351c roller rockers

Tony8470

Registered User
Well. I'm still in a rush to finish my engine because of my brother. Another story all in itself. And I have been cut short of plans on it.

Who all has 351C rockers and which ones are adjustible? I'm about to get a set of heads back that have NOTHING performance wise done to them:mad::mad: . And I want to at the very least get some adjustable roller rockers for them.

Do THESE look compatible?
 
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Tony8470 said:
Well. I'm still in a rush to finish my engine because of my brother. Another story all in itself. And I have been cut short of plans on it.

Who all has 351C rockers and which ones are adjustible? I'm about to get a set of heads back that have NOTHING performance wise done to them:mad::mad: . And I want to at the very least get some adjustable roller rockers for them.

Do THESE look compatible?

I have those type of rockers, but they are 1.8:1 ratio. The heads need to be drilled and tapped to accept the stud (3/8-16?? not sure).
 
Don't waste your money on adjustable rocker arms for stock heads. In fact it is an entire waste of money to use roller rocker arms for anything unless you exceed .550" lift, 300# spring pressure or 6000rpm.

And no, those will not work without major modifications and additional parts.
 
XR7 Dave said:
Don't waste your money on adjustable rocker arms for stock heads. In fact it is an entire waste of money to use roller rocker arms for anything unless you exceed .550" lift, 300# spring pressure or 6000rpm.

Dave, I'm not starting an argument, but please explain why.
 
At moderate lift levels there is no performance gain. Unless you exceed the design limitations of the stock setup there is no need to change it. The numbers I used are not absolute values but rather they are guidelines. Spend your money where it will make a difference. On stock heads roller rockers will not make any difference whatsoever other than the additional valvetrain noise.
 
would someone like me (with ported heads) benefit from roller rocker arms?
 
What you need to do is consider why roller rockers are used.
#1 - they can often be made lighter than stock rockers.
#2 - They can often be made stronger than stock rockers.
#3 - they can be both #1 and #2
#4 - For high rpm's, the friction reduction can be measurable.

Stock cam and valvetrain, no benefit since you won't see significant RPM's, and spring pressures are well within a range workable with stock parts.

High Lift cam, or intention for higher rpm runs, other than the fact you've got to do lots of other stuff as well, the roller rocker is basically necessary to gain the strength and the lighter weight.

Stock stuff has proven to be just fine up to just under 400rwhp.
 
Good deal! Cause I just got my heads today and they are going on. Ill put the regular rockers on and hope they torque down with no problems.
 
There is a lot of inaccurracy in a blanket statement like "In fact it is an entire waste of money to use roller rocker arms for anything unless you exceed .550" lift, 300# spring pressure or 6000rpm." There is no motor that cannot benefit from the addition of roller rockers.

If you have ever checked lift from rocker to rocker on stock stamped steel crap, you would realize that they can vary as much as 20 thou on a set. In fact my 71 351C had a 26 thou variance in the worst rocker with 5 rockers costing 15 thou or more. A 420 lift cam is now a 394 lift cam thanks to cheap stock rocker arms. That hp loss is fact that should not need to be explained. Aftermarket rollers are precisely machined to be identical thus providing exactly the same amount of lift as every other rocker in the set. The sled action of a stock rocker on the fulcrum is also different from that of a roller. In the course of its travel, the rocker moves back towards the stud. A roller rocker pivots on a trunion and has little to no horizontal movement. This horizontal movement combined with their inherent tendency to deflect can drastically reduce actuallized lift at the extreme point of a sled rockers travel.

On our 3.8's, increasing the ratio to 1.8 adds 18 thou left and a couple of degrees duration worth about 10 ponies. Adding that the potential lost power due to lost lift could be considerably more. Every little bit counts and considering that they can be found on Ebay for as little as $150 a set, very cheap power.
 
I'm not going to say what will benefit with roller rockers or that a certain engines don't need them.

However, watch what you're buying as not everything will fit our cars without alot work. If you want a set of roller rockers, you will want to look for a set of "bolt-on" pedestal mount rockers for a 351C. If the ones you're looking at require studs, then you're gonna have to fab up some guide plates as the rockers have no way of aligning them selves like a pedestal mount style does. At this point you will also require hardened pushrods as well.
 
ss_scuba said:
I'm not going to say what will benefit with roller rockers or that a certain engines don't need them.

However, watch what you're buying as not everything will fit our cars without alot work. If you want a set of roller rockers, you will want to look for a set of "bolt-on" pedestal mount rockers for a 351C. If the ones you're looking at require studs, then you're gonna have to fab up some guide plates as the rockers have no way of aligning them selves like a pedestal mount style does. At this point you will also require hardened pushrods as well.

The 351C guide plates will work perfectly on our heads. just get a rocker arm conversion kit for the 351C crane sells a kit. summit part number CRN-52655-16
 
Flex said:
Every little bit counts and considering that they can be found on Ebay for as little as $150 a set, very cheap power.

My statement comes from literally years of watching (and helping) people with supercoupes make power while some spend large volumes of money on things that do not net a performance gain on their SC's. Arguments about headers are a perfect example but that's another topic altogether.

