1. What is the rocker lift ratio for a 225? I have a '67, I read that they vary, is that by year or is that because the rockers are just built with varying tolerances?

2. If my cam readings do not match the cam card, how to I adjust the timing set to compensate? I mean literally, where is the adjustment made, do I need a special timing set with adjuster or do they all have this feature?

thanks,

Brian

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The factory designed the rockers to provide a 1.5 ratio, but they are actually only in the 1.45-ish range, so in your engine, all of the cylinders may have a slightly different ratio from each other also and the true 1.5 they were meant to have. The process for making these rockers isn't exact but gets you pretty close, so your cam specs may vary slightly from your cam card because it is also ground assuming a 1.5 ratio.

A multi-keyway timing gear set provides the adjustment needed to degree your cam if it needs adjustment.

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There's no such thing as too much cam....only not enough engine!

I find the best way to adjust is to buy a SB Chev cam degree bushing kit from Summit, then drill your cam gear (hole for locating pin) out to 3/8" and use the bushings to advance or retard the cam. The crank keyway method is hard because the gear presses onto the crank and it is not easy to get it off again to adjust the cam timing.

Lou

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Home of Slant6-powered fun machines since 1988

That's a good option also Lou, you can get spot on with a bushing while you are confined with a keyway being incremental in 2° or 4° steps of adjustment.

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There's no such thing as too much cam....only not enough engine!

Yes, I have the odd number (1, 3, 5, 7 deg) SBC bushing kit, and the even number (0, 2, 4, 6, 8 ) kit. If I get to within 2 deg, I usually call it good. I believe it would be tough for anyone to tell between 1 deg increments, even with a dyno.

Lou

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Home of Slant6-powered fun machines since 1988

I have used both methods. If you have a cam gear that has the slot in in it instead of the hole it becomes a little more tricky to use the offset bushings. That is usually only on stock type gears.

Rick

PS. when using the multikeyed crank gear I massaged the inside of the gear with sandpaper on a piece of pipe until I could slide it off and on the crank just applying a little bit of heat with a propane torch. The premium double rollers (JP & Rollmaster) are tight on the crank from the factory.

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

I just recently checked the rocker ratio on my older mechanical lifter engine at rebuild with the mild torque cam (.435" valve lift) using a dial indicator, and the rocker ratio was spot on 1.5:1. (At least on cylinder #1 intake....) I can see it going lower with a high lift cam in the final .100" or so as the rocker goes well past center.

Great info. I suppose if you were really a perfectionist and had the multi-keyed crank gear and you wanted to get in between (i.e. 1 degree increment) you could drill the cam gear also and use a bushing.

The offset bushing seems like an easier and more elegant solution; I wonder why the higher end sets don't just use single key crank gear, pre-drill cam gear and provide a bushing set that includes a zero (centered bushing) along with offset bushings? Are the higher end sets better in other respects, chain better?

Brian

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Yes, the higher end sets are better all the way around. Cloyes has a set they offer for select engines that is call the Hex-a-Just, that has an infinitely adjustable hex style eccentric bushing like that.
http://www.cloyes.com/hexajust.html

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There's no such thing as too much cam....only not enough engine!

I looked at the Cloyes catalog, unless I'm missing something, they don't appear to make these for SL6's...

See: http://www.cloyes.com/Images/HP_AppPagesB.pdf


brian

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I've never bothered using an offset bushing,most people over here just use the Rollmaster or JP sets and call it done. It's no big deal using a multi key way sprocket ,just degree it on the zero key way ,work out how far it's off and pull and re install the sprocket on the correct key way and recheck timing. I guess the offset bush is infinitely adjustable to within one degree,but seriously....what will you achieve? A perfectly timed number one cylinder,if your going that far you may as well check the valve timing on every cylinder while your at it!! As far as rockers go,with the last slant I built I used a dial gage to check actual lift at each valve and selectively fit rockers to achieve the same lift on all intake and exhausts...most rockers were within a reasonable range,but a couple were real shockers...way out compared to the others...so I was glad I checked. Not sure of exact ratio achieved bit it was slightly less than a 1.5 ratio,could have been a slight loss in the flexing of pushrods etc but they were pretty close.

Wow, that's good to know...

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