RB Cam Performing Right?

[gtxrt]

The 108 LCA is not ideal for manifolds.

why is that ? and what is a good lobe center line ?

 

[gtxdana]

Those valve springs with 175# on the seat are way overkill for that cam with hydraulic rollers. A 400# rate and 120# seat pressure would be plenty, which looks like what Howard recommends. You could use a quality 5/16 .080" wall pushrod with those springs.

 

[Road Grabber]

The pushrods were aftermarket Isky but they were rods that I had for many years. You could be right about the spring pressure being too much as they did bend after it was increased after I gave him the motor. I ran it for only about an hour with head gasket issues. Long story.
I gave it to another builder requesting the block deck resurfaced using cometic head gaskets which solved the problem but the new issue rose with bent pushrods and jumped set of lifters. However I wasn’t impressed with the dyno numbers from the runs he did before discovering the bent pushrods.

I’m curious what cam choice mentioned was better for these heads. I would put headers on if that’s a solution. But I also want to be happy with the potential numbers and now is the time to switch if need be.

I spoke to the builder and he wants to test with the stronger pushrods and headers but I also wanted a comparison with manifolds. That would show everything.

I have thought about the possibility of lifters not up to task bleeding down.
I heard Johnson or Gatorman? Lifters are very good if a switch is in the future.

I don’t know what the spring pressure is but I know he didn’t max it out to .060 gap.

 

[PRHeads]

My .02 is, it’s not all that easy to make 500hp from a pump gas 446…….. with exhaust manifolds.
The numbers don’t really seem that out of line to me.

A 446 with TF 240’s, rpm, 700 carb, 1-7/8 headers, and a CompXR274HR roller(538/534, 224/230-110) made:
528tq@4100/482hp@5200
(I feel like 10* more duration and an 850DP carb would have pushed that one to the 500hp mark…….but it’s using headers)

As I mentioned in the other thread, I feel the PR failure was the result of PR’s not up to the task.

*If the heads have the 1.460” diameter spring, and have not been shimmed up to 140-150lbs on the seat, there is likely some valvetrain unhappiness.
If the heads have the 1.550” springs, it should be fine.

I feel like the previous results can more or less be disregarded because of whatever was going on that caused the PR failure.

Put some 3/8” .080 wall heat treated PR’s in and retest……get some good data.

After that, if the primary concern is more power, I’d suggest headers and a bigger cam.

 

[PRHeads]

Question for BSB67….

What did your 505 make with the 6bbl and manifolds?

Then correct the HP/CI for 446”.

Then figure how much you’d lose by swapping out the solid roller for the OP’s cam.

 

[Dave6T4]

Possible valve spring bind. .530" lift, with 1.6 ratio rockers could be more than your springs can handle.

 

[Road Grabber]

check how much preload you have and how many threads do you see on the bottom of the rocker arm adjusting screw before you order new push rods. the spring pressure is overkill especially with that slow ramp cam. wonder what open spring pressure is at.

I did mention about the rocker threads showing. He will double check that. I believe it was two threads showing from memory

 

[PRHeads]

My PR not up to the task story……

30+ years ago I ported a set of 346 heads for a friend to use on a low deck 451 with a roller cam.
I did the porting and selected the parts going in the heads, did the set-up, and supplied the cam.

He had a local builder supply some other parts, and did some amount of assy.

No dyno time, right to the track(dragster).
Failed a couple PR in short order.
The engine builder was pretty sure it was either the springs or the set-up.
I had verified there was no coil bind or retainer to guide clearance issues when I assembled the heads.
My take on it was PR not good enough.

After a bit of back and forth, he was going to pull the heads and have the builder check everything out.

In the meantime, a few PR’s had been ordered to replace the bent ones.

A subsequent call from the PR supplier revealed that the pieces sent for the original order were indeed 3/8” .080 wall, but were not heat treated………and would have been “marginal” in that application.

