Hi guys

Bit of a Vette newbie from the other side of the pond, wondering if anyone can help. Had an engine rebuild for my 59 and decided to put a new Edelbrock carb and manifold on, so here are the problems. First, really difficult to get an accurate suggestion of the correct timing. I've set it at 4 BTDC to be on the safe side. I've seen anything from this out to 36 BTDC. Where should I be for normal driving?

This may be linked to the above, I don't know. She starts from cold without a hitch, barely even has to turn over before she fires and as long as you give her a gentle touch of throttle she purrs like a kitten (loud kitten maybe). I can quite happily amble along @ 20mph down the lane, get her out onto the freeway and open her up, all seems good, gets a little rumbly at around 4000rpm, but Im probably being fussy. Issue comes when you stop and want to restart........she won't. takes a long time and you have to keep your foot flat to the floor. Now I have noticed that when she is cold, the inline gas filter is 80-90% full, if you shut her down whilst still cold (ish) the filter stays nearly full and she will start on the button. If you run her till warm, turn off and come back in 5 mins, the filter is empty and she won't start, well not without some 10-15 seconds turning over.

So the obvious, new pump, new gas tank sender and filters, new HEI dizzy and leads, new plugs, new engine and new carb.....oh and new tank vent hose, what am I getting wrong?

 

Is the distributor totally stock?
If it is stock timing is 7 BTDC vacuum line disconnected for a 270 HP engine but you gave no indication of which engine.
if the springs have been changed for the mechanical advance to lighter springs. You use a dial back timing lighr and set the total mechanical advance to 36 degrees so full advance occurs at about 3k rpm.
Which HEI did you install and what are the advance specifications?
Gasoline on a hot start may be boiling out of filter.
Does the fuel pump you installed meet the requirements of the carb you installed?
Did you check the float level?
What temperature thermostat are you using?
After you turn it off and look down carburetor throat, do you see gasoline dripping?

 

No the Dizzy (distributor) is a new HEI one, swapped out the leads to 8.5mm silicon, engine is a 270 HP

 

Do you know the specifications of the HEI you installed? What is the total mechanical advance and what is the vacuum advance?
Who made the distributor and what is the part number?

 

If you are using ethanol containing gasoline try non-Ethanol if available.

 

Unfortunately I don't, it was fitted when the new engine was installed, as far as I am aware it came from Zip. Not really got a problem with the engine when it is running, or cold start, just won't start from hot.... I will try moving it to 7 BTDC and see if that helps the starting.

 

Welcome to the forum!

The large numbers like 36 BTDC are measuring the "all in" or total advance.. That reading is taken at 3000RPM+, when the distributor is adding all of it's centrifugal advance.
Numbers like 4-8 BTDC refer to an idle measurement, with the vacuum advance disconnected.

Think of it this way: Total timing (or 'all in') is the sum of the static (idle) advance, plus the max centrifical advance, plus the max vacuum advance.
When starting, you have very little centrifugal and vacuum advance.

When cranking hot, does it struggle/lumber to turn over? That can be a sign of too much advance.
Or does it crank normally, but just not fire up? That can be from lack of fuel, or too much fuel.

Fred

 

Hi guys, thanks for all the replies, a few answers

Using 99 octane fuel, as far as I am aware it still has to have 5% ethanol in it.

Cranks very fast hot, you can feel it trying to fire but it takes about 15 seconds. Once she has fired, runs but doesn't want to idle, little bit of gas and she runs beautifully. after you have run her for a while, she will idle, but as you leave her, the idle diminishes slowly down to a stall.

 

My best guess would be to start with the obvious and that is engine flooding on heat soak. This problem could be caused by not isolating the heat from the bottom of the aluminum AFB carburetor. If you look at a 1963 corvette AFB installation there is a gasket, then insulator and finally a stainless shield. You may not need all this but a good thick insulating gasket is something to consider, do some research.

