Rebuild Runs Rough

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T56MaxTorq

T56MaxTorq

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Rebuilt my 318 after a thrust bearing failure, installed in Duster and doing some tuning but it’s sick. It will start and idle ok, but not great, rpm fluctuation of 50-75 - like a misfire. Worse when warm. Take it up to 3000 (no load) rpm, acts like it has a misfire, rpms fluctuate too.

Engine is a 318 magnum, rebuilt short block, new rings. < 1 hour run time.
Turbocharged, 218/218 cam @ .050, degreed within 1* of spec, 113. 115 lsa
EQ Heads have been cleaned up and unshrouded to lower compression, probably in the high 8’s:1. Compression was 9.15:1 before cutting them up.
I run mega squirt efi with E85. Ran great on previous engine build. Didn’t run as rough as it does now.

I used the same fuel and spark timing map as before. Making slight mods. I first started it up and ran it with 18* spark advance at idle. Hates it, runs rough. It cleans up as I retard timing to 10. Run it up to 3000 @ 33* - same thing, runs poorly and like a misfire. I retard to 23*, runs better but not great, loses 400ish rpm and afr enriches (I can tune fuel and spark on the fly) I have verified spark advance on the balancer.

Ran compression test tonight. Maybe the valve seats are jacked up from port or rings/bores are total ****. All cylinders are 112-122psi at 6150 ft. Elevation.

Unique build and engine control indeed, not exactly sure what I should chase next. The retarded spark advance is fooling me. I’ll try and post a video, pics tomorrow.
 
I had a bad distributor reluctor once that was giving me fits at low rpm....surging until it came up and stabilized the reluctor on the shaft. At idle it was moving on the shaft just enough to cause a surge due to a ill fitting roll pin. Not sure if this is related to what you've got but you never know. Sounds like have a little bit going on there.
 
was the efi and cam etc all the same as before the rebuild?

Is it possible you are too lean?

vacuum leak?

what you are describing sound just like my 150000 mile ago rebuilt 273 , 1 cyl is in the 110 range and one is in the 120 range and the rest are in between. I leaned out the carb thinking now that I'm at 5000 feet (was a sea level car) I would need to do that. at 2500 rpm it seems to be misfiring and 2500 rpm, Hydrocarbons are 1000 greater than they were before the jet change. with less advance it seems to behave better but not great. drivability is not effected that I can tell.
 
fluctuation on a fuel injected engine is mostly the problem of a vacuum leak speak lean mixture. check it with a brake cleaner for vacuum leaks. If everything is Ok, i would highly recommend ( in any case ) to to run the EFI in the closed loop mode ( wide band sensor running ) and tune the mixture new, like you bought it new. Every engine needs his own calibrating and you changed a lot of the basic engine! Run a good matching ignition curve matching to your cam, compression ratio and fuel you're using. Good luck.
 
do a leak down test on cylinders /compression is low even for a 7 to 1 eng check pushrod length
 
2 plug wires swapped?
what is it, 5 and 8?

also, is the mega squirt self learning?
should you reset it for this build?
 
67dartgtgo said:
I had a bad distributor reluctor once that was giving me fits at low rpm....surging until it came up and stabilized the reluctor on the shaft. At idle it was moving on the shaft just enough to cause a surge due to a ill fitting roll pin. Not sure if this is related to what you've got but you never know. Sounds like have a little bit going on there.
Click to expand...

Distributor is completely stripped of components. I use a crank trigger instead of a reluctor in the distributor. Although this brings up a good concern I had. The trigger wheel was not 100% concentric when turning the crank over to set the pickup gap. I will investigate into this more. Thanks

Dana67Dart said:
was the efi and cam etc all the same as before the rebuild?

Is it possible you are too lean?

vacuum leak?

what you are describing sound just like my 150000 mile ago rebuilt 273 , 1 cyl is in the 110 range and one is in the 120 range and the rest are in between. I leaned out the carb thinking now that I'm at 5000 feet (was a sea level car) I would need to do that. at 2500 rpm it seems to be misfiring and 2500 rpm, Hydrocarbons are 1000 greater than they were before the jet change. with less advance it seems to behave better but not great. drivability is not effected that I can tell.
Click to expand...

