AdsoYo

iTrader: (1)

Ever since installing this engine in 2009 I've been dealing with this jolty back-and-forth bucking whenever the car is cruising. I've posted lots of questions to this board over the years and gotten help from lots of people but finally decided a professional needed to experience the car in person. I discovered I had the authority on LT1's himself, Ellis at Speed Secrets, living just a few hours away. When I got there I gave him the full history of the car, the problem, everything I've tried, everything people had suggested it could be. He plugged in his laptop with HP Tuners and we started the drive.

Almost immediately he said the bucking wasn't tune related and it felt mechanical, almost like a miss. He watched his laptop for a minute and said the tune looked great and started adjusting spark with VCM controls which didn't change the way the car felt. After a little more driving and talking he said it was most likely the rings and he would re-ring it. I said I did a compression test and got 180-205 on all cylinders and he said a leak down test would be more helpful. Terrible news for sure. He also confirmed something I had suspected this whole time: my exhaust sounded wrong. It's always had this weird background noise that's hard to describe; like popcorn popping or bubbles popping behind the normal sounding pulsations and he picked up on it. He didn't charge me for his time which was awesome, maybe he felt bad. I shared this story with a mechanic friend of mine and he said it's possible for rings to lose compression in certain conditions and hold it fine in others. He also said one or more rings could have been installed upside down. I've never done internal engine work so I didn't know either of those were possible.

I told Ellis this engine wasn't worth completely disassembling to change the rings. It doesn't make enough power and isn't fuel efficient enough. And since I'm not going to solve the bucking through tuning I'd most likely modernize to a LS3. He said best bang for the buck would be the LS376/480 crate motor. After researching I agree. $6,400 on Jegs or Summit with free shipping and a 2 year/50,000 mile warranty for about 50 more horsepower than I have now and better mpg's. Anyway, still considering a bunch of stuff and really just wanted to share what I was told.

VoyagerCamaro

Hate to hear that. But yeah that LS3 is hard to beat... Always wanted to go that route but there is just something about a LT1 that always brings me back lol

KW Baraka

iTrader: (7)

OK.....so you got a Golen engine from 2009/2009 time period?

IIRC, this was during the period when that company was putting out a relatively high number of bad LT1's. So, not really surprised by your situation.

Hope the next engine (GM Crate LS3/480) turns out better......it should .

KW

ahritchie

iTrader: (1)

Just a thought, wouldn't it be far more cost effective to do a mild rebuild on the 383 (re-ring, hone, bearings for around $1000 vs $7-8K+ by the time you convert to LS3?) Dump that baby cam for a much more aggressive cam too???!! Or were you running the baby cam due to cast crankshaft or something? If not, want to sell me that high dollar 24x conversion for pennies on the dollar?

Just saying, gas is cheap, and the 6-7K saved buys a LOT of gas!

AdsoYo

iTrader: (1)

I ordered this engine in April 2009 and installed it in May. I wasn't aware about those bad years, can you elaborate?

Well cost isn't an issue otherwise I would probably just live with the current engine. I have no other complaints with this engine besides the jerky cruising. 111 mph in the 1/4 and 22-24 mpg on the highway. The cam is just what came with the long block. And I'll be using the 0411 and BP wire harness on the LS3 but the rest of the stuff will be sold. Unless... anyone know if a gen 4 PCM will work in our f-bodies?

KW Baraka

iTrader: (7)

There was a several-year period from roughly 2005 to 2009 when Golen customers on the Impala SS forum bought poorly built engines; basic stuff....

This was a period when Golen was becoming 'all-the-rage' in the LT1 world....it was surmised that weak quality control coupled with poorly trained new-hires was the issue behind the bad builds.

So.....if you have piston rings installed upside-down, yeah.....that would be a perfect example of just poor build issues out of Golen.

KW

AdsoYo

iTrader: (1)

Well ****

kingtal0n

iTrader: (1)

If it has good compression and dyno tests well, and there is no blue smoke coming from the exhaust/pcv system during hard running, then it is not the rings. You put a pressure gauge that reads in inches of water on the crankcase and video tape it while you make a pass on the dyno to confirm rings, if the other obvious signs/tests are inconclusive.

BALLSS

OP

did this "authority on the LT1" explain the "why" it could be rings?

without a compression and leak down test..that is a big bat to swig after a few key strokes on a laptop and a test drive.

rings worn, broken or installed wrong by the noted builder?

does your motor use a lot of oil?

