HIGH POWER PROPANE PLUS 2 YEARS

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stroker
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HIGH POWER PROPANE PLUS 2 YEARS

Post by stroker » Thu Mar 12, 2009 4:09 pm

Please read HIGH POWER PROPANE BEFORE YOU READ THIS. Okay, the good the bad the ugly.

The BAD: 254 comp cam failed after 2000 miles. This engine was broken in on a dyno with the right oils before it was installed in my van, could not get number 1 lifter to quite down. After 2000 miles I decided to go to a 258 roller, a hair more lift and duration. Remember I am going for torque. The UGLY, I could still not get the motor to run good at idle and would not pass air care, (this is BC emission testing) It failed only at idle, when running at 40 miles an hour ran clean. When running at idle the motor would still jump from 600 rpm. to 1200 rpm. this was better but far from right. If you remember from my previous post I had always felt that there was a fly in the ointment with my vaporizer, also to note my power valve was running at 85% open, this gave us the best number on air/fuel and HP/Torque. Running less then this the air/fuel ratio was lean at 2700 rpm.

HERE IS THE UGLY: DO NOT TAKE YOUR VEHICLE TO A CERTIFIED SHOP UNLESS YOU KNOW THAT THEY KNOW WHAT THEY ARE DOING. After I left the shop went back to air care and the vehicle past, however at 40 miles an hour, to me it looked real lean, I should also mention the vehicle lost power. I went back to the shop and asked about the air care numbers, the mec^$%#@!ic said it was a little lean and to turn up the power valve a little. At this time I should have asked why the power valve, it was set on the dyno and should have been left alone but my bad my fault. Turned up the power valve 2 turns, and went to a car show 35 miles away all freeway driving 2700 rpm.On the way home oil pressure started to move around a bit and then dropped like a stone.I NEVER MADE IT HOME motor was gone. Because I did not do my own check on the shop and took someones word, all my work, $13K gone, back to square one. I found out later that the mec@#$%ic only turned back the power valve, did not work on the idle mixture from the vaporizer at all. Two lessons I have learned, I will always mark my power valve and I will never run without a wide band O2 sensor. These two things would have saved me a hugh cost and gave me piece of mind.

OKAY THE GOOD: Total rebuild plus a new crank, new vaporizer and dyno time, cost $5300. After a good warm up on gas, 3000rpm = 472.5 torque / old cam 475.7 at 3900rpm new cam = 501 torque / old cam 493.9. HP numbers new cam 3900rpm = 372/ old cam 366.8 5100rpm new cam = 430.9 / old cam = 4800 rpm 415.6. ON propane 3000rpm = 436.6 torque / old cam 435.6 at 3900rpm new cam = 454 torque 337.1 HP / old cam 452.5 torque 336 HP. New cam 5000rpm = 396.9 HP / Old cam 4800rpm 384.2 HP. Please remember this is in a very heavy 4x4 camperized van. All of the research I had done on cam choices did me proved me right. When you are working on a max torque low RPM motor there is no reason to put the extra costs up for a roller, the money can be better used elsewhere. If the quality of new flat lifter cams were not suspect (I have very strong views on why they fail when broken in right, at this time I will keep views to myself) I would rather be running one and use the extra money for partial costs of a trans upgrade or new gauges ect. This new motor made 18 in. manifold vac. old 19.5. New motor idled well at 700 rpm, it would seem the varying idle problem is gone.

I will be installing new motor in June 2009 as I am on Vacation until then. At that time I will post idle results, but from the dyno results I am very optimistic. If I have not answered any question or not clarified something feel free to contact me at thehook70@gmail.com or just post but please read HIGH POWERED PROPANE FIRST. Thanks.

Stroker


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Re: HIGH POWER PROPANE PLUS 2 YEARS

Post by Frank » Thu Mar 12, 2009 8:23 pm

I don't have any real experience in building and tuning engines but I'm having trouble understanding how a slight fuel mixture change could destroy your engine. It sounds like the camshaft and crankshaft were both wiped out. I would have expected melted pistons and burned exhaust valves instead.

Can you tell us more about what parts failed?

