Engine Guru's - Need help-Take a look
07-26-2011 | 02:19 PM
#11
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From: Western Ma.
So maybe the washed areas on tops is too rich fuel? As stated before, plugs were def. not lean. Two seasons ago, I jetted up one size after doing some pocket cleaning work and intake matching on these heads. Thought I was doing a good thing, and keeping it "safe", just in case.
07-26-2011 | 02:30 PM
#12
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From: Waterford,MI
It would help to know the exact cc's of that piston dome. Doing the math with accurate numbers would be the first thing to do. If it is 9.7, you're getting up there to the point of detonation with iron heads. One bad tank of gas is all it would take to melt it. Take a look at the undersides of the other pistons. If they are dark to black, you're making too much heat in the combustion chambers. The first change I'd make is a 120 degree thermostat from Arizona Speed and Marine. Keeping those heads cool is important! Then I would ditch the Edelbrock carb and get a Holley 800 or 850DP. The Holley is easier to tune and the Edelbrock tends to go lean just before the secondaries open, right where we always want to cruise.
07-26-2011 | 02:35 PM
#13
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From: Waterford,MI
I doubt if being too rich caused this. Usually it's too lean that causes this kind of heat. Look at the way Mercruiser sets up their carb engines. Plugs from them are always dark. Does this engine burn any oil? A little in the chamber can promote detonation and make it look like the engine is running rich.
07-26-2011 | 02:43 PM
#14
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From: Western Ma.
I doubt if being too rich caused this. Usually it's too lean that causes this kind of heat. Look at the way Mercruiser sets up their carb engines. Plugs from them are always dark. Does this engine burn any oil? A little in the chamber can promote detonation and make it look like the engine is running rich.
I really appreciate all the comments people. Helps me to feel like I'm not going through this alone.. in the dark.. LOL
07-26-2011 | 03:16 PM
#15
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From: OFallon,Mo.
Funny you mention the oil. I found 3 or 4 torn umbrella seals when I popped the valve covers off. Haven't even started down that road yet towards root cause. Not sure if this was one of the cylinders. I'll check tonight. I'll also be pulling pan and looking at all this from underside as well.
I really appreciate all the comments people. Helps me to feel like I'm not going through this alone.. in the dark.. LOL
I really appreciate all the comments people. Helps me to feel like I'm not going through this alone.. in the dark.. LOL
07-26-2011 | 03:34 PM
#16
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From: NY
I doubt if being too rich caused this. Usually it's too lean that causes this kind of heat. Look at the way Mercruiser sets up their carb engines. Plugs from them are always dark. Does this engine burn any oil? A little in the chamber can promote detonation and make it look like the engine is running rich.
Oil in the chamber is exactly one of those stack-up conditions I was referring to earlier, when combined with other unfavorable conditions sets you up for a bad day.
The dome volume on the L2465F piston at .030 is 25.7cc. I'd say his math on the 9.7 is pretty close.
07-26-2011 | 06:34 PM
#17
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From: TEXAS
Question?
My rat started knocking after coming off full throttle and this is what I found.
-Engine is GenIV 460 ci. Decked .010
-TRW L2465 pistons .226 dome
-Stock Peanut heads with some grind work, also milled .010 -Comp cam ,magnum #11-306-4 with .222 and .226 duration @.05, and .525 lift for both, and 110LSA
-Stock valve train except stronger springs
-Performer intake with 750edelbrock carb
-EMI exhaust
-Stock TBIV ignition
As I understand , these heads average about 119cc I estimate it has around 9.7:1 compression, without accounting for head mill. (maybe someone can help here)
As for quench, I estimate about .050 as is with stock gasket, but will verify this build.
Built with a budget at the time, and built for grunt, not top speed. Will still get me close to 65 in my 23fter at 5200rpm or so. Motor has maybe 150 hrs total. Surprisingly still had over 160 psi in that cylinder.Rings are still intact. Nothing went down below. Heads are still fine, but will verify. Runs on 93 octane.
Trying to get back in water and save some summer. What do you guys think caused this? I am no expert and could use some advice. Reversion? detonation? Other cylinders look fine, but this area seems washed on all of them.
