Benifits of (273) adjustable rockers...

I've been looking at ways to lower my E.t. (12.87 best) a little bit to beat my brother's Olds (12.55 best). I run a 12.5:1 318 with a 317/292 hydro cam with stock rocker gear. I've been getting speed tips from different "Mopar" guys, one of which is to run an MSD with wide gapped plugs (see my post about my current chrome box and wide gapped plugs). The other was to install the adjustable rocker gear from a 273 which I already have (its just badly worn out and scarred). My question is this: what advantages does running adjustable rocker gear give me? I assume higher RPMS due to correctly set valves and a "looser" setup, but I really do not know of any other benefit for doing this. I initially bought the set for $75 expecting to run a huge 600 lift roller cam in the future (not any more the 12.5:1 compression really limits cam lift). This setup now will rev to about 6000 rpm. Thanks!!

All you are doing with the adj. rockers is preloading the lifter slightly (a "negative lash") which will increase rpm due to a closer tolerance.If these rockers and associated gear are worn out as you say,I'd go to a set of roller rockers.Also I'd consider a cam change to a solid lifter cam as you already have the valve gear.All the notions about having to adjust valve gear all the time is bunk.I check my valve adj.once a month and have never had to re-adjust due to a rocker arm getting loose.

I got a good look at the set I have last night (they've been stored since I bought them at the Mopar Nat's in 1993 for $75) and they actually look better than I remembered. The rockers themselves look good, but the shafts have seen better days but are probably servicable with a polish on a lathe or something. I also think that these shafts for adjustable rockers came with a groove all the way around the shaft, which these don't have (they just have the oiling holes like the stock shafts). On my Dad's Duster we re-created these grooves in a stock set on a lathe. Would do you guys think? Is it worth the extra oiling to cut these grooves? I know small blocks have an oiling problem here anyway. Thanks!!

I think you are talking about the "bananna" groves...many aftermarket shaft have them...I'm not really sure about stock shafts.

Since I plan on using the 273 rockers on my 360 I bought a set of shaft from Hughes and just received them today...unfortunately since I'm still at work I never had a chance to look at them yet....urrgghh...the day is going so slow!!!

I think using the "bannana groove" rocker shafts is a good idea,especially if the rockers are unbushed.I've been using hardened chrome rocker shafts and Crane roller rockers on my big block Dart and haven't had a problem at all.If it was me,I'd use the 273 rockers and the hardened shafts.You can get these shafts from Mancini Racing and Mopar and Hughes as Diplomat360 has said.

I use the adjustable rockers on my 318 circle track motor. Make sure you have the 273 style rocker. The one's from Mopar are Very heavy, we also take a brake cyl hone and polish the inside of the rocker, this seems to help the shaft. We use the mopar chrome shafts and have no problems.

OK - I'm ready to install the adjustable rockers onto my 318. How do you set them? I've set valve lash on a BB Chevy before, but never on a SB Mopar. All my shop manuals tell me nothing of this - probably because chrysler didn't make adjustable rockers outside of these 273's. PLease tell me where to start!!

Thanks!!

Adjustments the easy part! I'm sure you can ask ten guys and get ten different answers, but heres how we do ours.
Valve covers off, bump the motor till the valve is all the way open, adjust the opposite valve of that cylinder. Just as soon as the rocker contacts the push rod, add a half to 3/4 more turn on the adjusting screw. It's that simple

That's the way I'd do it too,which is really the same for any engine regardless of make.And as a side note,the 1970 340 6bbl engines in the AAR Cuda and T/A Challenger had mechanical rockers with a hydraulic cam.

Thanks!! That does sound easy!! Now all I need is a brake cylinder hone and time (which I have less of than money)!!


[This message has been edited by The Dartman (edited June 29, 1999).]