[NeighborsComplaint]

Originally Posted by ZeGermanHam

Maybe you mentioned it previously, but are you still running a GM rear axle?

Yeah. 8.2 BOP.

Just got this delivered today ... hope I don't have t use it but at least I can march through my checklist now. Self contained, 2 wire + 1 hose connection. Installs in any orientation desired. Will hide nicely on the rad core support behind the battery ... if needed.

[patox]

Originally Posted by mf67gto

I had a problem on a '68 GTO like this that drove me crazy - even had a new reman'd booster on it. Could not get the tires to lock up and almost felt like manual brakes by how much pressure I had to put on the peddle. As last resort I went up under the dash and where the connecting rod comes out of the booster there was a felt pad or filter around it to keep junk from being pulled into the booster as the diaphragm moved back and forth. After removing it and hitting the brakes it almost put me thru the windshield. I think the filter was acting like a plug and not letting the booster do its job or allowing the diaphragm to move. Easy to check from sticking your head under the dash. This "tip" has helped out several folks in the past.

Hope this helps.

Any chances you can grab a pic to check?
I feel so very interpreted by everyones pain in this this tread... kind feel we need a group hug!

Only to add I have swaped 3 rear disk convertion kits because my wheel vintiques rally I 15x8 will hit every caliper installed...

Trying scarebird adapters for the eldo calipers... hope this will be the one... at least on fitment!!! then will see how they brake..

[Gary D]

Originally Posted by NeighborsComplaint

Well I finally threw in the towel and ordered a vacuum pump as a fix for my hard pedal and unresponsive 4 wheel disc conversion. I've tried everything but stand on my head to get the brakes to feel like a "normal car" including swapping to a dual diaphragm booster from a Turbo TA. 12" of vacuum is 12" of vacuum and just doesn't cut it apparently.

I ordered a prewired, self-contained unit from Leed Brakes that utilizes a Hella rotary vane pump similar to what late model GM's are using. The maker says it completely replaces engine vacuum as the vacuum source though I plan on installing a T and check valve so the engine vacuum is available in the event of a pump failure and will probably add a vacuum storage canister if the pump volume doesn't keep up.

One interesting thing I encountered from dialog with multiple "techs" is the claim that "All you really need is a vacuum reserve canister ...". Am I the only guy that thinks "if 12" of vacuum won't operate my brake booster now, why would a larger reserve of 12" of vacuum be any better?"

Wish me luck because the next step will be a complete do-over as the car just does not stop like it should. Any ideas? The low engine vacuum has persisted through 3 different camshaft/intake/carburetor combinations. It is what it is.

I know someone will recommend a Hydroboost but that's not an option. I don't like the way they look on a classic car.

I can start this by telling you my original booster (67 GTO) passed the tests for working properly...barely! I borrowed a new booster from a buddy and installed it. My brakes improved a little bit, but not enough to make me happy. I had already rebuilt my wheel cylinders and and had a new master, new shoes and fluid, it should've stopped hard and fast like it has for the 40 years I have owned the car. It didn't! I sent my original booster out for rebuild to Power Brake Booster Exchange in Portland, OR. That is all they do! I received my booster and installed it that day and "Oh my God" that car stops like it never has before. Booster Steve said it had a small hole in it and was also collecting moisture causing it to fail. Well that got me thinking about the new booster I installed in my other 67 Pontiac. It always had a hissing sound when it was cold and seemed to go away when it warmed up. One day I needed brakes pretty bad because of an idiot in front of me and I almost planted my headlights into his tail lights...Not good? I found another original and had it rebuilt and the same story. It stops like it never has before. Moral of the story DO NOT THROW AWAY ORIGINAL RE-BUILDABLE PARTS. Both of those "New" boosters were aftermarket and are now melted down to make bottle caps!

[killerboots]

Fought the same problem for 7 years but with front disc conversion and rear drums. Could never lock up the front brakes no matter how hard I tried, rears would lock up a little bit. I have a factory 9” booster car with 15” of vacuum. I replaced the booster a few times, no change. Added a vacuum canister, no change. I finally purchased a 9” dual diaphragm booster and installed it 2 weeks ago, front wheels locked up at 30 mph panic stop but after a trip around the block the wheels started dragging. Removed the push rod between master and booster, shortened it by 1/8 of an inch and drove again with an even better result. The front brakes now work and feel exactly like my factory power front disc 73. Two weeks of driving with working brakes, I couldn’t be happier. I hope this helps someone.

[NeighborsComplaint]

Well, after reading how one poster shortened his pushrod and it improved his braking, I tried that first. I slipped a flat washer between the MC and booster and braking improved. I added a second and braking actually feels normal with brake lockup occuring on panic stops like it never did before. Not content with the flat washers, I ground the push shorter and it's done and stopping like a normal power disc brake car.

