tbristol

I have a 1970 350 with the edelbrock performer intake and the 810xx something AVS carburetor, Very mild cam, From comp cams. The carb and intake were already on the car when I bought it. I had the motor rebuilt over the winter. .030 over and the higher compression pistons, to keep the stock compression. Everything else all new. Compression came out to 9.75:1 a little under the stock of 10.25:1 but for me that's fine. I use my car as a driver not a dragsters. Before rebuild motor was in bad shape burned oil horribly, leaked oil, oil would leak into cylinders and foul out plugs. It was worn out. Is that enough background?? you guys always tell me I don't give enough details.

So the motor has 2000 or so miles on it now, since rebuild. I have been smelling fuel all the time and the motor just wasn't running, like I thought it should. Getting harder to start. Would bog down on hard acceleration, plus the smell of fuel all the time.

So I finally had time today, to look at the idle mixture screws and the timing. UGH Timing is staying where it is at. 14 deg intial without vacuum hooked up. it is an HEI distributor. I have read so many articles on timing. My head is spinning. Plus I couldn't even find the bolt to loosen the distributor.

So I hook up my vacuum gauge. Proceed to turn in the idle mixture screws to start my adjustment. The screws were like almost 4 turns out. After turning out to best idle and vacuum they aren't even a full turn out. The car does seem to run better I took it out for a quick trip giving it the full treatment of easy starts to full on foot through the firewall and it ran good. But the whole difference in turns has bothered me. So I pull out a couple of spark plugs and they look almost good. A little lighter caramel then I would like. I know I should have checked them before hand. Also the idle mixture screws really don't effect the engine running to lean once you get past idle right?

So now I'm worried its running to lean? should I be worried? Was the old motor so bad, that it had to have that many turns out to idle. Now with the new motor all good and tight and new it doesn't need 4 turns out to idle. I'm scared to run the car now. I don't want to burn it up.. What do you guys think. Should I turn them back out??

Oh yeah, I know everyone hates the AVS carbs. I'm not looking to buy a new carb right now. If I do anything its going to be an EFI kit. Like I said my wife and I both drive the car everyday. So EFI would pay off eventually.

oldcutlass

The AVS carbs are fine. The 2 idle a/f adjustment screws are just that, they control your idle fuel mixture only. Once the carb opens up with the throttle they do nothing. What you neglected to mention is how much vacuum your gauge was reading? Was it steady? 14 degrees advance at idle may be a bit low if the dist wasn't modified.

tbristol

I'm getting 14psi vacuum it does jump a bit but I think that is from the tad bit bigger cam.

The problem with the timing is A. I couldn't even find the bolt to loosen the distributor. Any ideas how to tell me where it is?
B. It was on the car when I got it. I have no clue what brand it is or anything. The cap is red. But so are most of them.
C. So I have no idea what mechanical advance it has or Springs or anything. So that is why I just decided to leave it alone.

Fun71

14" vacuum seems fairly low for a "mild" cam but it really depends upon your camshaft specs. I have a 217/221 cam and I get a steady 16" vacuum with the HEI initial at 18*.

Unless you used forged pistons such as Speed Pro L2321F or similar your compression ratio may be less than anticipated. Aftermarket cast pistons are short on compression height so they yield less compression than expected if you don't take the shorter height into consideration. This shouldn't really cause an issue with the fuel issue you described, though.

OK, on to timing adjustments. Look at the block on the drivers side where the distributor stem goes into the block. There is a 9/16 bolt holding a metal piece that clamps the flange on the distributor to the block. Loosen that bolt and turn the distributor to adjust the initial advance.

tbristol

Yes, forged Pistons were used. The stock replacement cast Pistons had the big dish in them. I'm not sure what brand my motor shop used. It put the build way behind waiting on them. Something about having to basically make them. So I know they are the right ones.

As far as the timing. I know there is a bolt back there. I just couldn't see it. So can a take a 9/16 socket with an extension on it and feel it? I know it only has to be a little loose.

Let's talk the new dial back or whatever they are called timing lights. I'm using an old school timing light. No dials or switches. So I can basically only look at initial timing. I read some where that the new lights. You dial in the total timing then set the indicator on the timing mark to zero and everything is set. Is that true? I don't have the extra numbers on my dampner. So if autozone has the free loaners for those type of lights it might help me dial this thing in. yes? No?

Oh besides a leak or a big cam. what would cause low vacuum? How can I up it if I don't have a leak?

oldcutlass

Timing and carb adjustment.

Fun71

Sounds like you had to wait on the Speed Pro L2321F pistons. I know those were on backorder for a long time a while back.

I use a combination wrench (box and open) to loosen the distributor bolt, but a distributor wrench would make it a lot easier.

tbristol

Well it took me awhile to get to this. Work and other things going on. I bought a timing tape from summit. Installed it. So I didn't have to buy a dial back timing light. After reading about they don't stay on I marked all the numbers before I started it. Sure enough, tape flew off and shredded on start up. No big deal had all the marks. So, I adjusted the timing and now I'm at 18 degree initial and 36 all in at 3500. Re adjusted the idle fuel mixture screws and idle. I still can't get any more than 15 psi. The timing adjustment sure made a difference. My car was always a dog off the line. I just figured not a lot of mods to the engine. 3.08:1 rear end, heavier frame because of convertible. We enjoy driving the car. So we weren't concerned about it being fast. Now though, It will bark the tires on take off and get up to speed really quick. Best thing I ever did. Now though I would like to figure this low vacuum. I have a really cheap Guage I wonder if that might be??

oldcutlass

Did you adjust the carb and how many turns are the screws out from turned all the way? Are they about the same number of turns? Do you have any vacuum hoses disconnected or leaks?