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Old 06-22-2007   #21
strc09
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GTA Year: 1988
GTA Engine: Custom
Re: 383

So if I get the internally balanced setup then I won't need a new flywheel or balancer, right? Also, for a stock 350 what is the standard bore to make it a 383 so I can order the right set? Thanks.
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GTA: Grand Turismo Americano (Grand Touring America)
1 of 930 1988 Gunmetal Metallic GTAs produced (RPO 87U)
Built by Zeus Performance and tuned by Alvin from PCM4Less
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Old 06-22-2007   #22
MunsonGTA
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GTA Year: 1987
GTA Engine: Custom
Re: 383

Quote:
Originally Posted by strc09
So if I get the internally balanced setup then I won't need a new flywheel or balancer, right? Also, for a stock 350 what is the standard bore to make it a 383 so I can order the right set? Thanks.
if you go with an internal balance kit, it might come with a flexplate and balancer. if it doesn't, you will have to buy a neutral weight flexplate and balancer. the stock setup on our cars are external balance, your stock flexplate and balancer won't work with either setup. i'd look into getting a kit that comes balanced with the components that you need.

stock bore is 4.000, to do a 383 you need a bore of 4.030
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87 GTA: Forged 408 LSX short block, TEA stage 2 cnc ported 243 heads, BTR Stage 3 stroker cam, Fast 102 intake, NW 102 TB, Longtube headers, custom 411 ECM, custom harness, custom tuned, Performabuilt stage 2 4l60E with PTC 2800 stall, 9 bolt rear with 3.70 gears and TAP girdle.

11.16 at 123 mph.
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Old 06-22-2007   #23
FearThisGTA
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GTA Year: 1991
GTA Engine: 350 TPI Automatic
Re: 383

IMO, I would just get the ext kit, b/c with a TPI motor it will never make pwr at hight enough rpms to ever notice. But, thats just me.
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Cliff Jones
1991 GTA Trans Am
w/305,231 miles
on the original motor!!!!
Time of Death on motor, 4:07pm on 05/29/2010.
Hp:211.2@4200rpms/Tq.328.5@2700rpms
Best et: 13.959@97.05mph
Best mph: 98.3
Best 60' : 1.875 on BFG Comp TA's w/ 32 lbs of air in them
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Old 06-22-2007   #24
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GTA Year: 1991
GTA Engine: 350 TPI Automatic
Re: 383

Quote:
Originally Posted by MunsonGTA
if you go with an internal balance kit, it might come with a flexplate and balancer. if it doesn't, you will have to buy a neutral weight flexplate and balancer. the stock setup on our cars are external balance, your stock flexplate and balancer won't work with either setup. i'd look into getting a kit that comes balanced with the components that you need.

stock bore is 4.000, to do a 383 you need a bore of 4.030
On the internal kits they are not necesary, only on the ext kits do you get the h/bal and flex plate.
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Cliff Jones
1991 GTA Trans Am
w/305,231 miles
on the original motor!!!!
Time of Death on motor, 4:07pm on 05/29/2010.
Hp:211.2@4200rpms/Tq.328.5@2700rpms
Best et: 13.959@97.05mph
Best mph: 98.3
Best 60' : 1.875 on BFG Comp TA's w/ 32 lbs of air in them
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Old 06-22-2007   #25
MunsonGTA
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GTA Year: 1987
GTA Engine: Custom
Re: 383

Quote:
Originally Posted by fearthisgta
On the internal kits they are not necesary, only on the ext kits do you get the h/bal and flex plate.
i've seen kits on ebay that are internal balance that come with neutral flexplate and balancer to replace your stock units.
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87 GTA: Forged 408 LSX short block, TEA stage 2 cnc ported 243 heads, BTR Stage 3 stroker cam, Fast 102 intake, NW 102 TB, Longtube headers, custom 411 ECM, custom harness, custom tuned, Performabuilt stage 2 4l60E with PTC 2800 stall, 9 bolt rear with 3.70 gears and TAP girdle.