I didn't have to make a single other change though I installed the vacuum can afterwards so I still have some boost if the motor stalls. If anyone needs a brand new hi-tech vacuum pump, I'm your huckleberry as the return period is past.

[leeklm]

Nice to hear, always the simple things, right?

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[HWYSTR455]

You need to be sure you have the correct booster pin depth. Best way is to use a pin depth tool:

https://www.ebay.com/i/254608893852?...iABEgLek_D_BwE

For others, reference:

Put a hand vacuum pump on the booster and make sure it holds vacuum. Make sure you can blow thru the vacuum break that goes into the booster in one direction, and not the other.

More than once I've had bad boosters out of box.

Yes, the eldo calipers are critically dependent on the e-brake, to take up piston/disc free play. Bleeding is a pain, when you think you're done, do it 2 more times.

Just to ask, you bench-bled the master, correct?

The 1 1/16 bore is correct for your system.

As for pedal/pedal hole, etc, key is to have the rod be a square, straight-shot into the back of the booster. Also have the 'slack' taken up by adjusting the clevis. Power brakes = bottom hole in pedal.

General brake troubleshooting tech at Pirate jack's:

https://piratejack.net/tech-support/

Make sure you go to the bottom and look at other troubleshooting sections for different areas of the system.

If all else fails, replace the combo valve, they are know to be defective. Get the one from Pirate Jack.

I had pretty much the exact same setup as you, and originally had issues, and after going thru everything multiple times, turned out to be a bad booster.

.

[389]

I would put the right cam in that motor for street use. It would be faster, run smoother, not destroy motor mounts and sound better.. 12" of vacuum is a lot of overlap! That power band is way too high for street use... Back when I was hard headed and the 041 in my 455 I used to hate these posts but they were right. The last motor I had I listened to Jim Hand and swapped out the 041 for the Summit 2801, WOW what a difference!!!!

[NeighborsComplaint]

Originally Posted by 389

I would put the right cam in that motor for street use. It would be faster, run smoother, not destroy motor mounts and sound better.. 12" of vacuum is a lot of overlap! That power band is way too high for street use... Back when I was hard headed and the 041 in my 455 I used to hate these posts but they were right. The last motor I had I listened to Jim Hand and swapped out the 041 for the Summit 2801, WOW what a difference!!!!

Nah. 2801 is a towing cam in a 455.

I picked my Crane cam because it has the same duration, lift and LSA as the Wolverine cam Jim Hand favors. Good street manners and with my 3.55 gears and GM25 convertor, it has no soft spot and drives like a normal car but with a very choppy idle. Even off-idle it pulls like a freight train.

[HWYSTR455]

What's the specs on that Crane cam? Curious...


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[NeighborsComplaint]

Originally Posted by HWYSTR455

What's the specs on that Crane cam? Curious...


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I haven't revisited this thread in a while, but since adjusting the pin between the pushrod and MC the car stops on a dime now. Swapping out the Holley Street Avenger for a 750 Quickfuel Slayer also bumped my vacuum up from 9in to 13in and gave me a consistent idle speed.

Here's the cam card on my Crane 284281 H296. It is ground 4 degrees advanced (108 LSA)

[HWYSTR455]

Nice, thanks for closing the loop on the issue, helps others with similar problems!

Those Slayer carbs are a steal at under $400, amazing the value of those. Removable bleeds, downleg boosters, yeah, it's a steal.

The Avengers need work right out of the box, I think they get a bad rap, and have used them successfully. The Ultra versions are better, are better QA, but wow, they are like $650 or something.

I've used that same cam in a bunch of 400s. Also have used the one step smaller one as well, when using less gear.

Those cams like more initial timing, I would run 14-16 degrees, and got acceptable idle and vacuum.


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[NeighborsComplaint]

Originally Posted by HWYSTR455

Nice, thanks for closing the loop on the issue, helps others with similar problems!

Those Slayer carbs are a steal at under $400, amazing the value of those. Removable bleeds, downleg boosters, yeah, it's a steal.

The Avengers need work right out of the box, I think they get a bad rap, and have used them successfully. The Ultra versions are better, are better QA, but wow, they are like $650 or something.

I've used that same cam in a bunch of 400s. Also have used the one step smaller one as well, when using less gear.

Those cams like more initial timing, I would run 14-16 degrees, and got acceptable idle and vacuum.


