Needs these ansewered by the guys that have actually worked heads and played with valva angles..

Just got back from toying witth some Lt1 castings..Im not going to get into flow charts because im just paying mind to peak #s..

Stock@.700" was 199

Ported-210 This was a very turbulent rough finish with a steel carbide bit..No welding or filling of the pushrod holes,no short turn radius other than blening and no valve job..

vavle job-218cfm with a 40* and 30* 1st and second..

Polished ports-230 Used 120 grit fish on the intake walls and 80 grit on the roof and floor..

New valve job-248cfm this time tried a reccomended 3 angle with a 42.5 and 30 degree 1st and second...

Now this was all with the standard stock valves with the normal backcut..Im done testing until i order a set of 1.94" ferrea valves i guess..Unless there is still some room to improve my 3 angle valve job?Also am i right that a 5 angle would be a waste of time here since low lift #s are not any concern?Ive never seen any high lift improvments from switching to a 5 angle..Why would the 42.5 1st cut give me so much more than the 40 degree cut?Especially at such a high lift (.700")?

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FLUCK A SPELL CHECK<I CAN SPELL REALLY GOOD< IT'S JUST THE TYPEING THAT STINK AT!

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88 RX7 GTU, 97 Lt1/700R4,10" 3K stall, 4.30 gears,285CFM heads,12.4-1 compression, custom cam and 2700lbs...Daily driven!

[This message has been edited by LT1 1980 malibu (edited September 12, 2002).]

 

Well, most 3-angle valve jobs I've seen are 30/45/60. I don't completely understand the reasoning behind 30/40 or 30/42.5. Escpecially for high lift applications. Pro Stock Truck, Pro Stock, and a lot of heads-up guys have been running 50-55 degree seats for years, the benefits being increased high lift flow. They only do this on the intake valve I believe.

As for the advantages of a 5 angle valve job, I think the gains are minimal, especially on the intake side. Now, on the exhaust side, it there are definite benifits to having a radius below the valve, something only a Serdi cutter can do. I guess what I'm trying to say is the gains of a 5 angle over a 3 angle are small compared to the high-lift gains of a 50-55 degree seat over a 45 degree seat.

Anyway, I would recommend AT LEAST a 45 degree seat, and if you are truly lifting the valve up to 0.800", I would go with 50 degree seats. The only downfall is they don't last as long.

Good luck.

Shane