Teddy Allansson

Hello. What brand and messurment shuld i use to enlarge my valves. I know 2.07 and 1.680 Will be enough but what brand of stainless valves shuld i buy. Wanted ferrea but the lenght is intake 4.715 Exaust 4.668 (stock) and 4.735
why not The same lenght and Will these fit 45 degree heads? What lenght in Exaust shuld i buy.

shiftbyear

I believe the longer valve is to prevent coil bind with a higher lift cam.

Teddy Allansson

yes thats a good thing. But it shuld be some option.? And that they don't have The same lenght for intake and Exaust i cant understand

74sprint

The majority of cars are stock or close to stock and have hydraulic cams so; the exhaust valve is shorter because when it gets hot it will grow in length more than the intake. Just like a solid cam you have more lash on the exhaust side. Besides the difference between them (first 2) is 0.047" which the hydraulic lifter can handle. 0.047" in spring height would depending on the spring rate would probably be 10-20lbs at the most. In the old days we would grind and polish the valve tips if need be. Also the valve might be a sbc or Pontiac valve listed as Olds, they build for the majority not the minority, most of the time.


Ray

Teddy Allansson

Thanks for the info. Then i shuld but the 4.668 insted of 4.735? I was thinking about The rocker geometry. I Will use compcam 995-16 springs (i think they fit my e heads witout grinding) and The roller rockers 1442-16. Mondello performance (twister) sells 1.680/4.710 that he say is pep valves and intake 2.070 /4.710 i was thinking that would be perfekt. Edelbrock have 1.680/2.07 for their own cylinder head 60519 but they are 4.780 and stock is about 4.690 witch seams to big differens with stock valve covers and compcams rollers? Will go with stainless but im not place hardered seats

74sprint

stock valve length is 4.700"
stock installed spring height is 1.670"
I.D. of Inner Dia.: .697" of the dual springs

Go with the shorter valve, it is only off by 0.002", which is nothing. Same with the 4.710" valves. Longer valves will give you less seat & open pressure. With the 4.735" valve I would start checking the geometry but wouldn't be to worried about it. As for the springs, you will have interference with the stock valve seals and will need to have the guides narrowed/cut to fit 0.500" seals. Most times when the machine shop does this the cutter will also shorten the guide for you, which is good for guide/retainer clearance. These springs installed at stock height will give you 12.06 more lbs. of pressure. With the rockers you will need to have the rocker bolt holes re-drilled and tapped for the 3/8" studs, Olds heads have 5/16" rocker bolts. You will also need guide plates. Because you are going to new rockers you will need to check push rod length and rocker/valve geometry. You should be able to get away with less than $200.00 for machine work plus the valve job. Want some cheap Hp? get some roll cartridges and a long 6" tear drop carbide cutter and clean up the valve bowls and grind the runners until the casting line is gone, keep the sides vertical, this is worth 25-35Hp. You can use a high speed die grinder or a hand drill. Ask your machinist how close to the seat you can come, you will feel this BTSOYP.

Links:
SettingValve Stem Heights
Setting Valve Spring Heights
Home Porting Techniques


Ray