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My Slayer was a Holley Store refurb for $249 delivered. That was a no-brainer to buy and try. I don't know what was wrong with my Street Avenger as it would never return to curb idle. I could apply pressure on the throttle arm with my thumb and "force" it against the stop giving a 750 RPM idle, but it would always return to idle on its own with the throttle plates slightly tipped and of course, idling too high (950-1,000RPM). When "thumbed" closed, it would idle at 750 RPM until you released the lever and it would jump right back to the 1,000RPM idle leaving a gap between the throttle stop and the adjustment screw. I put up with it a lot longer than I should have.

When I put the Slayer on, it was like night and day. Nice low, lopey idle, smoother off-idle transition, better throttle response and overall way better driveability. Secondary response is seamless though the tires let you know what's going on. From a roll in second without kickdown to low, the car will light the tires and go sideways now where it used to just spin them hard. The Street Avenger was a lot less responsive and was like an on/off switch when pulling away from a stop. Throttle tip-in was always very abrupt. No hesitation, but the car was always "jumpy" just coming off idle which made tight maneuvering a challenge. I always had to cover the brake pedal with my left foot in situations like that.

I really like this Crane cam in my 455. I also had the prior version which had a bit more lift on the exhaust side (.505" vs .488"). I agree with the initial timing. I started at 12 degrees initial and found it really liked 16 initial. Hot starts were an issue though, so I am currently running 14 and it's still in its "sweet spot".

[leeklm]

"When "thumbed" closed, it would idle at 750 RPM until you released the lever and it would jump right back to the 1,000RPM idle leaving a gap between the throttle stop and the adjustment screw."

Bent throttle shaft will definitely show these symptoms...

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[NeighborsComplaint]

Originally Posted by leeklm

"When "thumbed" closed, it would idle at 750 RPM until you released the lever and it would jump right back to the 1,000RPM idle leaving a gap between the throttle stop and the adjustment screw."

Bent throttle shaft will definitely show these symptoms...

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Yeah, I thought either bent shaft, warped casting/bottom plate r throttle plate off center. Off the car it seemed to close fine. On the car and under vacuum, no bueno. I just gave up on it not to mention the tumble polished finished that turned nasty gray like an old junkyard carburetor almost overnight. I wish Holley would drop the "flash in the pan" and go back to the dichromate plating that lasted forever.

New:


A year later and the day after I spent hours polishing it to like-new with a Dremel and a buffing pad ... I went home, came back the next day and that's what it looked like. The guys at the shop were quite amused that I wasted 2 hrs polishing it off the car for this result.





I sprayed the new one with SharkHide Coating and it is holding it's shine so far.

[HWYSTR455]

When throttle hangs, also need to check the base gasket, and the intake opening, I've seen both be a problem before.

Also check choke fast idle adjustment and rods.


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[NeighborsComplaint]

Yeah, I checked that too. Never really found the source of the binding as I wasn't interested in fooling with the staked screws holding the throttle plates to the primary throttle shaft. It was time for a change.

Here's the new carb on my cosmetically freshened up motor and engine compartment:

[JUDGE3]

Originally Posted by AG

I would go manual and get rid of the big ugly booster. Just did this on my brother's car with front disc and a Wilwood master. Looks great and works great.

yes heave the ugly NOT NEEDED brake booster. I have used the manual front disc rear DRUM manual brakes on my last 2 cars and love it. I have a corvette manual master cylinder from master power brakes. they have the kit for manual conversion.

not knocking those who like high end brake equipment, to each his own, but if your car is as 90% most are, a lengthy cruise now and then and some quarter mile fun manual brakes are plenty.

I always wonder with all the big brake equipment are those guys going to an indy type track a lot and hammering their brakes and jerking the steering wheel into hard turns? nope lol but I get it, nice automotive equipment is cool.

manual brakes have great pedal feel, cure big cam low vacuum issues, provide clearance for nice tall valve covers for stud girdles, and clean up the engine bay. -brake boosters are ugly- and the hydro boost thing really tickles me. just sayin.....

[JC455]

You have an 81 T/A 4WDB dual diaphragm booster? That's for the newer "quick take up" master cylinder, yet you're using a 69 Vette M/C... The pushrod depth (I'm going from memory, but I'm pretty sure) is different between 81 and up vs. 80 and below.
You might do some measuring of the depth of the pushrod hole in your M/C vs. how much is sticking out for the 81 booster.

[HWYSTR455]

Originally Posted by JC455

You have an 81 T/A 4WDB dual diaphragm booster? That's for the newer "quick take up" master cylinder, yet you're using a 69 Vette M/C... The pushrod depth (I'm going from memory, but I'm pretty sure) is different between 81 and up vs. 80 and below.
You might do some measuring of the depth of the pushrod hole in your M/C vs. how much is sticking out for the 81 booster.

Check post #51


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