Flat tappet lifters, wear patterns, cam lobe taper and other things. Let's swap opinions and ideas.

[Kern Dog]

Please, no.

 

[hofferwood]

Say his name 2 more times----------------and he'll show up.

 

[RemCharger]

Say his name 2 more times----------------and he'll show up.

Not so fast!!..
Happy birthday to RJ Renton

 

[INTMD8]

My engine turned 550 HP and 675 Lb Ft of torque when I ran it on a chassis dyno at the Hot Rod Power Tour (as driven on the tour: full mufflers, air cleaner on, etc.). This was a "fun run" event, so I had no opportunity to tune anything. The horsepower dropped off after about 4900 RPM. Something was going on, and it likely is a fuel delivery problem. With 675 torque, Horsepower should be up over 600. But I haven't had time to diagnose the issue and find that lost HP.


EVERY TIME. Also, my father-in-law's shop won't even build a flat tappet engine without lifters that direct oil the cam (they do this through a small hole drilled in the bottom or a small groove in the lifter that allows oil to seep through on to the cam).

This dyno?

HawkRod is doing the 2023 Hot Rod Power Tour!

Nice! What lake in TN(?) is that? It's North Holston Lake. My picture is not a great shot, but it was really nice. Nice Hawk. Horsepower seems about right for full exhaust. Torque seems a bit high, but nobody would argue with you if you took them for a ride:rofl: As I said, I'm not sure...

www.forbbodiesonly.com

If so, loss of valve control IMO

 

[HawkRod]

This dyno?

http://[URL]https://www.forbbodieso...-rod-power-tour.262286/page-13#post-912558901

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If so, loss of valve control IMO

That's the other thought that came to mind, but my spring pressures are decent: 140# seated and 325# open. And these numbers are for "broken in" springs, not new ones that lose a few pounds after running. It just doesn't seem reasonable that these springs would start losing control at 4900 RPM?

 

[INTMD8]

It's not just pressures but can also be weak pushrods, springs very far away from coil bind at max lift, heavy components (large diameter springs/steel retainers, heavy valves).

Just my guess as my 426 hemi dyno looked just like that when I first got it. (And it suffered from everything I mentioned above.)

 

[HawkRod]

It's not just pressures but can also be weak pushrods, springs very far away from coil bind at max lift, heavy components (large diameter springs/steel retainers, heavy valves).

Just my guess as my 426 hemi dyno looked just like that when I first got it. (And it suffered from everything I mentioned above.)

You know, part of what you said just tweaked my curiosity (in red).

First, yes, ideally a spring should be about .050" before coil bind (at max lift) to minimize spring vibrations and harmonics. Off the top of my head, I don't remember what my measurements were. They were not ideal, but not either terrible. I'll dig up my folder at some point and look it up.

My heads have beehive springs, so they are quite light, BUT, my hydraulic roller lifters are pigs. Maybe? Although I guess those would then necessitate higher spring pressures to keep them in check?

I'm not sure what you mean by "weak pushrods". Do you mean pushrods that are too thin and that flex? Again, I don't remember what I have in my engine, but I'm thinking they are pretty decent.

Regardless, thanks for the ideas and brainstorming - I appreciate it!

 

[INTMD8]

Weight will make MUCH more difference on the valve side.

So lightweight valves, springs/retainers/locks are very helpful. Rocker weight can make a big difference.

Pushrod weight and lifter weight I'm sure can influence things but it doesn't seem to.

So you want the stiffest pushrods regardless of weight or you can get a pole vault effect.

I thought you were flat tappet.

For hydraulic roller, even with beehive I would think it needs at least another 25lb seat pressure and 50lbs over the nose.

 

[HawkRod]

Weight will make MUCH more difference on the valve side.

So lightweight valves, springs/retainers/locks are very helpful. Rocker weight can make a big difference.

Pushrod weight and lifter weight I'm sure can influence things but it doesn't seem to.

So you want the stiffest pushrods regardless of weight or you can get a pole vault effect.

I thought you were flat tappet.

For hydraulic roller, even with beehive I would think it needs at least another 25lb seat pressure and 50lbs over the nose.

Thanks for the thoughts - again, much appreciated!

I have aluminum roller rockers, aluminum Edelbrock heads and high quality stainless valves.

I'm not sure why lifter weight doesn't influence things - the mass of the lifter still has to be stopped and pushed down after max lift on the cam. Regardless, I agree with the spring pressure thoughts and I plan to increase spring pressure a bit.

Having said all that, I still believe the most likely culprit is fuel delivery. This engine combo was owned previously by @qkcuda
I bought the engine from him and freshened the engine since he had it, but his car ran well without these issues. The only notable change since he had the engine is the fuel induction and, of course tuning. Dave used a carb and I am using F.A.S.T. fuel injection. I am also controlling timing through the computer.

I have hijacked this thread enough, but at least I hope others find this discussion helpful regarding valvetrain and cams.

 

[INTMD8]

The lifter and pushrod weight don't seem to influence much as it's moving 1.5 -1.8 times slower and less distance than the valve side. (whatever the rocker ratio is)

 

[HawkRod]

The lifter and pushrod weight don't seem to influence much as it's moving 1.5 -1.8 times slower and less distance than the valve side. (whatever the rocker ratio is)

Great point, and of course I know that.

Ahem: But of course I need my brain to think of these things for it to be any value!!!

 

[INTMD8]

It's not always obvious.

The other effect there is that if it has say 150 seat pressure and 400 open and 1.5 rockers the pushrods/lifters are actually seeing 225/600 lbs

 

[qkcuda]

Thanks for the thoughts - again, much appreciated!

I have aluminum roller rockers, aluminum Edelbrock heads and high quality stainless valves.
View attachment 1756921

I'm not sure why lifter weight doesn't influence things - the mass of the lifter still has to be stopped and pushed down after max lift on the cam. Regardless, I agree with the spring pressure thoughts and I plan to increase spring pressure a bit.

Having said all that, I still believe the most likely culprit is fuel delivery. This engine combo was owned previously by @qkcuda
I bought the engine from him and freshened the engine since he had it, but his car ran well without these issues. The only notable change since he had the engine is the fuel induction and, of course tuning. Dave used a carb and I am using F.A.S.T. fuel injection. I am also controlling timing through the computer.

I have hijacked this thread enough, but at least I hope others find this discussion helpful regarding valvetrain and cams.

Hawk, are you still running the beehive springs?