Stump puller or Old Faithful?

[Stripes]

Hi Cliff,
My 469 with the 7k3 heads and the very mild cam finally broke a valve spring and its time to replace the heads and move to a hydraulic roller.

I plan to use a set of d-port Edelbrock 87cc non ported heads on the 469, iron intake, long branch exhaust. Stock crank and cast pistons.  My 69 Firebird convertable weighs about 3300 lbs, has a 700r4, 3:55 rear gears, a 2200rpm convertor, and a quadrajet.

I know you like more duration in a big 469, and a wider centerlines. So, I'm torn between a 230/236 @50 hyd roller on a 112CL, or a 236/245@50 on a 114CL for a street fun type vehicle, not a race car. So really the stump puller or the old faithfull? I've got power brakes, AC, and power steering.

I feel like the 230/236 would be enough duration, but with my past issues, I'm unsure.

[Cliff Ruggles]

What is the compression ratio going to be?

[Stripes]

455 .60 over(4.211), stock 4.21 stroke, flat tops, 87cc aluminum chambers, .045 compressed head gasket, estimated compression 10.12-1 with 0 deck clearance and 8cc flat tops calculated.

I didn't build the engine and don't have the old heads off yet, so I don't know deck clearance, but I will check it before I order the heads. I suspect 10-1 compression is a good estimate. (using Butlers compression estimator) If the pistons are down .020", then 9.74 to 1 is likely the lowest it could be.

I'm also considering a performer RPM intake. But that is easy enough to swap back and forth between the factory manifold. I know you indicated the factory intake was the best, but I'm unsure if the performer rpm was out at the time?

[Cliff Ruggles]

I dyno'd my iron intake, an HO (re-pop), and an RPM back to back on a 500hp engine.

All were port matched to a stock intake gasket.  The HO made 487hp, the RPM 491hp and the iron intake made 497hp.

Yes, it made MORE power than the taller and difficult to fit under the hood RPM intake.

So to at least 500hp no need for the RPM intake. 

I'll also add here that when you shove the carb up closer to the hood and start adding parts like drop base air cleaners/shorter air filters and such for clearance, they can rob even more power.

Plus it takes a little "cobbling" to use the RPM, throttle cable bracket needs shimmed up, hard fuel lines woln't reach the carb inlet, etc........Cliff

[Stripes]

OK, the iron manifold lives on.

Regarding hydraulic roller camshafts for this 468 edelbrock D port headed (251@.500 I) engine with long branch manifolds, I feel like I have narrowed it down to 3 cam choices. I realize all will function, its just a struggle knowing how much is too much or too little.

1. 230/236 @.050 on a 112 with .510/.521 lift
2. 230/236 @.050 on a 114 with .510/.521 lift
3. 236/242 @.050 on a 114 with .520/.540 lift

Which or what would you recommend?

[Cliff Ruggles]

Those cams are pretty small for HR's.

I tried one smaller 230/236/112 HR once, it did OK (will attempt to attach the dyno sheet), but not nearly as well anyplace as the larger custom grinds we typically use with .361" or .380" lobes.

For that reason if you are sticking with smaller lobes and a lot less valve lift/movement I'd go with the larger 236/242 cam on a 114LSA......Cliff

[Stripes]

Thank you for your input.

The plan intially was to go with the Stump Puller,  230/236 dur @ .050" lift .590"/.592" lift with 1.52 ratio rockers 112 lobe sep. However, the Edelbrock D port heads only allow .575" lift before bind in the out of the box  configuration from them. Butler and SD are both 8-10 weeks out to sell any heads with a port job or improved valve height, so I fell stuck with the lower lift comp cams. i dont have 2 months to wait for parts.

[Cliff Ruggles]

Nothing at all wrong with the smaller lobes, but keep in mind they are smaller cams even though they will share the same .050" specs on paper. 

The larger lobes will have more effective duration everyplace, so act quite a bit bigger.  If you are trying to keep up with them for power it's going to take a few more degrees duration.  Since they don't make (at least as far as I know) bleed down HR lifters idle quality will suffer just a tad with the longer seat timing cam.

If you want to mimic the power of the Stump Puller choose lobes with another 5-6 degrees @ .050" and at least as much at .006".  Keep the lift well under what the springs can handle, or down around .520-540".  Pushing it out on a 114LSA will help just make sure to put the ICL at 109-110 degrees so it's not "lazy" at low RPM's........Cliff