The full set of PR were replaced with ones def sufficient for the job…….and that was the end of the bent PR in that engine.

 

[Road Grabber]

My PR not up to the task story……

30+ years ago I ported a set of 346 heads for a friend to use on a low deck 451 with a roller cam.
I did the porting and selected the parts going in the heads, did the set-up, and supplied the cam.

He had a local builder supply some other parts, and did some amount of assy.

No dyno time, right to the track(dragster).
Failed a couple PR in short order.
The engine builder was pretty sure it was either the springs or the set-up.
I had verified there was no coil bind or retainer to guide clearance issues when I assembled the heads.
My take on it was PR not good enough.

After a bit of back and forth, he was going to pull the heads and have the builder check everything out.

In the meantime, a few PR’s had been ordered to replace the bent ones.

A subsequent call from the PR supplier revealed that the pieces sent for the original order were indeed 3/8” .080 wall, but were not heat treated………and would have been “marginal” in that application.

The full set of PR were replaced with ones def sufficient for the job…….and that was the end of the bent PR in that engine.

Good input. He’s measuring the actual length needed now. I’m not sure if that will be different from original typical aftermarket length sold because of the head surfacing and decking of the block but it will be for this engine.
I told him use Smith Bros. They are good pushrods made to specs. 3/8 thick wall.
You can’t trust anything new. I did make sure that he checked everything. You can only hope he has the expertise.

I’m suspicious of the lifters bleeding down under pressure. When you remove a valve cover I don’t think a high quality lifter will allow you to move the rockers at all.

I was able to do move some rockers when I checking preload before I brought the engine to the builder when I was having other issues. Doesn’t seem right that I should be able to push rockers down but maybe someone watching this post can add to that.


Thanks for your input.

 

[PRHeads]

I think you’re going to find that most aftermarket performance HR lifters have a fast enough bleed rate that they will bleed down after the engine is shut off when they’re subjected to the spring loads used with the typical performance retrofit cams.

Bleed down(or collapse) while running is often a function of how well the lifter is being refilled, which can be affected by the lifter design, oil pressure, how much air is entrained in the oil, and lifter to bore clearance.
As the rpm increases, the amount of time there is between cycles is diminished.

A good read on HR lifters is in the FAQ section on the Gaterman site.

TF heads have noticeably longer valves than OE, so they need longer PR’s.

I don’t know if this has been brought up before in this or the other thread…….but, were the lifters installed with the correct orientation?
If they’re in the wrong way, the link bars can contact the PR’s.

The correct orientation is the link bars go towards the center of the engine(or facing away from the valley wall).

 

[Road Grabber]

I think you’re going to find that most aftermarket performance HR lifters have a fast enough bleed rate that they will bleed down after the engine is shut off when they’re subjected to the spring loads used with the typical performance retrofit cams.

Bleed down(or collapse) while running is often a function of how well the lifter is being refilled, which can be affected by the lifter design, oil pressure, how much air is entrained in the oil, and lifter to bore clearance.
As the rpm increases, the amount of time there is between cycles is diminished.

A good read on HR lifters is in the FAQ section on the Gaterman site.

TF heads have noticeably longer valves than OE, so they need longer PR’s.

I don’t know if this has been brought up before in this or the other thread…….but, were the lifters installed with the correct orientation?
If they’re in the wrong way, the link bars can contact the PR’s.

The correct orientation is the link bars go towards the center of the engine(or facing away from the valley wall).

View attachment 1967569

The lifters installed correctly. I wasn’t aware of the longer TF valves but the correct number of threads were showing on the rockers adjustment screws. He will measure the distance for pushrods before ordering them and check for side clearance in the head/block.
He did say that a previous engine he did jumped a great deal after he exchanged headers with manifolds.
I want that confirmed and will share the results then make a decision. So far he said 446 hp and 485 torque. It’s torque I would think you feel while driving.
I’m going go back and watch some dyno tests to see if others have achieved high numbers with manifolds. I might be asking too much from the cast manifolds?….

