Valve Question?
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Joined: Dec 2004
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From: Kansas City Missouri
Valve Question?
Hey Everybody,
I am looking at some 2.02 intake and 1.60 exhaust valves in the parts forum. I want to keep the block stock but do some intake and head work. Will these valves be to much if I use them in my 91 heads for medium street applications and a little autocrossing? I realize the heads will need to be worked to take the valves. Input and advice as always is greatly appreciated.
I am looking at some 2.02 intake and 1.60 exhaust valves in the parts forum. I want to keep the block stock but do some intake and head work. Will these valves be to much if I use them in my 91 heads for medium street applications and a little autocrossing? I realize the heads will need to be worked to take the valves. Input and advice as always is greatly appreciated.
Team Owner
Joined: Dec 2000
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From: SE NY
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For sure you will need all new valve seats as 2.00/1.56 are the max for stock seats.
You should also deshroud (carefully) the intake valve. Start this work just beyond where the chamber begins to turn away from the adjacent water jacket.
You should also deshroud (carefully) the intake valve. Start this work just beyond where the chamber begins to turn away from the adjacent water jacket.
Racer
Joined: Oct 2005
Posts: 264
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From: La Grande Oregon
Ok, i'm sure this will spark something, what rpm are you turning? 1.94's will work good up till 6000 rpm. You can gain some flow by working the angle of the seat. How long are you running above 6 grand? Deshrouding the chambers helps at any rpm,remember it's a air pump, you need the same flow all the way through for best results. joe
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From: Kansas City Missouri
Originally Posted by bluealtered
Ok, i'm sure this will spark something, what rpm are you turning? 1.94's will work good up till 6000 rpm. You can gain some flow by working the angle of the seat. How long are you running above 6 grand? Deshrouding the chambers helps at any rpm,remember it's a air pump, you need the same flow all the way through for best results. joe
Race Director
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I know on the LT1 at least the gain from going with 2.02 / 1.60 valves is minimal over 2.00 / 1.56 In most cases you gain very little high lift flow but you actually have a substantial loss in low lift flow. The result is a net loss under the flow curve, which means less horsepower. Certainly not what you would be looking for when you consider the costs involved in going with the larger valves since you have to have new seats, etc.
Your best bet would be to stick with 2.00 / 1.56 and place the money you saved on head work towards improving the intake.
Your best bet would be to stick with 2.00 / 1.56 and place the money you saved on head work towards improving the intake.
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Joined: Dec 2004
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From: Kansas City Missouri
Originally Posted by Nathan Plemons
I know on the LT1 at least the gain from going with 2.02 / 1.60 valves is minimal over 2.00 / 1.56 In most cases you gain very little high lift flow but you actually have a substantial loss in low lift flow. The result is a net loss under the flow curve, which means less horsepower. Certainly not what you would be looking for when you consider the costs involved in going with the larger valves since you have to have new seats, etc.
Your best bet would be to stick with 2.00 / 1.56 and place the money you saved on head work towards improving the intake.
Your best bet would be to stick with 2.00 / 1.56 and place the money you saved on head work towards improving the intake.
Team Owner
Joined: Dec 2000
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From: SE NY
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If you want to retain low end as well as extend the torque curve consider an Accel base & AS&M LT runners. You might not extend top end as much as with the SLP siamese runners but nor would you lose low end.
Also, for nearly no $$ you can try the siamese intake base mod. Going to a 2,000RPM TC more than compensated for the low end torque loss and the extended pull up top is very nice. Being able to stay in each lower gear for another 1,000rpm (my A4 now shifts at 5,800rpm) realy helps performance.
For some info on porting #113 heads and much more you might find this reference very interesting:
"How to Build Max Performance Chevy Small Blocks on a Budget", by David Vizard (ISBM 1-884089-34-8).
Also, for nearly no $$ you can try the siamese intake base mod. Going to a 2,000RPM TC more than compensated for the low end torque loss and the extended pull up top is very nice. Being able to stay in each lower gear for another 1,000rpm (my A4 now shifts at 5,800rpm) realy helps performance.
For some info on porting #113 heads and much more you might find this reference very interesting:
"How to Build Max Performance Chevy Small Blocks on a Budget", by David Vizard (ISBM 1-884089-34-8).
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Joined: Dec 2004
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From: Kansas City Missouri
Originally Posted by 65Z01
If you want to retain low end as well as extend the torque curve consider an Accel base & AS&M LT runners. You might not extend top end as much as with the SLP siamese runners but nor would you lose low end.
Also, for nearly no $$ you can try the siamese intake base mod. Going to a 2,000RPM TC more than compensated for the low end torque loss and the extended pull up top is very nice. Being able to stay in each lower gear for another 1,000rpm (my A4 now shifts at 5,800rpm) realy helps performance.
For some info on porting #113 heads and much more you might find this reference very interesting:
"How to Build Max Performance Chevy Small Blocks on a Budget", by David Vizard (ISBM 1-884089-34-8).
Also, for nearly no $$ you can try the siamese intake base mod. Going to a 2,000RPM TC more than compensated for the low end torque loss and the extended pull up top is very nice. Being able to stay in each lower gear for another 1,000rpm (my A4 now shifts at 5,800rpm) realy helps performance.
For some info on porting #113 heads and much more you might find this reference very interesting:
"How to Build Max Performance Chevy Small Blocks on a Budget", by David Vizard (ISBM 1-884089-34-8).
Team Owner
Joined: Dec 2000
Posts: 90,675
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From: SE NY
Cruise-In II Veteran
Yes I have done the siamese intake mod; the before & after dyno pulls and performance data are on my site. It is siamese stock size base with stock runners.
If you would like pics of the modded base, send me an e-mail at jgkov@msn.com refering to this post.
If you would like pics of the modded base, send me an e-mail at jgkov@msn.com refering to this post.
Racer
Joined: Oct 2005
Posts: 264
Likes: 1
From: La Grande Oregon
The gear swap alone will help with your exiting speeds, if you need more try 4.10s, just a thought here, i know we all have steel cranks, however if you will have the engine out, check and make sure it wasn't a monday or friday engine and a cast crank wasn't stuck in by mistake, if you are going to play at 6000rpm, cast wont last. joe
Racer
Joined: Oct 2005
Posts: 264
Likes: 1
From: La Grande Oregon
The sodium exhast valves were first used on trucks for added cooling, for the money they cost you can almost go to titainum instead and be one hell of a lot lighter. As for the alloy seats i would have to guess that it simply makes a softer compond for unleaded use. (i'm sure someone will tell us)....for a racing applactions i've always ran hard seats simply because your always changing valves and seats anyway, plus hard seats will keep your flow rate the way you want it longer. joe