Stocker Cam Lobe Profile ?

[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.

[Alan Roehrich]

Originally Posted by 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.

Aubrey, I can get the valves made, and you can actually use the extra 0.100" installed height. I can have them made from the same blanks my valves are made from. Do not worry about getting the valve stem shortened. You adjust for the longer installed height by using a longer pushrod and a longer rocker stud, if necessary.

What is the largest diameter valve spring you can fit on the head without cutting the spring seat? If you can get a 1.540" or 1.550", that's ideal, if not, we can make something work.

What is your current installed height? You need at least 1.850 or so, if you have 1.750", which is small block height, then 0.100" to 0.200" longer valves would work much better. Between 1.900" and 2.050" is ideal. The right retainer and/or keepers can make that happen.

I'm not at all a fan of the beehive valvesprings for what you're doing. There are regular valvesprings that are a known quantity, we KNOW they'll work with the lobes you need, and with the valves you need, and they'll work at 8000 RPM.

By the way, with the modern lobes used on the really fast 427 Chevy Stock Eliminator engines, that cam is huge, no one I know running a 427/425 runs nearly that much cam, and they're turning 1000 RPM more than you, and making more HP. If you need more RPM, you can spread the LSA out to 109, or even 110, that will let it carry further without nosing over.

[Greg Reimer 7376]

Aubrey-- I put BBC valves in the 3814690 409 heads a long time ago.I still have the complete engine I did it to. Trim your guide bosses for a positive type seal(no O ring ),install a 2.19" BBC valve,use a BBC stock eliminator type spring,retainer and lock, then use a 1.72 BBC exhaust valve.A 427 3/8' pushrod with a stock rocker works on the intake, and the 409 3/8" pushrod for the exhaust will put you in the infield of the ballpark.There is a century or two of stock eliminator engine building experience on this forum trying to help you, we all like your car and want to see it absolutely fly. It does sound like your cam is about 6 degrees retarded. You need about .060" minimum P/V clearance on the intake, and .090-.100 on the exhaust.More spring tension on the exhaust will eliminate the bounce. If the engine goes flat above a certain point, I would blame the exhaust springs, if it putters through the intake, then that's the one with the low spring tension. Also, dyno results don't always carry through to the track. The best dyno is the drag strip.

[Aubrey N Bruneau]

Been there, and done all that, Greg ! On my old 64 Pontiac convertible, that's almost exactly how my heads were done. I sold that car to build this one !
One thing is for absolutely sure... there is no possible way on earth that I could achieve .100" piston to valve on the exhaust, without taking 20 degrees dutration out of the cam, and milling the piston a WHOLE lot !
It's all good... really. and the trouble is that it never really does "nose over"... especially down at sea level in Mission. Exhaust valve is always good... but probably due to a much more gentle lobe. No bounce.
It's just the damn intake.
BTW, the track... sea level ( as opposed to dyno )... yes, that was a lesson !

Alan, much longer valves create a new problem in geometry... particularly on the exhaust valve, because of the angles of the rocker stud in relation to the valve. Not ideal at all.
Not to mention, I already have my valves sunk into the heads at least ..050" deeper than stock ( piston to valve is a real problem )... so longer valves would be way up there.

Good news is, yes, I can fit 1.55 spring. That was my old combination.
Results were the same.
Maybe I should mention that my heads, at .510" lift, flowed 288 / 212.
Certainly not the potential of a large port BBC.

The right retainers and keepers ?
yup.... been chasing that one for a while !

When I first started racing the Firebird, I changed the rear gear in it. The first time I ran it at the Etown national event it started popping and banging at around 6700. Around 100 ft before the finish line. After the race I checked the valve springs. Found them to be at 200 and 380 open. Bingo! I thought. Changed the springs and retainers. Had 450 open. The next race I almost able to get to the traps ! I figured what is wrong now. When I got home I was going swap a fresh engine anyway.
When I took that engine apart to get the cam and lifters and other assorted parts, I found 3 loose pucks on the bottom of the lifters. The camshaft was a Bullet. I checked the numbers on the cam for the lobes. When I looked up the lobe profiles, the were dwell torque lobes . When I asked John Partrige about this, he told me those lobes were never meant to run over 6500. He told me that I need a asymmetrical rpm style lobe. So I ordered one from him. The cam he sent me went to 7400 with no problem, and I never broke any valvetrain after that. You are on the right track, sounds like you need a profile change.

[Paul Precht]

Originally Posted by Aubrey N Bruneau

Been there, and done all that, Greg ! On my old 64 Pontiac convertible, that's almost exactly how my heads were done. I sold that car to build this one !
One thing is for absolutely sure... there is no possible way on earth that I could achieve .100" piston to valve on the exhaust, without taking 20 degrees dutration out of the cam, and milling the piston a WHOLE lot !
It's all good... really. and the trouble is that it never really does "nose over"... especially down at sea level in Mission. Exhaust valve is always good... but probably due to a much more gentle lobe. No bounce.
It's just the damn intake.
BTW, the track... sea level ( as opposed to dyno )... yes, that was a lesson !

Alan, much longer valves create a new problem in geometry... particularly on the exhaust valve, because of the angles of the rocker stud in relation to the valve. Not ideal at all.
Not to mention, I already have my valves sunk into the heads at least ..050" deeper than stock ( piston to valve is a real problem )... so longer valves would be way up there.

Good news is, yes, I can fit 1.55 spring. That was my old combination.
Results were the same.
Maybe I should mention that my heads, at .510" lift, flowed 288 / 212.
Certainly not the potential of a large port BBC.

The right retainers and keepers ?
yup.... been chasing that one for a while !

Hi Aubrey, advancing the cam 4 degrees or more would give you a significant increase in exhaust V to P clearance and much more mid range torque.

[Robert Swartz]

Originally Posted by A56

Aubrey,
There is no rule that you have to have the most agressive lobe to go fast. There are so many Stock Elim. combinations that simply cant use an agressive lobe, usually due to VP clearances. I for one can use any profile I want on my Mopar 340, but you would laugh at small of a cam im using in the engine right now. Im using the header to draw the air into the engine, something you might want to consider doing. If you cant spin the engine to 7400 without problem, simply dont do it. Try to make more power in your usable RPM. I myself if I was in your shoes would keep your current lobes, or even go smaller or softer, then build a small set of headers. The engine still might sign off at 7200, but who cares. Try to make more power and TQ down low and in the mid range. Usually in our Stock combinations we dont have the cylinder heads to support high RPM anyways.

Mark Lelchook
F/SA #764

I'm not the tech expert that many on this forum are. For consideration sake, I'd explore this avenue. I bought some parts in Ohio from a guy that runs in I/SA, yes, it's a sbc. He told us he was running a real aggressive, big cam. After talking with people running similar combinations. He found that changing to a smaller cam, different headers, his car actually picked up. Food for thought. I'm finding stock to be much more challenging than running brackets. I don't even have a car ready for the track yet!

[Billy Nees]

Originally Posted by A56

Aubrey, Im using the header to draw the air into the engine, something you might want to consider doing. If you cant spin the engine to 7400 without problem, simply dont do it. Try to make more power in your usable RPM. I myself if I was in your shoes would keep your current lobes, or even go smaller or softer, then build a small set of headers.

Mark Lelchook
F/SA #764

I've been wasting my breath saying the same thing for years. It's nice to see that another header guy is thinking the same way that I do. I don't know just what that says about you though Mark.