Roller rocker vs. stock?

[Tabcon]

I've been considering a set of roller rockers for my engine build, but I'm having trouble justifying the cost. I've looked at the complete set up offered by Racestorations as well as getting the parts individually. I think I could get by for less bucks building the set up myself, but I'm still on the fence as to whether or not it's worth it.

The stock rocker pedestals I have are aluminum and I've talked to several people who have lightened and polished their stock cast iron rockers. Last night I lightened and polished a couple of rocker arms and pedestals and they really look great. I could add a hardened shaft and solid spacers and that would be it, but I'm a little worried if the stock components will hold up under the higher RPM's I'm anticipating of 7 to 8k. Are there any inherent weak spots in the stock set up after adding a hardened shaft and solid spacers?

 

[dougie]

Tab,

I've had the same questions when rebuilding my 6-cylinder Healey. Given the fact that the vintage groups I race with here on the west coast, (SOVREN, GRL, HMSA) do not allow rollers, I've strengthened, balanced and lighten my stock rocker system as much as possible and have been happy with the results.

Dougie

 

[skippymga]

Yep, we are in the same boat with Doug. Having just broke a rocker arm assembly shaft, make sure you get the hardened variety. Or mag the one you plan on using.

Scott - MGA #41 - The Pile

 

[Tabcon]

The only type of "hardened" shafts I've seen on the market now are of the "tuftrided" type. Tuftriding, or carbon nitriding is an old school surface hardening technique that also opens the pores of the metal allowing more oil to seep into the surface for additional friction reduction. If you use a tuftrided shaft, be sure that you polish it first as the raw tuftrided surface can be rough and will wear out your rocker arm bushings more quickly.

There are other types of surface hardening like ion nitriding and cryogenic processing that may be better though. Glock, the hand gun manufacturer, uses a process on their semi auto slides called "Tenifer" or "Melonite" which is basically a tuftrided surface that has also been Parkerized. The Tenifer coating has a 64 Rockwell C hardness and is primarily used on firearms, but is now being used on camshafts and tappets as well with great success.

https://www.burlingtoneng.com/index.html

I contacted Burlington and I'm going to send a shaft out to them to have a look at. If it's not cost prohibitive, I think I'm going to just buy a stock rocker shaft and have it Melonited. Depending on how things go, this may be a good coating for other parts as well.

 

[skippymga]

Huffaker is our motor builder and according to Joe, there hardened shafts on the market. Well worth the money given the options of what a broken shaft could do to your motor.

 

[Tabcon]

Huffaker builds great motors. I talked with them about my build, but being in New Orleans, I opted to do it locally. Seems like California has all the good stuff.

I looked at a few complete roller rocker assemblies, but they were way expensive. Most of them had needle bearing rocker arms which I didn't want, so I decided to piece my own together using uprated aluminum pedestals and alloy spacers from Baastuck, roller rocker arms from Harland Sharp and hardened adjuster nuts from Good Parts. I came out a couple of hundred bucks less than buying a complete assembly and got exactly what I wanted this way. Hopefully, it will work well. Hopefully, it will work period.

 

[Hap Waldrop]

The biggest reason to go to rollers would be to increase the ratio, if you're doing that, then go for it.

 

[Tabcon]

Thanks Hap.

Yes, increasing the ratio to 1.65.

I talked with the guys at Harland Sharp today and while they only list the stock ratio on their site, they will make the higher ratio also.

I was thinking that if the rocker shaft is a weak point in the valve train, couldn't you just go to a larger diameter shaft, like a 3/4"? I don't think one is offered anywhere, but having one machined should not be that big of a deal. Of course you'd have to rework your pedestals and rocker arms, but that could be easily done by the same shop as well.

 

[skippymga]

Hi Hap... how goes racin on the right coast?

 

[aeronca65t]

It's intersting to read all of this.

