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Allis B bore spacing and rocker ratio

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Anonymous-0

Well-known Member
I've got a good B with motor issues. I'm having evil thoughts about some custom performance improvements once my Bridgeport gets back in service. Mostly involving head and crank work. Since the motor is still running (sort of), I can't just grab the rulers and go at this. Would like to be all ready to rebuild when I tear into it.

So here's my questions.
1. What is the factory rocker ratio?
2. What is the cylinder bore spacing?

you would think these would be easy to find but multiple searches on multiple forums and the web have not turned these up....
 
I can not answer your question but can say that due to the fact it is a wet sleeve engine you can not do much to bore the cylinders out. You can buy sleeves that are over size but only 1/8 bigger bore.
 
Buy yourself a 20 buck old engine block and set with your measuring instruments and dream. Sleeves for 3 9/16 pistons is about max with machining and tie bolt support on the bottom end. Head gaskets would then have to be hand made.

3 7/16 will fit without machining and can be bought off the shelf. Best bet would be head work and stroking the crankshaft for extra sip.
 
The bore diameter is not an issue. There actually is a good selection of pistons 3" to 3.5" if you are willing to go to custom rods.
What I was interested is the centerline to centerline of the bores. For example inline chevy 6's are 4.40" from bore to bore.
Rocker ratio is of interest, I don't think I have 2 good rockers on this engine, clearance is huge but afraid to adjust it as valves have eaten a pocket into most of them). Was thinking of a reasonable way to replace them, but need to stay close to the existing ratio to avoid messing up geometry and finding pistons with the valves. Suspect it's around 1.5:1, but suspecting and knowing are different.
And while we're talking about it, anyone know the factory compression height (pin centerline to top of piston)? Looking at it it looks tall even with the piston well below 0 deck.
 
<a href="http://s436.photobucket.com/user/steve-ill/media/Valve-pistonclearance_zps66121139.jpg.html" target="_blank">
Valve-pistonclearance_zps66121139.jpg" border="0" alt="Head measurements photo Valve-pistonclearance_zps66121139.jpg"
</a>
 
I took some rough measurements last year when i was working on head milling and wondered how close i would get to the piston with valves. No guarantee on accuracy, but this might be a start.
 
Thanks Steve. That confirms what I was guessing. Most of my rockers are so shot that no 2 have the same pivot point or tip depth.
 
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