11.16 at 123 mph.
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Old 06-22-2007   #26
FearThisGTA
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GTA Year: 1991
GTA Engine: 350 TPI Automatic
Re: 383

hmmm, weird, I dont see why you would need them since its internally balanced? very strange.
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Cliff Jones
1991 GTA Trans Am
w/305,231 miles
on the original motor!!!!
Time of Death on motor, 4:07pm on 05/29/2010.
Hp:211.2@4200rpms/Tq.328.5@2700rpms
Best et: 13.959@97.05mph
Best mph: 98.3
Best 60' : 1.875 on BFG Comp TA's w/ 32 lbs of air in them
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Old 06-22-2007   #27
MunsonGTA
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GTA Year: 1987
GTA Engine: Custom
Re: 383

Quote:
Originally Posted by fearthisgta
hmmm, weird, I dont see why you would need them since its internally balanced? very strange.
why wouldn't you need them? you wouldn't be able to use external balance flexplate and balancer with an internal balance kit, if you did it would throw it out of balance. if you're installing an internal balance kit on a motor that is already setup like that, you'd have everything you need. but L98 motors are external balance, so if the kit didn't come with neutral balance parts, you'd have to buy them yourself.
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87 GTA: Forged 408 LSX short block, TEA stage 2 cnc ported 243 heads, BTR Stage 3 stroker cam, Fast 102 intake, NW 102 TB, Longtube headers, custom 411 ECM, custom harness, custom tuned, Performabuilt stage 2 4l60E with PTC 2800 stall, 9 bolt rear with 3.70 gears and TAP girdle.

11.16 at 123 mph.
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Old 06-22-2007   #28
FearThisGTA
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GTA Year: 1991
GTA Engine: 350 TPI Automatic
Re: 383

Mainly like you said they are internally balanced so their is no need for ext balancing. You would have to purchase a different balancer and flexplate ones that were neutral balanced. If you look at the Eagle kits and the Scat kits both are this way. And yes all one piece rear main seal engines are ext balance, thats why I would just get that one so you have all new stuff.
Most people who get the int bal assy's already have one, so there is no need to get a new bal and flexplate. It really boils down to the $$$ in the wallet.
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Cliff Jones
1991 GTA Trans Am
w/305,231 miles
on the original motor!!!!
Time of Death on motor, 4:07pm on 05/29/2010.
Hp:211.2@4200rpms/Tq.328.5@2700rpms
Best et: 13.959@97.05mph
Best mph: 98.3
Best 60' : 1.875 on BFG Comp TA's w/ 32 lbs of air in them
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Old 06-23-2007   #29
strc09
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GTA Year: 1988
GTA Engine: Custom
Re: 383

If our motors are exteranlly balanced then why won't the externally balanced kit work with the flexplate and balancer that I already have? I'm really not understanding that. I know...it's sad because I'm really trying to understand everything y'all are saying but it still seems Greek to me most of the time. Thanks for allowing me to pick your brains gentleman so that I can do a little research into what I'd like to do.
__________________
-Patrick

GTA: Grand Turismo Americano (Grand Touring America)
1 of 930 1988 Gunmetal Metallic GTAs produced (RPO 87U)
Built by Zeus Performance and tuned by Alvin from PCM4Less
Check out my website: Night Vision GraFX
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Old 06-23-2007   #30
MunsonGTA
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GTA Year: 1987
GTA Engine: Custom
Re: 383

Quote:
Originally Posted by strc09
If our motors are exteranlly balanced then why won't the externally balanced kit work with the flexplate and balancer that I already have? I'm really not understanding that. I know...it's sad because I'm really trying to understand everything y'all are saying but it still seems Greek to me most of the time. Thanks for allowing me to pick your brains gentleman so that I can do a little research into what I'd like to do.
it won't work because the rotating assembly that you plan to purchase, is going to be balanced with the parts they are going to give you, or should give you with the kit. if you were to use their assembly with your flexplate and balancer, it wouldn't work because they are aren't balanced together. your parts would throw everything out of balance. your parts are balanced to the stock assembly in your motor.

if the kit you plan to purchase is external balance, and it doesn't come with a flexplate and balancer, then it isn't balanced from the place you're buying it from. they expect that you are going to take it somewhere and have it balanced, which you could do with your stock parts. the shop that does the balancing will use your stock flexplate and balancer and adjust the weights to make everything in balance.
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87 GTA: Forged 408 LSX short block, TEA stage 2 cnc ported 243 heads, BTR Stage 3 stroker cam, Fast 102 intake, NW 102 TB, Longtube headers, custom 411 ECM, custom harness, custom tuned, Performabuilt stage 2 4l60E with PTC 2800 stall, 9 bolt rear with 3.70 gears and TAP girdle.

11.16 at 123 mph.

