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The car seems to be more responsive after changing the advance line routing and changing the timing. I moved the initial timing to 14. Prior to moving it it was a long ways from the top of the timing pointer. I am going to look at getting a dial type timing gun as well as have someone else assist to work the throttle so I can time it at 3500 rpm or so, I am going to keep an eye on fuel mileage. Hopefully with some changes that will improve. Does anyone know what the pulley in the attached picture is doing? It is the one with the goldish colored finish. It seems to spin off another pulley. I cant see any wires going to it so I am not sure what it is doing.
That gold-ish colored wheel is the idler pulley that came on big block A/C cars.
https://www.corvetteforum.com/...3793362-big-block-idler-pulley-pictures-wanted.html#post1591763453
"The A/C equipped big blocks MUST use the idler belt because their A/C compressor is driven off the water pump pulley ONLY as it doesn't go around the crankshaft. Without the idler belt the entire load of the alternator, fan, water pump, and A/C compressor would only be on the fan/alternator belt and it'll burn up from being overloaded."
The car seems to be more responsive after changing the advance line routing and changing the timing. I moved the initial timing to 14. Prior to moving it it was a long ways from the top of the timing pointer. I am going to look at getting a dial type timing gun as well as have someone else assist to work the throttle so I can time it at 3500 rpm or so, I am going to keep an eye on fuel mileage. Hopefully with some changes that will improve......
That sounds like a big timing adjustment and it should like that and run much better. Timing could easily be your whole problem with it under-performing.
Yes please get a dial back timing light, a Mr Gasket advance curve kit and a Crane Vacuum Advance limiter. Make sure the advance is set up to a vacuum manifold source, it should have strong vac at idle. You seemed unsure on this point. This will all have a big impact on HP and MPG.
Mechanical advance setting must be 36 degrees "all-in" at 3000rpm. (With no vac) Even 38 is OK if your compression is low enough. The Mr Gasket springs (gold & silver IIRC) are weaker than stock and help it to advance earlier than the stock 5000 rpm. Play with the springs until it is all-in at 3000. Play with the initial until you have 36 at 3000.
Then "check" but do not change your initial timing and report back. It will run best with 12-16 initial but you may have to mod the distributor internally to get that. Leave it where it is for now.
Then re-connect the vac can, and adjust the Crane Advance limiter until it only adds 12 degrees at idle. (Some of these are as high as 28.)
Should run way better get better MPG and should not ping.
leigh1322, would you happen to know part numbers for the kits you mentioned? I want to make sure I look at the right stuff. Would the distributor need to be removed to replace the vacuum advance limiter?
I assume the HEI that is in there is completely stock (weights, Springs, canister setting, etc)
Hi guys. Tomorrow I am going to pick up a Mr. Gasket distributor spring kit from the local auto store. Do I need to be concerned with the weights or just the springs. When I used to drag race I would install the lightest springs should I do that in this case as well or mix 1 of the lightest with one that's thicker? As far as the timing goes I think any additional changes I will do when I have another person with me.
With the big block idler blocking my view of the timing pointer it is very tough to find a good spot for a reading. Since the car does not have AC and I don't plan on adding is there any harm in removing it ? I also noticed that the timing pointer has points but it doesn't have a big notch in it to Mark the 0 location unfortunately since it is painted Orange I can't make out the numbers so I will have to go based on what you have mentioned as far as the 4 8 12 16 spacing. Not that I like assuming but I can't even get my fingers in there to rough the paint off the pointer. I am hoping that the springs and or weights in the distributor make a noticeable difference in the performance of the car.
Take the idler off. Get the timing pointer cleaned up. Read it, paint it sand it clear it whatever. make it so you can see what's going on down there. Get it timed. Then put the idler back.
Yes your pics look like the stock stiff springs.
What I have heard on the curve kit is start with one light and one medium spring. Not sure of the colors. The important thing is it's all-in at 3000 ish.
And throw the Mr G weights away & use the stock ones.
Yeah don't guess at the total timing, it's too important. Get all the idler junk out of the way.
2-4 degrees "off" in total can be 20-40 HP on a BB. I tested my LT1 & 6 degrees off was 35-40 HP.
The vac can is just for better idle & MPG & runs cooler.
Last edited by leigh1322; Jun 4, 2020 at 10:11 PM.
Today I swapped lighter springs in the distributor and set the timing on the car. The total is at 36 now. I drove it around and it is running nice and smooth. I didn't put enough miles on it to find out if the MPG has increased. I don't notice much difference in the power of the car. It feels strong in the mid range and at higher speeds. Off the line it barely spins the tires. Given the mismatch of carb, cam, and exhaust with the 3.08 gears I am not sure if it should spin the tires aggressively. Overall it cruises nice just different than what I thought it would do.
Before I turned it off I revved it a bit in the garage and noticed some smoke coming out the back. I am wondering if the carb is too rich and needs to be adjusted. What is the best way to adjust the 650 CFM -SPREADBORE Carb I have. Model 080555-1. I do not know if it has been modified from stock.
What did advance do when you hooked up vacuum? Shoulda jumped up 10 to 12. Adjust your fuel mixture? Get and install a wideband O2 sensor before even thinking about it. You start jetting a Holley leaner by SWAG and the engine will burn piston tops cuz you didn't give it enough gasoline.
