2.02 vs. 1.94 intake valves

Hello,

I have a friend with a cylinder head shop who has hooked me up with a set of heads. I was running a set of Trick Flow Twisted Wedge heads,but I wanted to get rid of them. They made good power, but I've had trouble with breaking valvesprings and rocker arm studs.

Anyway,the new heads I'm getting are a copy of the Pro cylinder heads. I was really excited about getting these heads! However, when I went to get them my friend told me he put 1.94 intake valves in them. The Trick Flows had 2.02 valves.

Here's the deal: I'm getting these heads for next to nothing because he's trying to sell my Trick Flows. I can't get too upset with him because he's done me a favor and he's my best friend.

However, it seems like I've taken a step backward though. How much will this affect power and torque?? The engine is a 60 over 350 with a 280 Comp Magnum cam. I'll be going from a Perfomer RPM to an Air Gap with a Speed Demon 650 carb.

Like I said, I know this a good set of heads. I'm just not happy about the 1.94 valves

i'd try em out, it's mainly a velocity and flow volume thing, that extra couple hundredths allows a significantly larger amount of flow, whole circle shape thing fluid dynamic people and/or people who have experience in upper level calculus will tell you so (i.e. me), but i always vote for try it and see what happens and then rework and see how much it helped, and worst case scenario, take em to a head shop and open em up, it's a pretty standard procedure to open em up to 2.02/1.60 when heads get worked

i'd try em out, it's mainly a velocity and flow volume thing, that extra couple hundredths allows a significantly larger amount of flow, whole circle shape thing fluid dynamic people and/or people who have experience in upper level calculus will tell you so (i.e. me), but i always vote for try it and see what happens and then rework and see how much it helped, and worst case scenario, take em to a head shop and open em up, it's a pretty standard procedure to open em up to 2.02/1.60 when heads get worked

I agree 100 %...well said

on the street, there is very little difference between the two. Have your valves backcut 30 degrees, both intake and exhaust, and concentrate on the valve bowls to remove any casting flaws.

Hot Rod magazine put 2.02 heads on a dyno motor and it made less power and torque than with the 1.94 heads they took off

well that's probably with 2 different head designs, what matters most with the head and it's power, is valve shrouding, chamber geometry and volume, and runner geometry and volume. and different heads vary in every aspect

the same head will flow better with 2.02 valves, there is no disputing this fact, unless the valve is extremely shrouded by a poor combustion chamber design or the engine was extremely dependent on high velocity airflow instead of quantity, which would be like a small torquey cam design, your magnum 280 should enjoy 2.02, but like i said, it's extra money, so i'd just give em a shot, heads arent that big a deal to change.

but that argument that 2.02s produceless power than 1.94s is like saying that a bigger exhaust cuts power, bigger valves, unless something is hindering their performance, are more efficient and thus flow better and produce higher hp numbers

I'm not here to argue about it but bigger is not always better, it's like having an intake that's too big. It might be good for high rpm horsepower but not necessarily for low end torque that's used on the street

The engine is a 60 over 350 with a 280 Comp Magnum cam. I'll be going from a Perfomer RPM to an Air Gap with a Speed Demon 650 carb.

Like I said, I know this a good set of heads. I'm just not happy about the 1.94 valves


I had a .030 over 350 with 1.94/1.50 iron heads and the 280H. Ran good. The cam needs at least a little gear and if it's an auto car it needs a converter.
I had a Torker II on mine with a 750 vacuum.
It was a good runner.

I'm not here to argue about it but bigger is not always better, it's like having an intake that's too big. It might be good for high rpm horsepower but not necessarily for low end torque that's used on the street

i agree completely, it is your complete setup that determines what you need, i was talking simply based on flow numbers, bigger valve = more flow, however, more flow isnt always necessary. however i dont believe any low end loss of torque would be noticeable, but i dk, i havent ran one set of heads with both 1.94/1.50 and 2.02/1.60 valves

Professional head porters like to keep valves at 50-52% of bore size for velocity. My friend spent $250.00 on a set of vortecs to go from 1.94 to 2.02 and didn't improve 1/100th. I took the heads and pocket ported them he picked up a 10th. It all depends on the combination of the head. How big the runners are, the pocket, and the throat area. The throat area should typically be between 85-90% of the valve size.

