ProTopLine sells there Lightening Heads with 2.08 2.05 or 2.02 intake valves how much of a difference can .03 or .05 of an inch make ??? just curious i would like to put the heads on a 383 with a stealthram. Thanks any info is Appreciated

 

You can decide. Perform the math. The difference is not in the minimal 0.030" or 0.050" diameter difference. Valve flow is all about perimeter flow. Calculate the circumference of the valve and compare it to the circumference of a 2.02" valve. The percentage difference can make almost that much difference in overall flow, especially at lower valve lifts. The area under the curve of the valve action plot can be increased at its ends due to a perimeter area increase in valve sizes.

 

Excellent technical advice.

 

Jeff, I think the area is even a bigger difference than the circumference (when you compute the ratios of the two) because you get the "R square" effect from the formula for calculating the area. But your point of the circumference definitely illustrates that there is bigger difference in the valve sizes than just the "couple of thousandths of difference" between them.

Enigma, other considerations to using larger valves are: 1) Larger valves must open further from the seat to get the maximum effect of the air flow. Thus you really need a high lift cam to go with a larger valve. 2) Smaller valve will have better air velocity at lower lifts, something that is important if the engine is more of a street engine than a strip engine. 3) Larger valves can suffer from shrouding if you are not using the largest bore possible. To get the full benefits of a 2.08 (or 2.10) you really need a 400 block. A 350 block will definitely hamper/shroud the flow of the larger valves.

If you are building an all-out race engine which will spend most of it's time operating at max rpms, then you want the biggest valves possible. But if it is going to be a street engine (with occasional track use), then a smaller valve would be a more prudent choice.

 

Long time no talk. For years people have always operated under the belief of smaller valves for torque/bigger valves for upper RPM HP. Seems to hold true. If you need more lift and duration because of the bigger valve size, you are looking at a cam that will operate in the higher RPM range better.

Velocity plays a big role in cylinder filling. Hence the use of 4 or more valves in some of the more exotic autos. The valves are all smaller, but allow the cylinders to fill at a faster rate.

 

More valves per cylinder allows more perimeter in the same area. Two 1" valve heads have 6.28" of perimeter in 1.57 in² of area in the chamber, while a single 2" valve head takes up 3.14 in² of area.

 

wow my threads never get responses like that... so since i will drive it all the tiem its better just to stick with the 2.02 since id rather have a torque beast then a screamer. thansk a ton guys

just to let you know you lost me with al the techinical advice

 

I like big valves and I don't know why.
I like to lift them way up high.
When the cam lobes spin
My face will grin
I'll pass your Toyota and wave Bye-Bye...

Couldn't resist. Must be the approaching full moon.

 

Also keep in mind, that the entire SYSTEM consisting of the port and valve, will only flow as much as the LEAST FLOWING place in the whole group of things.

In other words, you gain nothing by, say, jamming 2.08 intakes into swirl-port heads. Instead, all you accomplish, is to install a "bulge" in the tract; which forces the mixture to slow down at that point, and the fuel to pool out of the A/F mixture. You end up with less power and lower gas mileage, due to decreased efficiency; you can measure it on the engine dyno, as BSFC. You get the same result from "gasket matching" crappy heads. Ideally, the entire intake tract should be thought of as a whole, and each part of it matched to the others.

And; in a properly prepared port, undercut-stem 1.94" will conisderably outflow straight-stem 2.02" valves in a port not properly set up for them. This is a common kind of mistake to make with stock heads.

There's ALOT more to this than just cramming the biggest thing you can find into there. Which is why it always tickles me to hear people get all smug about their "202" heads, which then turn out to be untouched 882 castings or something that somebody just cut the bigger valves into without actually "fitting" them, and they can't seem to figure out why they're getting beat by people with supposedly lesser heads. They're victims of sales tactics and buzzwords, instead of actually deriving benefit from the work.

 

Hey Chris, I tried to tag up with you a few weeks ago but I never heard anything back. We do have to get together again.

When I first read your message, I was going to say "Whoa, you have it backwards". But you are most certainly correct, 2 x 1" valves do have the same perimeter length as 1 x 2" valve (3.14" for both) but the area of the single 2" is greater with the two 1".

In reality, the head designer would tend to use 2 smaller valves of equal (or greater) area of the big single valve and thus get the greater perimeter lenght as you state and collaborate with Jeff's earlier comment.

Also, the multi-valve head tends to favor spark plug placement in the center of the head - the best place to be. If I could only clean up on the stock market, I could afford those Arao heads that I drool over every night.

 

Right, multi-valve setups don't usually fit too well in a wedge head. Pentaroof works better, like in my 3.4 DOHC.

Did you try to phone? I've had some issues with my voicemail over the last couple weeks.

I'll be in Kamloops most of this weekend. I'll be out at the machine shop on Sunday, but I took Monday and Tuesday off, so there'll be time for beverages.

 

What Lightening Head? 180, 200.....?

I have flow numbers From Iron Lightening heads in diffrent stages of porting with diffrent valve sizes

Are you just going to buy them, and stick them on?

Unported heads stick with a 2.02 valve

If porting is going to be done? you can make more power with a bigger valve......Has to do with valve window/curtain area

Biggest thing is making sure the short turn is shapped properly to work with a 2.05 or 2.08 valve or you will lose power

Dont expect the head to flow its advertised numbers. It will flow less than they claim

Minimum Window Area
2.02 valve
.100=0.667238192
.200=0.957515311


Basic OD Window
2.02 valve
.100=0.634601716
.200=1.269203432

Minimum Window Area
2.05 vlave
.100=0.679465833
.200=0.975062499

Basic OD Window
2.05 valve
.100=0.64559729
.200=1.291194581

If you would like to see other lift points let me know

2.08 Valve on a 4.00 bore flow fixture

Lift---Int
.200-134.4
.300-195.1
.400-240.9
.450-259.8
.500-275.0
.550-286.2
.600-293.3
.650-297.6
.700-302.8
.750-308.3
.800-311.0
.850-314.2
.900-317.0
.950-317.7

same head but on a 4.125 bore flow fixture
Lift---Int
.200-138.0
.300-199.1
.400-245.6
.450-263.1
.500-278.7
.550-289.7
.600-296.1
.650-302.0
.700-307.5
.750-311.4
.800-315.8
.850-319.3
.900-322.5
.950-324.0


Those are not ProTopline Heads. Set of Bowtie heads done by another head porter.

I just kept that info because you can never have enough info/data to compare to your own findings


These numbers are from one of the First ProTopline heads I ever ported. They were 180cc Iron Lightening 2.05 valve. had more left in them

4.00 bore flow fixture

.200 131.4
.300 194.8
.400 239.6
.450 254.3
.500 272.1
.550 281.0
.600 284.4