Last edited by MunsonGTA; 06-23-2007 at 03:13 PM.
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Old 06-23-2007   #31
strc09
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GTA Year: 1988
GTA Engine: Custom
Re: 383

Okay. I'm going to have to give CNC a call to see what they've got. With those types of pistons what size head gasket do you think I would need? The internally balanced one says a .038 head gasket, would it be the same for the externally balanced one since it is the same type of pistons? Also, will those flat head pistons change my compression ratio?
__________________
-Patrick

GTA: Grand Turismo Americano (Grand Touring America)
1 of 930 1988 Gunmetal Metallic GTAs produced (RPO 87U)
Built by Zeus Performance and tuned by Alvin from PCM4Less
Check out my website: Night Vision GraFX
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Old 06-23-2007   #32
FearThisGTA
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GTA Year: 1991
GTA Engine: 350 TPI Automatic
Re: 383

Yes, it would be. If thats the comp ratio you want. Yes, all of that will depend on what head and the combustion area in that head. lmk, the kit # you are lookin at and what the comp ration is of the heads you are going to use and I will see what it will be for you, ok. hth
__________________


Cliff Jones
1991 GTA Trans Am
w/305,231 miles
on the original motor!!!!
Time of Death on motor, 4:07pm on 05/29/2010.
Hp:211.2@4200rpms/Tq.328.5@2700rpms
Best et: 13.959@97.05mph
Best mph: 98.3
Best 60' : 1.875 on BFG Comp TA's w/ 32 lbs of air in them
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Old 06-23-2007   #33
MunsonGTA
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GTA Year: 1987
GTA Engine: Custom
Re: 383

Quote:
Originally Posted by strc09
Okay. I'm going to have to give CNC a call to see what they've got. With those types of pistons what size head gasket do you think I would need? The internally balanced one says a .038 head gasket, would it be the same for the externally balanced one since it is the same type of pistons? Also, will those flat head pistons change my compression ratio?
are you using stock 64 cc heads? if you are, you'll want around 10:1 compression with those heads and the kit you plan to purchase. CNC should be able to help you figure out which kit you need. just make sure you get the same price if you call them, as you would on ebay. you can always get an .042 head gasket to lower your compression some with the kit you buy.

this would be a good kit. one kit

or this kit kit 2
__________________
87 GTA: Forged 408 LSX short block, TEA stage 2 cnc ported 243 heads, BTR Stage 3 stroker cam, Fast 102 intake, NW 102 TB, Longtube headers, custom 411 ECM, custom harness, custom tuned, Performabuilt stage 2 4l60E with PTC 2800 stall, 9 bolt rear with 3.70 gears and TAP girdle.

11.16 at 123 mph.
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Old 06-24-2007   #34
strc09
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GTA Year: 1988
GTA Engine: Custom
Re: 383

I've got a guys selling me a set of L98 aluminum heads (at a very good price) that he's cleaning up that'll be going on top. They'll be milled, hot tanked, and have the valves, valve seals, and guides replaced. Will any of that change the combustion area? Cliff, I was looking at the two kits that Munson posted from eBay on page one...Eagle Street/Strip Externally Balanced (the one I'm thinking about getting now) and Eagle Street/Strip Internally Balanced. The externally balanced kit comes with a new flexplate and balancer which I didn't see on there before.

I would hope that CNC would honor the eBay price even if I called them. That'd be wrong if they didn't. Speaking of which, has anyone ever dealt with them before?

Out of those four kits, where is going to be my best bang for the buck? Will I be looking at some good horsepower increases, especially with the new intake and runners I installed prior to the click, click boom? Also on the flexplate, will I need the 153 or 168? There was another question that I was going to ask, but for the life of me can't remember what it is now.
__________________
-Patrick

GTA: Grand Turismo Americano (Grand Touring America)
1 of 930 1988 Gunmetal Metallic GTAs produced (RPO 87U)
Built by Zeus Performance and tuned by Alvin from PCM4Less
Check out my website: Night Vision GraFX
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Old 06-24-2007   #35
FearThisGTA
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GTA Year: 1991
GTA Engine: 350 TPI Automatic
Re: 383

On the heads, you said he was going to mill them, how much? They already have a small comb chamber( 58 cc to be exact), I wouldnt want to go much smaller than that. You will need to find out how much he is milling them, b/c it could be to much. So to answer your first question yes, it will chg the comb ratio.

As for the rotating assy, IMO, I would get the ext bal one since its got everything you will need and besides, like I said before, you wont notice any difference anyway. Oh and btw, IMO, I would get the kit that has the Federal Mogal or Speed Pro Pistons, I would stay away from the KB's I have been hearin too many horror stories lately on them, mainly fitment problems.
__________________


Cliff Jones
1991 GTA Trans Am
w/305,231 miles
on the original motor!!!!
Time of Death on motor, 4:07pm on 05/29/2010.
Hp:211.2@4200rpms/Tq.328.5@2700rpms
Best et: 13.959@97.05mph
Best mph: 98.3
Best 60' : 1.875 on BFG Comp TA's w/ 32 lbs of air in them
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Old 06-24-2007   #36
FearThisGTA
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GTA Year: 1991
GTA Engine: 350 TPI Automatic
Re: 383