FWIW I have a Golen forged 383 short block I bought back in 2006. Still running although I assembled the motor beyond the short block. They were one of the more prolific builders then, maybe still are, and likely had more + and - comments about them because of the volume they did and car forums kept chatter up sadly so often on hearsay vs direct experience. so "internet stories" took off. Not saying Golen never FU something but if your motor has been running for 7 years with no issues other than this bucking condition you describe on Hwy cruise speeds....just trying to understand how rings cause that.

ahritchie

iTrader: (1)

Did it have this bucking condition with the original LT1 PCM before the 24x conversion? Or was the 24x done at the same time as the new 383?

Seems to me that variable should be eliminated as a cause.

As for the not enough power issue; I would suspect the very conservative baby cam and possibly the crappy heads would be to blame for that. Did you get a short block from them or a long block with their mystery heads with no flow sheet data?

AdsoYo

iTrader: (1)

He's felt that type of bucking before and I ruled out literally everything else. It can't be the tune because it does it in speed density open loop so that rules out MAF and O2's. I've had IAC at all positions, ran from way lean to way rich, had spark from 19-50 degrees and all combinations in between of those 3. I've run MAF only and power enrichment. I've set injection timing to after EVC, turned off DFCO, softened spark and IAC adjustment tables, you name it. It does it with stock LT1 injectors and my 30# Fords with stock fpr and my new adjustable fpr with no vacuum connected up at 60psi so that rules out the fuel system. It does it with any spark plug (hot/cold iridium/copper/platinum) at any gap (from 0.030-0.060") so it's not the plugs. My dad and I smoked a couple cigars into the brake booster hose and there are NO leaks (most fun I've had troubleshooting so far). There are no leaks in the exhaust. There's just nothing left. So based on what he felt, what I told him, what he saw on the laptop as we drove, how my exhaust pulses sounded, that was his determination.

Compression test was:
1: 190 3: 190 5: 200 7: 185
2: 185 4: 190 6: 180 8: 180

Haven't done a leak down, don't know if I will. The compression test was such a colossal pain in the ***.

I haven't actually kept a record yet but I will this year, I estimate I go through around 2 quarts between my annual oil changes (3-6000 miles). The bucking doesn't happen at highway speeds, it happens below about 60-65mph. From 50-60 it's more of a shaking motion than bucking, from 35-50 it's a super annoying back and forth jerkiness. Even at 70mph if MAP drops below about 45 it will buck back and forth.

Yes it had the bucking with the original PCM. I drove it with the original PCM from 09-14. After going 24x, nothing changed. And I think there was a misunderstanding somewhere, the engine DOES make great power. It's advertised as a 400hp long block so trapping 111mph is right on the money. All I know about the heads is that they're stock LT1's with bowl and slight runner porting and a 3 angle valve job.

hrcslam

You didn't mention VE tables. What adjustments have you made to the VE tables? The 411 PCM definitely uses them in MAF mode (so MAF is only part of the fueling), this will absolutely give you the symptoms you are experiencing. Not saying it is, but that is can definitely do exactly this.

The LT1 PCM is debatable on whether the VE tables are used in MAF mode or not (I've personally experienced a DRASTIC improvement in drivability by adjusting the VE tables in MAF mode on my 1995 OBD1 LT1). I will say I'm now exclusively in SD mode until I can get back on a dyno and calibrate my MAF correctly.

The VE tables are what Open loop fuels on until the MAF is warmed up, and then the MAF AND VE tables continue the fueling from there, especially at low RPM and idle areas (where you are experiencing the symptoms). You can adjust everything else all you want to, if the VE tables are off you'll get the bucking. Of course depending on the cam and engine specs, there's no way around the bucking at certain RPM's. But you have a small cam to your displacement, bucking shouldn't be an issue.

Do you have a dyno graph? If so, look at the TQ curve. Dips in it would indicate lower BMEP, which = less torque. You'll also see a corresponding dip in either the VE and/or MAF tables or an increase (richer) AFR on the dyno log. If that's the case, you could be experiencing excessive blow-by a certain RPM's due to cylinder warpage and/or harmonics. I doubt this is the case though, as that usually happens at much higher RPM's and power levels, if it happens.

I'm still convinced it's in the tune. Particularly the VE tables. What are you LTFT's for all cells below 2K?

