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914World.com _ 914World Garage _ Took a long drive today

Posted by: Hammy Mar 11 2005, 07:38 PM

Took a drive up to the foothills today. I Don't know much about mechanics so I have questions
Driving along the highway it seemed to be losing more and more power. The elevation change was from under 100 feet to up to around 3000 ft.. So from the little I know, it's the carbs right? The idle was really low when up high and it kept wanting to die, but when we got back down low it idled fine.
Also, while driving some twisty mountain roads, suddenly my brakes go out. Push them all the way to the floor and barely anything. Shit. But when pumped 2 or 3 times they'd work. Brakes need to be bled? Or what could it be? Why would they suddenly just start acting up? It was an interesting drive home.. Help

Posted by: jd74914 Mar 11 2005, 07:41 PM

QUOTE (Hammy @ Mar 11 2005, 05:38 PM)
Also, while driving some twisty mountain roads, suddenly my brakes go out. Push them all the way to the floor and barely anything. Shit. But when pumped 2 or 3 times they'd work. Brakes need to be bled? Or what could it be? Why would they suddenly just start acting up? It was an interesting drive home.. Help

i say bleed the brakes right away. like yesterday before you drive the car again

Posted by: vsg914 Mar 11 2005, 07:51 PM

Loss of power was probably because of the altitude and attitude. Thinner air and constant uphill. Carbs tuned to sea level can have severe prob at higher elevations. Dwell can play a role here also. Check the brake fluid level. Sounds like a possible leak.

Posted by: Hammy Mar 11 2005, 07:53 PM

So..How do i learn to tune carbs

Posted by: vsg914 Mar 11 2005, 07:57 PM

I'm a fuel injection guy, but there are many carb guru's here.

Posted by: SirAndy Mar 11 2005, 08:00 PM

QUOTE (Hammy @ Mar 11 2005, 05:38 PM)
But when pumped 2 or 3 times they'd work.

check for leaks. flush 'em, bleed 'em. check for leaks again, then bleed 'em one more time ...
get someone to help, cause it will make the job *much* easier ...

Andy

PS: also check the MC for leaks on both sides (behind pedal cluster and from under the car)!

Posted by: airsix Mar 12 2005, 01:41 AM

As a general rule of thumb a piston engine* will lose about 5% power per thousand feet of elevation. Even with perfectly tuned carbs an engine will have 15% less power at 3,000 ft ASL as compared to sea level.

Add to that the fact that as you go to higher elevation a carbed engine runs richer (unless re-jetted or adjusted) and elevelation change can really affect power.

*naturally aspirated (no turbo or supercharger)

-Ben M.

Posted by: Andyrew Mar 12 2005, 01:49 AM

Ya, turbo's do better with elevation and such... they spool more boost with the more drag on the engine, wierd.. lol

Give me a call in the morning, 529-9944, and i'll have you come over and we'll go over your car, bleed the brakes, check for potential problems, ext.

Andrew

Posted by: McMark Mar 12 2005, 01:51 AM

You can't tune your carbs to work in both high and low elevations. You pick the one you'll be in the most and tune it there. If you want elevation compensation, get FI. It's built in.

Posted by: Elliot Cannon Mar 12 2005, 01:52 AM

Check all the brake calipers and see if you can see any leakage anyware. If the calipers are dry that means the leak is probably in the Master Cylinder. If the seals in the Master Cylinder are leaking, you might not see any fluid leaking out. It is letting air into the system. Most people will discourage you from rebuilding the master c. and I don't think it's such a great idea unless you absolutely cannot afford a new one. So, bleed the breaks. Drive the car. Check for leaks. If no leaks detected and the pedal still goes down, change the master c. Try not to skimp on brake parts. Brakes are very important to your survival.
Cheers, Elliot

Posted by: brp914 Mar 12 2005, 10:31 AM

dont bother rebuilding the m.c. First, it's a PITA, second it wont last as long as a new. I tried it twice on both my teeners. On 1 it lasted a few years, but on the other only a couple days. I might add that if your brakes are ok now that they have cooled down, your brake fluid may be contaminated with water, which lowers its boiling point. That water isn't going to do your calipers any good either. Flush it all out and replace with a DOT 4 fluid.