So very stuck...

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R3N0

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So I have hit a wall, not literally. Under light throttle my truck runs fine, shifts through all its gears no problem. I step on the gas and I get this horrible rattling sound. Like the motor is being beaten with a jack hammer.first I thought the new transmission was the issue, put the truck up on stands and had a friend engage the transmission and give it some gas... no problem... the had him give it some real gas... bam rattles like crazy... climbed underneath( I know I know, not wise) put my automotive stethoscope to it and nothing. Okay... it's the engine... yup it's the engine. Horrifying sound. So we shut it down and I drain the oil, remove the pan... everything is tight and sound. Hmmm.... nothings broke or loose... looks absolutely great. Wtf? So we put the pan back up after cleaning it up. Move to the top of the motor, remove the valve covers... nothing everything is tight and within spec. SMH... okay compression test... 180PSI all cylinders... now I'm frustrated... looking at spark plugs... brownish coating... running dry... that cant be the carb has smallest rods , largest jets... and moderately light springs... when driving, the truck is eating gas... I know cause I've gone through a tank in half a week. Looking at spark plugs again... plugs dont lie. Okay let's test coil... MSD is putting out 7 ohms... within speck... test wires... wires good... WTH man... am I crazy? What am I missing? I'm running 91 Octane with an +7 octane booster... can I get engine knock that high?
88 Dodge w250 HD Power Ram
360 bored .030
Keith black hyperueretic pistons
Comp springs / Rods
Melling valves
91 swirl port heads ported and polished Int. 2.02 / Exh 1.96
Edelbrock performer air gap intake
Edelbrock 1406 Carb (too small?)
B&M flex plate
PATC Built Viper 2 series A518 46RH
4.10 gearing
35 inch tires
And a cherry bombed dual independent exhaust.
 
Yes, you can be getting detonation. Octane boosters are, well, I'll try not to be too mean but I think it's safe to assume you're not actually getting a +7 octane rating boost, if any at all.

The 340 in my Duster has a cranking PSI around 180 as well, I had to pull some timing to keep it happy under heavy load. I also run the 308 swirl port heads with 2.02"/1.60" valves, they've been ported and the chambers worked some. Cranking PSI can vary quite a bit on how you're doing your compression test, so it's not the most reliable thing to compare. My static compression is 9.8:1, also with KB hyper pistons.

Not sure what your timing is set at, but that will make a BIG difference. I'm at 20° at idle and 34° all in mechanical.

You also have a heavy vehicle, with a lot of rotating mass, and 4.10's aren't that crazy for 35's. I'm no tuning guru by any means, but if it's coming from the engine it could definitely be detonation. And those hyper pistons do not like detonation, so you want to figure it out.
 
My first thought is detonation also. Pull some initial timing out until it goes away. 93 octane may also help if it's available in your area. 65'
 
My timing at idle is about 24* with 36-38* overall, I also just checked my TV cable and found the the TV port still has about 1/4 inch travel still left in it at WOT on the carb. The flex plate is in good condition and the torque converter as well. We just installed this transmission 2 months ago. And I was getting this issue just before we rebuilt with the manual transmission that was in it. I'm wondering if the play in the TV cable is the motor fighting the transmission as the line pressure may not be reaching its max. But that seems odd as this was a problem with the manual trans as well which is why I moved to an automatic ( also driving in heavy austin tx traffic daily was killing my knees) in the first place. Any ideas on how to ease the detonation if that is the issue?
 
Yeah I may have to adjust the distributor, just figured that at 38* I was pushing it.
 
Yeah I know ots moving alot of mass... this motor is almost 400 hp, figured it wouldn't have this issue of power... also have a 9:1 CR.
 
Forgive me for this probably dumb question but by " pull timing" do you mean advance or retard?
 
Can you post a video with some GOOD audio? We got some old ears around here.
 
24 degrees at idle......Might be a good time to try manifold vacuum instead of ported to the can to get to that number. If I understand the concept correctly, light throttle would have little to no effect on base timing, whereas heavy acceleration would cause the base timing to retard when mv drops off (assuming the OP is in fact experiencing detonation). Just thinking out loud......
 
I thought the same thing with my 69 D200. It started rattling faintly, then under more acceleration it got louder and worse under full throttle. Found out one of the bolts that held the converter to the flex plate had come out completely and two others were on their way out and hitting the block! I didn't figure this out until I was pulling out the engine and trans because I thought it had spun a bearing, that is exactly what it sounded like! Do a quick check to be sure before wasting time like I did...
 
My timing is mechanical,checked the bolts on the flex plate all is good. I'll get the video and sound as soon as I can.
 
Post #12 about using MVA is veeeeeeeeeeeeeery good advice. Maybe cut back the initial to 10* & add 14* [ at idle ] with MVA. An adjustable VA unit is also reqd, screw Allen Key fully CW.

If you are not using VA [ either PVA or MVA ], then that is also contributing to the problem because the extra cruise timing of VA keeps the engine cooler. Detonation loves heat.....
I will bet if you tested the engine when cold, the noise is not there or reduced.

More on MVA benefits, scroll down to post #6.

www.hotrodders.com/forum/vacuum-advance-hooked-up-directly-manifold-bad-47495.html
 
I always use blue loctite on my flex plate bolts. Seen them loosen too many times in the past.
 
360 or 5.9?

Might be silly but if it's a 5.9-

Timing chain tensioner?

They can sound like the engine is getting ready to explode, or that there's two dozen marbles or ball bearings in the crankcase.
 
Okay, so I dialed back timing a little. Got the timing at 22* initial, any less and rockers start to tap. Tried to upload a video, server doesnt like the file size, though the video is only 30 seconds. My all in timing is at 41* to 42* (everything is just vibrating to much for my 45 year old eyes to catch up with). I'm pretty sure this is too high. I'll have to wait for the truck to cool down to pop the can cap so I can see what springs I put in there. If I remember correctly 1 is soft and the other is stiff. I believe I still have the other springs in the edelbrock spring and jet/rod kit.
 
As for the chain tensioner this motor has barely 15k on it and the trans hasnt even hit 500 miles yet.
 
I know I capped the vacuum advance and just went mechanical, maybe this was a mistake. But if I remember correctly I did this due to the springs I used. But if changing back would help make the truck run better I'm definitely okay with doing that. I didnt block the whole port just put a vacuum cap on the inlet.
 
I find it weird that I dropped the initial timing down and my all went up... strange... but I did have to change around the idle screws while setting it, maybe that played a part.
 
To upload a video it has to be on a video hosting site such as YouTube, then just copy and paste the link in the post text box.
 
Ok you need to seriously stop messing around and MAKE your timing do what you want it to do. 42 is too much and likely the reason it’s rattling. Forget vacuum advance FOR NOW, after you get a good baseline you can add that in later. Almost any mildly modified street type engine will run pretty good with 18 or so initial and 32 total with one light and one medium spring. So I always recommend that as a starting point. So find a way to limit the mechanical to 14 degrees, set the initial at 18, verify that as you rev the engine it increases to 32 around 3000 rpm or so and then, only then you can start tuning on it.
 
“Got the timing at 22* initial, any less and rockers start to tap.”

Not even sure what this means. Can you explain what you mean? There should be no noise from the rockers regardless of where the timing is set.
 
TT5.9mag said:
“Got the timing at 22* initial, any less and rockers start to tap.”

Not even sure what this means. Can you explain what you mean? There should be no noise from the rockers regardless of where the timing is set.
Click to expand...
I was adjusting the distributor by retarding the timing I would start to get a tapping noise. I'm making a guess that it's the rockers, but in all honesty it could be the hydraulic lifters as well.
 
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