[oldman66gto]

Reading in another post about "Bleed down Lifters"! Unfamiliar to me! Help!

I have a 428 in my '66 GTO, with a 3.55, P275R/15 BFG's, and am curious about the "bleed down lifters". What are they, and how do they work/help, and without pulling the engine apart, is there a way to tell? And sadly, I don't know what cam is in it! But it has a nice rumpity, rump sound and decent pressure from exhaust . Doesn't tell you much does it? Seems to have decent low end power with an Edelbrock & Torker. But, as we speak, I am having a brand new tri-power set-up installed, new distributor, along with a Tremec TKX 5 spd.
My Christmas present to myself!
Only had the car about 7 months. Sadly a previous owner's "ex" trashed all documentation, pictures, etc, of the restoration, which is about now 12 years old.

You guys are great with suggestions, ideas, sharing of experience, information, etc. And any advice is appreciated!

Help an old man learn!

So much to learn, and not sure the time frame left to learn!

Allan

PS: All of my previous experience is with Chevy engines!

[JLMounce]

Think of bleed down lifters as a precursor to variable cam timing. They effectively make the cam smaller at idle by bleeding off oil from within the hydraulic mechanism which allows the lifter to soak up some of the lift and duration.

The net effect is that you gain some torque and idle quality at idle and low revs, until oil pressure in the system and the speed of timing events increase to a point that overcomes the bleed of the lifters. At this point they are acting more like a regular hydraulic lifter and your cam effectively gets larger.

They are typically used on the RAIV cams in the community to get the performance of that large cam with a bit better street manners.

There's no real way to tell if those lifters are in your engine without pulling it apart. However, many people claim there is an audible clicking sound that they make.

[steve25]

All of these types of lifters make a ticking noise at idle when the oil is warm, some make more noise then others and the ones that provide the biggest improvement at low speed make the most noise .

Certain Cam lobe designs will cause any of these types of lifters to make more noise also.

[Jay S]

They were called Crane Hi Intensity variable duration lifters. They typically removed 6* to 10* degrees of duration at .050”. They are a bit quieter than Rhoad’s, and do about 2/3 of what an original Rhoads lifter would do as far as improving idle or vacuum.


https://rhoadslifters.com/product-ca...hoads-lifters/

[Half-Inch Stud]

Bleed down lifter are the original variable timing to get a big cam to behave:

Improve idle, Increase idle vacuum, power brake vacuum.
Theoretically improve idle & neighborhood MPG, carb ability to start and idle.
prevent EXH valve burning.

Demerit: ticking noises, sometimes like s sweing machine.

[Dragncar]

If you have a 428 that runs good, nice lump to the cam you might just want to leave it as is. Just getting a new hft cam to seat correctly to a new set of lifters can be a real challenge. You can do everything right and still end up with a flat cam.
The Tri Power does have a certain cool factor, but its not correct for the car anyway. Might not run any better the the Torker and Edelbrock(I don't like them) carb.
Myself, I would put a nice Holley 750 DP style carb and a RPM. Or.............. that new Victor Jr intake.
A new electronic distributor won't get you anything over a correctly done single point. But those new ones you can tune with your phone/laptop have some value on a street car.
Congratulations on your new venture into the Pontiac world. You are now one of the cool kids. And a 68 GTO with a 428 and 5 speed on the street is defiantly cool.

[oldman66gto]

Originally Posted by Dragncar

If you have a 428 that runs good, nice lump to the cam you might just want to leave it as is. Just getting a new hft cam to seat correctly to a new set of lifters can be a real challenge. You can do everything right and still end up with a flat cam.
The Tri Power does have a certain cool factor, but its not correct for the car anyway. Might not run any better the the Torker and Edelbrock(I don't like them) carb.
Myself, I would put a nice Holley 750 DP style carb and a RPM. Or.............. that new Victor Jr intake.
A new electronic distributor won't get you anything over a correctly done single point. But those new ones you can tune with your phone/laptop have some value on a street car.
Congratulations on your new venture into the Pontiac world. You are now one of the cool kids. And a 68 GTO with a 428 and 5 speed on the street is defiantly cool.

Thanks for your reply,
The plan is to install the tri-power for the '66 GTO "cool" factor! At 79 years of age, my "performance" days have passed!
The distributor, is to replace the large style "HEI" that was in it when I bought it. It is too large a diameter to fit, with the tri-power setup.
The "5 speed" changeover is to let me enjoy driving it, & go to some "C&C" type events, as well as the local "GTO" club events.
Car has just tripped 12,000 miles, & I think it was reset when the restoration was done. Found a "Valvoline" oil sticker, which showed next oil chang due at 1,200 miles, dated October 2012. The engine seems plenty healthy, & hopefully it will long outlast me!
The overall condition is almost "show quality" (my opinion), excellent bodywork, with no "waves" in the quarters, the "sails", nor the "roof", & excellent fit & finish!
Anyway, I hope it will allow me to relive my "youth", through my "old age"!

I appreciate this group, and the info that I've gleaned & learned from all of you! More & more is learned everyday, just like this "Bleed down Lifter" topic.

Thanks, and Happy New Year!