The fuel pump pressure is easily checked and you want approx 5-6 lbs. max at cranking or idle speed. Finally, if you have a heat riser, wire it open as that will help a whole lot keeping the heat off the carburetor.

If all this checks out then I would take a look at the float level and compare it to the spec for the carburetor. You can lower it a fair amount but to much and you get into other driving issues. Make sure the fuel lines are not to close to the cast iron heads or block because fuel will boil and pressure will increase and overcome the needle and seat inside the carburetor.

 

The carb does sit (with a basic gasket) straight onto the inlet manifold, certainly worth trying some form of heat shield, fuel lines are all standard spec although the inline filter to the carb does "hover fairly close to the rocker cover.

Any idea why when cold the filter stays around 80-90% full, but when hot, at about 20-30%. Also, when the engine has stopped the filter very quickly clears itself of fuel.

 

I agree - the "not wanting to idle" does sound like a flooding issue. Do you see black smoke when this is happening?
Hate to say it, but in my experience, this is a problem you "manage", rather than solve.

The one thing that made the best improvement in this for me was switching the intake manifold gasket to one with metal block-off plates.
As mentioned above, removing (or wiring open) the heat riser helps as well.

Basically, anything to keep heat out of the carb.

I live in SoCal, so it never gets cold here.. but these mods can impact cold-weather operation.

 

Top info guys

when you retard the timing back to around 25 BTDC it idles much better but runs like a can of bolts, I've been told you can go to 36 BTDC but this seems a bit excessive..... The engine certainly runs very well at 4 BTDC and I don't suppose moving it to 7 BTDC will do any harm.

I will try the insulator gasket, as this sounds like it could be the problem. Might sound a dumb question, but do you think a high temperature in the carb could increase pressure back down the fuel line, pushing fuel out of the filter? Would certainly answer a few questions if that could be the case.

Lived in San Diego for 2 years back when I was in my 20's so I know about the great weather. The UK is a little different lol. To be honest, as soon as the weather turns here, I put the car into garage, she is not good on cold, wet, UK roads....

 

I would be curious if the hot fuel is percolating and overcoming the needle inside the carburetor. When the engine is hot and after sitting awhile remove the air cleaner and take a look inside the carburetor to see if there is any wetness.

Any idea what type of fuel pump, excess pressure may be something to think about. Is this a new carburetor or rebuilt.

 

Morning guys

Its a new Edelbrock, the pump is a new AC Delco from Zip. Going to have a look at pump pressure and fit the heat soak today, will report back.

Many thanks again guys

 

If your distributor does not have vacuum advance then I would also map out the mechanical (centrifugal) advance curve.

I would target approx 16-18* initial timing and total wide open throttle timing (initial & centrifugal) approx. 34-36* BTDC.

If you are not sure what all this means do some research here first and maybe seek some help.

Lighting the fire sooner will reject more heat (energy) to the piston and less to the surrounding cast surfaces and water jacket, the engine will run cooler.

 

I think we need a better understanding of exactly how you are going about setting the timing on this engine. You are throwing numbers around some of which are initial timing, 7 degrees, and others are total timing, 25 and 36, as if they were the same type of timing.

 

I am running the same intake on my '61----the stock 270HP carbs as well. I was getting boil over and percolation at hot shut down in California with our terrible gas on hot days. I fabricated Masonite heat insulators out of 1/4 inch Masonite, and my carburetor bodies are now 60 degrees cooler. It still acts up sometimes, but the problem is 90% fixed. These carburetors were designed for better, denser, less volitle fuel than is available today.

 

Don't forget about climate change... that global warming requires a tuning change. :-)

 

104 here in Fresno today. Climate change is real....it's been happening for the past 4+ billion years. It's just not man made, that's all.

 

Got the same problem here in Arizona with my '65. Crate 290HP 350 which has the "hot slot" manifold. I plugged the slots but still have the issue with fuel boiling over after a drive and making a hot start difficult.
Curious how you made the spacer out of masonite.... where'd you get a piece of 1/4"? Are any ready made spacers available and do they really work?