New Engine - Knock under load - now tuning

[nogoodwithusernames]

Alright as the title says I'm getting a knock/rattle sound at low RPMs while under load. For sure engine speed related. Will do it taking off from stop and after changing gears.

Engine:
1956 cc setup for type 3
040 heads
New bearings, new CB crank and h-beam rods, new P&Cs.
About 10:1 compression with CB2250 cam
MS2 fuel and spark
1/4 tank of normal low octane fuel, will fill up on 91.

My thoughts are possibly spark timing or early detonation unless something catastrophic happened to my bearings?
Thanks for the help, and the entertainment that comes with posting on the samba.
_________________
71 Squareback, 1.7l T4 w/ crank trigger fuel and spark
(Conversion thread https://www.thesamba.com/vw/forum/viewtopic.php?t=732508&highlight= or https://shoptalkforums.com/viewtopic.php?f=1&t=151375&sid=f0542d44a322d290c29d6609fac7f215 )
74 914, 2.0L w/ D-Jet

-Derek

[Jessechop]

I would certainly side with donation. 10:1 will need hi test for sure

[sawed off]

Back the timing off a bit to see if it goes away. At least then you will know its just detonation.

[modok]

well, it might be fooling you, or it might not. In either case yeah, back of the timing 4d egree and see if it changes. preferably, immediately.
If you have to get out your laptop to do that, HAHA But, you could put in a knob if you wanted. I would.

[[email protected]]

it would help if you'd post what distributor and timing you are currently running, rather than everyone guessing.
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[mark tucker]

my 2028 has that cam with 1.34 rockers and 10.4 cr and about 80000 miles, but I havent a clue if it knocks on reg fuel as it's always had premium in it., get good fuel, and tune it.....or listen to it.is it detonation? is it bearing? is it crank hiting something? is it pushrod? is it piston skirt? your there listening to it what is it? is it valve adjustment? I can tell if my lash/adjustment is out .002 or more either way from the sound of the engine, not the lash noise. listen & think. hows the oil pressure? how new is the engine? how many oil&filter changes?is it a wristpin noise? buttons or clips?

[nogoodwithusernames]

Glad to hear everyone's thoughts. I'll hook up my laptop and pull back the timing a bit.

Definitely will get good gas too but I forgot to fill up on 91 before pulling the old motor.

John no distributor, running Megasquirt for fuel and spark.

Mark I wish I was that good but I'm not quite so experienced. I will get there but not quite yet.
_________________
71 Squareback, 1.7l T4 w/ crank trigger fuel and spark
(Conversion thread https://www.thesamba.com/vw/forum/viewtopic.php?t=732508&highlight= or https://shoptalkforums.com/viewtopic.php?f=1&t=151375&sid=f0542d44a322d290c29d6609fac7f215 )
74 914, 2.0L w/ D-Jet

-Derek

[nsracing]

Rattles are not good. Could be chewed rod bearings. Could be cam wiped out.

It is a good idea to pull the engine out and see for sure.

[[email protected]]

you still need to tell us your ignition timing. And at 10:1, cheap gas is not wise.
_________________
It's just advice, do whatever you want with it!

Please do NOT send me Private Messages through the Samba PM System (I will not see them). Send me an e-mail to john at aircooled dot net

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[rrcade]

Don't save nickels on gas Good gas (high enough octane)is cheaper than a rebuild right?
_________________
CHEAP - FAST - RELIABLE
You can only pick two of the above.

[nogoodwithusernames]

Just did a bit of a drive 'round the neighborhood with the computer hooked up and I don't have to keep so puckered up anymore

Pulled the timing back to 6.5° around idle and that cured it except for pulling up the driveway from a stop. I pulled a little fuel from idle as well if that matters?

Will get some good gas in it and see how it does maybe creep the timing up a hair if it'll take it.

Thanks for confirming my suspicions and for the tips!
_________________
71 Squareback, 1.7l T4 w/ crank trigger fuel and spark
(Conversion thread https://www.thesamba.com/vw/forum/viewtopic.php?t=732508&highlight= or https://shoptalkforums.com/viewtopic.php?f=1&t=151375&sid=f0542d44a322d290c29d6609fac7f215 )
74 914, 2.0L w/ D-Jet

-Derek

[vwkirb]

[rodgersbadassbus64]

Can you see if the noise goes away when you pull individual plug wires... maybe a piston knock or cam noise to much play, single thrust bearings with heavy springs?

[Max Welton]

[[email protected]]

he may be guessing like crazy for all we know, since he hasn't posted his ignition map.
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It's just advice, do whatever you want with it!

Please do NOT send me Private Messages through the Samba PM System (I will not see them). Send me an e-mail to john at aircooled dot net

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[Max Welton]

Derek, what are you triggering off? One of Mario's Cam-Sync devices? I always thought that was a neat idea. I went with a trigger wheel mounted to the fan. Accurate and good enough for wasted-spark.

Max
_________________
1967 Type-3 Fastback
Under the Knife https://shoptalkforums.com/viewtopic.php?f=24&t=151582
Home Stretch https://www.thesamba.com/vw/forum/viewtopic.php?t=767836

[Max Welton]

I checked your gallery. Crank trigger it is!

And truck coils. Nifty!

Max
_________________
1967 Type-3 Fastback
Under the Knife https://shoptalkforums.com/viewtopic.php?f=24&t=151582
Home Stretch https://www.thesamba.com/vw/forum/viewtopic.php?t=767836

[mark tucker]

I run about 15 idle degrees. nice and smooth idle., get some good fuel in it!!!

[nogoodwithusernames]

Hey look a bunch of new posts!
Max looks like you answered your own question, yep crank triggered. Thought about going sequential with one of mario's cam syncs but never got around to it so just running wasted spark.

Got good fuel in it again but will wait till next fill up to make sure there's not any or much cheap stuff in the tank.

I have the spark setup as straight mechanical advance right now. Vacuum signal is bouncing a lot still. Seems to be doing alright on this for now.

_________________
71 Squareback, 1.7l T4 w/ crank trigger fuel and spark
(Conversion thread https://www.thesamba.com/vw/forum/viewtopic.php?t=732508&highlight= or https://shoptalkforums.com/viewtopic.php?f=1&t=151375&sid=f0542d44a322d290c29d6609fac7f215 )
74 914, 2.0L w/ D-Jet

-Derek

[[email protected]]

I recommend ending your spark table around 4500 or 5k, since timing won't change above it anyways. By doing this you can use the additional cells for more resolution in the mid range (where you need it). This will help when you start really zeroing in on the proper timing map.

IE: 600, 800, 1000, 1200, 1500, 1900, 2300, 2800, 3200, 3700, 4200, 5000

Also, assuming you idle at 8-900, increase the timing in the 600 column, it will give you a more stable idle. Try 8 BTDC for 800, and 10-12 for the 600 column.

Right now your map is really raw, and your pinging is a result of that. It will probably be fine when you get it cleaned up even 1/2 way to ideal.
_________________
It's just advice, do whatever you want with it!

Please do NOT send me Private Messages through the Samba PM System (I will not see them). Send me an e-mail to john at aircooled dot net

"Like" our Facebook page at
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and get a 5% off code for use on one order for VW Parts ON OUR PARTS STORE WEBSITE, vwparts.aircooled.net