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Discussion Starter · #1 ·
New member here. After 25 years of raising kids, etc, finally bought myself another street rod. It's a 69 Nova with a 540 BB Chevy and a moderate hydraulic roller (pump gas). Everything is brand new. The car s equipped with power brakes and a vacuum reserve can. When I brought it home the power brakes were obviously not working. A quick inspection revealed that they had the hoses reversed on the vacuum reserve. Now the brakes are working but the exhaust smells terrible as if there is a vacuum leak. Reversing the hoses renders the power brakes useless but the exhaust smells "clean". I've gone over everything and I see no indication of leaks, but this is my first time using a reserve can. Any thoughts?
 

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Gonna guess the carb idle mixtures are adjusted for the wrong hose connection and now youve corrected that, the carb needs attention.
While your in there, might as well go over everything because you already know you'll find things you would do differently.
25 years of kids? Did you sell them for the Nova?
 

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Discussion Starter · #3 ·
Gonna guess the carb idle mixtures are adjusted for the wrong hose connection and now youve corrected that, the carb needs attention.
While your in there, might as well go over everything because you already know you'll find things you would do differently.
25 years of kids? Did you sell them for the Nova?
Sounds like a good starting point. Been out of the game for a long time so some of the basics escape me. I'll get there again.
The kids: actually I traded them with some cash.
 

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Little off the subject but you have a big block with cam and, most likely, down on vacuum some. Being able to stop good is, well mandatory. Have you considered hydro boost brakes?
 

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Guess you’d need to give a hint as to what you smell in the exhaust is fuel, oil, coolant, burning paint or what?

Two corner or four corner idle adjustment?

Cams have large effects on idle to that end “moderate” is a subjective opinion where data od the cam card is quantitative fact. The latter is information that can be worked with, the former not so much.

Bogie
 

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Discussion Starter · #8 ·
smells like unburned fuel...burns the eyes, the smell I associate with a lean condition. Sort of like standing behind a car burning methanol. Four corner idle adjustment on the carb.

Cam is a Howard hydraulic roller, Lift: .640 / .640, Duration @ .050: 243 / 249, Centerline: 108, 112 lobe center.

Again, when I picked the car up, the hoses were reversed on the vacuum reserve and the exhaust smelled "clean".
 

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Most generally smelling raw fuel in the exhaust is rich and something I’d expect with that cam. Those short LSA cams do foretell a lot of overlap, but I need to caution that with I haven’t done the math so don’t know the actual amount of overlap, LSA being an indicator not a measurement. But in overlap both the exhaust and intake valves are open so there is free communication between the induction side through the exhaust.

A question in my mind as yours is why it would do going rich with the vacuum hose to the reservoir being reversed. In the end the higher vacuums seen as the throttle is moderately advanced or coasting on a dropped throttle opens the inlet valve on the reservoir and low idle or WOT vacuum allows it to close thus storing negative to atmospheric pressure. The brake actuation side should be sealed not allowing a vacuum leak that when the system was reversed if it leaked it would lead you riches the idle that would end up being too rich when the vacuum reservoir plumbing was corrected.

Since this is a four corner idle carb and assuming the secondaries are adjusted open at idle the engine should get enough air without the curb idle stop being adjusted so far open that the transition circuit is bleeding fuel at idle as well as the idle circuits.

The other thought is fuel has pooled in the reservoir can and is being pulled out, this is not something I’d expect but since it was apparently plumbed reversed, there would be no valve action to prevent fuel being blown up there. Here again this gets into how overlap and late closing intakes generates strong reversion waves that do weird things. I take the reservoir off to shake it to hear if it’s wet inside. I’d check the carb to see if the secondary side is supplying air as well as fuel which leads to checking the primary side to see if the transition slots are not overly committed standard should be .020 to .040 inch slot exposed to the underside of the throttle primary plates with the throttle shaft set against the curb idle screw.

Bogie
 

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The brakes should only steal air when applied, once can is under vacuum the motor should run as before. On a sidenote def invest in a reserve vac can.

Did you change anything else? Maybe hook up a vac gauge and compare with brake line pinched and not- maybe the diaphragms leaking?

Also - are brakes plumbed into the rear port of the manifold (cyl 8 i think) or manifold/carb base (all cylinders)?
 

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Discussion Starter · #11 ·
It does have a vacuum reserve, plumbed into the carb spacer. The only thing I changed was reversing the lines on the can to the correct positions to get the brakes to work. The brake booster is brand new so I'm assuming it to be leak free. After the car sits for hours or even over night, pulling one of the hoses will release the stored vacuum, further pointing to no leaks.
 

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It does have a vacuum reserve, plumbed into the carb spacer. The only thing I changed was reversing the lines on the can to the correct positions to get the brakes to work. The brake booster is brand new so I'm assuming it to be leak free. After the car sits for hours or even over night, pulling one of the hoses will release the stored vacuum, further pointing to no leaks.
That eliminates that then :/ hmm - dunno, choke issue perhaps? Leaking needles? my new holley 850 direct from Holley leaked at both almost hydro-locking my brand new 383 on gas! Really worth checking!
 

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What color are the blocks?
It would be a real good idea to look on QFT website and get the calibration details and get back to the beginning. QFT's are usable out if the box but very generic in nature and so it may need some tweaking here and there, if out of the box it marginal for you anyway, it's a short trip to being way out in the weeds. It's also a good time to clean and check over everything, like throttle bushings. I've had issues with QFT nylon stuff.
 

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A way to test would be run the engine with the vacuum reservoir plumbed incorrectly and when the exhaust smells ok block the vacuum feed hose from the engine (needle nose vice grips) and see if the bad smell starts up again.
Hydro carbons (HC) are unburned fuel and when the mixture is rich ( 12 to 1 ) HCs are much higher than when the mixture is 14.7 to 1.
Around 15 to 1 HCs start climbing again but never reach the same levels as when it is rich.
Lean conditions cause the engine to misfire which is the cause for increased HCs. This also produces an oder but not the kind that burns the eyes and makes you want fresh air.
If the reservoir is hooked up wrong and the power brake booster is vacuum leak free I can’t understand how this could cause a vacuum leak. By you removing a hose and the system acting like it still has vacuum trapped has me confused.
Have you considered bypassing the reservoir and plumbing directly into the power brake booster. If you do this and it starts stinking try blocking the hose again and see what happens. Last question, when swapping hoses does the idle speed change?
If this last test causes increased smell it may mean the booster is not leak free.
Curious.
 
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