Professional head porters like to keep valves at 50-52% of bore size for velocity. My friend spent $250.00 on a set of vortecs to go from 1.94 to 2.02 and didn't improve 1/100th. I took the heads and pocket ported them he picked up a 10th. It all depends on the combination of the head. How big the runners are, the pocket, and the throat area. The throat area should typically be between 85-90% of the valve size.

makes sense...

there is actually a formula kinda thing for that? and you're talking talking throat area as height x width of the throat of the intake runner right? I wanna test it out when i port the next set of heads :) hehe

makes sense...

there is actually a formula kinda thing for that? and you're talking talking throat area as height x width of the throat of the intake runner right? I wanna test it out when i port the next set of heads :) hehe


The throat area is the area within one inch under the valve seat. The formula you're talking about is for finding optimal cross section for rpm. The easiest almost fool proof rules for the home porter are:

Raise the intake port runner .100" but don't touch the floor.
Widen the straight side of the port .050" but only blend the other side in the curve.
Pocket port using 85-90 percent of valve size and slim the guide boss without shortening the guide.
Smooth the short turn radius (the bottom of the port where it makes the turn to the valve) but only remove enough metal to radius it smooth.
Finish by polishing the intake to 60-80 grit finish and the exhaust to 220+ grit finish.

A debate! Cool!

One of these days I'm gonna get around to bolting these things on. I've got something going the next few weekends though. I'm anxious to see how well or not well these things work.

It was a totally different heads and cam, but does anybody remember the Danger Mouse series in Super Chevy a few years back? One of the best combos was Edelbrock's E-Tec heads with 1.94 valves and 170cc ports. It picked up 41 ft lbs of torque and 34 hp over the Etec-200 heads with larger ports.

The throat area is the area within one inch under the valve seat. The formula you're talking about is for finding optimal cross section for rpm. The easiest almost fool proof rules for the home porter are:

Raise the intake port runner .100" but don't touch the floor.
Widen the straight side of the port .050" but only blend the other side in the curve.
Pocket port using 85-90 percent of valve size and slim the guide boss without shortening the guide.
Smooth the short turn radius (the bottom of the port where it makes the turn to the valve) but only remove enough metal to radius it smooth.
Finish by polishing the intake to 60-80 grit finish and the exhaust to 220+ grit finish.


very descriptive ! and interesting! thnx.

what's the scoop on your 383 velle ?

I got 1 too...:D :D she's a 72, runs good for not really being tuned in yet....prolly a high 11 car on DRs...:cool:

The throat area is the area within one inch under the valve seat. The formula you're talking about is for finding optimal cross section for rpm. The easiest almost fool proof rules for the home porter are:

Raise the intake port runner .100" but don't touch the floor.
Widen the straight side of the port .050" but only blend the other side in the curve.
Pocket port using 85-90 percent of valve size and slim the guide boss without shortening the guide.
Smooth the short turn radius (the bottom of the port where it makes the turn to the valve) but only remove enough metal to radius it smooth.
Finish by polishing the intake to 60-80 grit finish and the exhaust to 220+ grit finish.

awesome post, Thanks man
*prints off a copy and runs outside*

very descriptive ! and interesting! thnx.

what's the scoop on your 383 velle ?

I got 1 too...:D :D she's a 72, runs good for not really being tuned in yet....prolly a high 11 car on DRs...:cool:


The Chevelle is my street cruiser/bruiser. It's got a 383 with Eagle rotating assembly, performer rpm heads, performer rpm air gap and just under went some more modifications. It had a Comp XE 284 hydraulic flat tappet cam and out the box heads and ran 12.64. I just ported the heads just like I mentioned above and put a small solid roller cam in it. (Erson 278) That dropped me to 11.59 best so far with only two runs. It also has 3.55 gears and 3000 stall with 295/50-15 ET street radials. The rear has stock boxed lower control arms and relocation brackets.

solid roller cam in non roller motor? i was thinking about that but didnt want the hassle for no major gain on normal driving, but 1 second from 12.6 down to 11.5 holy wow, i need to learn how to port good and get a solid roller in there.

solid roller cam in non roller motor? i was thinking about that but didnt want the hassle for no major gain on normal driving, but 1 second from 12.6 down to 11.5 holy wow, i need to learn how to port good and get a solid roller in there.


A roller cam will make more hp in almost all circumstances due to the area "under the curve". The best way to see the evidence is to look at a flat tappet cam lobe and look at a roller cam lobe. The flat tappet goes to a point kinda like a triangle and the roller is oval. This gives you a lot more duration at higher valve lifts where heads flow decent numbers.

The roller cam I went to is smaller at the seat (278 vs 284) and smaller at .050" (238 vs 240) than the flat tappet, but takes a big lead from .075" on up and keeps the valve open a lot longer at peak lift. What this resulted into was more cylinder pressure down low for better torque due to the intake valve closing sooner (smaller seat duration bleeds off less cylinder pressure) and more torque and hp throughout the rpm band due to greater air flow from the added duration of the valve being open longer at higher lifts.