Question about Hughes Whiplash Cam and Springs

[70bigblockdodge]

1.88 installed height minus
.518 lift equals
1.362 which is less than the 1.33 spec they are using for open pressure. Low 300s are good for .500+, 350#+ for .550"-<.600", 400#+ for .600" up.
This is all to control the lifter as it rides over the top of the lobe. If it comes off, or gets light pressure it will stop rotating and the lifter will fail. The lifter works like rolling a oxygen or other compressed gas tank. You lean it off to one side and rotate it it will move across the pavement. On a flat tappet the lifter is straight and the ground (cam lobe) is leaned/ground to one side, thus it moves across the lobe as it rotates.
Roller cams though they don't rotate they also need the wheel to not come off or get light on the lobe to prevent skidding when it comes down onto the lobe (think: airplane wheel on landing)
I think the concentration on seat pressure is from head rebuilder with stock springs if you get the seated height right the open pressure will follow because the original engineers designed it that way. Now you changed the cam lift and ramps (duration) and the spring needs to increase to handle demand. IMO seat pressure is just a result of the springs requirements.
Hope that helps.

 

[1970FuryConv]

Thanks, Great info!

 

[70bigblockdodge]

Thanks, Great info!

I will say there are many different opinions about valve springs.
Seat pressure IMO is nothing to worry about, it just holding the valve shut on the base circle. Yes your primo valve job may only need 20# to seal it, but you will not get enough pressure at max lift if it only starts at 20# installed height. Not enough movement to generate the pressure over the nose.

 

[badvs3vil]

I will say there are many different opinions about valve springs.
Seat pressure IMO is nothing to worry about, it just holding the valve shut on the base circle. Yes your primo valve job may only need 20# to seal it, but you will not get enough pressure at max lift if it only starts at 20# installed height. Not enough movement to generate the pressure over the nose.

So since I'm new to all of this, is that what makes these whiplash cams great for low compression engines?

 

[70bigblockdodge]

The intake valve closing early and the exhaust closing early helps to trap as much air/charge into cylinder to creat as much pressure as possible. Making the most out of the crappy compression ratio yet still having good lift to use the available head capacity.

 

[1970FuryConv]

Dave is spot on!

On the stock 1973 400 engine cam, the 2 barrel lift duration is 260° at intake and 268° at exhaust. For the 4 barrel carburetor it’s 268° intake valve duration and 284° exhaust valve duration. I agree that the Hughes cam’s shorter duration traps more air fuel mixture in the cylinder to create more power.

With a lift of .518 inches, the Hughes cam also exceeds the 4.34 inch lift of the stock 2 barrel cam and the .450 inch lift of the stock 4 barrel cam. This traps even more air fuel mixture in the cylinder.

I forget what year your 400 engine is but I doubt it’s much different than 1973. Ben

 

[badvs3vil]

Dave is spot on!

On the stock 1973 400 engine cam, the 2 barrel lift duration is 260° at intake and 268° at exhaust. For the 4 barrel carburetor it’s 268° intake valve duration and 284° exhaust valve duration. I agree that the Hughes cam’s shorter duration traps more air fuel mixture in the cylinder to create more power.

With a lift of .518 inches, the Hughes cam also exceeds the 4.34 inch lift of the stock 2 barrel cam and the .450 inch lift of the stock 4 barrel cam. This traps even more air fuel mixture in the cylinder.

I forget what year your 400 engine is but I doubt it’s much different than 1973. Ben

Mine is a 1977

 

[1970FuryConv]

I doubt the stock cam specs changed much from 1973 to 1977, especially because the 400 big block went out of production 2 years later. Lee Iacocca took care of that in 1979 after taking Chrysler away from the verge bankruptcy using a government loan. Anyway, with higher lift and shorter duration, the Hughes cam is much more efficient in trapping a large amount of air/fuel mixture in the cylinder. This makes more power. And with gas prices the way they are, we need as much efficiency as possible. UGH!

 

[John Kirby]

Do you have hardened valve seats? Not sure if a '77 had them. If not it's something that needs to be updated due to unleaded gas.

 

[badvs3vil]

Do you have hardened valve seats? Not sure if a '77 had them. If not it's something that needs to be updated due to unleaded gas.

Yeah I have 452 Iron heads.

 

[70bigblockdodge]

It is also ground with the intake lobe advanced to get it closed ASAP. There is not a lot of overlap in the cam so do not expect it to rev on top end easily. Does have a lot of exhaust duration to work well with exhaust manifolds.
I would be curious to know what 0-60mph or 1/4 mile time is when you get it together.

 

[Rennie]

Hello everyone,

I wanted to run this by everyone who is smarter then I. My engineer rebuilder who is setting up my heads right now and installing my springs called me. Keep in mind that I got everything from Hughes for this build, the cam, springs and lifters. My engine rebuilder is questioning the spring pressure, he said 155#'s is super high for closed pressure and he thinks that I would have issues with the cam break in with that high of pressure. He said he has never seen closed pressure that high.

So I guess my question is to all of you, I assume I should still have him continue with the install as per the cam card. I also assume the Whiplash cam is made to with stand this kind of pressure?

Let me know your thoughts please.


View attachment 518412

 

[Rennie]

My link to this cam shows the same specs except that the 1106 springs show 150#, not 155#.
Interesting...

 

[volksworld]

fwiw hughes uses those same springs on every big block cam that uses single springs...from his mildest up to a couple of rollers...the last thing i'm gonna do is second guess the cam supplier....i also called to ask if i should pull the dampers out for break in and he said no...i basically got the same lecture as 70furyConv...