[KULTULZ]

If the engine was origionally an early 4V, she most likely had 10:1 at birth. I would try an adjustable vacuum advance cannister first and if that does not fully get it, check the mechanical advance in the distributor.

If this engine has positive stop rocker studs, you would need to go to the studs for adjustable rocker arms.

[oldchevy1956]

Well after quite some time and much trial and error I have solved my pinging issue with my 69 351w engine. To the best of my ability the compression ratio is 10.25 to 1. It started out before the rebuilt at 9.75 to 1. These are my calculations and are not easy to do. I really do not think that compression was my issue. I also did a compression test and my compression as 140 to 142 lbs per cylinder. When I was removing the spark plugs I had noticed that most of them were loose in the cylinder heads and on one of them the white porcelain was loose in the plug. So I installed new plugs same heat range and did a test drive and the pinging was better but still there. I also began to notice that the pinging was not consistent. Meaning that at times it would ping very badly at slight or moderate acceleration and at times it would not. It would never ping at a constant speed but then it seems that most pinging will occur at acceleration of some sort. I was disappointed as I thought my plugs were an issue, but I guess not or only part of the problem. So I started out by changing to my old faithful autolite 4100 (1.08) carb which will run anywhere and anytime. I hoped this would solve my problem but there was no change. The 1.08 carb was jetted much richer than a stock carb but still the pinging was there. Keep in mind that the timing is set so that it is just a few degrees past TDC and just past the point where I get hesitation. In other words the timing is probably still retarded but I am not getting hesitation. So I put back on the engine my rebuilt 4100 (1.12) carb and I put much richer jets in the primaries as with the higher lift and long duration cam I need to richen up the mixture. With the larger primary jets, the pinging was much better and would appear to have solved the problem but then the pining was still there and real inconsistent. Now, I unplugged my vacuum advance and now the pinging was real inconsistent and even pinging as I drove a constant speed. So on to the next item on my list which was the timing advance curve. When I took apart the distributor I noticed that the advance springs were missing, so the mechanical advance was just not restricted at all and on top of that the mechanical advance would stick in different positions, hence my inconsistent pinging due to inconsistent advance. I fixed the sticking and installed some fairly stiff springs and now the engine runs great. I also have the vacuum advance hooked up. I have driven quite a few miles and now am on 89 octane gas and I have no pinging, and I have advanced the timing a little bit too. Not a real scientific test but from a dead stop in Drive, I can punch the gas to WOT and do a burnout for several feet and no hesitations and no pinging. Now I believe I may have burned up the locking differential unit as the last two burnouts my driver wheel was not leaving a mark on the road. Oh well. Thanks to all for your advice, comments and help.

[yackster]

Originally Posted by oldchevy1956

I have a 69 mustang with a 351 windsor engine that I just finished installing after a complete rebuild. The engine was over bored .30, the cast iron heads were completely done with some mild porting and new guides, seals etc. The crank was ground slightly and of course there were new pistons installed. It has a 4 barrel cast iron Ford intake with a fresh professionally rebuilt autolite 4100 1.12 carb. I also have a pertronix ignition and coil. The new cam is a long duration higher lift cam (.5 intake, and .5 exhaust) that requires a 2200 rpm stall torque converter. Now my problem is it pings real bad upon light to medium to heavy acceleration. It quites down at cruising speed. So I have backed off the timing so far that it now hesitates and bogs down; I have even taken off the vacuum advance thinking that it was advancing too far. I suppose it could be the mechanical advance but that was all functioning correctly before the rebuild and is fairly new. Anyway backing off the timing slightly helps but does not solve the pinging issue at all. I also think that it may be running somewhat lean so I put bigger primary jets in the carb and that did not help either. I may still need bigger primary jets but I need to purchase them first. I did have some issues with adjusting the hydraulic valves, could I have them too tight and they are not closing all the way? Any suggestions? I am an experienced mechanic and I am at a loss here.

Hello, I am sure someone said this already but? Retard your camshaft. crank the engine over for a compression test to get cylinder pressure where you want it, sweet spot for street engines is 175psi is ,

a big cam will close late, reducing cyl pressure, and pushing out the exhaust and up back into the manifold for poor idle feed of idle discharge. so you would advance it until it is in your spec range, or retard it, to reduce cyl. press. which will get rid of your pinging or detonation I have a 10.5:1 windsor, I degreed mine, and it made a lousy 145 psi, so i threw out my camwheel, and guessed, advanced cam until I had 210psi, cam sheet said 4 adv, now im 6 advanced. Never lost any high rpms, only gained, but i run 110 or 114 with 92 mix, everyones engine is different, so are cams.
yeah care about cam timing after you find cyl. pressure, than check it to see where its at and leave it alone. 10 to 16 inital timing, 30total for 10 to1 and up, but 9, you can run 34 to 38, but MSD billet distributors you would be doing back flips they are awesome

[elemental37]

you said you were working with the valve lash some I believe. Now granted, I'm taking this from an old chilton's manual and they ain't like motors manuals but the chilton manual on valve lash said 69 & 70 ford 351 Windsor engines were supposed to have .083 to .183 lash between the valve stem and rocker arm. The tech section went on to say if that lash tolerance could not be achieved that the only solution was using longer pushrods available in increments of .060. The last part I read of your replies said you had snugged the rocker arm nuts down tight? The valve lash must of course be measured with the valve at rest. I'm still tryin to figure out how I took my machined and .060 bored out 351W apart two years ago. I keep having to search through parts bins and boxes to find the parts to my engine. I think I missed a spacer behind the timing gear on the camshaft. fortunately, all I have to do is just pull the timing gear off to correct this. Haven't gotten to installing the timing gear cover yet. Well, hope this valve lash thing might help out. It sure would be easy if all you had to do was back off the valve lash a bit to solve your ping, just hope you haven't cooked any valves up to now. (I ain't a super motor head anymore so I may be out of my league or way out in left field in my thoughts on this, so my intentions are good even if I can't certify my opinion entirely as valid, so cut me some slack ye olde engine gods and priests)