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351 Cleveland-4v Rocker Arms?

Middleagecrisis

New Member
Thinking about swapping some 351 Cleveland-4v pedestal mount rocker arms on my stock 5.0 to get a little extra lift out of the factory cam. Looking specifically at the Melling MR888 rockers. They appear to have the same dimension as the windsor rocker arms from the pivot point to the spring pad, but are 1.73 ratio, compared to the 1.6 windsor rockers. Not to worried about pushrod interference, as I've run 1.72 ratio before on other 302/E-7 head motors and it wasn't a problem. Seems like a lot cheaper route than buying a set of roller rockers to do the same thing. Anybody ever done this before?
 

broncojunkie

Well-Known Member
I was pretty intrigued by your question. Never thought about it and I have some cleveland rockers lying around, somewhere (if I could find them lol). Anyway, I just did some quick research and found this thread on another forum which states that they won't work.

However, you can buy an individual rocker arm for about $8. You could order one and try it out. If I could find what I did with my box of clevo parts, I'd send you one. They're floating around in my old garage somewhere (I'm in the process of building a new detached garage and the other one is currently in a state of neglect).

Edit: Oh, and I do realize the link I posted says "460 rockers" but they're evidently the same as cleveland.
 

347HO

Active Member
To clarify...
You want to increase lift using non roller, rockers because its cheap?
My experience with increased lift... increases instability. Using non roller tip rockers increases this even more.

Question, how did melling get 1:72 ratio compared to modern 1:6 or 1:7 ratio rockers?
Is the decrease on the pushrod side or increase on the valve side?
Or... A little of both?

I'm interested how your geometry turns out.
 

Middleagecrisis

New Member
The cleveland motor moves the pushrod contact point in closer to the rocker arm pivot point to achieve the 1.73 ratio. Looks like I'll be buying one rocker arm to test this out in the future. BTW, I couldn't get your link from sbftech to open. Thanks!
 

347HO

Active Member
Interesting...
In my mind, I see this setup working but most likely needing some milling, shimming to achieve best valvetip geometry.
The extra inertia, particularly on the exhaust valve springs may need close attention when using factory stock springs.
Heat kills springs.

Sbftech has had issues for years now. Sorry you don't have access to all threads.
 

broncojunkie

Well-Known Member
The cleveland motor moves the pushrod contact point in closer to the rocker arm pivot point to achieve the 1.73 ratio. Looks like I'll be buying one rocker arm to test this out in the future. BTW, I couldn't get your link from sbftech to open. Thanks!

I had a little trouble with it, as well. I'm cutting/pasting the pertinent info:

The BBF or SBF 351C rockers are identical. The ratio is actually 1.73. These rocker arms CANNOT be used on a 302/351W. The trunnion distance is longer on a BBF/351C than it is on a 302/351C meaning the distance from the center of the rocker arm to the tip is longer. It is very close to a BBC. Now you can use a 1.7 rocker which is made for a SBF 302/351W. The ratio is actually 1.72. In terms of power. Sometimes yes, and sometimes no. It depends on a few items. It does give you more lift. This is true.
 

347HO

Active Member
In regards to bronco's post...
Keep in mind I've never done this because I'm more into doing things 1 time and also being as correct for the application as possible, even if I have to wait and save money for the budget.

If you look at ANY pushrod cylinder head's profile, you will notice the rocker stud and valve tip bore lines intersect at some point above the head. This in my mind means I can pretty much attain very good geometry using any rocker or rocker style.
It is only a matter of moving the rocker away or closer to the base. Hence why I mentioned milling the base and shimming for geometry.
The affect becomes pushrod clearance issues or valve stem length issues.

To be honest, I have Chevy style titanium valves in my setups to attain the geometry I need, plus they are shorter, lighter, and more stable.
 

Middleagecrisis

New Member
Finally got around to buying a Melling 351C rocker arm and mocking it up on my explorer engine. In summary, this isn't going to work, but I wanted to show pictures of why it won't work. Hopefully, this will answer any future questions on the possibility of swapping 351C rocker arms to get the 1.73 ratio on a windsor engine. Pic 1 shows the physical size difference, Pics 2/3 show the valve tip/rocker arm contact at no lift and full lift, with the 351C rocker arm only making partial contact on the valve tip. If this situation didn't break something, it would certainly cause rapid guide wear. No amount of shimming on the pedestal would correct this misalignment. Pic 4 shows the windsor rocker with the correct rocker arm/ valve tip engagement. On a positive note, I tore down my explorer engine after I did the mockup and it still had the factory cross hatch on the cylinder walls and no evidence of guide wear on the GT-40P heads. I was blown away how clean the motor was on the inside. I may just put on a new oil pump, re-gasket, add HP springs , add a HR reground HP cam and run it as-is until I can build a 347 with my Mustang block.
 

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347HO

Active Member
A few things I see from your pics;
If the spring is at correct install height, your valve is too long for the setup.

Shorter valve will get you closer to good geometry.

I mentioned you would have to mill the heads to get the rocker down for more distance, and shimming to reduce the distance.
In you case, milling is the option.

I'm thinking the rocker would be viable, but as said earlier, doesn't seem as simple as putting standard 1.7 rockers on first.
I myself am a "tinkerer" and enjoy "non standard" and sometimes not the easy bolt on typical builder... As you seem to be so... I applaud your willingness to experiment.
 
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