Is it possible that the engine could have been on the way out before Air Care test (resulting in bad idle) and that the failure after the fuel mixture change might have happened eventually anyway?

stroker
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Re: HIGH POWER PROPANE PLUS 2 YEARS

Post by stroker » Thu Mar 12, 2009 9:53 pm

First of all believe me when I say it was not a small adjustment. The Mec@#$%ic turned in the power valve more then halfway.To get the new motor to run at optimum on dyno it worked out to be between 13.7 - 14.1 air fuel, when I cut back power valve 1 turn, motor lost 20% power and went up to 15.3 - 15.7 air fuel. Another way to look at this is, if your gas powered car did not pass air care and all that was done to make it pass was put in a fuel pump with half the flow when the one that was in was already dyno tuned to optimum there are two things that would happen, you would hear the motor detonate as soon as you put the vehicle under a load and the second it would die a quick death. The reason air fuel is so much more important on propane is you can not hear detonation. 15.5 air fuel happens to be where I have been told Propane engines run best, I can only tell you my results on the dyno and there is no way I would consider running that lean. The new cam I had just installed did not fail, valves were toast as was the crank. I had put in very expensive coated SRP pistons and they were fine but marked up a bit,and of course rods resized. This motor a week before made lots of power, as stated in my article two years ago on this form, I strongly believed the vaporizer was not getting the correct signal from the mixer at idle, due to the mixer being a bit to large. The engine shop that I work with said, point blank, this motor detonated itself to death. Hopes this clarifies things. Stroker

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Steptoe
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Re: HIGH POWER PROPANE PLUS 2 YEARS

Post by Steptoe » Thu Mar 12, 2009 11:47 pm

When you are working on a max torque low RPM motor there is no reason to put the extra costs up for a roller, the money can be better used elsewhere.
Correct...I run a bottom end engine in the camaro 1200 to high 4000. and a lift over .5
I don't have any real experience in building and tuning engines but I'm having trouble understanding how a slight fuel mixture change could destroy your engine. It sounds like the camshaft and crankshaft were both wiped out. I would have expected melted pistons and burned exhaust valves instead.
Yes and it would take far more milage under far heavier loads (hill/ accerlation ) than u describe
And the power valve only has an effect at heavy loads and WOT
The biggest cause of cam failure is
1/ in the 1st 20 secs of fireup the engine is idled and not taken out 2500 to 3500 rpms
2/ The manufactures cam lube not used during assembly, but rather 'what is on the self'
3/ There is some contoversy as to using modern low zinc free oils on a new engine...personally i havnt made my mind up about this but us a high zn oil regarless, do intial break in and change oil/filters.

The big ends...If these where individually sized/platstgauged, dumby assembled, then lubed and then assembled etc there is no way they would have ANY damage...unless the pump was not new and pre primed before fire up...ie not fired till oil pressure was up....even if the pump was only giving 10lbs max there would be no damage.
IF there had been any issues this would have been seen when the run in oil and filter was cut open and inspected.

Another issue that may not be aplicable here but if LPG is used as fuel is on 1st fireup is way too lean AND the timing way over advanced, this creates huge heat, fast, expanding pistons faster than the bores causing piston shirts to collapse, Espec if it is AS=U&med the the pstons ARE all the same diameter out of the box, and not individually sized on the final hone, and the manufactures bore to piston reconmenations for LPG are not adgerded to..Note general most manufactures recomend 1.5 to 2 thu more for LPG
Hence why with a LPG engine I use Aussie ACL pistons, now avalible in the states. ACLs due to there internal gustting run the same as or smaller clearance than all other piston makes.

I would be checking the diamentions of the piston shirts against manufactures specs, and inspect under the miroscope.
The UGLY, I could still not get the motor to run good at idle and would not pass air care, (this is BC emission testing) It failed only at idle,
A high life cam tends to do this at idle rpms but comes right about 1100 to 1200 rpms

Bottom line engine failure sounds VERY STRONGLY like a build slapt togeather rather than using the old carptenders "measure twice, cut once" method

I had an issue some yrs ago on a engine, and had the opportunty to spend quite a few hrs by myself and them in the ACL foresnic labs in NZ, Those guys where so open and forth coming with info, and showing me stuff....it was a real eye opener...checking hardness on over heated pistons to microscopic examinations...there is no way anyone can put something over those guys

And stoker please use paragraphs in your posts m8 its a mission to sort thru lol.
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stroker
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Re: HIGH POWER PROPANE PLUS 2 YEARS

Post by stroker » Fri Mar 13, 2009 8:03 am

I am not making myself clear. The cam failed before the motor failed, it just took off some of the lob on #1. and caused pitting on a few others it was not a total failure. I put the new cam in and everything was fine except not passing air care and an idle that was not very constant, motor had lots of power. Next up, the van is 6500 lbs. would that be considered a load. This will be my last post as I am getting very upset that I am not getting my message across and or people are not listening.
STROKER

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Re: HIGH POWER PROPANE PLUS 2 YEARS

Post by Frank » Fri Mar 13, 2009 10:36 am

Sometimes it takes a few reads before information starts to sink in and I had the impression on first read that that your engine failed a second time. As I've never set up a non-feedback venturi system, I didn't realize that 2 turns were more than a minor adjustment. Sorry.

