Dusty
My question is How much can the rockers and bridges take lift wise.
I would love to put my .512/.525 228/234 dur@.050 112 lobe sep 284HDP cam from crower. It worked really good in my old 401 in a wagoneer, towed great, cruised really well down the highway, didn’t heat up and man when you kicked down from cruising at 2200-2500 rpm to passing gear and hit 4000 rpm you were really moving….. BUT since this motor doesn’t have the rear oil line upgrade as well I don’t know if she has much for bottom end upgrades like ARP rod bolts or anything
I think I’ll put that stick into the big motor when I get around to rebuilding it. In the mean while I would like to get her as close to .500 lift as I can and possibly a hair over.
Maybe a cam with a profile like .490-.495 / .500-.510 222-224 / 226 dur@.050 on a 112 lobe separation ballpark??? Even the old Summit 8601 has about the right gettiup fort what im thinking
Truck is a 1979 Cherokee, 4.10 gears, 9.8:1 CR, performer intake and edelbrock 750, running a 260 comp cam... 32" tires
I’ve even thought about swapping the performer intake for the air-gap I have sitting here but the performer seems to provide better drivability (port velocity down low) so im thinking get a cam that moves the torque curve around, I can care less what peak rpm is available just want peak torque when I need it and the power how I want it.
What do you think, can the rockers and bridges take it, with the 260H comp cam and springs would a spring swap be necessary if I keep her below .500 lift or right at. Spring swap isn’t a big deal just picking brains right now as I start thumbing through the cam book catalogs again.
Usually i would pickup a set of 360 heads with studs swap em on and rock and roll but this engine is just to clean to molest like that. thinking just a cam swap
thanks
DD #-o
KJMac
I've been told that .510 is the absolute max for the rockers. It is hear say though so keep that in mind!
82Waggy
If it is stock compression and short gears with stock tranny, try an Engle 5052 or 35018. You will need to check retainer to seal clearance.
Dusty
9.8:1 CR is what i have.
The 5052-H
.489"
254¬? adv dur
.305" cam lift
209¬? dur@ .050
112¬?
35018-h
.466"/.496"
248¬?/260¬?
.291"/.310"
207¬?/216¬?
112¬?
Ahh with the specs i put above both the cams arent far off from what the 260 grind is, they are a little smaller than what ive got. Im actually shooting for larger especially with the 401, something that will open up my rpm range so that im not falling on my face at 4000rpm
the lift numbers are good if that is the max that the bridged rockers can take, but im thinking a dur @.050 closer to 222/226 might yeild an rpm range window closer to what im shooting for. Like is said i had the crower cam 512/525 lift 228/234 dur@.050 112 lobe seperation that was just a hair lopey but darned close in performance to what i want again with the same drivetrain setup, but since i dont have stud heads on this motor i need to figure out how close i can get to that cam profile without eating the rockers.
So from what ive heard locally and over the net .500-.510 is about the max the bridges can take. still trying to figure that part out.
Thanks
DD
82Waggy
Need to know a little more about your setup.
What kind of vehicle is this engine in?
Rear end gear ratio?
How did you end up with 9.8:1cr?
Stock heads or have you deburred the runners and port matched?
Dusty
im a bone head im editing the specs as you were replying .... ha
laugh at me later.
Truck is a 1979 Cherokee, 4.10 gears (possibly going to 4.27s) TH400/QT, 9.8:1 CR speed pro pistons (actual ratio is 9.72:1), port matched, balanced aseembly with ARP rod bolts, headers, performer intake and edelbrock 750, running a 260 comp cam... 32" tires
I had to call the original builder of the motor to find a little more out.
When i posted it i must have forgotten to paste in the last paragraph. Go figure no wonder i was scratching my head.
Thanks again for the input
DD
Dusty
big bone head #-o
82Waggy
Well, If you are running a 260H cam now and are looking for more RPM, adding ten degrees more duration would run the point at which peak torque is produce up about 500rpm. With 9.8:1 CR and your low gears you could probably handle a 270 duration cam without much if any bottom end torque loss.
Going from an LSA of 110 to 112 would also help widen the torque curve some.
If your heads are at or near stock, there is not much flow to be gained on the intake side above .424 lift. If you deburr the runners and port match to the intake manifold it may be worth lifting the valves to around .470". You would need to do a lot of port work to get much additional intake flow above .500 with stock heads - though the exhaust seems to flow pretty well at .500 lift.
Sorry, but I do not know what the lift limitation is for bridged rockers and stock valvetrain.
