I just had my 68' 225 rebored .040, and head shaved .100''. The engine runs fine until I get onto the highway. At a steady speed, no noise, but as soon as I give a bit gas, the engine is rattling, which I believe is detonation. The noise is constant until I get off the throttle, it dissapears. The carb is a carter BBS 1bbl with, I think, the stock jet size. I removed the plugs (champion RN12YC, colder plugs than the stock RN14YC), they seem to bit a little bit white, but more like a light brown color. Timing is set at 8 BTDC, I dont have an advance timing light so no idea of total timing. I disconnected the vacuum advance and its still rattling. Compression ratio is supposed to be 9.2, I've been running 91 octane for the last 2 tanks ans it seemed to have helped a bit, but not much.

So.. Should I increase jet size or check the distributor (stock points), go to a colder plug (which one would work best with my combo). Is there any replacement jets for my carter BBS or I have to redrill the stock one?

Thanks, Fred

I have just gone through what you described with a new rebuild.

What rpm are you at when this occurs?

The govenors are different in the two distributors, 9r govenor for the points and 15r on the electronic. But sometimes if you get a rebuild they mix and match parts. Using a 15r, there is too much timing coming on at the higher rpms.
Use a stiffer spring on the weights so the mechanical advance doesn't kick in so quick.

Another thing to do is stick a 3/32 allen wrench in the vacuum advance can and unscrew it 2 turns. That may help, and can be used for fine tuning.
My advance that is stamped 11r on the arm and I run it 3 turns out.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

The distributor is the stock one, I just had the block rebored and crank turned down. If the vacuum advance is disconnected and the pinging is still present, isnt it pointless to try to adjust the vacuum pot?

Back off your initial timing......

stock timing on a 64 is 2.5 BTDC (not sure what a 68 is).

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

You will need to check the total timing, you will most likey have to take some mechanical advance out of the curve.
DD

Timing must be looked at and probably ajusted & recurved. But I bet that 1b carb is very lean for your setup. If it is lean, timing is just not going to help much.

A quick test to save time & work would be to put a few gallons of race fuel in with your pump gas. If the pinging goes away you know the fuel & timiing will fix it.


Jess

9.2 sounds low for the work you had done. I had .100 taken off the head and bored 30 over. This resulted in a cr of 9.8-1.
I agree that you probably have too much inital advance for a stock timing curve at your current compression ratio.

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I tried to play with the initial timing, when I retard the timing, RPM drops and idle is getting rough. Would going to a brand new distributor off ebay help? Im not a big fan of points ignition.

Just remembered that I calculated my CR before having the engine rebored. How much would it usually be with a .040 rebore, piston .200 down the hole and head shaved .100? Around 10:1?

Should I just try to score a new head and shave it less so I can be in the 9:1 range? I dont think fuel mixture is an issue, the plugs seem normal. And would timing really fix it with a CR of around 10:1 and 91 octane gas, I really dont wanna pay for 94 octane.

SlantFred,

I just had my engine rebuilt and I have atleast .10 shaved plus more off the head. My set up has no smog stuff, I can send a picture if you want. The strange part is I can't get mine to ping at all and I am running 30 degrees initial plus mechanical at 2000 rpm plus another 13 degrees vacuum advance for 43 degrees total.

After all that work, just rebuild the distributor or better yet convert it to a Pertronix setup and bag the points. That setup bolts in about 15 minutes.
Mine is a 74 so I am running the Mopar orange box with a MSD Blaster 2 coil, MO-3000 rotor, BlueStreak cap, 8mm wires and NGK plugs gapped at .040. It runs super clean with a light cinnamon color to the plugs.

You could have some bad vacuum leaks on the intake manifold causing the problem. Try using the Aussie gaskets. I ordered mine a week ago since I have atl east three minor leaks.

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

I dont have any smog stuff either, everything is bone stock 68 stuff. Plugs are light cinnamon color. I have to check the timing this weekend. What octane are your running Ted? Would I be better off buying a new distributor or going pertronix? Ignition is a MSD 6A box with blaster SS coil. Plugs are gapped at .045.

I use Cenex gas here in the Puget Sound area. It is farm gas and is rated a 92 Octane for mid grade. I can run 89 our low grade but on super steep hills on really hot days (over 90 degrees) I can hear a faint ping at 60 mph, none at 50, just when the vacuum is high so I have full advance. Soon as it drops to 10 or 12 pounds on the vacuum gauge it goes away. So I am on the edge, but never a rattle like I used to hear on the same hill before the rebuild. I think the added compression ratio actually helped.

So your using points with a MSD box????
I would buy a electronic distributor to eliminate the point gap variance, worn out shaft problem. Once that is out of the equation, you can focus on tuning again. Get your distributor rebushed and buy the $10 pickup assembly and convert it to the electronic version. Hook it up to the MSD and that will be a constant. While you have the distributor apart, check your weights springs that they are moving freely and write down what govenor you have. Should be stamped a 7R or 9R. Also note what numbers are stamped on the vacuum advance arm. Again is should say 9R, 11R, etc. Once you have that documented then you can determine how much advance your getting and if you need to put stiffer springs on or not. It sounds like you may have to, however I would go electronic pickup on the distributor first so you know your getting a good consistent signal.

Are you using the stock 1 barrel? Holley or Carter?

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Ok I just checked my timing tonight. 5 degrees at 750 rpm and ONLY 21 degrees at 2000 rpm and up with the vacuum disconnected. With the vacuum connected it is 36 degrees. The mechanical advance seems too low and vacuum too high, but its still pinging with the vacuum line disconnected on the highway. Could it just be running too lean (the plugs are a light brown whitish color). If so, is there any jets available for a stock carter bbs 1bbl carb or I have to redrill it?

Here in Sweden the Carter is mostly found on the 170.
Could be that.

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Lasse

Signet -66 225
Holley 600 Offy-5270 Dutra Dual,regrind. cam 272 0,420 110, head shaved 0.100 slight.ported
MSD6A
A904
7 1/4 3.23

I am not sure if Edelbrock jets will work in the old Carters. It sounds like your running pretty lean. The only other item you can try is decarbonizng the engine, either by running some Seafoam or using water. Too bad you don't have a 1920 Holley. They are pretty simple to set up and jets are available most anywhere. Four screws for the cover and you can pull the jet. Pretty quick change capability for tuning.

Maybe some one else can share about re-jetting the Carter. It doesn't sound like timing is your problem. I had a Holly 1945 on my engine and it would ping just as you described like your Carter. I found out later it massive vacuum leaks. After taking Doctor Dodge's advice and switching to the 1920 Holley, all the pinging problems went away. (The 1920 carb body is one piece, not two like the 1945). I also ran a couple of tank fulls of Seafoam and that cleared everything up in the head and pistons. Runs very well considering I still have a few gasket leaks on the intake manifold. I am running a #57 jet (rich) to compensate until my Aussie gaskets get here. Now that I have made the carb change, it has really allowed me to focus and concentrate on the intake leaks and recurving the distributor and tuning (cutting on the vacuum advance for more timing, etc.) If your car has a cable throttle the swap is about 15 minutes. If not, just find the older 1920 that was cam actuated.

Hope some of this will help.

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG