What should I do next to the fox

James1989

New Member
Sep 16, 2020
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Houston
Hey Guys, I’m new here so not sure where to post this. I have an 89 GT with Gt40p heads, ported Gt40 intake, and a Lunati cam, .510 lift and 284/292 duration, Subframe connectors and a 75mm throttle body with the egr blocked off and about to put some underdrive pulleys on. The car feels sluggish on the lower rpms, what should I do next. Gears? I have 4.10s I’m installing soon. What should be next
 
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Dan02gt

10 Year Member
Mar 2, 2003
709
297
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Greenville, NC
I agree with General karthief on the gears. That cam isn’t helping your low end either. Lunati rates it from 2000-6000 RPMs making not the best choice for poor flowing GT40p heads.
 

schwerdt1

Active Member
Sep 15, 2020
154
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Caddo Mills, TX
4.10? 3k rpm at 50mph, not a good time. Really wont notice anything with the pulleys. Id go some sort of power adder... 75-100 shot, or turbo kit.
 

Habu135

Advanced Member
Jan 10, 2019
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3.73 gears if you're keeping it relatively "stock". 3.55 or lower if you plan on going whole hog. My H/C/I equipped 5 speed had 4.10s when I bought it and they were too much for the street. Maybe I'll regret 3.73s if I stroke it, but for now 3.73 is perfect.

I agree that pulleys aren't worth the work and "gains".
 

James1989

New Member
Sep 16, 2020
22
1
3
18
Houston
4.10? 3k rpm at 50mph, not a good time. Really wont notice anything with the pulleys. Id go some sort of power adder... 75-100 shot, or turbo kit.
Will keep that in mind, and I have a twin turbo kit from dna motors but I haven’t heard the best from that company, the kit is new though. Thoughts on it?
 

James1989

New Member
Sep 16, 2020
22
1
3
18
Houston
3.73 gears if you're keeping it relatively "stock". 3.55 or lower if you plan on going whole hog. My H/C/I equipped 5 speed had 4.10s when I bought it and they were too much for the street. Maybe I'll regret 3.73s if I stroke it, but for now 3.73 is perfect.

I agree that pulleys aren't worth the work and "gains".
Will keep that in mind. What heads do you recommend?
 

schwerdt1

Active Member
Sep 15, 2020
154
99
38
49
Caddo Mills, TX
Will keep that in mind, and I have a twin turbo kit from dna motors but I haven’t heard the best from that company, the kit is new though. Thoughts on it?
Have not heard of dna. Its a good amount of work to do. What is your main goal with the vehicle? Certain power level, maybe a certain time you wanna run, or just a fun, quick and reliable street car. I'd work on matching up the top-end to all work well with eachother. Get it taking in the right air/fuel and expelling it efficiently(decent heads,165-170's) and a good exhaust set up. That'll wake it up a good amount.
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
18,774
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polk county florida
That cam + 410 gears + twin turbo, now that's a plan.
Look, read up on some of the build threads around here, pay attention to the turbo builds if that is where you want to be.
Are you doing the work yourself?
Got a place to work?
Need help formulating a plan?
 

Boostedpimp

15 Year Member
May 8, 2003
1,124
406
124
NJ
Hey Guys, I’m new here so not sure where to post this. I have an 89 GT with Gt40p heads, ported Gt40 intake, and a Lunati cam, .510 lift and 284/292 duration, Subframe connectors and a 75mm throttle body with the egr blocked off and about to put some underdrive pulleys on. The car feels sluggish on the lower rpms, what should I do next. Gears? I have 4.10s I’m installing soon. What should be next

You will have to figure out your overall goals for the car because your already talking turbo kit. If your staying with the basic setup you have now then I would say the 75mm and lack of rear end gears aren't helping your low end with that cam.. I honestly would probably drop the tb down to whatever the opening on your intake is. Most likely a 70mm or even possibly a 65mm and look to trade or sell the 4.10's for some 3.73. 4.10's will obviously work and wake the car up on the low end but will get old quick with any type of highway cruising in my opinion. Under drive pulleys get allot of hate and it is because when you use them you will need to make sure your charging and cooling systems are upgraded as well so in many cases they are not worth the hassle. I'd hold off on them until you've already upgraded the alternator and swapped to an electric fan personally.

If your going with the turbo kit then you'll be upgrading or changing around everything weather or not you plan for it
 
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Habu135

Advanced Member
Jan 10, 2019
772
477
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40
California
That cam + 410 gears + twin turbo, now that's a plan.
Look, read up on some of the build threads around here, pay attention to the turbo builds if that is where you want to be.
Are you doing the work yourself?
Got a place to work?
Need help formulating a plan?
Agreed. You need to have a plan to work toward. Otherwise you'll be spitting into the wind and in time will get discouraged.