74-76 13B Half-Bridge,51 Webber sidedraft,no ignitors,running [2] MSD ^AL boxes,Rcaing Beat wires,Full Racing Beat Off Road Race Exhaust and Stock plugs.The problem is as follows-------Timing is wayyyyy off,like 30 BTC,although it is locked in the Dizzy,no power,getting intermittent spark from plugs,L1,T2 sometimes not firing or the other way around,on diagonal.Plenty of spark from the coils[i found out the hard way,it was the HIGH_LIGHT of the the day]So can someone HELP!Thanks.

 

I would personally start from scratch....remove the dizzy, set the timing to 0, then drop the dizzy and time away

 

How on earth are you running the trailing ignition without an ignitor? If you wired the MSD to pick up off of the magnetic pick up for the trailing that's your problem. You cannot run the trailing directly off the magnetic pickup. It will be sparking every 90* and into the intake stroke, which will cause detonation. Also, if you're not running a leading ignitor you have to run direct fire. Without more specifics on how your igniton is set up I'm willing to bet you did something wrong.

 

Nail on head/etc

 

Hyper4mance2K, I'ved ran this set-up before on a Big street-port 6-port motor on a 1st Gen,NEVER had a problem ,until now on this half-bridge.I have replaced the 2 MSD Blaster coils with s4 coils and also using S4 trail plugs.Although the centrifugal advance is welded with weights to the outside and dizzy set dead-on,why is the timing that far off 30 BTC?When i should be about 20 ATC.I'm i correct by assuming this?I'm just trying to understand what's really going on with this system.Plenty of spark when grounded on the strut tower,but when installed it misses,WTF is up with that.The MSD 6al"s are ran through a noise filter if thats helps you better understand.Thanks.

 

+1

 

If you're getting spark at the strut tower and not the block, check your engine to chassis grounds.

 

Yes,i'ved added a couple of grounds to the motor,still getting intermittent spark on lead plugs.It misses very bad and i even changed plugs.Even ran a direct-fire system with a MSD 6AL and still the problem is there.Plugs are wet with no signs of fire.Thanks.

 

Where are you in Fl? I might be able to take a look at it sometime next week. i'll be in Miami the 11th-17th.

PM me.

 

Can you swap the cpomponents from lead to trail one component at a time? This will identify what component is the culprit. Personally , I try not to use the MSd stuff when trying to diagnose perfomance issues with the electrical system. I did have an issue where the grounds to the MSD boxes were sketchy.
Almost sounds like you are getting a bad or low signal from the trailing sensor in the dist. and it is shaking. An oscilloscope would be great. This is where the ignitors would be beneficial.

gd

 

Make sure the MSD box has a good ground itself. And power source. I get my power off the + battery cable at the starter solenoid, or you can use the + output from the alternator. Always use a fuse for the MSD + wire.

You can bypass the MSD and have the ignitor fire the coil. Very good way to check what's wrong.

 

Why always use a fuse? I never have. What size fuse?

 

I'm in Fort Myers,2 1/2 hrs away from Miami.Got rid of the MSD on Trail side,using ignitor instead,Wired Lead for Direct fire wasted spark MSD set-up.Problem still exist misfire under load.Checked compression------100PSI front,95PSI rear.Front has level 3 bounces,but the rear shows 2 level and 1/2 bounce.Car stars right-up no hesitation,assuming chiopped side seal and or crack corner seal.MAy explain why plugs are allittle wet on the rear side.I'll have an update on my finds.THANKS TO EVERYONE FOR THE GREAT HELP!HAPPY HOLIDAYS.

 

At what rpm are you timing the engine at? With a locked dizzy you should be timing at 4k rpm and have the timing pulley marked for full advance. Even w/o a locked dizzy, one can't time the normal way due to the high idle of a half or full bridge. One can use an MSD on the leading because they always fire at the same time. The trailing requires 2 MSDs because they don't fire together. Since the trailing does so little, it's best to leave them stock. On the 2nd gens, the ecu switches the trailing coil from T1 to T2 based on crank position from the cas.

 

You can run 1 msd on the trailing as long as you run it through the cap and trigger it from the ignitor.

 

Really, that I did not know. Thanks for the correction.

 

With a locked distributor the timing is locked. No need to time at 4K. Common misnomer. You can even check the timing spread at idle. No problem. It doesn't change.

if the plugs are oil wet, then it seems like it might just boil down to a mechanical prob.

gd

 

A locked dizzy has the timing set at full advance. So either one remarks the timing pulley for timing at idle, or times at 4k.

 

Gawdodirt,i believe you are correct by saying it is a machanical problem.Rear housing has a cracked corner seal or stuck side seal[chipped].I'll take it apart to see what is really going on with it.As stated before,it starts with touch of the key,just under load it breaks-up and misses.And yes the plugs do show signs of oil,slightly wet.So maybe a faulty ignition had lead to this problem.Thanks Trinituner.

 

Before you tear the engine down, run a full can of Seafoam through it with 1/8th of a tank of fuel. I sometimes works better if you pour 1/2 the can quickly down the carb, at idle or a little above, so it stalls out, then add the rest to the fuel tank. Let the engine sit for a few days, then take the car out and run it hard. Assuming the ignition is working correctly. 2 bounces indicates a stuck or cracked side seal. A bad corner seal should only yield 1 bounce.

 

Is it safe to say that me doubling-up the side seals springs may have contributed to this?A cracked or chipped side seal or possibly stuck side seal?The motor ran great,until ignition problems and now this.I'll try the seafoam and if that fails,then i have no other choice but to remove and take apart rear side of the motor only.I'll update as soon as i find the problem.THANKS,Trinituner.

 

Why did you double up on the side seal springs? Never heard of anyone doing that and can see no reason to do it. Only logic I could possibly see is extremely high boost, but that still makes no sense. Did you reuse old springs?

 

Has anyone successfully used 2 springs per side seal? I bet a side seal got caught on the intake port and chipped.

 

SIDE SEAL<SIDE SEAL,recovered 5 1/2 from the rear rotor.The other half M.I.A.I had doubled the side seals springs because they were used and felt weak,big mistake on my behalf i guess.No damage was done to the motor,i had it ALL torn apart on Sunday at noon and completely rebuilt by of 7.00 p.m last night,minus the double spring application.If time permitts,i'll have re-installed tonight and give an update.THANKS to ALL who have contributed to this thread,Happy Hoildays Trinituner.

 

A touch of the key and it starts right-up,you gotta love that Brap,Brap,Brap.Carb needs to be fine tuned,alittle stumble and break-up.Other than those issues,LOTS of FIRE out the exhaust and i mean ALOT!MAybe alittle too rich but i love it,keeps people from riding my ****.Any ideas for the carb mixture screws to balance rotor chambers?Thanks.