Lean is possible. Would mean my afr gauge is out of cal. (However, I am running E85 and using a gas gauge, maybe I can borrow/buy a lambda) But that’s certainly possible. I will see if I can make it run smoothly by playing with fuel. I will also disconnect and plug all vacuum lines to see if it acts better. I must think of a good way to check for intake-head gasket leaks.
 
plymouth4onthefloor said:
fluctuation on a fuel injected engine is mostly the problem of a vacuum leak speak lean mixture. check it with a brake cleaner for vacuum leaks. If everything is Ok, i would highly recommend ( in any case ) to to run the EFI in the closed loop mode ( wide band sensor running ) and tune the mixture new, like you bought it new. Every engine needs his own calibrating and you changed a lot of the basic engine! Run a good matching ignition curve matching to your cam, compression ratio and fuel you're using. Good luck.
Click to expand...

Yeah this is a weird one. Vacuum leak is again, plausible, maybe it’s affecting only 1 or 2 cylinders instead of all 8. I ran the same map and curve as before but it’s just giving me such a hard time. I thought I already had a pretty good map. I shouldn’t be having this issue. Even advancing the timing at idle to 13,14,15 it begins to act sickly. I don’t have a closed loop system. I have full authority of fuel, ignition. I was also thinking of fueling up with gasoline and trying that. Get it back to basic.

teringer said:
do a leak down test on cylinders /compression is low even for a 7 to 1 eng check pushrod length
Click to expand...

A leak down was on the list for sure. What fools me is the compression numbers are all average. I was certain I’d have a cylinder <100. I do live high altitude and the pressure last night (with thunderstorms too) was 78kpa. Pushrods were the same as before and I adjusted the rockers per Hughes tech.


diymirage said:
2 plug wires swapped?
what is it, 5 and 8?

also, is the mega squirt self learning?
should you reset it for this build?
Click to expand...

I had 1&3 swapped for the first startup:BangHead:

It’s been triple checked, now. I originally thought I had washed out 1&3 with E85 and that was the result of the shitty idle. 1&3 are the lowest compression numbers. 5 psi below the rest. Maybe it is still the issue. I’ll try a wet compression test, Ive only done a dry one.

Mega squirt is not self learning, it is calculated using speed density. I am using The same maps as previous engine build. Only hard parts I’ve changed was the crank and crank bolts - I went to studs. Everything else is the same.
 
Mega squirt is not self learning, it is calculated using speed density. I am using The same maps as previous engine build. Only hard parts I’ve changed was the crank and crank bolts - I went to studs. Everything else is the same.
E85 requires more fuel than gasoline to make the same power.
 
Just off the top from the description of the issues with the advance it sounds like either cam timing is off or valve adjustment is too tight.

If there is a question about the ignition put your timing light on the coil wire and see if you have smooth consistent flashes or broken up flashes.
 
Cranking pressure comes out right for your altitude and a guess at the ICA.

What has changed from the last build? Is the turbo new/different? Cam new/different?

LSA looks typical for a turbo cam.

How many cc's do you think you removed in the heads?

If all of the engine is the same, and fuel is the same, then just sounds like an ignition or sensor issue.
 
mderoy340 said:
Mega squirt is not self learning, it is calculated using speed density. I am using The same maps as previous engine build. Only hard parts I’ve changed was the crank and crank bolts - I went to studs. Everything else is the same.
E85 requires more fuel than gasoline to make the same power.
Click to expand...

I adjusted fuel for E85 by adding 30% and trimming it with afr gauge from there on.

TrailBeast said:
Just off the top from the description of the issues with the advance it sounds like either cam timing is off or valve adjustment is too tight.

If there is a question about the ignition put your timing light on the coil wire and see if you have smooth consistent flashes or broken up flashes.
Click to expand...

I put the cam in straight up and degreed it. I have a hydraulic roller, Hughes rockers and pushrods. I installed the rockers to spec, 2 turns of the adjuster on base circle. Geometry isn’t perfect but not too bad, I expect I’d only get 50,000 miles of service out of this engine. They’re magnum style rockers.

