Outer Limits 4x4 Board

Since rebuilding the engine, my brakes are fairly inneffective unless I've been conciously gearing down to produce vacuum. When the engine runs normally, the new cam doesn't leave the valves closed long enough to build vacuum.

Is there any way to get more boost for the brakes? (the clutch is heavier too but I can deal with that, I just want to be able to stop!!!)

Thanks

fit an alternator off a diesel with a vac pump on the back, or an electric vacuum pump. also check your ignition timing, your cam would have to be fairly radical not to make decent vacuum.

Also make sure the brake booster check valve is working - pretty much as soon as you lift off the throttle you should have plenty of brake boost for the next time you hit the brakes, and it should stay there for a couple of days.

It was the guy at the brake place who said it was the valve timing to b lame. I still haven't worked out exactly how it goes, sometimes I have vacuum, sometimes not. I fitted the vacuum resevoir from the cluth into the brake line so I have a reserve there and mostly now its ok but I really want the brakes to be 100% predictable.

I do have access to the alternator from a 3B engine. Will this create an extra drain on the engine or does it only pump when it needs to? Maybe this could be a good way to go.

Would I use the vacuum pump by itself or in addition to the manifold vacuum?

Thanks.

V8 Middy wrote: I do have access to the alternator from a 3B engine. Will this create an extra drain on the engine or does it only pump when it needs to? Maybe this could be a good way to go.

Would I use the vacuum pump by itself or in addition to the manifold vacuum?

Thanks.

the load from the vac pump is negligible, you wil not notice it. use the vac pump on its own and just plug the manifold vacuum.

Brian...

Could you run the alt with the vacuum pump (eg hilux) and just not connect the alt to the charging system in the car and purely use it for the vacum pump on the back?

+dj_hansen+ wrote:Brian...

Could you run the alt with the vacuum pump (eg hilux) and just not connect the alt to the charging system in the car and purely use it for the vacum pump on the back?

yeah you could but it would be a pretty dumb, a whole extra belt and brackets and everything just to run a vac pump is a waste. you might as well put it where the existing alternator is and use it as an alternator - even if you leave the other alternator there, there's no harm in having two alternators.

if you only want vacuum, get an electric vacuum pump, then there's no oil to plumb in, no brackets to make/modify, no belt, just two wires and a hose.

Of course if you were looking to set up a nice winch system, a 24V alternator with vacuum pump would make a lot of sense!

Personally, I would check the system for leaks since as someone else said vavle timing would have to be pretty extreme not to have decent vacuum. I recently had a similar problem where my clutch booster was playing up, sometime working, sometimes not. Then I ended up with no brakes booster at all. It turns out that the clutch booster was leaking all the vacuum from my pump leaving nothing for the brakes.

Have you done any checking to see how much vacuum is actually available? I used an old VDO boost/vacuum gauge to measure vacuum in various parts of the system to diagnose the problem. Just hose clamp a piece of similar sized hose onto the back of the gauge and clamp a cheap plastic barbed joiner at the other end. Then you can, with the engine running, disconnect various parts of the system and plug the gauge in. (Your engine may well run like a bucket of shit while the lines are off of course but don't let that worry you).

I would start with the port and move out along the system looking for leaks. If you have no vacuum at the manifold port then Make sure that all other lines running into the manifold are OK by pinching them off (or pulling off and blocking with your finger if the hose is big) in turn and seeing if the vacuum increases at your brake port.

I figure that an engine with a cam so hot that it does not produce enough vacuum to run the brakes would not have any bottom end torque at all and hence be worthless in a 4WD anyway. The problem must be elsewhere.

Keep us up to date!

Richard.