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top end breaking up
- Thread starter big bearded bastard
- Start date
Philly87
1/2 ton status
Just a couple of thoughts if I may...
Lets keep in mind that you went from a 72cc cylinder head to a 64cc cylinder head which means you increased compression. Higher compression means its harder to light the fuel mixture in the cylinder therefore increasing the demand of your ignition components.
Granted we aren't talking about extreme cylinder pressures here like what would be made by boost or nitrous but none the less don't forget to check the basics.
How old are the wires and the coil on this rig? If you had wires that were going bad or a coil that was getting weak and you presented it with higher demands by adding compression to the mix you may have pushed the seconday side of the ignition to its limits if you are using older parts.
Just a thought but I'd check the seconday side of ignition things as well such as wires, coil, cap and rotor along with the other suggestions made by the rest of the gang like fuel, ignition module, etc...
-Phil
Lets keep in mind that you went from a 72cc cylinder head to a 64cc cylinder head which means you increased compression. Higher compression means its harder to light the fuel mixture in the cylinder therefore increasing the demand of your ignition components.
Granted we aren't talking about extreme cylinder pressures here like what would be made by boost or nitrous but none the less don't forget to check the basics.
How old are the wires and the coil on this rig? If you had wires that were going bad or a coil that was getting weak and you presented it with higher demands by adding compression to the mix you may have pushed the seconday side of the ignition to its limits if you are using older parts.
Just a thought but I'd check the seconday side of ignition things as well such as wires, coil, cap and rotor along with the other suggestions made by the rest of the gang like fuel, ignition module, etc...
-Phil
zombie1969
1/2 ton status
I remember back when the 87s were getting replaced because the blocks were cracking in the lifter valley.Didn't know the rollers were the 2 bolt only you learn something new every day.Bottom line on using old lifters is its a gamble I am not will to take.Some guys can do it and get lucky but do you want to do all that work and not replace a relatively inexpensive part and hope luck is on your side.Not me.
big bearded bastard
Registered Member
i have new bosch platinum plugs, accel 8 mil plug wires, brand new accel high output coil....new cap new rotor......thats whats leading me to believe the dizzy is the culprit....it does have a lil play in it....it will get changed this weekend.
up and down play means nothing... side to side of ANY kind is bad juju.....
I hate the Bosch plats, nothing but AC Delco's in my GM's...
I hate the Bosch plats, nothing but AC Delco's in my GM's...
big bearded bastard
Registered Member
i wouldnt purchase them for myself, a friend is a bosch rep and gave them to me for free...figured id give them a shot
I would bump the fuel pressure first. Also the L05 heads on that 350 were about the same size chamber (i had asked this question first) and the vortecs out flow them quite well and I would deff ramp up the fuel pressure.And again like you said tip in throttle and your fine but when you mat it you start breaking up. you can normally tell if its ignition or fuel. IMO i would read more into what the sensors on TBI trucks do and how they create the fuel maps for these engines. And another things ive picked up is using AC Delco plugs then to run alot better in small blocks
Edit: 191/193/810 casting 5.7 350 heads are 64-65cc in stock form thats coming from a guy whos one of the top guys of thirdgen.org (Fast355), Those heads are great for anything under 4100-4200 rpm and run into a brick wall at 4500, the heads you swapped in flow like a champ compared to the stock heads. I believe flow numbers are 170 cfm intake at .500 lift (stock cam doesnt get over .410 lift) And look up the number for a vortec and youll see that engine is more than likely leaning out. Is it pinging at all?
Edit: 191/193/810 casting 5.7 350 heads are 64-65cc in stock form thats coming from a guy whos one of the top guys of thirdgen.org (Fast355), Those heads are great for anything under 4100-4200 rpm and run into a brick wall at 4500, the heads you swapped in flow like a champ compared to the stock heads. I believe flow numbers are 170 cfm intake at .500 lift (stock cam doesnt get over .410 lift) And look up the number for a vortec and youll see that engine is more than likely leaning out. Is it pinging at all?
This could very easily be your whole problem, unless the engine called for platinum plugs the engine won't run very good and i've seen my fair share of pistons with holes in them from people running platinum plugs when the engine didn't call for them. I have found the NGK V-power plugs to be the best and i've been running them for 20 + years without any issues.
Yep, like 4X4 said, ditch the platinums.
I don't do the amount of actual work on engines he does, but I'll bet I could almost match him for the number of times I have told folks to get rid of them and it fixed the problem.
There is nothing wrong with the plugs, they are not defective. But they require an ignition system that is designed for them.
I was hanging out on the automotive forum on CompuServe when they first started coming out.
The companies were pushing them hard.
We finally created a stock message that we could just direct folks to when they wrote in with skips and misfires after putting in the new platinum plugs.
We were seeing 8 to 10 questions a week, average.
Some weeks 5 or 6 per day..........
Also dual-fire spark plug wires. Don't know if they still make them or not. Had two conductors in each plug wire.
I don't know what the heck that did, but the range of problems they caused was unbelievable.
I swear, I think they burned out some clutches...........
I don't do the amount of actual work on engines he does, but I'll bet I could almost match him for the number of times I have told folks to get rid of them and it fixed the problem.
There is nothing wrong with the plugs, they are not defective. But they require an ignition system that is designed for them.
I was hanging out on the automotive forum on CompuServe when they first started coming out.
The companies were pushing them hard.
We finally created a stock message that we could just direct folks to when they wrote in with skips and misfires after putting in the new platinum plugs.
We were seeing 8 to 10 questions a week, average.
Some weeks 5 or 6 per day..........
Also dual-fire spark plug wires. Don't know if they still make them or not. Had two conductors in each plug wire.
I don't know what the heck that did, but the range of problems they caused was unbelievable.
I swear, I think they burned out some clutches...........
Maybe a long shot, but I'll bring it up in case it rings a bell for you...
I had a similar problem when I first swapped to fuel injection. Getting to a certain RPM made it start popping, shaking and just falling on it's face - couldn't rev any higher. As the ECU called for more advance, the rotor began to overrun the terminals in the cap. The advance increases as RPM increases, so I thought I was limited in RPM, but dialing back the advance let it rev higher. It turns out the distributor needed to be moved over a tooth or two. In my case it was because I had locked the mechanical and vacuum advance out (to let the computer do the work), but in your case it could be that it got re-inserted in the wrong spot.
Maybe this is a silly question, but how do you know you have the right length push rod?
I had a similar problem when I first swapped to fuel injection. Getting to a certain RPM made it start popping, shaking and just falling on it's face - couldn't rev any higher. As the ECU called for more advance, the rotor began to overrun the terminals in the cap. The advance increases as RPM increases, so I thought I was limited in RPM, but dialing back the advance let it rev higher. It turns out the distributor needed to be moved over a tooth or two. In my case it was because I had locked the mechanical and vacuum advance out (to let the computer do the work), but in your case it could be that it got re-inserted in the wrong spot.
Maybe this is a silly question, but how do you know you have the right length push rod?
