Stocker Cam Lobe Profile ?

[Aubrey N Bruneau]

After splitting one more Comp Cams tool steel retainer on an intake valve, in Mission last weekend... I think maybe I FINALLY get it....
The components being actuated by the intake lobe in my engine, cannot be properly controlled over about 6500 RPM, without inconceivably high spring pressures.
The exhaust is fine. 200 pounds seat does just fine.

What I am learing, is that there are torque engines, IE, Oldsmobile, Buick, etc ( running to MAYBE 6400-6500 RPM through the traps )... and the are RPM engines, IE, small block Chev / large port BBC Chev, etc. ( going through the traps above 7500 ).
The torque engine can make use of the EXTREMELY aggressive ramps of the "dwell" lobes... knowing that valve train control does not become a factor in the upper RPM.
The high RPM engines require more gentle ramps, which often tranlsates to longer durations... which ends up being a good thing because the duration is needed in order to draw the torque curve up a bit, so it's most effective in the higher RPM engine.

The 409 is regarded by many, including my man at Comp Cams, as a torque engine.... yeah, phrases like, "oh that ol' 409 made a lot of torque" !
sure.... compared to a 283 2bbl, I quess it did.
But it's NOT A TORQUE engine. I've known that for decades.
Unfortunately, it's also not really an "RPM" engine either.
Runs hard in production form, and that's about it.

This puts me in an awkward place for cam lobes. I need a more "RPM oriented" ramp... but no so much a large port 427.
The lobes don't seem to exist in the cam world. I've been to Bullet, Crane, and Comp.
I have a "distributor" account with Comp, so, I'm trying to deal with them.
In response to an email I sent to my guy at Comp, in which I described in extreme detail what I had, what was happening, and exactly what I am looking for in a lobe, I have been informed that they have "created" a new lobe for me.
Now, before committing to all this, I was hoping that a few guys could advise me if I seem to have the right idea.... or am I all wet ? ! !

thanks for listening
I'm sure some of the responses will have words that I can't even pronounce ! !
( I often say to friends that "These Stock / Super Stock guys employ technology that makes the space shuttle look like a hay-baler ! )

[Alan Roehrich]

Call Tim Cole at Comp.

Tim Cole
Competition Cams
Performance Accounts Manager
901-795-2400 ext. 575



And 200 on the seat will NOT work on a competitive lobe for your 409. At all. It starts at 250 on the seat, and 525 open.


I'd also strongly suggest Ferrea stainless valves.

Feel free to send me a PM, or an email, and I'll try to help you make your valvetrain work.

[Greg Reimer 7376]

When stuff in the valve train starts going nuts in a Stock Eliminator setting,the first thing you want to do(besides check to make sure that the rocker arm slots are long enough),is to check spring tension. When RPM exceeds the ability of parts to follow each other, studs break, locks come out, valves hit stuff they were not designed to hit, springs go nuts, metal fragments appear around valve train parts, ceramic base lifters shatter with bad consequences,this stuff happens. I used to run a 283 7800 in high gear, never had a problem because I was just lucky,I guess. The 283 had light parts in it. Spring tension was around 125-140 on the seat, 275-300 over the nose.The exhaust valve in a 409 probably weighs close to twice the 283 weight. I would think that the intake would be way worse. That seemed to be the side of the engine you had problems with. I hope it didn't do any more damage to the engine than that.I think that I would start finding out what the big block guys are doing, then move in that direction. I don't remember turning a 409 anywhere near as tight as you do, they really were big torquers . A good 409 would work if you went into the house moving business,that's for sure.

[Aubrey N Bruneau]

Gee, Alan, I have 230 / 470 on the intake. It's seems good to about 7000. Trouble is, the engine is spinning 7200 through the traps now. I have about .065" piston to valve, and I've never seen evidence of the intake valve ever getting close. The exhaust however, at .035" piston to valve, leaves quite a "map" !... though no actual contact.
Where the valve float tell-tale sign is.... is the valve locks. The exhaust are all nice, clean, and black, like they just came out of the package. The intake are ALL scuffed up, hammering the lip off, and "peeling" the groove in the valve a bit.
I respect your guidance completely, Alan... however, this is my third time around in the valve train, crushing the most spring pressure that can be fit in there... and it just CONSISTENTLY goes out of control. I'm convinced that it's simply an inappropriate lobe for the application.

