daboatman1

Was wondering if anyone has experienced the use of rhoads hyd. non roller lifters? I have a bit of a bumpy cam and instead of moving down to the next size stick. I thought I could get lazy and just swap out the lifters. To help tame down the idle. I love the sound but my out drive tells me otherwise. My motor is as follows, 496 old school stroker, 9.3:1, merlin oval port heads,holley 800, comp cam .236/ .242 @ .050 .560 lift. max rpm 5100. I thought the added 1/4" stroke would help with the idle. I also have the Dennis Moore book on performance marine bbc. He does say max cam for my application should be no larger than .226/.236 @ .050. I thinks he's probably right. Any thoughts?

Cord

iTrader: (2)

I used them once on a much milder cam. They didn't do a whole lot to smooth things out and I was left with a really annoying valve tick. You might look at having the carb custom tuned. I bet the correct carb setup will get that idle to be stable enough that the drive doesn't bang into gear because of the high idle speed. You can also try trimming the drive up to the trailer position before dropping it into gear. This will reduce the efficency of the prop so it it'll shift a bit easier. Just start trimming it back down immediatly so you don't beat up the u-joints. When I had the blackhawk on my boat, this method was suprisingly effective. I'm able to trim my drive up to the point that the props are out of the water though. That could be a critical factor.

Griff

That cam is not that big. It should idle at about 900 rpms in neutral and about 750 in gear.
What rpm are you at????

Raylar

The specifics of your cam specs don't have some of the most important things that really affect idle quality. First, what is the LSA on the cam, and how much overlap does it have ?
Also, was the cam dialed in on installation. We find almost all cams are off from the factories as ground. Some are off as much as 3-5 degrees from their intend straight up position and this can also have a negative effect on idle if they are retarded. Always, Always dial in your cams! Your cam specs seem fairly mild for your motor spec if they are accurate. You should have a very decent idle, unless the LSA or overlap numbers are unusual. Sounds like its time for you to do a little more checking and detailing. You should be able to tame the "beastly idle"
Good Luck
Raylar

BadDog

Could you use some sort of momentary contact kill switch to make the engine stumble a bit before shifting aka Alpha? A simple circuit could be designed that could sense you are in neutral and detect going into forward to kill several spark cycles for x number of seconds or fractions thereof. OMC Cobra uses a design such as this. I believe the Cobra setup kills 4 of 8 or something like that. My kids boat has this setup and between setting the idle low and this circuit it almost dies when shifting but comes back as soon as you are in gear. If you shift slow enough it seems to engage the gears at what sounds like about 300 rpm just before it dies then picks right back up. Of course with the Cobra or Alpha drive a quick crisp shift is best but the ignition kill is very effective.

daboatman1

Thanks for some great input. I definitely do not want noisy lifters. It sounded to good to be true. Griff you are right on 900-1000 rpm in neutral/ 800 in gear. Some specifics on my cam are 112 lobe separation & installed on a 110 centerline. 234/244@ .050 .564 .567 lift. I never have dialed in a cam before , but it looks like I going to start. I'm now suspicious of comp cams cause the last motor I built (468) had the next smaller cam 226 /236 @.050 .540 lift. Advertised with a slight lope at an idle. NOT! It purred like a kitten except when cold. That is why with the bit larger stroke I selected the next lager cam. Wonder if it was mis marked?

I do have a shift interupt that kills the spark to the coil when shiftin in & out of gear.
It does help some.
I read the 4 pages on the best crane cam. Great reading. Thanks again.

Edward R. Cozzi

Rhoads lifters have a reputation for being hard on the valvetrain. Anybody ever heard this?

Madmax

We ran Rhodes lifters on our Buick 455 drag motors back in the early 90's. They are REALLY REALLY clattery at idle. I think they helped a lil bit, but not much with the idle. We quit using them after 2 motors, and went to Lunati. Usually timing and carb adjustments will help with idle the best.. I wouldn't run them, they will drive you crazy with the sound.

Edward R. Cozzi

I seem to remember them causing pressed-in rocker arm studs to pull out once in a while. When we switched back the problem stopped. The noise reminded me of solid lifters.

robyw1

They aren't so bad on the valve train as they are on the cam surface. Whatever you do DON'T try them on an EFI engine. They will play havoc with the knock sensor.

Roby