C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

l98 - What next for more power?

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Old 07-10-2007, 08:40 AM
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dan_t
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Default l98 - What next for more power?

Hi all,

being in the UK makes this a bit more akward than it is for some of you guys so I'm trying my best with whats availible...

I don't have a lot of spare cash each month so I'm looking for "little mods" that I can do a bit each month and that'll make a noticeable difference overall.

I know I could wait and save, but I get bored and need to tinker!

Motor so far -

1984 Block (Xfire) with Stock Forged Pistons (Bottom end bearings replaced)
1987 Alloy Heads (128?) on Felpro 1010's
Compression ~ 10.8:1
Summit 262/272 Flat Tappet Cam Link
1986 TPI intake system
1992 7730 ECM (Map sensor) with Super8D tune
1992 Injectors
No AIR injection or EGR
No Cats and Muffler Elim's

Running through an TH700r4 Auto4 built with Alto frictions and uprated sun gear.

Quickest 1/4 drag time so far
14.01 @ 98mph

Where do I go next?

Roller Rockers?
Ported TPI? (BBK Intake looks promising!)
LT1 Intake conversion?
Headers? (Are the "Cheap" ones OK?)
More aggresive Cam?
Cat-Back? (is an LT1 Exhaust an upgrade?)

Any other suggestions?
Car is not my DD so I can sacrafice drivability if needs be!
Old 07-10-2007, 09:01 AM
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emo-vet
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hello dan_t,
how are ya.
if you want to do a free mod or two, how about if you havent already remove the heavy disk known as the " frisbee" of the front of the water pump to remove a little extra drag.
then there is of course the other free mod, the throttle body bypass mod that deletes the radiator coolent going to the throttle body.
but in england " the mother country" being cold as it is may not be suited there.
just a couple of thoughts for you any way!
regards
shae
Old 07-10-2007, 09:06 AM
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dan_t
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Frisbee isnt there - 84 Engines are internally ballanced as well I belive

Air pump has been gutted to reduce drag further
Old 07-10-2007, 09:18 AM
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mseven
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intake (lt, mini, SR ) pick your poison , LT headers (if not already done)
Old 07-10-2007, 10:27 AM
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BADDUCK
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Originally Posted by mseven
intake (lt, mini, SR ) pick your poison , LT headers (if not already done)
Intake will help without going back into the engine. More aggressive cam will give you the biggest pop. Wait and do cam RR's and upgrade springs at the same time. If by cheap headers you mean shorties, NO.
Old 07-10-2007, 10:49 AM
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dan_t
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I see summit do some LT headers for around $350 would these do the job?

My biggest problem with things like this are shipping costs!

and TAX
Old 07-10-2007, 10:50 AM
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dan_t
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with regard LT1/Miniram type setups...

are they a gain gain mod? I've heard that you may gain some hear but loose some there. Also that the mini ram may not work well with my Auto due to the change RPM's?
Old 07-10-2007, 06:02 PM
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emo-vet
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Originally Posted by dan_t
I see summit do some LT headers for around $350 would these do the job?

My biggest problem with things like this are shipping costs!

and TAX


well the cheapest shipping to over seas from usa is " usps" united states postal services!
you save about 30-40% getting stuffed shipped with them say over fed ex, ups,bax global,ect!
secondly see how much your locoal customs allows goods $ amount up too, then get supllier of goods to write on customs form so that the amount is under the amount alllowed before you have to pay taxes,customs/duty fees!
regards
shae
Old 07-10-2007, 07:17 PM
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BADDUCK
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Originally Posted by dan_t
I see summit do some LT headers for around $350 would these do the job?

My biggest problem with things like this are shipping costs!

and TAX
Yes, the Hedman Elites are good headers. I would think shipping would be high.
Old 07-10-2007, 07:35 PM
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jghmczo6
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350ci / L98's do not breath well (poor lungs) as senior members of this forum have pointed out. Headers are probably tied for first place with the stock TPI for disabling power. I've changed the headers and exhaust first and noticed a big performance / response difference immediatly. The top part (TPI) has many variables from the Super Ram, Mini Ram, to the Holley Stealth Ram all of which are pricey IMO. I suggest you continue to search this forum and ask questions then make you own decision.

