[FONT='Arial','sans-serif']Tuning my 340 issues In short… I’ve got a newly rebuilt 340 w/ 10.25 pistons, thick Felpro head-gasket, the TA 288-284 cam, an MSD 6AL box, MSD pickup in a factory “Dave the Ignition Man” modified 1112109 distributor (from a 72 350), the Crane adjustable vacuum advance (w/ blue springs), mild porting and a Carter Competition Series 600 CFM carb that I rebuilt… And I hope that’s not my problem. I’m also running on Arco 91 octane pump gas. I started off by setting the timing up at 32 degrees overall timing, with no vacuum, and it just pinged and then pinged some more. I soon discovered most of my issue was in the Crane vacuum advance, it was adding about 20 degrees. So, I closed the gap on the Crane hard stop and then reduced the overall timing to 25 degrees w/ no vacuum. This brought my initial timing to 3-4 degrees at 750 RPM (no vacuum) and w/ vacuum it went to 10 degrees and upped it to about 1000 RPMs. With vacuum my “total” timing was at 28 degrees… I’m not sure why it didn’t go another 3 or 4 degrees more, since I was hitting about 3300 RPMs with the Crane blue springs that should have put it all in at 3200. My issue is… it still pings lightly when I hit it hard enough to get a second gear chirp with a factory TH350, light shift kit and 2.5x rear gears. I know the gears are not ideal but the posi 12 bolt w/ 3.55 gears is not ready yet. My main issue now is (other then the pinging) it‘s hard to start, seems like excessive cranking. I’m a little disappointed because I was assured by “some” people that 91 octane was plenty for these 10.25 pistons and TA cam combination. Am I doing something wrong? As usual I welcome to all comments and suggestions… Thanks [/FONT]
Remember you can tune the sensitivity of the crane vac. advance usinghe allen wrench inside the port, this can lsow down the rate vac advance is added. To start with I would stop ussingthe vac. advance untill you get it running good with no ping then add 10 degrees only of vcuum advance from there. Shoot for 33-36 degrees total timing (initial plus mechanical). You are onthe irght track!
Yes I think I'm on the right track also. I was under the impression that the larger the initial timing setting (14 degrees) made it harder to start the car then if it were at 4 degrees. I've reduce my initial setting to about 3 or 4 degrees and the car still is slow to start. I'm thinking I may have carb issues?? Looking back on it, I did jump to the stiffer pink compensation springs because early on I thought it might be pinging from being too lean. I think I might now be making it to rich because I'm not drawing enough vacuum, while it cranking, to properly bring the metering rod down. Just something else to play with.
My stock 340 with 10 1/4 compression doesn't run well without octane booster. I'm going to convert it to HEI, go through the carb and fiddle with it to see what I can do. Keep your progress posted. Every so often I tell my self that at $5 - $10 for a jug of octane booster is a waste of money because it doesn't add that much so I run without it. Next thing you know I'm running down the road wondering why my car isn't running well, then I remember what I did and get some booster. I've messed with the timing but haven't had much luck. I am waiting to get my upgraded distributor before I get too excited myself. I will be eager to hear how yours does, maybe learn from your work. Good luck.
Sean, your description is how I was adjusting my timing, initial & mechanical advance. Even with the vacuum advance unplugged I can not run Initial and mechanical advance at 30 degrees which is why I dropped it to 25 degrees. It also maybe the gas... ARCO 91 octane is the cheapest in town. Regarding the adjustment on the Crane vacuum advance... Fully clock-wise is the fastest advance response, correct? Thanks
My mistake, it's the TA-284-288H cam on page #60 & 61 of their 09 catalog. Had the numbers right but in the wrong order.
I'm guessing your talking about the 284-88H? Seems like a very mild cam. A bigger cam would help bleed off cylinder pressure and make pump gas a little easier to use.
Yes, I'm aware that a bigger cam will help, but I am building this for my daughter to drive too, and I think I might be pushing it now. After she gets tiered of buying gas for this car, and I get it back... I'm sure that I'll go w/ a bigger cam. The cam in it now is as big as I can go without having to make changes to the valve train components, and then there's the torque converter too. I don't mind tuning it back a bit, she's not interested in speed, she just wants it to sound mean... and it does.
I would try some good 93 octane from Chevron, Shell, or BP. Now is not the time to try get it to run right on cheaper gas. When you say excessive cranking do you mean you have to turn it over for a while before it finally fires or is it hard to turn over? Turns over fast but no fire is fuel related. Slow cranking would be from too much advance, however, you don't look like your running excessive timing.