Greg, that is the mis-conception ! ! ! !
A large port 409 is really NOT a big torquer ! The 63-65 340 horse small-port car engine, and the truck engines, have fueled that "big torque" belief... but like an L78 compared to a 366 school bus engine.... it's a VERY different animal.
Oh, my valves are 141 and 124 grams.
I got off lucky this time, as far as damage goes. It DID put a light crack in the num 4 cylinder, which was sleeved from the last time this happened. But it doesn't seem to leak coolant there. The head of the valve broke off, and got tossed through the intake, into num 1 intake runner. No problem there. The stem got bent and knocked up away from the piston. Engine still ran, and I actually limped it at 40 MPH to the finish line.
The valve seat area is a bit of a mess, and that's where the coolant leaked. Not catastrophic though.
As far as RPM.... a 63 425 horse 409 ( I'm allowed that cam ), from the factory, routinely gets shifted at 6200-6300 RPM. The late 64 425 HP engine, which used the Z11 cam, would do 6500.

The cam I'm looking at, stretches my advertised duration on the intake, from the current 290, to 299 ( my stipulation to Comp, was that I wanted to maintain my current duration @ .200" ). My concern is that this will really bleed off cylinder pressure below 5000 RPM.
Am I right to be concerned ?

[Bob Mulry]

Call me crazy....but isn't the 409 a 3.500" stroke or about the same a 350 SBC????????????

Call John Partridge at Bullet Race Cams 662 893 5670 and see what he says????????

Bob

[Paul Precht]

Originally Posted by Aubrey N Bruneau

Gee, Alan, I have 230 / 470 on the intake. It's seems good to about 7000. Trouble is, the engine is spinning 7200 through the traps now. I have about .065" piston to valve, and I've never seen evidence of the intake valve ever getting close. The exhaust however, at .035" piston to valve, leaves quite a "map" !... though no actual contact.
Where the valve float tell-tale sign is.... is the valve locks. The exhaust are all nice, clean, and black, like they just came out of the package. The intake are ALL scuffed up, hammering the lip off, and "peeling" the groove in the valve a bit.
I respect your guidance completely, Alan... however, this is my third time around in the valve train, crushing the most spring pressure that can be fit in there... and it just CONSISTENTLY goes out of control. I'm convinced that it's simply an inappropriate lobe for the application.

Greg, that is the mis-conception ! ! ! !
A large port 409 is really NOT a big torquer ! The 63-65 340 horse small-port car engine, and the truck engines, have fueled that "big torque" belief... but like an L78 compared to a 366 school bus engine.... it's a VERY different animal.
Oh, my valves are 141 and 124 grams.
I got off lucky this time, as far as damage goes. It DID put a light crack in the num 4 cylinder, which was sleeved from the last time this happened. But it doesn't seem to leak coolant there. The head of the valve broke off, and got tossed through the intake, into num 1 intake runner. No problem there. The stem got bent and knocked up away from the piston. Engine still ran, and I actually limped it at 40 MPH to the finish line.
The valve seat area is a bit of a mess, and that's where the coolant leaked. Not catastrophic though.
As far as RPM.... a 63 425 horse 409 ( I'm allowed that cam ), from the factory, routinely gets shifted at 6200-6300 RPM. The late 64 425 HP engine, which used the Z11 cam, would do 6500.

The cam I'm looking at, stretches my advertised duration on the intake, from the current 290, to 299 ( my stipulation to Comp, was that I wanted to maintain my current duration @ .200" ). My concern is that this will really bleed off cylinder pressure below 5000 RPM.
Am I right to be concerned ?

Hi Aubrey, The intake valve chases the piston and will never hit it unless V to P clearance is non existent or something is really out of wack. Valve float will make the exhaust the problem. If you have twice the clearance on the intake as the exhaust your cam is retarded quite a bit which could be causing the lack in torque.

[pmrphil]

Aubrey, it seems that you have discovered the problem (valve float/lack of control) and Alan has confirmed it also - a bit more spring pressure, a better (or lighter, if possible) valve, maybe a different type of spring, too? You say it's good to 7,000, but I'm wondering if with all the problems you are having if it's possible it's starting earlier and is not quite yet noticeable? Without a doubt, lack of valve control requires more spring to correct it. Good luck.