Hope this helps
Old 07-11-2007, 06:24 PM
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Vito.A
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Dan T,
I spent 3 years at Upper Heyford. Raced at Santa Pod. Still have lots of friends there.
I will get bashed, but I think the best bang for the buck has been the rear end gears. I replaced the stock 3.07 with a 3.75 Richmond Performance gear set. Around town performance is fantastic and it actually picked up the 1/4 mile times more than any other mod I have done.
The only problem is the stock auto trans rear end is a Dana 36 and it is notoriously weak. A Dana 44 out of a manual trans car is the preferred path, but can be expensive.
Regards,
Vito
Old 07-11-2007, 07:29 PM
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1991Z07
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Originally Posted by dan_t
I see summit do some LT headers for around $350 would these do the job?

My biggest problem with things like this are shipping costs!

and TAX
Make friends with someone stationed at a local U.S. base...

They can order the stuff for you, not pay any tax and MIGHT get it shipped cheaper as it goes to an APO address.

Drink an Abbot Ale for me...too hard to find back here.
Old 07-11-2007, 10:28 PM
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mrc24x
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Headers and exhaust would be my first choice, second I would go with headers and exhaust, then a close third would be headers and exhaust. Did I mention......
Old 07-12-2007, 10:55 AM
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Vetracr
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If you want some tips for mods on the cheap, heres a few;

1) Pull the TPI plenum and remove the rectangular obstruction behind the throttle body blades. Its there to help the EGR port flow but It restricts air flow into the engine.

2) While your filing down the aluminum obstruction lay a gasket on the plenum mouth and scribe the port outline. Grind the openings up to be larger than the scribe lines and radius the entry.

3) After you've finished with the entrance lay plenum gaskets on the ports from the plenum to the runners and scribe the outlines. Open the ports to the scribe lines and then grind and radius the port entrances for a smooth transition into the runners.

4) Pull the stock exhaust manifolds and remove the heat shields. You will see that the welds from the flange to the pipes is on the inside of the pipe restricting the flow. Get out your grinder and remove the weld blocking the flow and radius the entry into the pipes. You can add a few tack welds to the outside of the pipe flange interfaces if your concerned about weakening the welds.

FYI I did all of these mods on my 86 L-98 and they worked fine.

Good luck mate.

Larry
Old 07-12-2007, 06:30 PM
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dan_t
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Originally Posted by Vetracr
If you want some tips for mods on the cheap, heres a few;

1) Pull the TPI plenum and remove the rectangular obstruction behind the throttle body blades. Its there to help the EGR port flow but It restricts air flow into the engine.

2) While your filing down the aluminum obstruction lay a gasket on the plenum mouth and scribe the port outline. Grind the openings up to be larger than the scribe lines and radius the entry.

3) After you've finished with the entrance lay plenum gaskets on the ports from the plenum to the runners and scribe the outlines. Open the ports to the scribe lines and then grind and radius the port entrances for a smooth transition into the runners.

4) Pull the stock exhaust manifolds and remove the heat shields. You will see that the welds from the flange to the pipes is on the inside of the pipe restricting the flow. Get out your grinder and remove the weld blocking the flow and radius the entry into the pipes. You can add a few tack welds to the outside of the pipe flange interfaces if your concerned about weakening the welds.

FYI I did all of these mods on my 86 L-98 and they worked fine.

Good luck mate.

Larry

Any noticable differences from the porting?
Old 07-13-2007, 03:32 AM
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emo-vet
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hey dan_t,
whats your opioun regarding the shipping tip i gave you?
or doesnt it count for any thing ?
shae
Old 07-13-2007, 11:23 AM
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Originally Posted by dan_t
Any noticable differences from the porting?
None that I could quantify. Performance gains short of cams, heads and headers come in small steps. I know the intake flowed better with the mods but how much, your guess is as good as mine. For the price I couldn't complain.

Larry
Old 07-13-2007, 11:59 AM
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dan_t
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Originally Posted by emo-vet
hey dan_t,
whats your opioun regarding the shipping tip i gave you?
or doesnt it count for any thing ?
shae
Cheers Shae - will look into what the limit is here in the UK!
Old 07-13-2007, 12:00 PM
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dan_t
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Originally Posted by Vetracr
None that I could quantify. Performance gains short of cams, heads and headers come in small steps. I know the intake flowed better with the mods but how much, your guess is as good as mine. For the price I couldn't complain.

Larry
I guess any improvement is an improvement!! will look into it!

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