 years.

Re: Gen 5 LT1 L83 L86 heads

Posted: Mon Nov 06, 2017 8:46 am
by In-Tech
I would imagine so. 24mm(~.945") is what stock LS1 is. Most aftermarket LS rods/pistons go back to original SBC size of .927". A_VAS mentioned it being weird on the LT so I am just curious how weird. :)

Re: Gen 5 LT1 L83 L86 heads

Posted: Mon Nov 06, 2017 1:36 pm
by A_VAS
I don't have the box the pistons came in to make sure....but going from memory I think they used the .984 diameter (25mm) pins like the LS9

the LS9 with titanium rod used the .984 pins...and from what I can find nowhere else in GM used that. Maybe someone can confirm the pin size for sure...I didn't write it down. Pistons were from Diamond and designed to work with the stock rods/pins.
There aren't many mfgs so far that offer something to re-use the stock rods. Most switch to the .927 pin requiring you to buy rods with your pistons.
Vengeance Racing was selling a set they had custom made from Wiseco, that dropped in with stock rod. Not sure those are available anymore.
This set I used came from DIamond, and thru Brian Tooley.
https://www.briantooleyracing.com/lt1-4 ... 33456.html

Re: Gen 5 LT1 L83 L86 heads

Posted: Mon Nov 06, 2017 7:45 pm
by sanfordandson
In-Tech wrote:
Wed Jul 19, 2017 3:42 pm
Have you physically verified that the deck is the same 9.240"?
I have. Gm spec is 9.235-9.245.

Re: Gen 5 LT1 L83 L86 heads

Posted: Wed Nov 08, 2017 12:04 pm
by CGT
In-Tech wrote:
Fri Jul 14, 2017 11:11 pm
Does anyone know what the designations mean? I assume LT1 is the corvette, L83 is 5.3L Truck and L86 are larger valves and 6.2L Truck and Camaro, but I do not know for sure.
Does the Gen 5 have the same deck height as the Gen 4? Does anyone have detailed drawings or prints of the Gen 5? I'm interested in the fuel pump mounting and location.

Sooooooooo, I cut up a L83 gen 5 head. \:D/ :mrgreen: Sorry for the cell phone pics, more to follow.


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Warranty cylinder head? I have a couple myself I've been looking at.

Re: Gen 5 LT1 L83 L86 heads

Posted: Wed Nov 08, 2017 5:15 pm
by In-Tech
No Warranty. One of the dyno shops that call me in for tuning had a pair laying on the floor. The one I cut up had a broken rocker pedestal boss so the shop owner gave me the bad head and I immediately cut it up :D I am still looking for a cheap single L86 head to cut up and play on the flow bench with if anyone has one. I've learned some things on this L83 head I've been playing with and am piecing together a complete engine to dyno and prove or disprove my theories. [-o< One is how a flow bench doesn't tell the whole story.
This whole project has me riled up to finish my flow bench(only been started/backburnered for over 3 years now :oops: ) that uses a 100 hp electric motor to drive a screw supercharger, mass air flow based and can do wet flow too. Alot of health problems the last couple years but the goal is Jan1 for initial test(dry flow). I really think we are all going to learn quite a bit flowing a port in boost :D

Re: Gen 5 LT1 L83 L86 heads

Posted: Wed Nov 08, 2017 6:24 pm
by Carnut1
After you get your first electric bill you will never want to use that bench again!

Re: Gen 5 LT1 L83 L86 heads

Posted: Wed Nov 08, 2017 6:56 pm
by CGT
In-Tech wrote:
Wed Nov 08, 2017 5:15 pm
No Warranty. One of the dyno shops that call me in for tuning had a pair laying on the floor. The one I cut up had a broken rocker pedestal boss so the shop owner gave me the bad head and I immediately cut it up :D I am still looking for a cheap single L86 head to cut up and play on the flow bench with if anyone has one. I've learned some things on this L83 head I've been playing with and am piecing together a complete engine to dyno and prove or disprove my theories. [-o< One is how a flow bench doesn't tell the whole story.
This whole project has me riled up to finish my flow bench(only been started/backburnered for over 3 years now :oops: ) that uses a 100 hp electric motor to drive a screw supercharger, mass air flow based and can do wet flow too. Alot of health problems the last couple years but the goal is Jan1 for initial test(dry flow). I really think we are all going to learn quite a bit flowing a port in boost :D
I have a couple that are slightly damaged. Been thinking about trying a set on a ls3, plugging the injector boss. Headers are the hang up as far as being able to use shelf stuff. Id like to see how they stack up to the earlier heads. They look better in several ways.