I'm in California where the octane level of nearly all the gas stations top out at 91. However, Union-76 does have higher octane ratings and I do plan on filler her up there next time. I'm sure it will help. Till then I'm going to try an additive. Currently the car is down because I've had issues with the power-steering pump and hose (another story), and it's going to be raining here off-and-on till next Wednesday. Stay tuned for further detail next week. Thanks,
Drew, double check with Dave....does his setup require 12v? The original coil wire has built-in resistance and will only give 9v to the distributor. Pinging could be too much timing, or a lean fuel/air mixture. Consider both possibilities. Is the car pinging under full acceleration, or under part throttle? If it pings under full acceleration, you have too much mechanical advance since there is no vacuum. If it pings under part throttle, slow or limit the vacuum advance. I bet most of your questions would be answered in 'the Wizards' thread, 'power timing your Buick V8'. http://www.v8buick.com/showthread.php?t=63475
i was gonna say theres a station in san jose that sells higher octane but you beat me to it. it sucks out here in cali as far as gas goes. bout 10 years or so ago we used to be able to get 92 octane. now if you want anything higher then 91 you have to go searching. you will find a station here and there that sells 105 octane:TU: :beers2:
Hi Walt, It's pinging is only under "real hard" acceleration... so I'm just about there. MSD provides their own wires for the coil, so that's not the problem. However, I am using the original +12v coil line/wire as the "keyed" power-on input for the MSD box. I'll check the voltage level on that wire, if it is low it doesn't seem to be causing a problem. I thought that it might be a bit lean so I dropped the size of the compensation rod (0.070 x 0.037") but left the jet (0.098") alone. That change did not make much difference, so I next change to a heavier spring (pink) and it was about that time I noticed the excessive cranking on start up. I'm guessing on this but I think the heavier spring combined with a lower vacuum (since the timing is backed off) is causing my starting issue. I changed the spring back to the orange but I haven't tried starting it yet. Right now the car is all wrapped up because of the rain.
i am no mechanic, but if you are using the original wire from ignition to the msd or dizzy you are not getting full 12volts. i think it is 9.6 volts. make sure you are getting the full 12 volts. jim
I once tried a HEI on my 66 Special. It was very difficult to start, and ran lousey. I gave up at the time, but now I think it may have been the low voltage. Live and learn! If it's pinging under hard acelleration, I would say there's too much mech advance, or it's too lean. The power rod TIP size is important under WOT. Go smaller to richen. Or try a bigger jet. The springs control mixture under cruise conditions. I put a water injection system on my old Turno Regal (with 4bbl). It helped control pinging. Consider that if all else fails.
What is the heat range of the spark plugs? I'd leave the vac advance off until you get the issues sorted out. Without knowing your a/f ratio, it's just guessing on everyone's part as to whether or not it's a mixture issue. See if anyone local has a wideband you can borrow, you can get detonation from both lean or rich mixture.
I am going to order an HEI conversion from him and I've been asking him questions about the setup and he confirmed that you do need to run a new full 12 volt lead to the coil. You should be able to go from the same ignition fuse on the box and run it to the coil. You are not getting the full hot spark that you should be getting if you are using the resistor wire.
I'm using the original +12v coil line as a keyed "Power on-off" signal only, not the power source. The MSD box power source line goes directly to the battery, via the starter motor. MSD coil voltage is not the issue here, as I do know a wee bit about electronics. "Before I couldn't even spell enjinear, and now I are one". ou: I don't think that I'm running lean either. Going back to over some of the Carter and Edelbrock tuning chart data (on metering rods and jets) I'm see some major discrepancies between the two carbs (Carter Competition series Carb and the Edelbrock Performer Series) when I thought they were virtually the same carb. I'm tuning the carb according to Edelbrocks data and the carb I'm running is the Carter Comp series... because I figured that the Edelbrock data was more up to date. At any rate, the smallest metering rod that Edelbrock offers has a tip diameter of 0.037" and the smallest one that Carter offered had a tip of 0.047". According to the Edelbrock (1406 cart) I'm 12% rich and for Carter I'm completely off their richness cart. On the other hand, I did do some porting and the cam should be letting in more fuel so who knows what my actual A/F ratio is? I think that NJBuickRacer is right, until I know where the A/F ratio is... I'm in the dark. I think that after I get about 500 to 1,000 miles on this engine I'll take it to a performance shop and have the carb tuned professionally. Anyone have a chart that indicates hotness on AC-Delco spark plugs? Today I'll look and see which plugs I used, I assume they are middle of the road because I didn't specify. BTW... I also gaped them at 0.045". Thanks for the feedback guys... keep the suggestions coming.
I know Dave Ray told me that the input voltage for MSD units wasn't specific, the small red wire that ruens the MSD on and off can be between 6.0 and 16.0 volts, and the unit won't care. I had sojmewhat of a similar issue with one of my 340's, Dave got me OFf the Carter C/S disaster of a carb I was trying to get to run on it, onto a 600 cfm Holley, and that fixed it nicely. Then, I ran across a rare aftermarket manifold for the engine, uses a Q-Jet. Dave did an 800 cfm carb off a 455 for it, and now, it runs even better, doesn't ping on California pump premium 91 mule drippings. Regards, Milton