I never even think about the rocker arms in my 1500 Spridget. The rocker arm assembly has only been off once since 2002.(when I spun a rod bearing and had to pull the head and crank). I usually only check the valve adjustment once or twice a season and it's always fine.

My rocker arms are stock, street setup with about 50,000 street miles plus at least 50 race weekends (including several 2, 3 and 4 Hour enduros. Stock cam and valve springs.
It really never take it past 5800 rpm (a waste of time with this engine). That may be why it's lasted so long.

(I'm heading to the track in 48 hours......I hope I didn't just jinx myself )

 

[Hap Waldrop]

Thanks Hap.

Yes, increasing the ratio to 1.65.

I talked with the guys at Harland Sharp today and while they only list the stock ratio on their site, they will make the higher ratio also.

I was thinking that if the rocker shaft is a weak point in the valve train, couldn't you just go to a larger diameter shaft, like a 3/4"? I don't think one is offered anywhere, but having one machined should not be that big of a deal. Of course you'd have to rework your pedestals and rocker arms, but that could be easily done by the same shop as well.

I guess it's posibble, but don't know it's necessary, do the shafts brake on the tractor-3/4 motors? HS normally uses a thickwalled busihing for the shaft, so I guess you go a bit bigger. Yes for sure you'll have to relocate the pivot point to relfect the new ratio, either by modifying the existing pedestals or making new ones.

 

[Hap Waldrop]

Hi Hap... how goes racin on the right coast?

Fast and Furious Scott.

 

[Monkeywrench]

Thanks Hap.

Yes, increasing the ratio to 1.65.

I talked with the guys at Harland Sharp today and while they only list the stock ratio on their site, they will make the higher ratio also.

I was thinking that if the rocker shaft is a weak point in the valve train, couldn't you just go to a larger diameter shaft, like a 3/4"? I don't think one is offered anywhere, but having one machined should not be that big of a deal. Of course you'd have to rework your pedestals and rocker arms, but that could be easily done by the same shop as well.

I guess it's posibble, but don't know it's necessary, do the shafts brake on the tractor-3/4 motors? HS normally uses a thickwalled busihing for the shaft, so I guess you go a bit bigger. Yes for sure you'll have to relocate the pivot point to relfect the new ratio, either by modifying the existing pedestals or making new ones.

Hap,

They do. There is a an oil hole in the shaft at the #4 cylinder (I think it's the exhaust side) that is right next to the pedestal stud hole. The rear most pedestal stud doesn't go into the head very far so it moves around... eventually the shafts break between both holes. Most just buy the pedestal kit from the UK that has big billet blocks and wraps around and captures the end of the shaft. It's pretty well documented (and common) failure point.

Tab,

You're not going to run over 7k reliably, though some racers are spinning them higher in the heat of battle. These are "sprint" motors that see rebuilds every 4 events or so, and the valve cover comes off between every other sessions or so to check clearances / do an inspection.

 

[Tabcon]

This reminds me of that old commercial for Tootise Roll Pops. "Just how many licks does it take to get to the center of a...CRUNCH!"

Just how many times can you rebuild a 45 year old engine before it goes crunch?
After a while, it's just patch, patch, patch.

My 7k estimate is a bit optimistic, I know, but a fella can dream can't he.

 

[Monkeywrench]

Built right (and it sounds like you are), they can run a 6500 redline all day.. okay maybe not all day, but it's reliable.

 

[Hap Waldrop]

Hap,

They do. There is a an oil hole in the shaft at the #4 cylinder (I think it's the exhaust side) that is right next to the pedestal stud hole. The rear most pedestal stud doesn't go into the head very far so it moves around... eventually the shafts break between both holes. Most just buy the pedestal kit from the UK that has big billet blocks and wraps around and captures the end of the shaft. It's pretty well documented (and common) failure point.

Yep, I seen folks have the same sort of pedestals on Spitfires, worked with few of them myself, and a few MGBs as well.