Tibo

iTrader: (15)

I am wondering if any one has used a moderate or raprd leak down lifter.
(I am going to use them in a stroked 305 engine with a cam that is oversized by about 10*. Also, for the camshaft, how big should I go on the exhaust opening and Lobe Center Angle?)
If so, what is your experience and where did you get them? I have installed them on cars and had good experiences, but I would like to have other peoples input before they go in my car. Thanks Alot

Vader

Tibo,

Since you're asking about lifter leakdown (bleed rate), this is obviously a hydraulic cam installation. Are the lifters going to be flat or roller?

85TransAm406

iTrader: (1)

i've run the Crane and the rhodes lifters. Rhodes lifters are a quality product. The Crane lifters are just rejects from regular production that had too low a tolerance, causing it to leakdown too much, but it's not extremely precise. That's why they don't make noise like the Rhodes, they aren't leaking down as fast. I did run them back to back (I collapsed a Crane one on dyno day and changed them the next day to Rhodes and ran another dyno run). The Rhodes actually seemed to work as advertised. But I'm sure the Crane ones work OK, just not as "well" as the Rhodes.

Tibo

iTrader: (15)

Hydralic Roller lifters.

Vader

To my knowledge, no one manufactures aftermarket high bleed rate lifters with a roller. Some engien manufacturers are using variable valve timing and altered bleed rate cam followers, but not very widely. Roller cams by their nature can have a more aggressive ramp, allowing a shorter duration at a comparable lift, thereby eliminating the main problem that street engines experience with higher lift cams. They just aren't as necessary with a roller cam, so no one makes them.

85TransAm406

iTrader: (1)

that's why i assumed flat tappets.

Gumby

Can someone school me in leak down lifters???

I know what he is saying, he has a cam that has to much for his valve train, so you use a lifter that leaks real bad so it doesn't break things.

What advantages does that have to running the right size cam.

Matt

85TransAm406

iTrader: (1)

when you use a leakdown (variable duration) lifter, it only leaks down at lower RPMs, making it act like a smaller cam. When the RPMs get higher, there isn't time for the oil to bleed off, so they act like the normal lifters.

Tibo

iTrader: (15)

Vader,
I am looking for moderate leakdown lifters, not rapid or fast bleed lifters. I want these lifters so that I can have a bigger cam than the computer would normally allow that has the ability to breath more air at higher rpms and yet still be streetable at low RPM cruising. Also the last thing I want to have to worry about is a higher than normal valve acceleration and worn lobes, reliability is a must. Can I hear more about the Rhodes, what were they?Thanks.

85TransAm406

iTrader: (1)

The Rhodes are flat tappet hydraulic lifters.

AJ_92RS

Just an FYI,

David Vizard has done tests with them and unless the cam you're using them on has more than 290* advertised duration, they actually will cause a loss in HP above 4000RPM

305sbc

iTrader: (3)

leakdown lifters are a waste of time. Just get the correct cam in the first place and you'll be 10x happier.

AJ_92RS

My thoughts also.

They're in my '72 Camaro. I bought it like that.

Me no like. Me building new 350 for spring. No have to worry about them anymore.

Joshua

Rhoads lifters make A LOT of noise. Kinda sounds like a couple bad exhaust leaks. I don't know how much something with a knock sensor would like that.

Vader

As for installing more cam than the computer will allow, for what you would spend on a set of high-bleed lifters (if they were even available for a roller cam) you could purchase an Intronix Pocket Programmer II, some blank EPROMs, and get some of the free software flaoting around that will help you reprogram that ECM to "accept" any cam you want to install.

Tibo

iTrader: (15)

Vader,
Where can I buy this magic wand and tools you speak of???!!! I'll have to run a search on this. So I guess the cansus is to not do it. Thanks.
AJ_92RS In the guy's test, were they moderate or rapid leak-down lifters?

85TransAm406

iTrader: (1)

Why search it? It is the basis for the whole diy-prom board. General consensus not to do it? Then why would they have a whole board about it?

AJ_92RS

They were Rhoads Fast Bleeds.