 

[BSB67]

Yeah. At the end of the day there needs to be a lot of extrapolating of my actual experiences and data to draw any conclusions. My stuff is really not that close to what the OP has and therefore not particularly robust for comparison. With that I still stand with what I stated earlier, 500 hp.

Question for BSB67….

What did your 505 make with the 6bbl and manifolds?

The average of the three best runs was 569 hp.

Then correct the HP/CI for 446”.

I don’t know how to do this with any certainty. Data and experiance suggest that the relationship is not proportional.

Then figure how much you’d lose by swapping out the solid roller for the OP’s cam.

I don't know how to do that with certainty either. Also, and as you know I've used a couple different cams and the "smaller" one added about 10 hp, I think. On paper, I would guess that the as-measured-at-the-valve, the 0.050" and full lift numbers are not that different between mine and his. But as you know, I strongly believe that shorter seat timing and faster off-the-seat rate of the solid roller does have a big positive impact on exhaust manifold motors more that the commonly evaluated cam specs. But that's just my opinion. And, his cam is pretty lazy off the seat and has more overlap, hurting him some, IMO.

Also, the 6 pack on my motor was limiting. It is not limiting on his motor. Further complicating any extrapolation from my engine. If he was at 500 hp, I doubt he would pick up 30 hp with a better intake like I did.

I considered the above when I gave my estimate, along with how my 440 6 pack ran, as described below.

For the 440, I do not have J607 engine dyno numbers. And I think we can agree that working backwards from track data is a bit sketchy and everyone believes that their method is better/correct. The specifics of the 440 car are: 4250 lb race weight, 108.6 mph, in good fall air at Edgewater. Moroso puts the uncorrected net hp at 415 hp. From Wallace, reasonable weather correction from those track weather data to the J607 standard is 1.02 or 1.03 correction factor. That puts the corrected hp to 425-ish. But that's still net hp, not gross like an engine dyno. So, what is the water pump, fan, power steering, alternator and compression bent exhaust with 2 1/4" muffler and tail pipes costing hp wise at the track that would not be part of a engine dyno session? I truly believe that 440 hp is reasonable, maybe low.

That 440 6-pack had 10.3:1 CR with Speed Pro pistions, 221 degree cam w/ 0.455" lift. Locally ported iron heads with 2.08 and 1.74" valves. You may recall flowing these heads at 256 cfm at .450" lift.

So extrapolating both up and down from what I have experience with, I'm still on board with the 500 hp.

 

[PRHeads]

As I said previously, all this point…….. I don’t have a lot confidence that the numbers achieved with the flexible PR’s are going to be the last word for what that combo ends up making.

I will say this, my experience has been that in a combo like that……… when the cam is on the small side……… you rarely end up seeing the HP end up being higher than the TQ.
So, to end up at 500hp, you’d be looking to see a TQ number solidly over 500, and then have the TQ curve not drop off too fast after peak.

Have we established that the current power numbers were from actually using the ex manifolds?

 

[gtxrt]

221 degree cam

Didn't that purple shaft cam have 231 duration ?

 

[PRHeads]

I don’t know how to do this with any certainty.

I wasn’t trying to be too scientific.

Throwing some stuff at the wall…….
569hp from 505” is 1.126 hp/ci
446 x 1.126 = 502hp

I’m going to say the SR is an easy 20-25hp over the HR, if for no other reason than the upper rpm potential.

So, I’m calling it 475-ish hp…….. which appears to be 30 or so more than it made while munching up PR’s.

Flat top zero deck 446(KB pistons), RPM heads with prep & bowls done, SD/Holley 850, 1-7/8” headers, 234/240-112 HR.

544tq@4300/518hp@5600

 

[BSB67]

Didn't that purple shaft cam have 231 duration ?

No.
The 231 degrees is the Mopar Performance BS of multiplying the advertised number by 0.85. The 221 degrees is the measured 0.050" duration of the 272 cam.