327 with Pertronix Runs Rough and Backfires

[Peter S.]

I recently replaced my points with the Pertronix Ignitor and Coil.

I followed the instructions and bypassed the ballast resistor.

I couldn't get the wires through the bottom of the distributor so had to pull the distributor.

I put the distributor back in and lined up cylinder one wire on the distributor when the engine was at TDC on the compression stroke of cylinder #1 (by felling the push of air in the spark plug hole on cylinder one).

It started. I then rotated the distributor CCW a little and set the timing with the timing light to about 8 before TDC without the vacuum advance, which goes to about 12 when the vacuum advance is connected.

The engine starts and runs, and doesn't idle too bad, but as soon as I give it some gas it sounds bad and sometimes backfires.

Is it something to do with the Pertronix, the timing or am I looking in the wrong place?

Help! The summer is here!

[Keith B.]

Re: 327 with Pertronix Runs Rough and Backfires

to trouble shoot reverse everything you did and put points back in

[Mark E.]

Re: 327 with Pertronix Runs Rough and Backfires

These symptoms can be caused by improper ignition advance, either centrifugal or vacuum.

Remove the cap and apply vacuum to the VAC to check the breaker plate is moving freely... I wonder if it somehow became jammed while installing the module. Make sure the new wiring isn't interferring with this. Twist the rotor clockwise and verify it snaps back to position with no binding or resistance.

With this said, there's no real performance advantage to these aftermarket electronic ignitions, so reconsider going back to points. Simpler, less prone to sudden failure and easier to diagnose.

[Duke W.]

Re: 327 with Pertronix Runs Rough and Backfires

I put the distributor back in and lined up cylinder one wire on the distributor when the engine was at TDC on the compression stroke of cylinder #1 .

!

I have no idea what you mean. A common cause of your problem is an improperly assembled or installed distributor because the rotor is misaligned with the cap terminals.

Prior to removing a distributor one should rotate the crank to the align the balancer notch to the initial timing point on the timing pad, NOT TDC! With a properly installed distributor (gear dimple pointing the same direction as the rotor tip, and #1 plug wire next to the right (passenger) side of the cap window) drop the distributor in and once seated rotate it until the points just begin to open, and the timing should be in the ballpark, and the plane of the cap window should be near normal to engine centerline (C1 and C2 single point and TI).

If you have some kind of electronic gizmo in place of points you can only guess.

You didn't state the specific engine, but the VAC should add 12 to 24 degrees. Mechanical lifter engines cannot be timed in the normal way because centrifugal starts at 700 and they will not idle stably below 700 long enough to do the job. They must be timed to 36-40 at an engine speed above where the centrifugal advance is all in.

Duke

[Peter S.]

Re: 327 with Pertronix Runs Rough and Backfires

Thanks for your help everyone. I have a decent timing light now so hopefully I can get it running.

[William F.]

Re: 327 with Pertronix Runs Rough and Backfires

Pertronix or the 1 wire M&H points replacement trigger beats the heck out of fooling with points- deciding which set to buy, setting and resetting dwell IMHO.

[Keith B.]

Re: 327 with Pertronix Runs Rough and Backfires

Pertronix or the 1 wire M&H points replacement trigger beats the heck out of fooling with points- deciding which set to buy, setting and resetting dwell IMHO.

Yes the 5 mins it takes to check the dwell every 5k miles or so and replacement every 12k miles or so is so difficult on a pleasure car. Give me a break

[Mark E.]

Re: 327 with Pertronix Runs Rough and Backfires

Yes the 5 mins it takes to check the dwell every 5k miles or so and replacement every 12k miles or so is so difficult on a pleasure car. Give me a break

Keith,

You have a good "point", but play nice.

William,

Point sets from GM, AC Delco, or Standard Motor will work fine. Avoid "high performance" sets with higher spring tension; they wear the distributor cam lobe prematurely.

[Duke W.]

Re: 327 with Pertronix Runs Rough and Backfires

All the name brand point sets, including Delco, Echlin, Standard, Blue Streak (a SMP house brand) Niehoff... and others are manufactured by Standard Motor Products - same part, just a different box and marketing channel, and this applies to most electrical system replacement parts. GM has not manufactured these parts in house for over three decades, but it's amazing how many guys insist on "Delco" because they think it's "original". NOT! SMP is a Tier 1 OE supplier. They produce a lot of current OE parts for all OEMs, and also supply vintage parts sold under a half a dozen or more brands, INCLUDING DELCO, but who knows for how long.

I wrote an article about this that is probably in the restoration documents sticky and is also on the Corvette Forum in a thread started by me (SWCDuke).

The 28-32 oz. point sets may wear the rubbing block faster than the basic 19-23 oz. versions, but they are necessary to get maximum performance over about 5500 revs. Just pay a little more attention to keeping the lobes/rubbing block properly lubricated.

You should read the article

Duke

[Mark E.]

Re: 327 with Pertronix Runs Rough and Backfires

All the name brand point sets, including Delco, Echlin, Standard, Blue Streak (a SMP house brand) Niehoff... and others are manufactured by Standard Motor Products - same part, just a different box and marketing channel...

GM has not manufactured these parts in house for over three decades, but it's amazing how many guys insist on "Delco" because they think it's "original".

I prefer Blue Streak, Standard's premium line- they are different, and nicer, than the "standard" Standard brand, featuring a copper plated base and better terminals. I haven't seen "new" ones for years, but NOS sets are available on eBay. GM/ACDelco may perform fine, but look cheaper. Some have the spring tension wire terminals (vs. screw down terminals) which don't inspire confidence.

The 28-32 oz. point sets may wear the rubbing block faster than the basic 19-23 oz. versions, but they are necessary to get maximum performance over about 5500 revs. Just pay a little more attention to keeping the lobes/rubbing block properly lubricated.

Good point for those still redlining their engines. I suspect folks on this forum sporting an original engine rarely venture beyond 5,000 RPM. (Now waiting for posts from folks who do this regularly. :-) )

[Duke W.]

Re: 327 with Pertronix Runs Rough and Backfires

The article reviews about six SMP-manufactured point sets having different features, not including unisets. The NAPA/Echlin part numbers are listed and these can be cross referenced by any parts souce that sells other SMP-manufactured brands.

You should read the article. So should everyone else who thinks they might have to buy a point set someday.

Duke

[David Z.]

Re: 327 with Pertronix Runs Rough and Backfires

Duke's Points article is attached.
Dave Z

[Mark E.]

Re: 327 with Pertronix Runs Rough and Backfires

Duke- Interesting article.

Below are photos of three Blue Streak points. Their part numbers are the same as Standard's regular line (e.g. SMP DR-2270P in the "regular" line has the same application as Blue Streak DR-2270P). DR-2270P fits Corvette and most GM V8s in the points era. I believe DR-2270XP is the "high performance" part with a heavier spring. DR-3575CX is the uniset.

I spent a few minutes looking for a cross-reference to NAPA which are in Duke's article, but with no success.

I like Blue Streak because they have a heaver gauge base, a felt pad to lube the cam, robust terminals and overall look high quality. All are vented. I'm not sure if the contacts are small or large as mentioned in the article.

20230717_154020.jpg

20230717_153445.jpg

[Duke W.]

Re: 327 with Pertronix Runs Rough and Backfires

I like the fact that ALL have the little lubricator pad that I mentioned in the article stating that all points sets should include this. Bluestreak is SMP's "premium" line of electrical parts. It looks like the DR-2270X is the 19-23 oz set and the DR-2270XP is the 28-32 oz set.

Duke