I am going to run my 292 on propane, and the word is a propane carb (mixer) likes a pretty strong vacuum signal at idle for best driveability. From what I've read they aren't as forgiving as a carb with low vacuum. So I was looking at a set of Rhoads lifters to get my idle vacuum up. The Santucci book said to run big-block, not small-block lifters or oiling issues would happen. Rhoads lists the same number for both small and big block lifters apps. Can I run these, or is there a specific L6 lifter I need to call to get, or are these to be avoided?
Thanks,
Rick
I'm lost on how the lifters are going to affect vaccum, fill me in.
I am using lifters (and cam) from Schnieder Cams, as they swear they are made in USA and a quality lifter.
Rhoads lifters bleed down more at idle, making your cam appear "smaller" to the engine, theoretically giving more vacuum due to less duration/lift at idle. Then when you rev it up, no more bleed down, so you get your top end charge too. I've never ran a set of these, and was curious. Schneider is good stuff.
Heater, the Rhodes lifters are designed specifically to bleed down, at a controlled rate, while the engine is running.
Because of that the effective duration of the cam is significantly shorter.
As the engine speed increases the time for the lifter to bleed is reduced and the cam behaves as it would with normal hydraulic lifters.
Or at least that's the theory, it depends on the lifter pumping back up between each cycling of each valve and I've heard of people playing with what weight oil they are running to adjust how much low speed bleed they get.
56 Rhodes has been around for quite some time (I remember seeing an ad of theirs in the late 70's IIRC) you should be able to call them and ask.
It does sound like a neat project.
And here's a little tip if you're worried about oil getting to the cam lobes. A while ago I ordered a set of Crower "camsaver" lifters, and what Crower did was to take a standard Chevy hydraulic lifter and machine a .002" groove along the bottom half of the lifter, parallel to the long axis of the lifter body, which will allow oil to flow down the bottom half of the lifter and get more oil to the base of the lifter. If you want to duplicate this, you can take your lifters (whatever brand they are) to your friendly local machine shop and have them machine a .002" groove down the bottom half of all your lifters, the same as Crower did, or if you have a milling machine handy, you can do it yourself. That's probably a lot less expensive than buying them from Crower, too.
Yup - they can be tweaked slightly by playing with oil viscosity, oil pressure, water temp, etc.
The different brands of high-leak tappets have different leak rates.
Ah, I remember reading about that now. Thanks for the lesson guys.
How about running an accessory vaccum device or canister to help with idle vaccum.
The vacuum can / pump will help with accessories, but won't help the Propane mixer (carb) he's running.
Nothing you can do about actual engine vacuum.
A can will store manifold vacuum to allow power brakes to work a few times, electric pump the same, but both are momentary.
Paninc, I thought one of the selling points of the Rhodes lifters was more manifold vacuum?
it is. He was replying to heater.
They do. I have ran them, on a 6 and they will mellow out a cam at idle but yet let it wake up when you get on it. Tom
Yes - a pump won't help, the Rhoads will unless the cam is really tiny (like a stock 216). The bigger the cam, the more the improvement.