Why is 305 TPI conversion burning through distributor caps?

[knokturnalnicholas]

I am nowhere close to being a mechanic but I am minimally astute about car problems and repairs. I've had my 87 FJ60 for about 5 years and (like everyone I'm sure) put a good bit of money into the repairs. When I bought it there was a 89 Chevy 305 TPI engine it it that was installed in 1991. Over the past few years I have had to replace my distributor cap about every 2000 miles. Each time I can see the burn mark on the metal inside the cap. I have also replaced the distributor, ignition coil, spark plugs and wiring in this time frame. I have also discussed moisture and cracking with a few of the mechanics and there is no indication those are the potential problems either. Each time I (or a mechanic) replace it I check everything that I have already had replaced and look for indicators of what else it can be. The only thing that continues to burn out on me is the distributor cap. What am I missing?

 

[Landpimp]

I know little of chevy(but do have the same motor in a c20), but is there maybe a vent line from the cap that us not going the right place? I know of the 2f without the cab vent line conected will burn thru the caps in a few 1000 miles.

 

[knokturnalnicholas]

I will post a pic of the distributor cap installed. The engine is starting to stall on me again while I'm driving (unless I constantly rev the engine) so I will also post a pic of the inside of the distributor cap. Hopefully that will help.

 

[SteveH]

Too much voltage to the cap? Have you tried genuine GM caps, or a high performance cap? Is the 'burn mark' a carbon trail between the cap terminals, or is the problem a case where it's literally burning the metal piece out of the cap? Pix would help.

 

[Elbert]

Stock GM type coil and stock GM cap and rotor button?

 

[knokturnalnicholas]

The parts are stock quality. The last time I had the distributor, cap, and coil replaced by a mechanic the parts came from Napa Auto Parts. After it quit on me a few times the mechanic told me that he was unsure what was causing it but recommended I keep an extra distributor cap for when it goes out on me. I recognize how silly that sounds so I'm hoping someone may have a better solution than that.

 

[Dynosoar]

I would 100% recommend using a delco cap and rotor. I run a TPI engine and have had BAD luck with aftermarket caps and rotors. Do you have a HEI distributor or the smaller distributor with the external coil? I have had terrible luck with the grey distributor caps for some reason.


Dyno

 

[Elbert]

I've had one or two dist caps on my 5.7 vortec also destruct....have no clue why. All my stuff on the engine is GM. You can order most of the GM stuff right off the rock auto web site...for common parts.