As for rebuild, I'm thinking I may be ok down below. Will I be able to find this piston for replacement? I realize TRW has been absorbed by SpeedPro? Will a replacement piston be the same? I read somewhere about oilers being changed, etc. Not sure which way to proceed with this. I will remove that rod and check for straightness, and check bearing clearance. Anything else I should be doing? Thinking about checking all clearances while I am there. Not sure yet. Maybe re-bearing while open? Oil pressure is good. 65 at idle cold. I see some of my lifters have started to lose their crown. I will replace as well. Maybe time for a better cam? I wouldn't mind changing heads if price was right, or maybe open these up with bigger valves?
Always happy to get an extra mph or two. But have to stay somewhat reasonable with money.
Thanks for your insight.
Rich
-Engine is GenIV 460 ci. Decked .010
-TRW L2465 pistons .226 dome
-Stock Peanut heads with some grind work, also milled .010 -Comp cam ,magnum #11-306-4 with .222 and .226 duration @.05, and .525 lift for both, and 110LSA
-Stock valve train except stronger springs
-Performer intake with 750edelbrock carb
-EMI exhaust
-Stock TBIV ignition
As I understand , these heads average about 119cc I estimate it has around 9.7:1 compression, without accounting for head mill. (maybe someone can help here)
As for quench, I estimate about .050 as is with stock gasket, but will verify this build.
Built with a budget at the time, and built for grunt, not top speed. Will still get me close to 65 in my 23fter at 5200rpm or so. Motor has maybe 150 hrs total. Surprisingly still had over 160 psi in that cylinder.Rings are still intact. Nothing went down below. Heads are still fine, but will verify. Runs on 93 octane.
Trying to get back in water and save some summer. What do you guys think caused this? I am no expert and could use some advice. Reversion? detonation? Other cylinders look fine, but this area seems washed on all of them.
As for rebuild, I'm thinking I may be ok down below. Will I be able to find this piston for replacement? I realize TRW has been absorbed by SpeedPro? Will a replacement piston be the same? I read somewhere about oilers being changed, etc. Not sure which way to proceed with this. I will remove that rod and check for straightness, and check bearing clearance. Anything else I should be doing? Thinking about checking all clearances while I am there. Not sure yet. Maybe re-bearing while open? Oil pressure is good. 65 at idle cold. I see some of my lifters have started to lose their crown. I will replace as well. Maybe time for a better cam? I wouldn't mind changing heads if price was right, or maybe open these up with bigger valves?
Always happy to get an extra mph or two. But have to stay somewhat reasonable with money.
Thanks for your insight.
Rich
07-26-2011 | 07:07 PM
#18
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From: bensalem, pa
i had a set of cast dome pistons do the same thing im my mustang. i tried to go cheap and it cost me, broke in the same spot. right where the valve relief is real close to the ring gland. the casting is week right there and under the pressure it didn't hold, plus they had the large reliefs for a big cam and 2.02 valves. i talked to a rebutable engine builder and he told me i should have never went to a dome cast piston. i think your marks on the top of the piston is the aftermath of the failure.
07-26-2011 | 07:29 PM
#19
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Posts: 7,663
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From: Edgerock Baby!!
Make sure both valve seats are still in the head. (Big blocks drop valve seats) There is no real detonation damage there, look for a source of debris.
07-26-2011 | 08:37 PM
#20
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From: Waldorf, Md
Rich,
It looks like the pistons have been flycut for valve clearance. You just cannot do that with those pistons. They get real thin right at the back edge of the ring groove, then they burn through and then you get the "death and destruction" that you have here. That was just the first one to go
The others will be right behind it, have seen it too many times.
I cant post a picture but if you want I can e-mail you a doctored up one to show you exactly where I am talking about.
Bill Koustenis
Advanced Automotive Machine
Waldorf Md
It looks like the pistons have been flycut for valve clearance. You just cannot do that with those pistons. They get real thin right at the back edge of the ring groove, then they burn through and then you get the "death and destruction" that you have here. That was just the first one to go
The others will be right behind it, have seen it too many times. I cant post a picture but if you want I can e-mail you a doctored up one to show you exactly where I am talking about.
Bill Koustenis
Advanced Automotive Machine
Waldorf Md
