Author Topic: 1976 Trans Am: LS3 Swap, Hydraulic Clutch, TKO600 and other tidbits  (Read 46504 times)

scarebird

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Re: 1976 Trans Am: LS3 Swap, Hydraulic Clutch, TKO600 and other tidbits
« Reply #120 on: February 26, 2016, 07:19:49 PM »
Ours uses a 4" elbow, can send more pix if needed.


TransAm_Stan

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Re: 1976 Trans Am: LS3 Swap, Hydraulic Clutch, TKO600 and other tidbits
« Reply #121 on: June 07, 2016, 08:25:25 PM »
And for another update...

Been living with this swap for a few months now.  Have about 250 miles on this engine.  this thing pulls like a bear!  Its a really fun combo on the street...

One thing that bothers me is the decel exhaust crackling.  Under 2K rpm in an off throttle situation this thing crackles like hell.  Sounds like a combo of a backfire and a fart.  A loud fart.  Not happy with that sound at all.  All that I have read is this is a LS engine trait that can be tuned out with adding fuel in the off throttle situations, at a loss of 2-3 mpg.  Looks like I will have to live with the crackle until I can get this car on a dyno & get her tuned.

All the electrical gremlins have been addressed.  Loose grounds do funny things...

Still looking for a dyno & a tune closer to me.  No luck yet.

Took off a coil & a quarter.  While my stance is seriously now on the bitchen side, the tire does bottom out on the inner fender.  A quarter coil too much. I would seriously investigate updating the front & rear suspension, but I know darn well it would be stiffer & at this point I do not want that.

Still haven't messed around with the airbox.  Sounds like a plan for this winter...  LOL

All in all I am fairly happy with the way things have turned out.  Could be a lot worse! 
76 White exterior, Blue interior "Toastee"
LS3, TKO600, Hydroboost
Hydraulic clutch
Western Hurricane rims

76 White 400 4sp. blue/white interior (project)
Can't get any more apart than I have it!

scarebird

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Re: 1976 Trans Am: LS3 Swap, Hydraulic Clutch, TKO600 and other tidbits
« Reply #122 on: June 07, 2016, 10:24:47 PM »
How did they run the exhaust?  Mine is transverse muffler, 2-1/2" inch using the Camaro exhaust manifolds and cats.

cal30_sniper

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Re: 1976 Trans Am: LS3 Swap, Hydraulic Clutch, TKO600 and other tidbits
« Reply #123 on: June 07, 2016, 11:08:04 PM »
It's not just an LS thing, it's a pretty common problem with a stick car with headers and fuel injection. It's caused by late combustion due to high manifold vacuum/low MAP. When you decel against the gearing, it creates pretty high manifold vacuum, leading to a very low density of the air/fuel mixture in the cylinder. Because the mixture is at such a low density, it has a very hard time combusting before it leaves the cylinder. This results in the combustion completing inside the hot exhaust header primary, leading to the dreaded pop. I fought it in the tune for weeks when I set up the Holley Stealth Ram/TPI Computer/T56 combo on my roommates 92 bird. I eventually found that a combination of spark advance (only under high vacuum/low MAP conditions) and a slight richening of the mixture at those levels got rid of 95% of the popping. The spark advance gives the mixture more time to combust inside the cylinder, and the richening of the mixture helps speed up the combustion enough that it happens inside the cylinder rather than inside the exhaust.

Many fuel injection systems offer a decel fuel cutoff mode. GM started doing it in 89 with the '165 TPI ECM. I'm sure the LS has something similar. If you can get that to kick in, it will solve your problem by removing the combustible mixture altogether under those conditions.
'73 Formula 350
'88 Trans Am GTA L98
'86 Suburban C20 454/NV4500

Formula build thread: http://transamcountry.com/community/index.php?topic=75375.msg705571#msg705571

TransAm_Stan

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Re: 1976 Trans Am: LS3 Swap, Hydraulic Clutch, TKO600 and other tidbits
« Reply #124 on: June 08, 2016, 01:19:39 AM »
How did they run the exhaust?  Mine is transverse muffler, 2-1/2" inch using the Camaro exhaust manifolds and cats.

I used Hedman 1 ¾” ceramic coated mid-length headers and Pypes Transverse 2.5" system.  No cats.

