Hydroboost using new parts question

[Tbruz]

Pretty much decided to go with all new parts(versus rebuilt or boneyard pull) for a Hydorboost upgrade on my 1997 2 door Tahoe.

I understand from my reading of posts that the rebuilt HB units do not have a spring/plunger/star washer assembly inside the bore that goes between the Master Cylinder and the HB unit. Recommendation is to remove these essential parts from your old HB unit and reinstall in your rebuilt one.

Does any one know if new AcDelco units p/n 178-578 or 178-579 come with these essential parts or do I need to hit a boneyard to score these parts?

Would love to hear form somone who has used all new parts versus a donor truck for any pitfalls or issues to watch for.

I can post up all of the PNs I think are needed if anyone is interested.
Thanks
Tbruz

 

[SunlitComet]

the new ones are usually equipped with them already. the two concerns you have are you will need a cooler that is not made anymore so an alternative will be needed. tube and fin design 2 row say 12-16 long. and you can not mount a nbs mc to the obs boosters with out machine and loosing the retention ability of the pushrod parts.

 

[Tbruz]

Thanks Sunlit.
I got the PS cooler and mounting bracket already from GM, Pn's 26041420 and 15655032 for around $90.
Cardone PS filter for $20
All new hoses, 36365490,36365460,36368460 from RockAuto around $80

Picked up a new OBS Master Cylinder AcDelco 18M-712 from Ebay for $50
That MC works with both AcDelco HB units 178-578 and 178-579.

The spendy item is the HB unit at around $400. I'm being very cautious about pulling the trigger on either 178-587 or 178-579 until I know EXACTLY which one I need.
Would you happen
to know differences between those two HB units?
Tbruz

 

[SunlitComet]

there are internal differences i would need to know the power steering pump you bought or the brake classification your are using or the model, frame size and engine you are basing your parts purchase from in order to ensure you pick the correct one.

 

[Tbruz]

Sunlit,
PS is AcDelco 15909826.
Appreciate your help and your continual sharing of your knowledge.
Tbruz

 

[SunlitComet]

178-578

 

[wtbtahoe]

I know that this is an old post, but does anybody have an updated parts list? Most of these have changed and some of the superseding part #'s aren't available. Thinking of doing this to my '99 OBS Tahoe two door two wheel drive truck.

 

[Tbruz]

Go to RockAuto.com and look up the items for a 1997 diesel Tahoe. Those had HB brakes from the factory. If I recall correctly the biggest issue I had back then was locating the correct brake pedal.
8 years later and I still daily drive and love the 2 door. The HB upgrade has performed flawlessly.
Tbruz

 

[wtbtahoe]

Hi Tony,

I don't know if you remember, but you helped me with my factory driving lights switch and harness a few years back.

I went on RockAuto and there are two different HB units- with either a blue or gold accumulator- which appear to have different mounting configurations. Does one have the correct offset for the vacuum booster pedal setup? And did you go with a reman unit or step up to the new AC Delco? Thanks again for your help.

 

[Tbruz]

Back when I did this I went all new parts. I suspect that "new" is not an option today. My unit has the gold accumulator and fit without any additional alignment plates or issues. I think that the HB brake pedal itself is going to be the tough find- everything else, HB unit, master cylinder, PS cooler, PS pump and the lines themselves are wear items that someone should be remanufacturing.
Tbruz

 

[wtbtahoe]

Found the brake pedal 15906961, and almost all the other parts at RockAuto. But one concern I have for the HB unit is that my Tahoe is also supercharged, with a Whipple SC that is hung on the D side of the engine, and comes very close to the factory original MC. Any thoughts? I understand that the HB unit is about an inch longer, so I am concerned it will interfere with the intake elbow.

 

[wtbtahoe]

Keep reminding me how much you dig it, so I'll stay motivated to do this. And, did you add the PS cooler too?

 

[Tbruz]

Ill try and post some pics with dimensions of where the HB unit sits when mounted. Its about 8" off off the firewall (end of mounting bolt) and about 7" off of the edge of the DS valve cover.
Yes I installed PS cooler as well. PS cooler was the simplest component of all this upgrade to install; it mounts next to AC condenser on Driver side front of radiator support(once the grill is removed) and plumbs from return of PS pump to steering box. Again the absolute easiest part of the HB upgrade. BTW, the toughest aspect is replacing the brake pedal; followed by installing the HB unit itself. MC, PS pump and PS lines are easy to replace and likely due to be replaced on a 1999 vehicle anyways. This has to be the best braking upgrade possible on this vintage truck.- doesn't really firm up the pedal but it is serious braking improvement. Also there is a "comb" of sorts that sits under the HB unit and keeps the lines in order.
Tbruz

 

[wtbtahoe]

Thanks TBruz, I'll check out the measurements and see if I can fit the HB without clocking it.

 

[Tbruz]

Found this in my file; may help you out.
Tbruz

 

[wtbtahoe]

Thanks for the info. You know, I just noticed that you're in Windham NH. Are you anywhere near Swanzey NH? That's where I found my Tahoe and had it shipped out here to San Diego. Bought it with only 10k miles on it from the og owner almost 10 years ago, and he just contacted me the other day and asked if I still had it.

 

[wtbtahoe]

9 years, can't count any more....still a while ago.

 

[Tbruz]

Swanzeys about 50 miles due west of me; my 2 door came from South Carolina about 10 years ago with 80K miles; has about 230K on it now.

 

[wtbtahoe]

Pretty close, you might have snagged mine if the timing was a little different.

I checked your measurements, and I think the interference point with the elbow will be the accumulator. Any chance you could check the dimension from the firewall? With all of the SC plumbing in the way, it's hard to get a good measurement; it lools like the dimension is around 6 7/8" from the firewall to the end of the accumulator? Definitely can't use the larger accumulator, for sure. Thanks so much.

 

[Tbruz]

Here's a pic of the Accumulator for reference; its an 1.25" gap from the end of the accumulator to the MC mounting bolt and an inch lower.
Thanks
Tbruz