Hello,

I have been away for a while due to other committments, life, motorcycles and cars .... I pulled the old 'vette out yesterday and reminded myself of the "issues" I had when parked. Once this COVID is over I plan to do a rally or two. Most likely the Monongalia Melee or similiar.

Back to the HBoost. At low rpms I have nearly no brakes and the steering is nearly impossible. Steering and cornering at low speeds is an "interesting" exercise. I can compensate with some heel / toe and rpm! Do I merely need another PS pump? It had been replaced prior to the HB installation? Or should I rip the damn thing out and go back to stock??? I am running Wilwood brakes (Corvette Engineering kit) front and back. The brakes actually worked very well until I got "boosted" ... Or is there an oriface that needs to be included somewhere; I don't think so as I do not seem to have enough flow??? I want to drive this car hard ... its not a show queen ... maybe HB is the wrong answer??

Now, suspension had been upgraded with Vette Brakes kit, bigger sway bars, fiberglass rear leaf, (I don't like it) and Bilsteins. I think I have a 330 or a 360 rear and "stock" BB springs up front. The car is an LS-5 w a 489 kit, ~~ 490 crank hp. The handling is ok, ... but it is the vertical transtitions that are difficult. What are you giuys using as a baseline for similar events? I don't want to go Coil overs or anything too far away from the stock suspension architecture.

Thanks Chris

 

hydroboost:
there are, if to remember correctly, some washer like shims in the power steering pump
behind the pressure side hook up. It’s been a long time on this one... so you ether add
or subtract these washers to increase or decrease pressure
also, you should always have 2 separate return ports on the fill can, do not use “T’s” .
idle should be 750ish

Suspension do you have a rear sway bar you should the Bill Steen shocks you have are they the sport or heavy duty? What weight springs upfront and did you cut any to lower it further?

 

Hi,

No T fitted, I am not sure about the shims as I did not perform the install; excellent point!!

Front springs are not cut; I believe they are stock BB w air; maybe 475lbs? I remember I did NOT fit the 550s like I wanted to I have a rear sway bar.

Thanks for the reply!

 

Almost forgot - shocks are Bilstein sports

 

ok shocks
change the front springs to the 550’s and cut I think 3/4 a circle off

front sway bar is the biggest you can get at VBP or whoever is still in business
as far as the rear goes, If memory serves there were three available get the one in the middle
the bigger one will make your *** come out in front the smaller ones not worth the time

when Re-shimming the power steering pump only go one washer up or down and then try it out believe it or not it’s a big difference

 

Hi Paul,

Excellent advice. Oddly enough when I had the suspension done I wanted the 550s and allowed myself to be talked out of them. Got you on the sway bars; I beleive Dick Gulfstrand (??) advised the same and I always took that to heart! I will get a new PS pump from Duntov and have it installed.

Thanks for the help, again!

Chris

 

pm me if you need any further help on it
mine in dialed in:-) took a while

Dick Golstrand ... spent some time with him before he passed
we have one of the 427 C5 Goldstrans
the only vert

 

Bah, just get one for a 2004 3/4 Chevy/GMC pickup. They had HB std & the pump reservoir has 2 return lines. A std Corvette PS pump doesn't have enough line pressure.

BTW - check if that pump will accept a V-belt pulley, forgot I'm running a serp & that pump is a native serp.

 

Double return line pump is good, I read going C4 pump with external reservoir was even better. Can't find the thread right now.

Went newer model truck pump myself and ordered the shim kit to reduce pressure. With the shims you adjust how 'light' the steering feels: I used almost all shims but it's personal.

 

The HB system will work fine on your car when all is good. Issues with both the HB and the steering at low engine speeds is almost always going to be the pump. The steering system is an open center system meaning the fluid is always flowing from the pump through the system and back to the pump reservoir. Only when a restriction is introduced does the pressure build. The steering gear has a torsion bar in it that when torqued will restrict and redirect the flow of fluid allowing assist. the pump only provides the needed pressure to perform the work up to the max pressure setting (relief set point). GM indicates that on a passenger car sitting still at idle the pressure should be between 125 and 200 psi fully warmed. easily attainable if the pump is working correctly. The HB works similarly, when the brake is applied the flow of fluid is restricted and redirected to produce assist. There were two different master cylinders produced with the difference being the depth of the plunger hole using two different depressing rods but being your having issues with both steering and brake assist I would start with the pump.

Neal

 

Start with the obvious, have you bled the system? Air in a HB system will give you noise and be hard to steer. PSI from the steering pump will be about 1200 for GM and you DON'T want to reduce it if you are running HB, it will have a negative impact on the system. I run a HB on my car, with a double return and a unit off a 2001 Suburban.

 

Stock front springs with BB & air are around 325 rate. They are still very soft, they are very long (15-16 inches) to handle the weight and are hard to remove because of it.

If you have a 330 rear the Moog 474s would be a good choice. If you have a 360 rear the 550s may be the better choice. You want the front and rear ride rate to be balanced. Right now your front is a little soft (at 325) vs the rear (at 330) and the rear probably feels much stiffer on tar strips, undulations, etc. The front has a lower ride rate (cps) than the rear. Right now your front wheel frequency is probably at 1.25 while the rear is at 1.77 . That is far too much of a difference They should almost match. I would guess the front feels soft, has slower transitions and feels like it wallows vs the crispness in the rear. That may be the "vertical" issue you mentioned.

You need stiffer front springs to fix that. And shocks need to match the spring. With Bilstein Sports you should be good, but some guys like the HDs in the front and Sports in the back with the f/g spring..

Front sway bar should be the 1-1/8" unit from a 78-82 model. They're out there.

I have 27 years Pro Solo racing / tuning experience and that is almost exactly how I set up my BB. Minus the adjustable shocks, but I like to tune!