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Author Topic:   2.02 valves vs 2.05 or 2.08 valves is there a noticable differerence
WILDphil
Member
posted January 08, 2002 06:16 PM
running bigger valves help give more torque....which broadens your power band...therefore making you faster. if you have enough motor right now....wait. if not,spend. it always costs more to go faster......LOL....or just buy my rolled 383 now.


General
Member
posted January 08, 2002 07:35 PM
For that kind of price tag , I'd wait till next year and buy Iron Eagle's , if they are legal !

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Hendren Racing Engines
Rutherfordton , NC
(828)286-0780


CUSTOMPERFORMANCE
Member
posted January 09, 2002 01:09 AM
2.02 valve plenty big, use the heads you havenow and change later. sounds like they wanted to take you for a ride.


WILDphil
Member
posted January 09, 2002 06:50 AM
sounds to me like you need to find a different engine builder!!!


sdhnc29
Member
posted January 09, 2002 10:12 PM
Do you mean the end's of the spring's were broken on the flat , or the spring was broken in half ?? If the tip's were broken , then this is usually a sign of valve float . If it was broken in half , then it was simply spring failure . If your going to stick with a single spring and a lower lift , then you should use a Vasco spring that Crower sells .I'd give you the part number , but I'm at home , and can't for the life of me remember the number !

Unfortunately , valve spring's are an engine builder's nightmare !! Spring breakage is the one thing that we have little or no control over . The best cure is money ! Cheap spring's break !! Expensive spring's break , but not too often ! As the engine owner , you should invest in an on car spring tester , and check your spring's after every race . Preventative maintenance will save a dropped valve !

A double spring would not necessarily cure your problem themselves . But if you are running in a higher RPM range , 7,500-8,000 , with stainless valves , then you will need a double spring , and I'd invest in the best one's you can buy for your application . If this is your application ,high RPM w/stainless valves, then you will need a spring that will go 150-160lbs on the seat , and right around 400 open , especially if your cam profile is aggressive , or your running high ratio rockers . The Vasco spring that I mentioned earlier is the best single spring that I've found , but even it will only go 140lbs on the seat , and about 350lbs open . Email me , or give me a call , and I'll be happy to supply you with a few spring numbers that you can choose from .

Steve

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Hendren Racing Engines
Rutherfordton , NC
(828)286-0780


awkwardjeff
Member
posted January 11, 2002 02:24 AM
One thing nobody mentioned was the bore size of this motor.....I don't care if it's a flat tappet or roller.......if the valve is tooo big it won't flow around the cylinder wall.......for a 350 block....say 4 inch bore plus the clean up 4.030 I would NOT EVER get into a 2.08 valve UNLESS it's a canted vavle that opens away from the wall...

The cylinder wall will shroud the valve face and NOT let air/fuel flow around the entire area.........a smaller valve will flow much better numbers in a small bore with the same lift.

I have never tried to fit a 2.08 valve in a 4.00 bore, but have a few friends that have, both ended with bent valves from hitting the cylinder wall, or more correctly the DECK of the block trying to get into the bore......I believe a 2.08 will fit in a 4.030 bore but the flow is so restricted that it hurt performance......

I would like to hear Steve's comments on this thought.

Jeff

sdhnc29
Member
posted January 11, 2002 12:42 PM
Your right Jeff , to a point . Back in the old day's when we were using 2.100" valves in 23deg. heads , we had to notch the top of the bore for valve clearance . But this was for aluminum dart heads with spread valve spacing . You can use a 2.08" valve in a 4.030" bore , and yes , at peak lift there will be some shrouding from the cylinder wall . But as you go up in valve diameter , your low lift flow number's increase dramatically !! At peak lift , with the valve stuck in the bore , only about 1/8 of the valve diameter is going to be shrouded . At this point , you still have all the rest of the square inches of the valve moving air . You are right about the larger valve being affected by bore shrouding , this will affect high lift flow a little , but will have no affect on low lift flow . As you know , the engine sees low lift twice , yet it only sees high lift once per cycle . So often overlooked is low lift flow ! I have never gone to a larger valve , and not gained air flow and over all performance , especially if your using methanol .


Steve

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Hendren Racing Engines
Rutherfordton , NC
(828)286-0780


awkwardjeff
Member
posted January 11, 2002 02:11 PM
Steve, Thanks for the comments and thoughts on the big valve in a small bore.

I personally like a 2.05 in a 4.030 inch bore and a 2.08 in a 4.155 bore.

I may re-visit my cam selection and intake runners and try a big valve in the small bore.....

What you say makes good sense, I just see the big end drop off too much for what I like......but if I got a big enough gain on the bottom side it would be well worth the trade off..........

As always you give sound, real life knowledge.......Thanks, Jeff

PAPPAW
Member
posted January 11, 2002 03:12 PM
Quite honestly , I have not messed with the AFR Chevy heads . I can tell you that there Ford heads are very good from what I've seen , and they flow very well . Everything that I build for limited late models around here are with the Dart Iron Eagle , due to rules . If they ever change the rules , then I might have to look into them myself

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Hendren Racing Engines
Rutherfordton , NC
(828)286-0780


sdhnc29
Member
posted January 11, 2002 05:55 PM
No problem Jeff ! It's fun to share thought's and experience's on this forum ! Everyone might not always agree , but at least it gives food for thought .

Steve

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Hendren Racing Engines
Rutherfordton , NC
(828)286-0780


WILDphil
Member
posted January 16, 2002 12:53 PM
Sound's a lot more reasonable !! Good luck !

Steve

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Hendren Racing Engines
Rutherfordton , NC
(828)286-0780


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