AdsoYo

iTrader: (1)

That's a good idea but unfortunately it isn't the VE table, forgot to throw that in the list. With HP Tuners you can disable the VE table by going to Airflow>Dynamic>High RPM Disable and setting it to an RPM below what the car would ever see while running (like 400). The PCM uses only the MAF above whatever value is in the High RPM Disable box. Stock setting is 4000, so below that RPM the PCM uses a hybrid MAF+VE algorithm. Since it still bucks with VE disabled, I have ruled it out. However, I did tune the VE with my wideband by running open loop and setting the entire open loop table to 1, then adjusting with AFR error a couple times. Also I've never heard of the MAF needing to be warmed up

I have a dyno graph from 2010 and there's no dips in the torque curve or afr curve.

I run the car in OL MAF+VE at all times since the bucking is much worse in closed loop, but when I did run closed loop, LTFT's were either zero or +/-1.

hrcslam

The MAF uses a heated wire, it needs to heat up (it doesn't take long at all though, not like an O2 or cats). The reason VE tables are used below 4k is because of drivability issues with MAF only.

hrcslam

What adjustments did you make to the O2 delay and target voltages? That will effect fueling of it is off.

RealQuick

iTrader: (14)

That makes me think it is tune related

ahritchie

iTrader: (1)

I highly doubt a LS3 is gonna get significantly better mileage than 22-24 mpg highway....that's a lot better than my 383 although I've got a much bigger cam, 4.10's ect....

As for the lack of power issue, I was just going off your remark "it doesn't make enough power"; others can run that trap speed with just a cam, plenty of more aggressive 383's running 120+ although they usually have reputable ported heads and bigger cams. 400hp flywheel is like 350ish at the wheels or less. Who tuned it? Maybe pick up a spare PCM and let PCM for less mail order tune it....mine had great driveability with a much bigger cam with their mail order tune. They are familiar and have tuned plenty of 24x LT1s...

BALLSS

so if he has felt this kind of bucking before and attributes it to rings....what about the "rings" does he say is wrong?

your compression is good as are your track times for your combo.

This ring cause is new to me so just trying to understand the "why".

Not knocking your abilities on self-tuning to attempt to FIO but from this side of the keyboard it sure sounds like a tune issue.

I assume you are not lugging the motor when this bucking occurs

hrcslam

This. The compression checks good, the dyno chart is smooth, as are the fueling tables, and I'm going to assume no oil consumption issues. I don't see how it could be the rings.

There's something in the tune not adjusted correctly IMO.

OP, what headers are you running (LT, ST, Mids?) and what adjustments to the target voltage and delay have you made for the headers; this directly effects fueling trims, BEFORE STFT and LTFT are made, and the timing of the trim cells they'll happen in. The O2 tables have authority to adjust the fueling instantaneously, minutely before STFT adjustments are made. If the timing and targets are wrong it'll be adjusting the wrong cells the wrong amount. Although the log may show good, what's actual is wrong. Again, not saying this is it, but it very well could be.

For my LT's and cam/engine combo, I decreased Target Voltage and increased the delay.

AdsoYo

iTrader: (1)

It made everyone including myself think it's tune related.

I ran a PCMforless tune for the first year after installing the new engine. I also ran PCMforless for a few weeks after going 24x because I didn't have HP Tuners yet. They actually screwed up the tune and didn't account for the LT1's firing order so the car REALLY ran like crap. After getting HP Tuners I saw that all they did was take some numbers out of a 13x4 cell block in the low load/low rpm area of the VE table, adjust injector flow rate for my injectors, and add a few degrees of spark to WOT. I did not think that tune was worth what I paid, I actually felt ripped off. In both cases the car still bucked. So I had a professional tune it on his Mustang Dyno in 2010 and he couldn't smooth it out. We ran out of time so he said I could bring it back and he'd try again. Brought it back the next year (it's on the other side of the state from where I live) and again he couldn't smooth it out. After going 24x a guy from hptuners forums overseas wanted to take on the challenge and I've been working with him for over a year and we've managed to improve the bucking but it is by no means close to gone. Other guys from the forums have given me things to try and sent tune adjustments, nothing has helped.

Not lugging, I cruise around at 1800-1900 rpm. The only speculation I have on the rings is they were installed incorrectly (like upside down) or didn't set correctly. I didn't ask him to explain the technicalities. I just asked if he thought it could be something much easier like the cam, valve train, or lightweight flywheel and he said no.

I'm running mids. I've had the voltages high and low, never made a difference. O2 delay was increased up to 25% I think but that didn't make a difference either. But I'm running open loop anyway.