This exhaust package has a unique sound.  During regular driving, 3K and under (approx) there is a very nice mellow throaty sound.  Get into the throttle and it sounds like I have an exhaust cut out installed.  I like both sounds.  A sound for every occasion, so to speak.
« Last Edit: June 08, 2016, 01:34:52 AM by TransAm_Stan »
76 White exterior, Blue interior "Toastee"
LS3, TKO600, Hydroboost
Hydraulic clutch
Western Hurricane rims

76 White 400 4sp. blue/white interior (project)
Can't get any more apart than I have it!

Re: 1976 Trans Am: LS3 Swap, Hydraulic Clutch, TKO600 and other tidbits
« Reply #124 on: June 08, 2016, 01:19:39 AM »

TransAm_Stan

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Re: 1976 Trans Am: LS3 Swap, Hydraulic Clutch, TKO600 and other tidbits
« Reply #125 on: June 08, 2016, 01:29:53 AM »
It's not just an LS thing, it's a pretty common problem with a stick car with headers and fuel injection. It's caused by late combustion due to high manifold vacuum/low MAP. When you decel against the gearing, it creates pretty high manifold vacuum, leading to a very low density of the air/fuel mixture in the cylinder. Because the mixture is at such a low density, it has a very hard time combusting before it leaves the cylinder. This results in the combustion completing inside the hot exhaust header primary, leading to the dreaded pop. I fought it in the tune for weeks when I set up the Holley Stealth Ram/TPI Computer/T56 combo on my roommates 92 bird. I eventually found that a combination of spark advance (only under high vacuum/low MAP conditions) and a slight richening of the mixture at those levels got rid of 95% of the popping. The spark advance gives the mixture more time to combust inside the cylinder, and the richening of the mixture helps speed up the combustion enough that it happens inside the cylinder rather than inside the exhaust.

Many fuel injection systems offer a decel fuel cutoff mode. GM started doing it in 89 with the '165 TPI ECM. I'm sure the LS has something similar. If you can get that to kick in, it will solve your problem by removing the combustible mixture altogether under those conditions.

Thanks for the detailed explanation of whats going on with the "popping".  If I ever find someone who I trust to give me a ECU tune, believe me this decel tuning is first on my list.

I have been resisting the urge to try a hand at my own mapping.  I know it is a steep & expensive curve.  I just don't want to put in the time to learn this particular trade.  Plus risking the meltdown of my motor due to my incompetence is not a highly desirable outcome.  Since I can't find anyone close I might have to risk sending it away to a reputable tuner.  Any suggestions?
76 White exterior, Blue interior "Toastee"
LS3, TKO600, Hydroboost
Hydraulic clutch
Western Hurricane rims

76 White 400 4sp. blue/white interior (project)
Can't get any more apart than I have it!

cal30_sniper

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Re: 1976 Trans Am: LS3 Swap, Hydraulic Clutch, TKO600 and other tidbits
« Reply #126 on: June 08, 2016, 08:05:51 AM »
It's not just an LS thing, it's a pretty common problem with a stick car with headers and fuel injection. It's caused by late combustion due to high manifold vacuum/low MAP. When you decel against the gearing, it creates pretty high manifold vacuum, leading to a very low density of the air/fuel mixture in the cylinder. Because the mixture is at such a low density, it has a very hard time combusting before it leaves the cylinder. This results in the combustion completing inside the hot exhaust header primary, leading to the dreaded pop. I fought it in the tune for weeks when I set up the Holley Stealth Ram/TPI Computer/T56 combo on my roommates 92 bird. I eventually found that a combination of spark advance (only under high vacuum/low MAP conditions) and a slight richening of the mixture at those levels got rid of 95% of the popping. The spark advance gives the mixture more time to combust inside the cylinder, and the richening of the mixture helps speed up the combustion enough that it happens inside the cylinder rather than inside the exhaust.

Many fuel injection systems offer a decel fuel cutoff mode. GM started doing it in 89 with the '165 TPI ECM. I'm sure the LS has something similar. If you can get that to kick in, it will solve your problem by removing the combustible mixture altogether under those conditions.

Thanks for the detailed explanation of whats going on with the "popping".  If I ever find someone who I trust to give me a ECU tune, believe me this decel tuning is first on my list.

