Lets choose a blower cam

[Paul_G]

Time to get the teeny cam and valve springs out and put in something that belongs there. When I put this 440 together it was just supposed to be temporary since the engine in the car was hurt. Well, now it is going to stay.

What it is;
69 Road Runner convertible
1976 440 truck engine, iron heads, fresh rebuild to stock, ring gaps opened to max spec.
OD automatic, LU converter speced @ 2800 stahl
410 Dana
F1 Pro Charger, making 10 PSI when over 4000RPM

This is a street cruiser not a race car. Dont want anything radical, just a cam that will let the engine breath and sound good.

I had this cam so it went in to the engine when I rebuilt it, like I said, it was supposed to be temporary.
Comp XE256H-10, 212/212, 0447/.455, 110 LSA

 

[PurpleBeeper]

I’ve never run a supercharger, but I think you need stiffer valve springs to keep the valves closed under boost. I believe low overlap helps maintain boost as well (?)

 

[dvw]

Wide lobe center and extra exhaust duration. My blown 340 from memory is around 245/255, 540/560 112 lca. For years it had 214/224, 447/467 114 lca. The bigger cam with a looser converter was worth .7 in ET and 5 mph. Drives the same on the street. Even when it had a tight converter it drove good. With the bigger cam and tight converter, it was no quicker in ET but was still the 5 mph faster.
Doug

 

[PRHeads]

Crower 271HDP(32242) or 282HDP(32243).

It will need real valve springs.

 

[Paul_G]

Crower 271HDP(32242) or 282HDP(32243).

It will need real valve springs.

I was hoping you would chime in. Yea, I beleive valve springs is the issue. Sympton is below.

Low compression 1976 440. Has been rebuilt using stock pistons, new rings and bearings. 452 heads with unknown springs. It has a smallish Comp XE256H cam, 212/218 @50, .447/.455, 110LSA. I had this cam and lifters so they went in the engine.

The car this engine went in has an F1 Procharger in it making about 10 PSI max. Now here is the problem. Just over 5000 RPM, full throttle, the engine has a rapid fire pops out of the carb. Otherwise it performs really well. Runs smooth, pulls hard. Idles like stock.

The trans wont shift yet at 5000, so I cant really flat foot the throttle. Been all over the thing trying to figure out the popping. AFR at WOT in the mid 11's. Timing from 2500 on up is 29°. Best I can come up with is weak valve springs lifting off the seat.

I talked with three cam companys yesterday, and this is what they each suggest.

>Comp; K21-224-4 233/236 Duration, 488/491 lift, 110 LSA. And they have a kit with cam, springs, keepers and locks, and timing set. Makes it easy.

>Howards; 721941-12 224/234 Duration, 518/543 Lift, 112 LSA. He gave part numbers for springs and everything else.

>Snyder Cams; Not much info from this guy, 284 Duration, 465 Lift, 114 LSA.

<Comp knows this is a blown application yet only suggests a 110 LSA? Makes any difference? I am not sure.

<Howards has a wider LSA @ 114, but that lift may be a little much. ????

<Snyder has a huge duration number and smaller lift on very wide LSA @ 114. Such a radical ramp for flat tappet?

The Crower 271HDP lands right in the middle. 222/234 Duration, 486/496 Lift, 112 LSA. I will call them on Monday and get part numbers for springs and lifters and keepers and locks.