Roller Camshaft Rpm Range

[Bewy]

I think it is valve train or electrical:
- check for broken v/springs
- what ign system? If dist is electronic & has a magnetic p/up, check the air gap. As rpm increases, so does centri force. If the p/up air gap is too tight, it could make contact at higher rpms with the reluctor & cause a backfire.

The engine will also run MUCH better with about 20* initial timing...smoother idle..... more vacuum.

 

[RustyRatRod]

That's about the same duration as the stock 340 cam. They'd ring out 7K so I'd think a roller of comparable duration would certainly RPM more than a measly 5100. Sounds like a valve spring issue.

 

[BSB67]

It’s a Holley 3310, fuel pressure I don’t know there’s no gauge on it. I’ll probably install one I’m guessing the fuel pressures should stay at constant 6-7 psi even in the upper rpm’s

3.5 psi measured at the carb with 0.110” N&S will support over 550 hp.

 

[TT5.9mag]

3.5 psi measured at the carb with 0.110” N&S will support over 550 hp.

Depends on the flow rate of the pump.

 

[BSB67]

Depends on the flow rate of the pump.

For clarity, as measured at WOT.

3.5 psi at 0.110” defines the flow rate. If the pump has insufficient flow, it will not maintain the 3.5 psi.

 

[TT5.9mag]

For clarity, as measured at WOT.

3.5 psi at 0.110” defines the flow rate. If the pump has insufficient flow, it will not maintain the 3.5 psi.

No, you need more information to solve for flow rate.
Coefficient of discharge, and head pressure or differential across the orifice just to get started.

So like I said, depends on the pump.

 

[BSB67]

No, you need more information to solve for flow rate.
Coefficient of discharge, and head pressure or differential across the orifice just to get started.

The fuel bowl is is at atmospheric pressure, so the dP is 3.5 psi. It is reasonable to assume that the coefficient of discharge will be the same for all Holley 0.110” N&S.

This information was determined by testing, not a theoretical exercise.

 

[TT5.9mag]

The fuel bowl is is at atmospheric pressure, so the dP is 3.5 psi. It is reasonable to assume that the coefficient of discharge will be the same for all Holley 0.110” N&S.

This information was determined by testing, not a theoretical exercise.

Ok so at best we can agree you have a reasonable assumption. Got it.

 

[Slantsix64]

Guys! I’m going to start with fuel first and go from there. Upgrading the line to 3/8 check my rubber hose from tank to the lines etc.also I just realized I have a lawnmower fuel filter before the carb lol. Going to start with the simple stuff.

 

[TT5.9mag]

Guys! I’m going to start with fuel first and go from there. Upgrading the line to 3/8 also I just realized I have a lawnmower fuel filter before the carb lol. Going to start with the simple stuff.

I wouldn’t introduce more variables just yet. Leave the 5/16 line for now. Get rid of the “lawnmower fuel filter” (lmao) and test pressure.

 

[BSB67]

Ok so at best we can agree you have a reasonable assumption. Got it.

You meant to say real test data for which a reasonable conclusion can be drawn.

 

[TT5.9mag]

You meant to say real test data for which a reasonable conclusion can be drawn.

Nope I meant to say exactly what I said. And I used your own words. Reasonable assumption.

 

[PRH]

My .02……
If it occurs at the same point in each gear, sort of like a switch at that particular rpm……..and recovers very quickly after you shift and the rpm drops……. It’s not likely fuel.

My first inclination is “valve float”(some sort of valvetrain instability), but I can also see it being ignition related.

 

[BSB67]

Nope I meant to say exactly what I said. And I used your own words. Reasonable assumption.

So you think that it is not a reasonable assumption that two Holley 0.110” N&S would have the same discharge coefficient.

 

[Slantsix64]

I think it is valve train or electrical:
- check for broken v/springs
- what ign system? If dist is electronic & has a magnetic p/up, check the air gap. As rpm increases, so does centri force. If the p/up air gap is too tight, it could make contact at higher rpms with the reluctor & cause a backfire.

The engine will also run MUCH better with about 20* initial timing...smoother idle..... more vacuum.

I believe the gap is set at .08 with a brass feeler gauge, but I’ll double check. I’m running the stock Mopar electronic ignition.

 

[Slantsix64]

What do you guys think about the Mancini Orange Box they sell? Right now I have a generic auto parts ECU.

MRE - Orange Ignition Control Unit

 

[RustyRatRod]

So you think that it is not a reasonable assumption that two Holley 0.110” N&S would have the same discharge coefficient.

It's totally volume dependent. Let's say one is being fed LESS than it's maximum flow. The other is being fed either it's maximum flow or more. So we know from flow the one being fed more will discharge more up to it's maximum flow rate. Right?

 

[TT5.9mag]

So you think that it is not a reasonable assumption that two Holley 0.110” N&S would have the same discharge coefficient.

I didn’t say that. Don’t put words in my mouth. I said at best you have a reasonable assumption.
I’m saying there is a distinction between making an assumption (reasonable or not) and a scientific certainty.

 

[TT5.9mag]

What do you guys think about the Mancini Orange Box they sell? Right now I have a generic auto parts ECU.

MRE - Orange Ignition Control Unit

Could possibly be an issue but again, don’t introduce more variables yet. Do some TESTING!

 

[BSB67]

I didn’t say that. Don’t put words in my mouth. I said at best you have a reasonable assumption.
I’m saying there is a distinction between making an assumption (reasonable or not) and a scientific certainty.

My mistake. Let me reword it.

Do you think it is a reasonable assumption that two Holley 0.110” N&S would have the same discharge coefficient?

 

[BSB67]

My .02……
If it occurs at the same point in each gear, sort of like a switch at that particular rpm……..and recovers very quickly after you shift and the rpm drops……. It’s not likely fuel.

My first inclination is “valve float”(some sort of valvetrain instability), but I can also see it being ignition related.

I agree with this. But fuel is an easy check.

 

[BSB67]

Could possibly be an issue but again, don’t introduce more variables yet. Do some TESTING!

This we agree on.

 

[crackedback]

IMO, that cam should allow a 360 to make decent power to 5500+, so something is off.

 

[junkyardhero]

i call jobs like these: death by 1000 cuts

tune is out just a little bit: wrong heat range of plugs, or gap; distributor is off a little, pick up clearance, ecu, advance rate/area; fuel is off a little, pump can't deliver at higher RPM, fuel line not adequate, filter is bobo; carb tune is off a little, needle/seat or jets

mechanical is out a little: springs aren't set up right, binding, aren't correct for the application; lifters going into pump up, floating the valves a little bit; carb linkage binding, not attaining full throttle; wrong intake or a severe port mismatch, pushrods too long/short or rockers adjusted incorrectly

and so on, and so forth.

check everything, but most importantly only change one thing at a time! just shotgunning parts at it is a terrible practice. while fixing it on a lucky guess is cool and all, doing the diagnostics and eliminating variables is more beneficial in the long run.

sounds like you're on the right track, you'll get it amigo!

 

[teringer]

Did you dial in the cam it could be over advanced cutting top end