I’ll check out the coil wire with the light. Good tip, didn’t think of that.
 
nm9stheham said:
Cranking pressure comes out right for your altitude and a guess at the ICA.

What has changed from the last build? Is the turbo new/different? Cam new/different?

LSA looks typical for a turbo cam.

How many cc's do you think you removed in the heads?

If all of the engine is the same, and fuel is the same, then just sounds like an ignition or sensor issue.
Click to expand...

Only major things changed were the crank, the crank bolts are now studs, the oil pump, and I did multiple oil system mods. Ported all the holes and made the oil pump pickup a custom larger diameter pipe. Oil pressure is nice and happy. No valvetrain noises. I inspected the oil filter after 30 min run. Just some residual metallic fuzz, no chunks or slivers.

I also did all the unshrouding and cleaning up the edges of the combustion chamber. I think I removed 3-4cc total from the chamber and block. I cleaned up the intake ports and matched them to the heads. Everything else is the exact same before the thrust bearing failure.

Cam IVC is 42

Yeah I’m thinking the crank trigger may be at fault. It seemed a little eccentric on the pickup when setting the gap. Maybe play with the noise filter. Surely something is making it run poorly. With so many changes, I just pray it isn’t anything engine mechanical. From the compression test, I really don’t think so.
 
I suspect that IVC of 42 is at .050' lift....I was thinking of 'advertised' closing.

Yeah, nothing really changing that stands out. 3-4 cc's won't change CR all that much, as you surmised.

Suspect the fuel too.
 
we ran alcohol in a late model and needed about 45percent more jet in a carb , is your fuel percent correct for e85?
 
nm9stheham said:
I suspect that IVC of 42 is at .050' lift....I was thinking of 'advertised' closing.

Yeah, nothing really changing that stands out. 3-4 cc's won't change CR all that much, as you surmised.

Suspect the fuel too.
Click to expand...

teringer said:
we ran alcohol in a late model and needed about 45percent more jet in a carb , is your fuel percent correct for e85?
Click to expand...

Yes ivc is at .050

I most likely had a winter e85 blend with the last engine. More gasoline, as much as 10% more. I probably have a more true e85 blend, now. I’m still able to trim fuel, I have full control, and its attitude feels right on my afr gauge. As I tune, and force a lean idle, the gauge goes towards 15:1 and beyond that it runs poorly, vacuum is reduced, as one would expect.
 
T56MaxTorq said:
Yes ivc is at .050

I most likely had a winter e85 blend with the last engine. More gasoline, as much as 10% more. I probably have a more true e85 blend, now. I’m still able to trim fuel, I have full control, and its attitude feels right on my afr gauge. As I tune, and force a lean idle, the gauge goes towards 15:1 and beyond that it runs poorly, vacuum is reduced, as one would expect.
Click to expand...
How does it run when you fatten it up?
 
The engine's thirst for timing, I think is telling you it needs more time for the fuel to find oxygen to react with.So Yeah I would be looking for a lean situation. How are the float bowls receiving venting?
 
It hasn’t seen anything richer than 13.5: 1 while diagnosing this problem. Thats what I have set its “warmup enrichment” to. Its hot idle is indicated as 14:1

I’ll run it richer and report back.
 
AJ/FormS said:
The engine's thirst for timing, I think is telling you it needs more time for the fuel to find oxygen to react with.So Yeah I would be looking for a lean situation. How are the float bowls receiving venting?
Click to expand...

I’m not sure what you mean. It runs poorly at idle and rpm with 18*/33*, if I retard ignition to 10*/23* it runs slightly better. By better I mean it has more consistent vacuum and rpm.

No float bowls, MPFI
 
T56MaxTorq said:
I’m not sure what you mean. It runs poorly at idle and rpm with 18*/33*, if I retard ignition to 10*/23* it runs slightly better. By better I mean it has more consistent vacuum and rpm.

No float bowls, MPFI
Click to expand...
Ohchit :(;wrong thread

then back to post 17, for same ending.