Selling (or recommending) roller rockers as a "cheap source of power" is much more misleading than a blanket statement that they are a "waste of money" for many applications. Stating that added lift will result in added power is a misconception at the very start. Even at fairly high levels of HP there may not be a measurable difference.

I personally performed a test with stock pushrods and stamped rocker arms vs. CM pushrods and 1.8 RR's on my 12 second XR7. On both the dyno and the track there was no improvement. Nada. I thought my car was a good candidate for the 1.8's because I have a very low (for the HP level) lift cam (.491) and some very good flowing heads that should have responded to more lift (the best there is) but even so I did not see any gain.

Instead there are things that people can spend money on that will net REAL performance gains (like actually having the heads ported, etc) which is where I tend to focus my recommendations.

So "waste of money" really isn't an absolutely accurate statement, but if you were to create a priority list of things to help your SC make power RR's would be very close to the absolute bottom.
 
Roller tips

Well guys, I "aint" gonna challenge any of the info here :)
I have heard the Dyno figures (no improvements) over stock sled or ball pivots before, so I can understand that. I have used the CC's roller tip rockers---BB chebby on a 460 for 1.72 with guide plates wo/hardened pushrods because of the composite guides. I used a Crane RV grind cam, which was not enough cam to really benefit from rollers. Because of the wear pattern of the stock rockers on the sled fulcrums, you will get a hell-ub a clatter if you change any cam specs over stock later on. That necessitates changing the rocker arms.

The question I have, that does not seem to get mentioned in these discussions, is "Is there any benefit---maybe only for long term use---that at least a roller tip will provide (in addition to corrected ratio values) as far as the scubbing action across the valve tip by the stock rocker arm? Many moons ago, I read that a stock rocker creates more side loading on the valve stem, thereby increasing valve guide wear. That may not be significant enough to worry about. Have any of you who build lots of engines have any info on the valve guide wear issue? CC roller tip rockers and stud kits are relatively cheep, compared to full roller rockers, and may be worth consideration---even on mild cams.
TX YB
 
Comparing mass produced stamped steel rockers to any aftermarket roller is no comparison. The example provided from my 1972 Mustang's 351C should make it painfully obvious that a motor could actually being losing performance due to not even achieiving the lift it is supposed to from the stock camshaft.

Add the 18 thou lift of a 1.8 to the 26 you are losing from the bad rocker in the case of the 351C and we are talking 44 thou lift. Dave please do not try to sell me on some tale that there will not be any power increase from this addition. That is entirely the idea behind swapping to bigger lift cams. Many aftermarket cams provide big power gains to even stock motors with that amount of lift.

Your example does not equate to all others equally. You are at a point where you have exceeded stock lift by by a considerable amount. 1.8 rockers would put you at .511 lift. This would require considerable changes in fuel and exhaust on a carburated vehicle much less a fuel injected supercharged motor. Any missed variable; MAF, TB, injectors, restrictive exhaust, computer calibration, increased belt slip from increased rpm's etc etc could result in a seeming no benefit dyno run. The install of the rockers themselves is different from stock rockers requiring appropriate thickness of shims for each rocker individually. Making the statement that I never saw any improvement so you won't either is a major reach.

I too have been hot rodding cars for 25 years including every domestic under the sun from muscle cars to fuel injection. I have in fact done a lot of work to an NA 89 3.8 as well proir to the SC including fabricating my own larger throttle body, cutting and welding and porting the intakes for improved flow, modifying Mustang short tube headers to work etc etc. My own ported heads flowed 210 Int and 145 Exh with the stock tiny 1.78 Int 1.45 Exh valves. The only addition for lift was 1.8 rockers. This car is quite fast and really pulls hard in the upper rpms. I even beat a new V6 mustang to 65 mph a few nights ago.

Don't forget that the Cobra 5.0 came from the factory with Crane roller rockers. Ford didn't do that just for laughs. The addition is noted in the Ford Technical Performance Handbook as well.
 
Tony, there you have it. At least one thing that all can agree on is that the roller rockers will put less strain on the valve train and if you are racing it, that would be a good thing. Remember at 6000 rpm each valve opens and closes 50 timer per second.

Mike
 
Mike8675309 said:
...
Stock cam and valvetrain, no benefit since you won't see significant RPM's, and spring pressures are well within a range workable with stock parts.
...
Stock stuff has proven to be just fine up to just under 400rwhp.

An otherwise essentially stock SC motor has many other issues to worry about before sweating the ease at which it can push it's valves open. Dave's got actual experience, but I've also see the posts for years on this board of folks that simply get no appreciable gain from roller rockers when done simply for a performance improvement. Seat of the pants.. maybe, but it's easy to fool that. Take it down the track, or on the dyno, and you see nada without doing some other work as well.
 
Dont waste your money. I have harland sharp ajustables on mine. Wish I would have stuck with stock. Just one more thing you have to mess with.:mad:
 
Additional Valvetrain Noise?????

XR7 Dave said:
On stock heads roller rockers will not make any difference whatsoever other than the additional valvetrain noise.
Additional valvetrain noise?? :confused: Where does the noise come from? With a juice cam, the roller tip should never loose contact wtih the valve stem. Are you saying that the roller bearings themselves are noisey?

Confused 68COUGAR
 
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