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4 degrease BTDC is way to low for your motor. This was a smog spec but in reality it was bogus.
I'd start at 8 and go a bit more until it's pings then back it off a degree at a time till
it stops pinging.
Is your BB a 400 hp (hydraulic cam) or 435 hp (solid lifter cam)? 2 completely different animals.
4 degrease BTDC is way to low for your motor. This was a smog spec but in reality it was bogus.
I'd start at 8 and go a bit more until it's pings then back it off a degree at a time till
it stops pinging.
Is your BB a 400 hp (hydraulic cam) or 435 hp (solid lifter cam)? 2 completely different animals.
Thanks Babbah, I will try to set the timing this morning with my old timing light and start at 8 degrees and move to more advance. My 512 block is being rebuilt as we speak and I will have it set up as close to original as possible including solid lifters since it was a 435 car but I don't forecast being ready to install that till early next spring so I am trying to get this one up and running in the mean time.
I am about to look like a fool as I think the present block is a solid lifter set up but how do I know? It sounds like a solid lifter but I am no expert. Of course I will realize when I pull it apart. How would that effect the timing when I go to set it up? Would the solid lifter need more advance? I have no idea what cam is in it either but it does have large rectangular port heads.
Welcome to the firehose club (I really like that one!), I went felt the same way early this spring (although I had quite a bit of non-Vette experience). You're making good headway, if you have the Rect. Port Heads it's a fair bet that it' still Mech. Lifters. If you hear lots of ticking when cold and it gets quieter as it warms up that's another point to Solids/Mech. I think pulling a Valve Cover and checking Lash is the only sure way but maybe another member knows a trick. I agreee with babbah, I have about 12 initial and it's happy (but I run 110/91 Oct. mix).
Thanks suprspooky,
Here is a picture of my fan set up. I loosened the fan shroud and centered it as much as possible and found that I had a full 1 inch of clearance between the end of the fan blades and the fan shroud. (so theoretically I could squeeze in a fan nearly 2 inches bigger.??? How much should I have?? Maybe this is part of my cooling problem. As you can see I have the spacer which eliminates the fan clutch mechanism. (I presume this gives me maximum cooling.)
Should I pull out the fan and replace it with one and inch or so bigger? Does anyone know how big the big block fans should be and how much clearance there is between then end of the blades and the shroud. One more project tomorrow to remove the fan and measure it. I see the corvette places have 17.5 inches for sale for the 1969 big block. I will measure mine and find out.
Blade depth looks similar to mine (I still have factory fan/clutch), I'll make some measurements for you tonite.
I was having the exact same issue with my 71 BB. Would start and run awesome when cold. I can drive it all day at speeds with lots of highway air hitting the rad. As soon as I hit even a bit of traffic the car would heat up a bit more and start sputtering, rough idle and then would die. Very hard to start like it was out of fuel. after letting the car sit for 30 min would run fine again till the warm up. So we changed the rad to a Dewits, gone over the whole ignition system. Re built the carb, wrapped the fuel line with insulation, nothing worked.
Nothing worked until we removed the intake manifold and found those exhaust bi pass channels that rout hot exhaust gases though the intake and under the carburetor to heat it up in cold weather. Weill that was the problem. The area under the carb was getting so hot there was a melon size build up of cooked/burnt oil residue ( on the underside of the intake ) The New intake gasket came with plugs that cover those bi pass ports. they actually make the right gasket to cover the ports up. Once installed, I never had that problem again. Just had a little issue adjusting the choke as it was not kicking off to well as it was not receiving the heat it once did. So we installed a electric choke and now all is good to go. So you have to bite the bullet and pull it apart. Oh, the actual problem is our new fuels with out led additives burn much much hotter and cause that over heating of the carb through the bi pass and fuel vaporization in the carb. Good luck.
Blade depth looks similar to mine (I still have factory fan/clutch), I'll make some measurements for you tonite.
Thanks, on that note supr, I have just come to realize the I am missing the lower fan shroud extension. I didn't realize there was a piece missing, so I have just ordered the lower shroud and the seal kit so I will get that next week. Perhaps that would really have messed up the airflow through the rad and around the engine. Hmm
I was having the exact same issue with my 71 BB. Would start and run awesome when cold. I can drive it all day at speeds with lots of highway air hitting the rad. As soon as I hit even a bit of traffic the car would heat up a bit more and start sputtering, rough idle and then would die. Very hard to start like it was out of fuel. after letting the car sit for 30 min would run fine again till the warm up. So we changed the rad to a Dewits, gone over the whole ignition system. Re built the carb, wrapped the fuel line with insulation, nothing worked.
