Posted By: sam64
Detonation? - 12/31/13 02:23 AM
Is this a sign of detonation?only 2 pistons have this 6&8. Spark plugs look ok,fat if anything.they are off my sr headed 512 low deck running 110 fuel.
Detonation?
Posted By: TRENDZ
Re: Detonation? - 12/31/13 03:05 AM
Not detonation.... Debris. Something went through the engine.
Posted By: Cab_Burge
Re: Detonation? - 12/31/13 03:07 AM
Pitting can be the early signs of detonation, pull those two rods and pistons out and look real hard at the rings and ringlands for damamge 
Which intake and carb are you running? Also which brand and spark plug heat range? Can you add a good close up picture of those two plugs? BTW,if the rod bearings fall out of the rods, no crush left, that is a sure sign of detonation also 
Which intake and carb are you running? Also which brand and spark plug heat range? Can you add a good close up picture of those two plugs? BTW,if the rod bearings fall out of the rods, no crush left, that is a sure sign of detonation also
Posted By: sam64
Re: Detonation? - 12/31/13 03:27 AM
Quote:done chunked the plugs,m1 intake w 1050 dom jetted 90 square,timing was 38 deg.the head looks the same on those 2 cylinders.yes the bottom end will come apart later,using the heads on a 499 lowdeck.
Pitting can be the early signs of detonation, pull those two rods and pistons out and look real hard at the rings and ringlands for damamge
Posted By: MR_P_BODY
Re: Detonation? - 12/31/13 03:31 AM
Quote:
Is this a sign of detonation?only 2 pistons have this 6&8. Spark plugs look ok,fat if anything.they are off my sr headed 512 low deck running 110 fuel.
I think that is early signs of detonation... if you
look close you can see it gets worse the farther out
it goes towards the edge of the piston
Posted By: Hot 340
Re: Detonation? - 12/31/13 03:34 AM
Whats the head look like? Was it possibly making contact?
Posted By: sam64
Re: Detonation? - 12/31/13 03:38 AM
it's right at.040 quench,i guess maybe I don't need that much timing.this was my first real attempt at race motor[not just a flat top 440 w a cam]lol.
Posted By: TRENDZ
Re: Detonation? - 12/31/13 03:50 AM
you will need to look, but i'd bet that the pits are actually dents. the heads and pistons will be mirror image patterns.
Posted By: MR_P_BODY
Re: Detonation? - 12/31/13 03:57 AM
Quote:
you will need to look, but i'd bet that the pits are actually dents. the heads and pistons will be mirror image patterns.
If this was debris it should have marks on the cyl
wall also in that area.... JMO
Posted By: sam64
Re: Detonation? - 12/31/13 04:07 AM
Quote:yes pretty much,the head looks the same as the piston but the cylinders don't look bad.it's odd that it's only those 2 cylinders.at least this one made 8 passes,last one ate the cam in 2 passes.
you will need to look, but i'd bet that the pits are actually dents. the heads and pistons will be mirror image patterns.
Posted By: MR_P_BODY
Re: Detonation? - 12/31/13 04:12 AM
Quote:Quote:yes pretty much,the head looks the same as the piston but the cylinders don't look bad.it's odd that it's only those 2 cylinders.at least this one made 8 passes,last one ate the cam in 2 passes.
you will need to look, but i'd bet that the pits are actually dents. the heads and pistons will be mirror image patterns.
I would expect the head to look similar if its detonation
but not the cyl wall
Posted By: Mopar-Al
Re: Detonation? - 12/31/13 06:08 AM
For it having only 8 passes, it seems to have a lot of oil and gas residue on that piston. I assume you cleaned them off a bit to? Looks like hot spots detonating.
Posted By: loaderpro
Re: Detonation? - 12/31/13 07:43 AM
The next time you pull that engine down you need to smooth out ALL the sharp edges from around the valve reliefs and the crown , this will increase airflow and help to reduce detonation. Sharp edges on any race piston is a definate no-no. This is a CP 14-1 piston with the edges gone.
Posted By: Crizila
Re: Detonation? - 12/31/13 04:32 PM
Quote:Quote:
Is this a sign of detonation?only 2 pistons have this 6&8. Spark plugs look ok,fat if anything.they are off my sr headed 512 low deck running 110 fuel.
I think that is early signs of detonation... if you
look close you can see it gets worse the farther out
it goes towards the edge of the piston
collapsed top ring land, no bearing crush, will tell the tale.
Posted By: sam64
Re: Detonation? - 01/01/14 03:28 AM
Quote:I will look into doing that.and thanks to all that replied.happy new racing year to all!!
The next time you pull that engine down you need to smooth out ALL the sharp edges from around the valve reliefs and the crown , this will increase airflow and help to reduce detonation. Sharp edges on any race piston is a definate no-no. This is a CP 14-1 piston with the edges gone.
Posted By: dvw
Re: Detonation? - 01/02/14 04:06 AM
Remove the ring and look at the ring grooves. In my experience if it's detonating the upper grooves will be pitted as well.
Doug
Doug
Posted By: JACK1440
Re: Detonation? - 01/03/14 07:44 PM
We have a simular situation going on also. Pulled the heads to send them out for port work. When I looked a #6 piston I noticed it looked sunk in and also hand the dings so, we pulled her out. When we knocked that piston out we found a broken skirt and the piston was melted and sunk in the center. We had blown a head gasket ealier in the season due to a timing blunder that blew between #4 & #6. My guess is the piston was like that then. Anyways when we pulled a couple rod caps the bearings looked worn also, #6 being the worse and just starting to flake. That was with a 1150 Dom and 100 jets, 38 deg timing, 110 gas. My thinking is to go a step or 2 colder on the plug. Crazy thing is the car ran a 9.95 the last time out.
Posted By: Bigbeep
Re: Detonation? - 01/04/14 08:07 AM
To the OP. What compression ratio were you running? Remember, the more squeeze means less timing usually. I made this mistake when I built my first 440 with any squeeze. Tuned it just like it was an 11.5 to 1 engine and beat the bearings out, wrist pins, and busted mains on 2 and 4. The crack on main #2 went from the bearing saddle about 3" into cylinders 1 and 3. Thankfully it was a filled block and it slowed down before something real bad happened. Beep
I made this mistake when I built my first 440 with any squeeze. Tuned it just like it was an 11.5 to 1 engine and beat the bearings out, wrist pins, and busted mains on 2 and 4. The crack on main #2 went from the bearing saddle about 3" into cylinders 1 and 3. Thankfully it was a filled block and it slowed down before something real bad happened. Beep
Posted By: JACK1440
Re: Detonation? - 01/04/14 03:56 PM
ouch. we are in the 12.5-1 range on compression
Posted By: GTX MATT
Re: Detonation? - 01/04/14 08:23 PM
Detonation, 38 degrees is too much timing for closed chambered heads and good quench, it would probably be faster with 34 degrees and not detonate.