Oh and get the first kit Munson pointed out. Its got all of the goodies one would need to build a good street motor.
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Cliff Jones
1991 GTA Trans Am
w/305,231 miles
on the original motor!!!!
Time of Death on motor, 4:07pm on 05/29/2010.
Hp:211.2@4200rpms/Tq.328.5@2700rpms
Best et: 13.959@97.05mph
Best mph: 98.3
Best 60' : 1.875 on BFG Comp TA's w/ 32 lbs of air in them
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Old 06-24-2007   #37
MunsonGTA
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Join Date: Jun 2004
Location: Ravenna, OH
Posts: 1,948



GTA Year: 1987
GTA Engine: Custom
Re: 383

Quote:
Originally Posted by strc09
I've got a guys selling me a set of L98 aluminum heads (at a very good price) that he's cleaning up that'll be going on top. They'll be milled, hot tanked, and have the valves, valve seals, and guides replaced. Will any of that change the combustion area? Cliff, I was looking at the two kits that Munson posted from eBay on page one...Eagle Street/Strip Externally Balanced (the one I'm thinking about getting now) and Eagle Street/Strip Internally Balanced. The externally balanced kit comes with a new flexplate and balancer which I didn't see on there before.

I would hope that CNC would honor the eBay price even if I called them. That'd be wrong if they didn't. Speaking of which, has anyone ever dealt with them before?

Out of those four kits, where is going to be my best bang for the buck? Will I be looking at some good horsepower increases, especially with the new intake and runners I installed prior to the click, click boom? Also on the flexplate, will I need the 153 or 168? There was another question that I was going to ask, but for the life of me can't remember what it is now.

i wouldn't get the vette heads milled unless they actually need it. they are already 58cc, any milling done is only going to make that smaller and raise the compression higher. with the aluminum heads you can run 10.5:1 on pump gas with a decent tune. you'll need a 153 tooth flexplate. i'd get one of these 2 kits if it was me. the more expensive kit if you can afford it.

this kit

or this kit
__________________
87 GTA: Forged 408 LSX short block, TEA stage 2 cnc ported 243 heads, BTR Stage 3 stroker cam, Fast 102 intake, NW 102 TB, Longtube headers, custom 411 ECM, custom harness, custom tuned, Performabuilt stage 2 4l60E with PTC 2800 stall, 9 bolt rear with 3.70 gears and TAP girdle.

11.16 at 123 mph.
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Old 06-26-2007   #38
strc09
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GTA Year: 1988
GTA Engine: Custom
Re: 383

Thanks fellas, I'll let him know not to mill them too much. He was going to clean them up because the Vette that they came off of had a problem with number three and it damaged the valves. Other than that, the heads were in really good shape. What do you think the compression ratio will be with those heads?
__________________
-Patrick

GTA: Grand Turismo Americano (Grand Touring America)
1 of 930 1988 Gunmetal Metallic GTAs produced (RPO 87U)
Built by Zeus Performance and tuned by Alvin from PCM4Less
Check out my website: Night Vision GraFX
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Old 06-26-2007   #39
MunsonGTA
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GTA Year: 1987
GTA Engine: Custom
Re: 383

Quote:
Originally Posted by strc09
Thanks fellas, I'll let him know not to mill them too much. He was going to clean them up because the Vette that they came off of had a problem with number three and it damaged the valves. Other than that, the heads were in really good shape. What do you think the compression ratio will be with those heads?
unless the head is warped, or has damage to it, i wouldn't have it milled at all. the only reason to mill a head is to remove scratches, if it's warped, or if you want to bump up compression. the compression ratio will depend on the kit you buy, the chamber size of the head after they are done being worked on, and the head gasket you go with.
__________________
87 GTA: Forged 408 LSX short block, TEA stage 2 cnc ported 243 heads, BTR Stage 3 stroker cam, Fast 102 intake, NW 102 TB, Longtube headers, custom 411 ECM, custom harness, custom tuned, Performabuilt stage 2 4l60E with PTC 2800 stall, 9 bolt rear with 3.70 gears and TAP girdle.

11.16 at 123 mph.
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Old 06-26-2007   #40
FearThisGTA
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GTA Year: 1991
GTA Engine: 350 TPI Automatic
Re: 383

^agreed, if the heads need it, just have him "flatten" them.
__________________


Cliff Jones
1991 GTA Trans Am
w/305,231 miles
on the original motor!!!!
Time of Death on motor, 4:07pm on 05/29/2010.
Hp:211.2@4200rpms/Tq.328.5@2700rpms
Best et: 13.959@97.05mph
Best mph: 98.3
Best 60' : 1.875 on BFG Comp TA's w/ 32 lbs of air in them
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