When do you 'need' to go to roller rockers?

[401 Pacer]

Am gonna build a hot 401 and am wondering at what cam level are roller rockers advisable?

I don't subscribe to the "hang every hot rod gizmo on an engine for bling bling's sake" Usually you can build an engine on a REALISTIC budget that is plenty strong and durable for the REAL WORLD.

The application will be a Pacer (duh!) with an autotragic trans. Gonna have me sum air conditioning too. Am looking more for tire melting torque than a 10k redline. Not sure what rear end ratio yet, but it'll be pretty lame.

Am going to just clean up the ports and valve pockets, maybe CC the heads, throw a Perf RPM Air Gap on top with probably an Edelcrock carbonator (or for goofyness' sake, a Thermoquad).

Will plumb some twice pipes and wuz wonderin if stock manifolds would suffice. Pacer's used a specific left manifold....and I don't think anyone offers off the shelf headers that'll fit this chassis (rack and pinion steering dontcha know).

Comments-insults gladly accepted. Thanks

[jeepsr4ever]

My rule of thumb is lift of over .540 and a duration of over 240

[Dusty]

you might look at the edelbrock shorties they may fit big may fit but they are the tightest set fit into the same space as the stock manifolds

[fuzz401]

My rule of thumb is lift of over .540 and a duration of over 240

boy I am screwed my cam .500/.510 lift duration @.050 = 246/250 and I have roller rockers

but then how much power can a 401 make with a little cam that pushes a brick wall on a 4" lift with 33" tires down the 1320 at 12.05 to 12.45 :!:

[jeepsr4ever]

My rule of thumb is lift of over .540 and a duration of over 240

boy I am screwed my cam .500/.510 lift duration @.050 = 246/250 and I have roller rockers

but then how much power can a 401 make with a little cam that pushes a brick wall on a 4" lift with 33" tires down the 1320 at 12.05 to 12.45 :!:

:t:

[Mudrat]

My rule of thumb is lift of over .540 and a duration of over 240

boy I am screwed my cam .500/.510 lift duration @.050 = 246/250 and I have roller rockers

but then how much power can a 4=banger make with a little cam that pushes a brick wall on a 4" lift with 33" tires down the 1320 at 12.05 to 12.45 :!:
Not bad for a 4-banger there Fuzz :!: :t:

[401 Pacer]

My rule of thumb is lift of over .540 and a duration of over 240

That must be a huge thumb or a teeny rule! :-)

So, what cam(s) would you recommend for a torque monster....

Mildly ported heads
Performer intake (would like an air gap for the looks as long as it's not too big a mistake!)
Stock exhaust manifolds (headers aren't available or easily installed on Pacers) with dual exhaust
HEI ignition
Oiling system mods
998 trans (non lock-up)

Rear ratio not set yet, but am thinking around 3.23, maybe as low as 3.54 if those are available for a model 20

Pacers weigh about 3,000lbs

Wouldn't mind a lumpy idle, as long as it pulls like an electric motor (torque from zero on up!). I don't want to run a loose converter so am somewhat limited to how radical the cam is.

All suggestions, corrections, cussing and insults most welcome!
Thanks!

[401 Pacer]

bump



(no, that wasn't my head)

[AMX69PHATTY]

Cams are a tough topic. Seems a lotta folks use the Summit Cam & Lifter kits. Clevite / Elgin also sell some AMC Cams. Comp Cams Catalog shows what RPM range there cams are for. Overlap I think is the thing that causes lopy idle and what RPM range the motor makes torque at, low overlap = low rpm power.

[401 Pacer]

Thanks for the reply, called Comp Cams (generally my favorite cam company) and they couldn't give me a clear answer either....got the impression they were pushing for the Extreme Energy cams, but those have an awful lot of lift and quick ramp rates (they open the valves fairly violently).....I don't want to modify the valve train too much....would prefer to stick with standard rocker arms and stay away from monster springs.

The other thing is that my exhaust will be relatively restrictive (stock manifolds, dual pipes)....so that's another critical factor.

ARGH! I hate selecting cams cuz I always go thru these mental gymnastics

[ironman_gq]

Try Engle they have cams ground specifically for AMC engines not just a chevy grind on an AMC blank. Give them a call they should be able to help you out.

[82Waggy]

At what lift do your heads flow the best? Stock heads don't gain much after about .450 lift. Mildly ported typically top out at around .500".

Ramp rate is the name of the game for an AMC. Since they have large diameter lifters than say a chevy, you can accelerate the valve alot quicker and get more curve. Engle has some good stuff for AMC's - more appropriate than most other grinds.

All BS rules of thumb aside, AMC's are not as undervalved for their displacement as alot of others and therefore don't need as much overlap as say a BBC.

How much compression are you running and what is the real rpm range of your build?

[82Waggy]

Delete

Geez, what happened?

Posted the same thing three times!!!

[82Waggy]

Delete Multi

[401 Pacer]

Welp, my plan is to build a relatively mild beast...with the intention to make gobs of torque as I prefer my engines to last (high rpm is what stresses engines, not power levels)

Head work will consist of removing any flash or obstructions and matching intake ports to the gaskets...am not going to go hog wild and remove half the weight of the castings! LOL Will blend the bowls and knock down any sharp edges in the combustion chamber.

