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.

[Paul Precht]

A 3.5" stroke is almost identical to the 350Chev, not a big torque motor, add to that, big ports and two fours, not good. A smaller duration, less aggressive cam with a bit of advance would be something I would try if it were me. With a four speed, you should be able to run 125 MPH and keep the engine at or under 7,000 RPM with the proper gearing and cam timing.

[Alan Roehrich]

Aubrey, so long as without lash, the clearance between the intake valve and the piston is greater than the clearance between the piston and the head, you have plenty. In other words, if you have 0.055" piston to valve, and 0.045" piston to head, you're good.

On the exhaust, you need about 0.075". The piston chases the exhaust valve shut, and the exhaust valves are known for bouncing on the seat. Yes, they'll show a light spot in the carbon on the face of the valve and the top of the piston. If you want to go fast, that's what you do.

Yes Aubrey, you need at least 250 on the seat, and 525 open, you need the same pressure, and the same parts, that we run on a 396/375, or a 427/425.

You really need about the same lobes as we run, you're allowed 0.507" and 0.519", you can run the same lobes, and use pushrod length to kill off some lift on the intake.

I'd take a wild guess and say a good starting point for you would be 254/266/108, in at 106. You might try a 107 LSA, in at 105, to move the power band down.

The Ferrea valves I run in a 427/425 iron head should work, they'll "adjust" the diameter.

[Aubrey N Bruneau]

I knew you guys would like this subject !

Yes, short stroke... VERY quick revving.
Phil, it IS good to 7000..... it's the 7400 that it saw on my fastest qualifying run... which BTW, seems to be a pattern. The higher RPM range DEFINITELY had the car going better speed and ET ( though 7400 was NOT deliberate ! ).

If I shorten duration, and / or advance the cam, I'll have to rely on this thing becoming a mid-range torque monster, in order to achieve that elusive 125 MPH. It won't do it.
Paul, when we went back to back on the dyno, and the cam was retarded 4 degrees, the engine torque curve moved up, but didn't change numbers. Peak HP jump by 18, and the engine hung at peak HP through 6700 RPM. It doesn't lay down... and I LIKE THAT ! ! ! !

My cam may be a little "out there" already, Alan ?
264 / 272 @ .050", on a 108.
I've contacted Ferrea a few times about making valves for me.... they flat out REFUSE.
2.20" / 1.735", but about .100" / .125" shorter than BBC.
Spring installed height is also much shorter than BBC... it's basically the same as small block. My current spring was Comp's strongest beehive, with a 11 gram tool steel retainer. Shimmed stffer on the intake, the spring was almost stacked.

At this point now, I'm willing to give up 10 potential HP, by using a softer ramp intake lobe. Due to recurring disasters, this engine's cylinders are right at ..074"- 075" over.
In addition to this, due to multiple repairs, and grinding that has gone on with these heads, they would no longer pass tech. I have another pair of virgin large port castings... actually they are the "better" 583 's. I don't want to take chances with the them.