Will backfiring Grenade my engines?

[artificialreef]

While trying to start a beater I bought that sat for bout 2 to 4 years, I thought the first thing for the motor to do was replace all the fluids and do a points plugs and condenser tune up. I dripped a little oil in each chamber when I changed the plugs. I kind of grew up in the generation just when points were getting replace by EI. I did one set of points when I was a youngster. Anyhow I gapped the boat i have nows to what the manual says and they were poppin and backfireing like the 4th of july. I think I got lucky with the points I did when I was young. I just bought a used snap on dwell meter that I think I will try next but my question is am I blowin the sh@t out of all my gaskets trying to tune this thing? I really dont have the cash for dual electronic ignition swaps and kindof dig doing it old school

 

[WizeOne]

Re: Will backfiring Grenade my engines?

it'd help to know what you are working on!

 

[artificialreef]

Re: Will backfiring Grenade my engines?

Guess it would help if I told you what motors they are. They are the beloved twin 470's. It wasnt running hot it was just backfiring. I hope the force will take the path of least resistance and blow out the flame arrestor. Just curios if anyone knows. I will get it tuned soon enough and find out.

 

[artificialreef]

Re: Will backfiring Grenade my engines?

the reason I am asking is i will stop f### with them and save up for the EI conversion.

 

[artificialreef]

Re: Will backfiring Grenade my engines?

OK! no one wants to chime in. Allright I am going to answer my own question. The motors are from 1983 any added stress to any components on them are liable to cause catastrophic engine failure so I will save up for the EI. After i try the dwell meter.

 

[stonyloam]

Re: Will backfiring Grenade my engines?

It wasnt running hot it was just backfiring.

OK what could cause a backfire? Well it seems to me that the only path to the carb is through the intake valves, so either your intakes are hanging open (not likely if you have decent compression) or your timing is WAY off (maybe but it does run) or you have your plug wires crossed (best guess). The fact that it runs at all shows that your points are doing their job, they may not be adjusted correctly but they are energizing the coil and giving you a spark, so I would look elsewhere. If your wires are crossed you could get spark during the intake stroke and cause a backfire, and be running on only the two "correct" cylinders. Just me making a guess. good luck. Oh! It may not destroy your engine but it sure isn't doing it any good.

 

[Don S]

Re: Will backfiring Grenade my engines?

OK! no one wants to chime in. Allright I am going to answer my own question. The motors are from 1983 any added stress to any components on them are liable to cause catastrophic engine failure so I will save up for the EI. After i try the dwell meter.

DUDE!!!! This thread was less than an hour old when you posted that reply. People are not sitting around waiting for your question. Give people a chance to read and reply.
What is EI ??? I don't understand Text Messaging short hand.

Anyhow I gapped the boat i have nows to what the manual says and they were poppin and backfireing like the 4th of july.

Say What ??????

 

[coastalcruiser]

Re: Will backfiring Grenade my engines?

if you have your points set up to the proper gap and have backfiring your ignition is now probably way out. You need to set timing with a timing light.

 

[bhammer]

Re: Will backfiring Grenade my engines?

As Don said, DUDE!!!

Now me, you need to start from the beginning if you don't know it was running right before. Find TDC, make sure your distributer is correct and set your timming. Then, using your dwell meter adjust your points.

I had a 470 as well. I upgraded to the Pertronix ignition and kept the points in the boat kit just in case....

 

[180shabah]

Re: Will backfiring Grenade my engines?

Also, don't forget the fuel side of the equation. Are you running from a nice clean fresh supply through carbs that are recently rebuilt and tuned?

 

[catchbats]

Re: Will backfiring Grenade my engines?

At the very least you'll burn your valves letting it continue to backfire.

 

[artificialreef]

Re: Will backfiring Grenade my engines?

Yeah Don, you are right an hour is a little short. I sometimes have a few belgian brews when I get on this thing and dont make alot of sense. The question was a sober one though. Just my own replies were a little goofy. I tried to find TDC by myself with a commpression tester. I screwed the compression tester into the #1 cylinder and took off the testers dial and held the hose while i turned the crank. I got air bursts on 2 rotations of the rotor though. What i mean is I turned the crank and watched the rotor turn. Got to a point where the compression hose burped a little bit, removed the hose and the cylinder was down. Continued to rotate, got another burp. Removed the hose and the cylinder was there. Made note of the distributor post and connected all the wires. The timing marks even lined up. The motor wont run unless i advance the timing beyond the marks. With a light I try to bring it back down to the 4 degrees in the manual and it stalls.

Do you think I am finding tdc correctly? Maybe off 1?

 

[cheburashka]

Re: Will backfiring Grenade my engines?

Whatever is causing it needs to be fixed before you go over to EI (Electronic Ignition.) Changing over is mildly challenging even if you're going from a working points system to electronic. If you start with an engine that doesn't run at all, you'll run into a whole lot of problems.

I'd side with those who said plug wires. Also, your way of checking TDC seems kind of crude. Did you check the advance weights in the distributor?

 

[artificialreef]

Re: Will backfiring Grenade my engines?

Bro? How do i check the advance weights in the distributor? I am not a mechanical idiot.

 

[Silvertip]

Re: Will backfiring Grenade my engines?

Got it backwards Bhammer! You first set the dwell (or use a feeler gauge). THEN you set timing. Dwell affects timing but timing does not affect dwell. When you set the points with a feeler gauge you need to have the engine turned so the points are open their widest. Then adjust the gap.

 

[bhammer]

Re: Will backfiring Grenade my engines?

Got it backwards Bhammer! You first set the dwell (or use a feeler gauge). THEN you set timing. Dwell affects timing but timing does not affect dwell. When you set the points with a feeler gauge you need to have the engine turned so the points are open their widest. Then adjust the gap.

Dang, hate when I do that, good catch.... that's why I switched out my ole 470 with pertronics, then switched out the boat.

 

[coastalcruiser]

Re: Will backfiring Grenade my engines?

Stick your thumb OVER the #1 cylinder spark plug hole. Rotate the engine until you feel pressure on your thumb. That's the compression stroke. TDC is at the top of this stroke.

 

[KRH1326]

Re: Will backfiring Grenade my engines?

When I rebuilt my beloved 351w, and had it all opened up in my shop, I TDC'd #1. Just put the timing cover on loose, then set on the damper. I marked it at the pin.

I took the damper over to my vise, and carefully secured it. I then took a hacksaw and made a VERY legible line on it. I even used a protractor and marked out 10 BTC, and made another VERY legible mark.

When I tune it 20 years from now, I will still find those marks.