I don't expect to run more than 9.5:1 CR. Rear end ratio won't be any lower than 3.73ish, more likely closer to 3.23 (or whatever model 20 ratios that are close).

STOCK exhaust manifolds
DUAL exhaust, no catholic converter....probably 2.25" or 2.5" diameter
Stock stall speed torque converter
HEI ignition
Performer or Performer Air Gap intake
Edelbrock AFB or Thermoquad carb
Typical oiling system mods
Stock valve train (within reason) would prefer to retain stock rocker arms if this isn't a major mistake.

In a nutshell, a careful stock rebuild with the noted improvements....not going racing! Just want reliable long life with extra power. Idle quality is not important, a lope would be nice to perk up passerbys. Thanks!

[AMX69PHATTY]

Roller Rockers free up some "free" horsepower due to less friction from the roller bearings instead of metal rubbing against metal at both the valve tip and rocker knuckle, and therefore they also generate less heat than stock stamped steel rockers and rocker knuckles. They also allow for adustment to the valve lifter preload. If buying new, might as well go ahead and get 7/16" studs, which helps to stabilize the valve train. If the heads are '74 or newer, then the rocker mounting bosses need to be machined down by about 3/8", pushrod guide plates must be purchased and installed, and hardened pushrods must be used. If the heads are '73 or older they're already set up stock for screw in studs and no guideplates are required. Either way roller rocker costs can be a little much. Harland Sharps are nice pieces, they even sell bolt-on type for the late model heads that require no guide plates. Cost is a wash compared to the extra parts and machining to modify late heads for screw in studs. A member at amcforums.net is a Harland Sharp dealer and offers very competitive pricing, think user name is Hornet X.

[401 Pacer]

Yep, I unnerstand about all the goodnesses that rollers give you, but for the power level and cheap-bastard criteria I've set forth there's no way they're worth the money (the total cost of converting to rollers...parts and labor)

Rollers only really shine when you're running gobs of lift and expect to be revving the bejesus out of it. I'd prefer to keep the lift below .450 and the revs no more than say 5500. This should allow it to last forever plus a couple of hours. Big duration/lift cams need big (high tension) springs....while heavy springs are needed to prevent valve float (and loss of power) they exact a parasitic loss unto themselves....something that many seem to overlook or forget. This power drag on an engine that won't see the higher revs that those springs were intended for is ridiculous.

Unless I intend to race, I ALWAYS run the lightest spring tension I can get away with. This is turn lightens up all the other valve train bits (pushrods, rockers, retainers, longer lobe and valve and seat life). Just uncommon common sense to me.

Bottom line is that the secret is in the sauce and PROPER combination of parts. To blindly throw higher performance parts onto an engine when they're not needed is a waste....I prefer to get wasted other ways LOL!

So unless the stock rocker arms tend to break if you stare at them too hard, I'd prefer retaining them and run a milder cam. Does anyone know what the max lift and spring tension that stock rockers can tolerate AND LIVE a reasonable life? TIA

[AMX69PHATTY]

Will they be stock Stud mounted rockers, or late model, '74 & up, bridged ?
Stock aluminum bridges with stock springs are prone to breakage as I understand.
I'm with you on the rollers, rpm's, losses, and cost.

[401 Pacer]

Yup, '74 and up...aluminum bridge style. As I said before, while I'd prefer to stick with stock I won't do so if they can't handle much more lift than stock without failing....that's even more wasteful than spending the money on converting to roller rockers!

[AMX69PHATTY]

Do believe there are replacement bridges made out of steel availble, maybe even from BullTear.

[401 Pacer]

Thanks for the tip....found them...but after crunching some numbers the cost of the rockers and bridges comes real close to rollers! The only difference at this point is the labor to mill the rocker bosses and the price of the studs....but then why stop there? Guide plates and gold plated pushrods will get thrown in next! I really need to get my Crystal Ball fixed so I can pick the winning lottery numbers to afford all these trinkets!

[jeepsr4ever]

Thanks for the tip....found them...but after crunching some numbers the cost of the rockers and bridges comes real close to rollers! The only difference at this point is the labor to mill the rocker bosses and the price of the studs....but then why stop there? Guide plates and gold plated pushrods will get thrown in next! I really need to get my Crystal Ball fixed so I can pick the winning lottery numbers to afford all these trinkets!

No sh#t huh!!

[1980_Cj7]

AMC= Adds More Cost.

Hey, I just realized MC's nickname is the last two letters of AMC. (And I'm not linking that in any way to the statement above, just found that interesting and cool. But don't mind me, I'm a little slow in catching on.)

[401 Pacer]

Hell, not counting my middle name, my initials are the first 2 letters of AMC!

Now someone come across with some free roller rockers, guide plates and pushrods....and no one gets hurt :razz: :sa: :t: =D>

[Dusty]

ive got a comp 260 that is .447 lift that i would gladly give away, its coming out of my 401, used but with no flat spots about 15k miles on it.....

:lo1l:

you want the valve springs too?

if i had lower compression id be in better shape but the higher compression its just not enough cam opted for the crane 272 and im tickled to death

running stock bridge rocker arms

[401 Pacer]

Thanks for the kind offer but I think I'll pass. Your generosity is much appreciated just the same!!