As I recall, you are running a non-feedback Technocarb system so there are 2 manual adjustments on the fuel system: an idle mixture adjustment on the vaporizer and a power adjustment in the fuel line to the mixer. This is a venturi system, which is different than an Impco system because the venturi vacuum directly affects fuel flow. Venturi vacuum in an Impco gas valve system controls the lift of the gas valve which in turn then affects fuel flow. Because venturi vacuum at idle is extremely low, the idle mixture on venturi system is controlled by providing positive fuel pressure to the mixer.

The fuel delivery characteristics of a venturi system is highly dependent upon the venturi vacuum produced by the mixer. The vaporizer tries to maintain a constant pressure to the mixer and venturi vacuum increases with increasing air flow through the engine. The power valve is between the vaporizer and the mixer and controls the flow so that the fuel mixture at a particular air flow is correct.

So now that you have your engine back together, you mention that you have a new vaporizer. Is this the one mentioned in the original posting or a replacement of that one?

Because of low venturi vacuum at idle, Technocarb does not recommend using low-restriction (K&N type) air filters with their mixer-based systems. They find that the additional (if minute) pressure drop produced by an OEM-style air filter helps idle and low-speed operation. Also, low-restriction air filters don't do a very good job of filtering. See BITOG air filter study for more information.

What kind of air filter are you using?

Do you have a explanation for reason that your idle is now good?

If you have a theory on why new flat lifter cams fail when broken in right when the quality is not suspect, please share it with us (on a new thread). I'm sure everyone here would be interested.

[I added a few spaces to your original post to make it easier to read.]

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Steptoe
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Re: HIGH POWER PROPANE PLUS 2 YEARS

Post by Steptoe » Fri Mar 13, 2009 3:35 pm

The cam failed before the motor failed, it just took off some of the lob on #1. and caused pitting on a few others it was not a total failure.
Cam failure is only caused by what i say above, and not using the correct rated valve springs for that cam
Assuming the cam, lifter and springs where not faulty, the only reason for failure is due to not assembing using correct procedures...and the same goes for the crank.
Next up, the van is 6500 lbs. would that be considered a load.
That depends on the final ratio of the gearbox, diff and wheel size...if the vechicle has to 'labour' from standing start and 'labours' up hills...having to use near to or full throttle all the time ....once up to speed and cruising no...momentum is a big factor here....If over advanced intial+ cent +VA is getting up above 38 /43 degrees even at cruise the pistons are still coming up when firing loading the wrist pins, big and small ends...but it takes a huge milage before the bottom end finally gives out if the gear ratios are correct....if not correct then it still takes several 10s of 1000s of miles.
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Mattelderca
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Re: HIGH POWER PROPANE PLUS 2 YEARS

Post by Mattelderca » Mon Mar 16, 2009 1:41 pm

OK, let me try to understand a bit better.
"Pistons where OK but marked up a bit" where were they marked up? On the crowns? if not I would not blame detonation.

It appears you had an oil pressure failure which took out your bottom end. A lean mixture would not cause an oil pressure problem. What type of motor is it? You say a 383 stroker but I could not find a maker, ie, ford, chev, Mopar?
You refer to the first engine as a 350 so I assume Chevy. I also understand that with most roller cams you need to run a bronze oil pump drive gear, is this something you did on your engine?

I am thinking you are too quick to blame the LPG setup and how it was tuned. Got any pictures of the damage? and what was the condition of the oil pump and drive when removed?

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Re: HIGH POWER PROPANE PLUS 2 YEARS

Post by turbine guy » Sat Jun 20, 2009 1:28 pm

- Cam lobes wiped off due to too high of lifter to lobe interface pressure.
- Trash from lobes damaged the cam, main, rod bearings, and oil pump.
- Lean mixtures in a dry fuel engine (Of which vapourised propane qualifies.) does not cause detonation. This is a wet fuel phenomenon only.

Due to no latent heat of vapourisation, I'm not surprised your "valves are toast". In high powered propane applications, you need good intake valves, and adequate heat transfer between the valves and the seats to survive. (i.e. propane spec seat interface widths.)
Steptoe is probably right, the engine wasn't built right the first time.
If you can't get your message across, try harder. There is a lot of experience here on this board, it's up to you to get your point across, and be willing to openly hear the replys.

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