Engine rebuild woes Options

[william1764]

Just had completed a full engine rebuild of my stock 2.0L (with Webers) to a 2.3L by a small Porsche indy in Maryland (2.256 big bore, 10:2:1 compression, mild cam). Carbs were also rebuilt to accommodate new build. Unfortunately, engine runs like crap with incessant backfire out of exhaust and carbs (during both acceleration and deceleration). Hard to even really tell yet how the increase in displacement feels due to the bucking and backfiring. However, I do know that power seems to peak at mid 4K range. Planned to have dyno'd but until this is resolved no point. Their estimated build time of 2 months took 14 months and still not drivable so I'm a bit frustrated. Indy acknowledges that he doesn't know what the issue is. Said he suspects its carbs but not certain. Wants me to invest in a new set. To be clear, the carbs have worked perfectly for the last 10 years up to the day i dropped off to their shop. Indy acknowledges no issue with carbs when he received. Frankly, I've lost all confidence and contemplating having another shop look at this issue and resolve. In all fairness, this is not a hack shop...very reputable. I don't want to bash/mention names. Requesting recommendation of an indy, ideally in Maryland, that is capable of assessing and hopefully fixing the issue.

[iankarr]

This sounds like a timing issue. What type of distributor are you running? have you verified that all spark plug wires are connected, and in the correct firing order on the dizzy?

[nditiz1]

Care to share who the Indy is?

I'm not an expert, but am knowledgeable in dual carbs and have quite an assortment we can run through as far as jetting. Bring it on up and we can run it through some tests.

[william1764]

This sounds like a timing issue. What type of distributor are you running? have you verified that all spark plug wires are connected, and in the correct firing order on the dizzy?

I thought possibly a timing issue and its interesting they have not mentioned this as a possibility...focusing only on carbs. Not sure about type of distributor. I attached pic...maybe you're familiar? I have not verified spark plug wires/firing order with them.

[william1764]

Care to share who the Indy is?

I'm not an expert, but am knowledgeable in dual carbs and have quite an assortment we can run through as far as jetting. Bring it on up and we can run it through some tests.

Thanks. I'll message you name of shop however I wish to keep that out of the forum post for now.

[930cabman]

Just had completed a full engine rebuild of my stock 2.0L (with Webers) to a 2.3L by a small Porsche indy in Maryland (2.256 big bore, 10:2:1 compression, mild cam). Carbs were also rebuilt to accommodate new build. Unfortunately, engine runs like crap with incessant backfire out of exhaust and carbs (during both acceleration and deceleration). Hard to even really tell yet how the increase in displacement feels due to the bucking and backfiring. However, I do know that power seems to peak at mid 4K range. Planned to have dyno'd but until this is resolved no point. Their estimated build time of 2 months took 14 months and still not drivable so I'm a bit frustrated. Indy acknowledges that he doesn't know what the issue is. Said he suspects its carbs but not certain. Wants me to invest in a new set. To be clear, the carbs have worked perfectly for the last 10 years up to the day i dropped off to their shop. Indy acknowledges no issue with carbs when he received. Frankly, I've lost all confidence and contemplating having another shop look at this issue and resolve. In all fairness, this is not a hack shop...very reputable. I don't want to bash/mention names. Requesting recommendation of an indy, ideally in Maryland, that is capable of assessing and hopefully fixing the issue.

Sorry for your misfortune, but these things do happen. Do you have the ability to check things like spark timing, valve clearances, compression values? Keep us informed of your findings and it's unfortunate not everyone out there will stand behind their work.

[BK911]

This sounds like a timing issue. What type of distributor are you running? have you verified that all spark plug wires are connected, and in the correct firing order on the dizzy?

Many fuel related issues are timing issues.
Set dwell/timing before messing with carbs.
Good luck!!

[emerygt350]

Just looking at the picture tells me the plug wires are wrong or the distributor is not in the 'normal position' for these engines. Wire one should be on the left driver side in the picture. Looks like it is heading over to #3. It could just be the way they stabbed it but backfiring like that makes me think wires are off position.

[william1764]

This sounds like a timing issue. What type of distributor are you running? have you verified that all spark plug wires are connected, and in the correct firing order on the dizzy?

Many fuel related issues are timing issues.
Set dwell/timing before messing with carbs.
Good luck!!

Will look into. TY

[william1764]

Just looking at the picture tells me the plug wires are wrong or the distributor is not in the 'normal position' for these engines. Wire one should be on the left driver side in the picture. Looks like it is heading over to #3. It could just be the way they stabbed it but backfiring like that makes me think wires are off position.