Nothing worked until we removed the intake manifold and found those exhaust bi pass channels that rout hot exhaust gases though the intake and under the carburetor to heat it up in cold weather. Weill that was the problem. The area under the carb was getting so hot there was a melon size build up of cooked/burnt oil residue ( on the underside of the intake ) The New intake gasket came with plugs that cover those bi pass ports. they actually make the right gasket to cover the ports up. Once installed, I never had that problem again. Just had a little issue adjusting the choke as it was not kicking off to well as it was not receiving the heat it once did. So we installed a electric choke and now all is good to go. So you have to bite the bullet and pull it apart. Oh, the actual problem is our new fuels with out led additives burn much much hotter and cause that over heating of the carb through the bi pass and fuel vaporization in the carb. Good luck.
They CVO,
Much appreciated for your ideas. I have done nearly everything but not the so I will yank of the carbs (getting good at that, I have done it so many times now) and the manifold and either check on that gasket or put the correct one in place to block of the passages. I am running out of ideas but the heat riser valve is gone now but I will take it to the next step and make sure the channels are blocked off.
Thanks for your input!
Pete
Thanks, on that note supr, I have just come to realize the I am missing the lower fan shroud extension. I didn't realize there was a piece missing, so I have just ordered the lower shroud and the seal kit so I will get that next week. Perhaps that would really have messed up the airflow through the rad and around the engine. Hmm
Lower shroud extension on a 69 BB???
The fiberglass shroud is one piece.
Lower shroud extension on a 69 BB???
The fiberglass shroud is one piece.
Yep, I realize it is a one piece but if you look at the AIM, there is an add on piece at the bottom called the fan shroud extension which attaches with 3 screws, GM part # 3956089 which completes the circle, my car has lost that piece somewhere along the way.
BTW Babbah, I was working on the timing but got some results that don't make sense to me so I will try again tomorrow and better document what I have. Even after advancing the timing, the car got too hot at about the 15 minute mark again and would not run. But it was running slightly better as the choke began to open.
A friend of mine came over who knows far more than me. Right away he noticed the timing was jumping around and pulled the distributor. Old distributor so that was rebuilt. He also noticed that the carb was not responding correctly to idle adjustments and choking. Seemed to only run once warm while it was choked. As the choke came off the car died. He was relatively certain that the car was running way to lean and had one if not more vacuum leaks.
So, we took off carbs and the intake manifold and made sure all was properly sealed. Then all new gaskets in all three carbs. All carb and manifold surfaces true and machined flat.
Radiator was removed and boiled out to ensure it was functioning properly.
New electronic ignition with 6500 rev limiter and new ignition cap and wires. Plugs gapped to .035
Here is where we are at. Plan to run it this week so more to come!
You mentioned timing was jumping all around. Have you looked at the harmonic damper to be sure it is OK. The rubber cushioning ring can deteriorate and allow the two parts to move, making it almost impossible to time correctly.
Ralph
Thanks Ralf,
I did read that somewhere else. I know for a fact that the distributor was very worn out so thought we would start with it. If we still have issues, I have a spare balancer and will have a look at that.
Much appreciated.
Pete
I hate to have threads that are not properly closed.
So final update.
Car runs perfectly now! Largely thanks to a friend of mine who knows these machines.
Overheating (in my opinion) was largely due to vacuum leaks causing car to run too lean and not idle properly.
Secondly, worn distributor causing timing to jump around all over the place. The retarded timing leading to overheating.
The car now runs very smooth and very cool. Carb bases and fuel lines are about 100-110 deg instead of climbing past 160.
Carbs were rebuild and mating surfaces machined flat. All new gaskets in all three carbs.
Distributor completely rebuilt and points removed and replaced by the electronic ignition.
New spark plug leads.
I will eventually install the TI distributor but one thing at a time. Now back to the alignment and finally certification I hope!
Thank you everyone for the help.
I would post a video if I knew how!
I'm glad to see you finally have it solved. You should check your Harmonic Damper anyway, my 68 still had it's original and it was close to letting loose completely (if a couple more chunks worked their way out anyway). It didn't show up via timing light it was a pure visual inspection, once it was on the bench, I found I could move the outer ring front/back more than an 1/8" on the hub.
Last edited by suprspooky; 01-11-2017 at 03:07 PM.
I don't think you have an ignition issue, it sounds like fuel is boiling in your bowls and bubbling like boiling water. It cause to much air in the boiling fuel and the floats don't react well like cavitation. They don't put enough pressure on that seat to stop the fuel from coming in, then you have to much fuel in the bowls and dumps through the inlet tubes when braking.
10-24-2016, 10:52 PM