I back calculated your total chamber volume from the 9.15 previous Scr and added your estimated 4cc increase to re calculate your Scr to 8.62
I calculated your swept using a 3.94 bore
I grossed your 218/218/115 hydraulic roller cam up by 52 degrees to get a cam with advertised specs of 270/270/115,which, in at 113, equals an ICA of 68 off the assumed advertised.
I plugged in 6150 altitude
The overlap works out to 40* using the assumed advertised specs.

Static compression ratio of 8.62:1.
Effective stroke is 2.47 inches.
Your dynamic compression ratio is 6.68:1 .
Your dynamic cranking pressure is 97.76 PSI.
V/P (Volume to Pressure Index) is 71

This does not match your 110/120 psi, so I assume some erroneous input(s), on my part. But the point is the same; she has a fairly late-closing intake angle, which means the intake manifold, at idle, is gonna be full of air going everywhichaway, which, if the injection timing is too early, will pump a lot of fuel back up into the intake, driving your AFR crazy. If you can, put the computer into open loop, (oh I see you did), and richen her up, and inject as late as you can, to dry up the intake and avoid that backflow.
 
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If the thing is not firing evenly, then I would not rely on the AFR to tell me where the mixture is. Unburned fuel is not seen at all by the O2 sensor, but unused oxygen WILL be registered, and, as a result, your AFR readings look lean.

7e5hangten360 said:
isnt 2 turns on the rocker adjutment too much?
Click to expand...
Too much lifter piston compression would sure cause the symptoms...... seems worth investigating.

As for the ICA, I suspect it is in the low 60's due to ground-in cam advance; that gives you cranking pressures like what you have.

Any exhaust restrictions going on OP? Like something got dropped down the turbo outlet pipe? Is the turbo spinning freely? I know it won't likely be spooling at idle but it ought to be free. That is one more exhaust restriction that is going to effect back pressure and effect cylinder clearing and filling.
 
AJ/FormS said:
Ohchit :(;wrong thread

then back to post 17, for same ending.


I back calculated your total chamber volume from the 9.15 previous Scr and added your estimated 4cc increase to re calculate your Scr to 8.62
I calculated your swept using a 3.94 bore
I grossed your 218/218/115 hydraulic roller cam up by 52 degrees to get a cam with advertised specs of 270/270/115,which, in at 113, equals an ICA of 68 off the assumed advertised.
I plugged in 6150 altitude
The overlap works out to 40* using the assumed advertised specs.

Static compression ratio of 8.62:1.
Effective stroke is 2.47 inches.
Your dynamic compression ratio is 6.68:1 .
Your dynamic cranking pressure is 97.76 PSI.
V/P (Volume to Pressure Index) is 71

This does not match your 110/120 psi, so I assume some erroneous input(s), on my part. But the point is the same; she has a fairly late-closing intake angle, which means the intake manifold, at idle, is gonna be full of air going everywhichaway, which, if the injection timing is too early, will pump a lot of fuel back up into the intake, driving your AFR crazy. If you can, put the computer into open loop, (oh I see you did), and richen her up, and inject as late as you can, to dry up the intake and avoid that backflow.
Click to expand...

Hmm, I see what you mean now. Mega squirt 2 is set up as a batch fire style injection, meaning it squirts one bank, then squirts the other, 360 crank degrees apart. Unfortunately, it’s not sequential and I don’t have much choice other than timing each batch, which would make it great for some cylinders, but the others not so much.

I started it up between rain storms and first looked at my tooth logger, which I can see every tooth and the missing tooth on display in the tuning software. Everything looked normal. I was able to enrich the mixture and it seemed to like it, I noticed I had a lot better throttle response. I believe a lean condition is mostly at fault here. Thanks to everyone who has chimed in.

I must have made too many adjustments at once to the ignition, fuel, and warmup because my laptop started to lag, the interface threw a fit, and it pegged full rich without commanding it and ran very rough. I couldn’t correct it, either, even after making a drastic lean adjustment. I let it die. I couldn’t restart and decided to let it cool off. I think I’ll have to just start all over with the fuel/ignition maps when I have more time.
 
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