Interesting. Will verify if correct

[Tdskip]

Simple things first, understand the frustration and concern but the suggestion to make ignition and fueling are correct.

Having an separate independent shop - or friend - check compression or even better leak down test if the above doesn't sort it out.

Hang in there.

[ndfrigi]

yes looks like wrong spark plug wires installation.
Driver side rear: #1
Driver side front: #2
Passenger side rear: #3
Passenger side front: #4

On dizzy: #1 should be at around 11 o’clock (TDC)
# 2 around 8 o’clock
# 3 around 5 o’clock
# 4 around 2 o’clock

you get the idea and sometimes TDC changes which should follow #1 also and same with others.

[nditiz1]

The distro looks to be a Mallory. I believe when I ran one in my 2056 it was 180 out, so the plugs might not be wrong here.

As said, timing, Carbs linkage sync'd (If they messed with the linkage, that would be a major player), Carb adjust.

[william1764]

Great advice all, thank you.

I failed to mention that both times I went to pick up car the indy said he drove it earlier and it ran great. In both instances it ran horribly for me...exhaust backfire, carbs popping, bucking, etc. all the way home (25 minutes). I sent him video recording of my drive home last week that captured the constant backfiring...he said he experienced none of that. How is that possible?

[william1764]

The distro looks to be a Mallory. I believe when I ran one in my 2056 it was 180 out, so the plugs might not be wrong here.

As said, timing, Carbs linkage sync'd (If they messed with the linkage, that would be a major player), Carb adjust.

Yes, I believe it is a Mallory. Regarding linkage, they redid the linkage set-up. They also installed new idle/main jets and 32 Venturis. Replaced floats, carb seals, etc

[emerygt350]

Only thing I can think of is cold engine ran, warm didn't, but I don't think that is the case hear. A stuck choke shouldn't cause those symptoms. Two wires off will. I had two wires off and it idled just fine but as soon as you gave it gas it was awful.

[Shivers]

Great advice all, thank you.

I failed to mention that both times I went to pick up car the indy said he drove it earlier and it ran great. In both instances it ran horribly for me...exhaust backfire, carbs popping, bucking, etc. all the way home (25 minutes). I sent him video recording of my drive home last week that captured the constant backfiring...he said he experienced none of that. How is that possible?

Someone thought the Yugo was a good idea...Anything is possible if he didn't get it warm running it around the block. Weird stuff can happen when they warm up. Valve lash too tight, engine gets hot and valves are left open. Coil going bad, first it runs fine then it gets hot and car runs like crap. All sorts of stuff can happen. Don't beat your head against a wall, start at the beginning. Good luck.

[wonkipop]

Great advice all, thank you.

I failed to mention that both times I went to pick up car the indy said he drove it earlier and it ran great. In both instances it ran horribly for me...exhaust backfire, carbs popping, bucking, etc. all the way home (25 minutes). I sent him video recording of my drive home last week that captured the constant backfiring...he said he experienced none of that. How is that possible?

Someone thought the Yugo was a good idea...Anything is possible if he didn't get it warm running it around the block. Weird stuff can happen when they warm up. Valve lash too tight, engine gets hot and valves are left open. Coil going bad, first it runs fine then it gets hot and car runs like crap. All sorts of stuff can happen. Don't beat your head against a wall, start at the beginning. Good luck.

it could be a bad coil on the way out. looking at your photo it looks new.
some do come out of the box not good these days?

it could also be any of the other things.

to be fair to the engine builders sometimes these things can be confounding.
they will run the car and it won't do it for them.
but this does sound a bit like they should have got it good and hot and driven it for 20 minutes/half an hour.
properly test driven it.

if they get the faults up then its going to take a good mechanic with a good instinct for where to look. i would judge them by their reaction to the issue once they have made it happen. if necessary take one of them out in the car with you and drive it until it does it with the mechanic in the car. and then see what the reaction/comeback/opinion is.

and make up your mind about them.

stay cool and don't lose your confidence.

[nditiz1]

Adding more info OP supplied in a PM-

"The engine idles smooth and revs smooth."

So bucking, popping, backfire, under load could point to a weak ignition system. Better to check that coil. If you have a spare throw it in and try it, would only take a few minutes. You can also check that one with a meter.

[Badinfluence1]

I had a funky distributor that I had similar problems with- It was dry when I took it apart- I added gear oil and it smoothed out (IMG:style_emoticons/default/popcorn[1].gif)