I have been resisting the urge to try a hand at my own mapping.  I know it is a steep & expensive curve.  I just don't want to put in the time to learn this particular trade.  Plus risking the meltdown of my motor due to my incompetence is not a highly desirable outcome.  Since I can't find anyone close I might have to risk sending it away to a reputable tuner.  Any suggestions?

I haven't fooled with anything newer than OBDI, although I've thought about getting into it a few times. I would suggest against getting a mail order tune. If you've deviated much at all from stock, it just isn't likely to work out well. If you decide not to do it yourself, I'd take it to a shop that has good reviews and leave them to tune and drive it over the course of a week or so. Dyno tuning will get you down the track fast, but you need a good street tune to get rid of these kind of issues.

Personally, if I ever get an LS motor, I'll probably just get the stuff to tune it myself. Not really any more risk tuning a computer than tuning a carb/distributor combo as long as you are conservative with your inputs and know what each parameter controls. Just like using Microsoft Excel, anyone can do it, and most people can get pretty good at it with plenty of research and some experience.
'73 Formula 350
'88 Trans Am GTA L98
'86 Suburban C20 454/NV4500

Formula build thread: http://transamcountry.com/community/index.php?topic=75375.msg705571#msg705571

scarebird

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Re: 1976 Trans Am: LS3 Swap, Hydraulic Clutch, TKO600 and other tidbits
« Reply #127 on: June 08, 2016, 11:03:37 AM »
ah.  Mine has a nice crackle to it when decelerating; love it.  At idle it is dead quiet, but howls nicely when the spurs are put to it. 

A few years back I had a 2004 Trailblazer that I sent a spare PCM for a more performance oriented tune - gained a few horseys and another 2 mpg (14 to 16).  This for around $150.

cal30_sniper

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Re: 1976 Trans Am: LS3 Swap, Hydraulic Clutch, TKO600 and other tidbits
« Reply #128 on: June 08, 2016, 11:30:08 AM »
Suprisingly enough, it's a sign of a really good tune at low MAP. The closer I got my VE tables to stoichiometric, the worse the popping got. I've had the same thing happen with a well tuned quadrajet and free flowing exhaust backed up by a T56. The 454/Quadrajet/Headers/NV4500 in my Suburban also did it before I fattened up the jet/rod and idle mixture combination to about 12:1 with a closed throttle. No more popping at that point, but it took primary rods out of a 500 Cadillac with some honed out .080 jets to get it done. Those 80s truck carbs are set up for really large jet/rod combos.
'73 Formula 350
'88 Trans Am GTA L98
'86 Suburban C20 454/NV4500

Formula build thread: http://transamcountry.com/community/index.php?topic=75375.msg705571#msg705571

TransAm_Stan

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Re: 1976 Trans Am: LS3 Swap, Hydraulic Clutch, TKO600 and other tidbits
« Reply #129 on: September 25, 2017, 04:17:40 PM »
It has been awhile since I have checked in.  Not much has happened around here, to me, or the car.  Maintaining, so to speak.

I think I am going coil overs to try to get my front tire off of the inner fender on bumps. If I didn't cut off that extra quarter coil!  I have to do more research.  What I really need is a front rim with more back space. But that would be like the holy grail, since I am using Hurricanes.  I suppose I could go back to the stockers & see if that helps.

Anyhoo, I just wanted to say Hi to all my TA friends.  Several of you have been an invaluable source of information in my LS3, wet clutch,  Hydroboosted, 5 speed project.  Hats off to you.

Blue Skies.

Stan
76 White exterior, Blue interior "Toastee"
LS3, TKO600, Hydroboost
Hydraulic clutch
Western Hurricane rims

76 White 400 4sp. blue/white interior (project)
Can't get any more apart than I have it!

T/A Addict

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Re: 1976 Trans Am: LS3 Swap, Hydraulic Clutch, TKO600 and other tidbits
« Reply #130 on: November 14, 2017, 04:57:02 AM »
Excellent stuff Stan, I'm going to refer back to this build often as I work through mine. Wish this forum had a subscribe to thread option like others.
Jeff
2016 Victory Cross Country
TATA '72 455 HO Auto
79 T/A 403 Solar Gold
2010 Challenger R/T  PCP

Re: 1976 Trans Am: LS3 Swap, Hydraulic Clutch, TKO600 and other tidbits
« Reply #130 on: November 14, 2017, 04:57:02 AM »
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