What's the biggest valve combo for 8V heads

[bakes]

I have done the 44m valve thing just wondering whats the biggest valve combo seen or done on our 8v heads? valve specs please pics don't hurt. let keep the Bull to a minimum and real!

[GLHNSLHT2]

even the 44mm valves get so close to the wall that the shrouding starts to come into play. I've heard of some actually getting more flow out of a +1mm setup than a big valve head.

[bakes]

even the 44mm valves get so close to the wall that the shrouding starts to come into play. I've heard of some actually getting more flow out of a +1mm setup than a big valve head.

was that with deshouding ? all mods welcome to push the limits

[tvanlant]

You can't go much larger than the 44 & 36.8 because the seats are about to touch each other (and sometimes do interlock depending on the seats being used).

[bakes]

Ok but what about going from a 8mm to a 6mm stem and longer length ?

[BadAssPerformance]

You can't go much larger than the 44 & 36.8 because the seats are about to touch each other (and sometimes do interlock depending on the seats being used).

Yep, thats the IMSA 'big valve' sizes and they work well

Larger? IIR, Forward Motion E3 head has interlocking seats and 44mm/38mm valves.

[Warren Stramer]

I have done the 44m valve thing just wondering whats the biggest valve combo seen or done on our 8v heads? valve specs please pics don't hurt. let keep the Bull to a minimum and real!

Ok no bull then, Over the winter I spent alot of time on the flow bench developing my first "big valve" head. My benchmark head i've been comparing it to is my +1mm G head I ran 10.6s with. I've done back to back flow tests mainly on intake side and I can say the +1mm head has better low lift cfm up to about .475 valve opening than the 44mm intake.
After .475 lift the big valve head takes off and flows considerably more up too .700 lift which is the most lift I tested at.

My big valve 44mm intake flows the same at .600 lift with or without the valve installed in the guide/port. At high lifts the port becomes the controlling factor as if the valve is not in the picture.

Up to .433 lift the valve/ seat area is controlling flow, and is the curtain area-to-valve area convergence point with the throat area I have.

The +1mm head with a 1.637 diam. intake has a 1.473 throat, and a cutain area-to-valve area convergence at .409 lift.

So if you are using any of the currently available cams, and a +1mm valve you would probably have the most flow area under the curve with the +1mm intake.

Big valve heads can I think be the ultimate setup IF some other tricks are done along with the big valves. I hope to find out.

[BadAssPerformance]

Very interesting Warren So, how far does a valve actually open with an S60 cam on hydraulic lifters?

[Warren Stramer]

Very interesting Warren So, how far does a valve actually open with an S60 cam on hydraulic lifters?

That is a good question, I bet it is not near .499
I guess my point is this........If you run a cam that only lifts the valve to say .430 lift (like the factory rollers) then there is NO use worrying about cyl. head flow numbers beyond that lift cause the port NEVER sees it!

[BadAssPerformance]

That is a good question, I bet it is not near .499
I guess my point is this........If you run a cam that only lifts the valve to say .430 lift (like the factory rollers) then there is NO use worrying about cyl. head flow numbers beyond that lift cause the port NEVER sees it!

Hmm.. I might have to measure one

And that is a very good point I wish a flowbench could measure at 20psi tho

[Warren Stramer]

Hmm.. I might have to measure one

And that is a very good point I wish a flowbench could measure at 20psi tho

I don't see how it can be measured, what the lift is in a running engine depends on a lot of variables........oil psi,oil temp,rpm,lifter type,lifter wear,lifter/bore clearance, spring pressure, ect. How do you propose to measure actual running valve lift with a hydralic?

[BadAssPerformance]

LOL, I was thinking non-running... running.. would need a really really fast dial indicator?

[Warren Stramer]

Ya that would be a trick!, way back when I was messin with a FM 505 cam I checked the differance in net valve opening between a filled hyd. lifter and a adjustable lifter set at zero lash.
The retainer to stem seal clearance was only about .040 with either lifter, in a running engine the hydralic collapses some unkown amount from the pressure of the spring. they give up some lift, and the stiffer the spring, the more they yield.

[BadAssPerformance]

Hmmm, even at 80psi oil pressure, if they could be gauranteed to be pressurized.

[Warren Stramer]

Like I said JT, I dont know for sure too many variables. I've always wondered.................ok I just had a idea, an obvious way to measure the actual running lift, the valve stem should leave a wear mark above the guide, I will measure and get back.

[BadAssPerformance]

Thats a great idea!

[boost geek]

My big valve 44mm intake flows the same at .600 lift with or without the valve installed in the guide/port. At high lifts the port becomes the controlling factor as if the valve is not in the picture.

Big valve heads can I think be the ultimate setup IF some other tricks are done along with the big valves. I hope to find out.

Now, if you were to use a 655 head with big valves and an intake to match or excede the head...

[Warren Stramer]

My hunch was correct, Just measured actual valve travel from obvious wear pattern....... .475 lift S3 was lifting the valves a grand total of .428 inches with hydralic lifters!

Here is my solution........................

[BadAssPerformance]

Doh!

Nice solution!

[turbovanman²]

Ok no bull then, Over the winter I spent alot of time on the flow bench developing my first "big valve" head. My benchmark head i've been comparing it to is my +1mm G head I ran 10.6s with. I've done back to back flow tests mainly on intake side and I can say the +1mm head has better low lift cfm up to about .475 valve opening than the 44mm intake.
After .475 lift the big valve head takes off and flows considerably more up too .700 lift which is the most lift I tested at.

My big valve 44mm intake flows the same at .600 lift with or without the valve installed in the guide/port. At high lifts the port becomes the controlling factor as if the valve is not in the picture.

Up to .433 lift the valve/ seat area is controlling flow, and is the curtain area-to-valve area convergence point with the throat area I have.

The +1mm head with a 1.637 diam. intake has a 1.473 throat, and a cutain area-to-valve area convergence at .409 lift.

So if you are using any of the currently available cams, and a +1mm valve you would probably have the most flow are under the curve with the +1mm intake.

Big valve heads can I think be the ultimate setup IF some other tricks are done along with the big valves. I hope to find out.

No disrespect but a flow bench doesn't really measure under boost so are you sure there is no power to be had switching to a larger valve with matching port even though on a flow bench, its doesn't show it?