convert to manual brakes on their C4? Wanna do this *maybe* since my cam does not pull enough vacuum. I should clarify, the brakes work great as long as you only hit them once. But after you expell the initial stored vacuum, they are a BEAR. Staging is what I hate the most. You have your foot on the brake the entire times and the motor just doesn't have enough vacuum to supply the booster with enough vacuum to properly work. When "bump" into the lights I have to press so dang hard its like trying to move a brick wall, and then I can't get any RPMs for the launch or the car pushes through the lights.

At the topend, whe you leave off the gas when going through the traps, it will throw you through the window ----lots of vacuum there.

At any rate, maybe manual brakes would be the ticket. Imagine I could do what we did with my fathers chevelle that had the same problem. We just removed the booster and mounted the master cylinder to the firewall.

Vacuum pumps are heavy and don't last, we had a 200+ dollar one in the chevelle and it only lasted a few months before wearing out...that is when we went to the manual brakes.

His brakes are great all around in every situation.

Thoughts are appreciated.

 

haven't done it on a c4, but did on a c3...m/c for manual is SMALLER bore to generate sufficient line pressure with lower available input (no boost)...1'' man vs 1-1/8'' power IIRC...repositioning of actuating rod should also be done to increase mechanical advantage of operator on m/c...typical ratio for race set-up is 8:1 ratio for manual brakes, 6:1 for power assisted...ratio change will require longer pedal stroke.

you might look at adapting a c3 manual m/c.(compare bore sizes to start)..no black magic in brakes, we have all kinds of junk on circle track cars and they all work

 

Have you tried a vacuum resovoir canister? They are pretty cheap and may give the results you need for drag racing.

 

with DynaBob... try the vacuum reservior first. If it doesn't work out, then converting to manual brakes would be an option. You can then delete the ABS module located behind the driver's if you so desire (simplify the system, and take it further down the road to purpose built racer).

The vacuum reservoir sell for around $50 or so (that's what I get for them, anyway).


Good luck!

 

Tried it but they do not work either when you need to hit the peddle several times real quick,,,,actually seemed worse since the little bit of vacuum it does make needs to refill the entire resevoir.

 

Since you do drive your car on the streets sometimes when you are looking for targets of opportunity, motorcyles seem to be your preferred prey. Check this out http://www.hydratechbraking.com/products/c4vette/

yedi

 

Don't know if this will help. But, at GM we use a small very light electric vacuum pump and reserve on our Duramax Diesels. But, I don't know if it would produce enough vacuum for your needs.

 

Check a truck junkyard for a vacuum pump. They're fairly common on some domestic and especially foreign medium duty trucks. I've rarely ever seen one of them fail. You would want to get the driven speed right though. Most of them would be designed for engines with a maximum RPM of 3K or less. Some of them are actually driven off of the rear of the alternator, but would be adaptable, I would think. If it's off of a small diesel, I'd say underdrive it by about x2.5 and if it's on a gas job, by about x2.

 

hydroboost it

 

This was the motor in my hot rod before I got the Vette...

I had a 292/292 adv duration cam in it and no vacuum at idle, I tried the canister and it didn't do squat. Don't waste your money, I just developed a feel for it, meaning push like a bitch.

 

I ran an 85 Buick GN master cylinder on my last hot rod for the same reason - cam would not pull enough vacuum at idle. It was designed for the GN turbo-charged engines. It is electric and does not rely on vacuum. They have a name for being unreliable, but mine worked well for about four years until I sold the car. Manual brakes work fairly well with drum brakes, but they are a real bear on discs. I would only convert to manual as a last resort.

 

Jeese,

I converted to manual along with wheelsup, give me a call.

Dave

 

I don't think I'd agree with you unless you mean on a C4 they're a real bear. I drove a '66 with manual brakes for many years, discs all around. It was heavy, but it stopped very, very well. And the feel was excellent in my opinion.

 

I too have tried the canister on another car i once had and didn't work like it claimed. Cam wasn't that huge either,only .220/.230@.050 too. Strange......is it a gimmick!?

 

I knew lots of C3 guys were doing this, but not aware of the C4 kit..

 

Will do, Jeb and I were on the phone yesterday and he gave me some ideas as well. He is using the strange mastercylinder kit.

Good to hear from you man - gotta get together sometime this summer/fall and rip it up together. You should plan a trip to Beaver or Keystone you would like Keystone track....

Thanks for all the suggestions.....I looked at the hyro setup the other day, but 600 is a little expensive for me - got twins on the way, looking a new house, and just trying to keep my head above water

 

Monte Carlo?

 

Put a vacuum canister on mine last week and it didn't do squat. I'm sort of getting used to having no boost, but do not look forward to a panic stop. The electric pumps cost about $300 (didn't the LT5 use one?).

 

Jes......let me know what you come up with. Chris's engine is making about 7-8 inches at idle. I think h'es going to have the same problem as you.

Phil....if you read this, that rack mod worked fairly well.