2.08 size valves too big for stock bore?
05-04-2007, 05:23 PM
#1
2.08 size valves too big for stock bore? I bought a used set of Patriot stg 3 ls6 heads and they come with a 2.08 int. valve and a 1.60 exh. valve. Well my question are these valves too big on the stock bore? I'm planning to flycut my pistons was curious if there would be any issues?
05-04-2007, 07:33 PM
#3
There is a formula floating around that says the intake valve should be no larger than 52% of the bore. If larger than valve shrouding will occur. So take the diameter of your bore and multiply it by .52.
05-04-2007, 09:26 PM
#6
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Many people have run a 2.08" on the stock bore with good success. I haven't seen a lot of stellar dyno numbers, but at the track they haul you know what.
As a head porter, I want to get a set of 243 castings for my personal car, change the seats on them, and port them to accomodate a 2.08" valve if that tells you anything.
I'm suprised there hasn't been 15 ppl say they're too big yet.
Ben T.
As a head porter, I want to get a set of 243 castings for my personal car, change the seats on them, and port them to accomodate a 2.08" valve if that tells you anything.
I'm suprised there hasn't been 15 ppl say they're too big yet.
Ben T.
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05-04-2007, 11:56 PM
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The valves aren't the problem. Having a 2.08" isn't going to hurt midrange or lowend power production, it's having a much larger intake runner cross section. The bowl for a big valved head must be opened up, but the rest of the port doesn't have to be opened up quite so far. Depending on how large the ports are will dictate if they are too big for your motor- not the valve size.
Keep in mind, usually a 2.08" valve will be accompanied by a large port. Once the porter has the seats chagned, he's going to be looking for all the flow he can get to make the extra labor (seat installation) worth it. That usually means a lot of aluminum is going to be flying.
Ben T.
Keep in mind, usually a 2.08" valve will be accompanied by a large port. Once the porter has the seats chagned, he's going to be looking for all the flow he can get to make the extra labor (seat installation) worth it. That usually means a lot of aluminum is going to be flying.
Ben T.
05-05-2007, 02:54 AM
#12
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On stock bore, unless you're running mega cam with high compression, 2.055 would be max needed.
What is the point of having a huge valve and be restricted on intake of air.
For discussion read J-Rod's "cfm requirement by rpm'" in JRP cam sticky.
What is the point of having a huge valve and be restricted on intake of air.
For discussion read J-Rod's "cfm requirement by rpm'" in JRP cam sticky.
05-06-2007, 05:30 PM
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Something to chew on...
LS7 4.125" bore 2.200" valve
L92 4.060" bore 2.160" valve
LS3 4.060" bore 2.160" valve
LS1 3.898" bore 2.080" valve
All of these FOUR motors would have an intake valve that was 53.x% the size of the bore. The LS7 and a LS1 with a 2.08" intake valve would both have 53.3%.
(Changes in valve angle also exist)
I'm really thinking I want to do some 2.08" LS6 heads for my personal LS1 car. If they don't work that well, good news is they're replaceable.
Ben T.
LS7 4.125" bore 2.200" valve
L92 4.060" bore 2.160" valve
LS3 4.060" bore 2.160" valve
LS1 3.898" bore 2.080" valve
All of these FOUR motors would have an intake valve that was 53.x% the size of the bore. The LS7 and a LS1 with a 2.08" intake valve would both have 53.3%.
(Changes in valve angle also exist)
I'm really thinking I want to do some 2.08" LS6 heads for my personal LS1 car. If they don't work that well, good news is they're replaceable.
Ben T.
05-06-2007, 05:32 PM
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Originally Posted by 01 BERGER CAMARO SS
I have a friend running stage 3 MTI heads with a mild can and he put down some good et's. Dont c why you would have a problem.
Ben T.
05-06-2007, 05:46 PM
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If those heads are for 3.90" bore,and Patriot put those valves in, then it should be OK. Sometimes though, bigger isn't always better. If the valve gets too big then you can get some shrouding on the side of the combustion chamber. If you are worried, call Patriot, they are the ones that should be able to give you some good flow info on those heads.
05-06-2007, 07:50 PM
#17
Actually the heads were made for a 4.1+ bore engine according to Gunnar. But the heads already come with a 5 angle valve job. So would that help with keeping it from shrouding? I know bigger doesn't mean better but that's what came with the heads and I didn't know this size of valves would cause a problem. On SDPC there are selling Ferrea valves for 12.95 each and was thinking if that would be a good idea to swap them out for them?
05-06-2007, 08:38 PM
#18
Swap the valve out? If I think thats what you are talking about you cannot do that. Swapping the seats and the valves have to be done at the same time. A smaller valve will basically fall into the seat. I cannot comment any about the effeciency of the subject matter at hand, sorry. I only wanted to post about the valave size.
05-06-2007, 10:32 PM
#20
At this point in time as long as they clear the bore I would run them. May not be ideal but not worth the cost to do the other options. Like was said above you can always call Patriot and see what they say.