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When Stroker Motors Go Bad....
Well...
Taking a nice casual drive home Saturday morning when all of a suddon in stop and go traffic I hear a high speed rattle. I immediately kill the motor and coast to the side of the road. 40 mins later my car is towed home and the fact finding mission begins.... The first clue is an exhaust rocker out of adjustment, second clue is a plug that has been beaten to a pulp. We dig in and pull the head.... Here's what we find..... http://i208.photobucket.com/albums/b...r/IMG_1313.jpg http://i208.photobucket.com/albums/b...r/IMG_1314.jpg http://i208.photobucket.com/albums/b...r/IMG_1315.jpg JUST WONDERFULL!!!!! We pull the other head, here's what we find there... http://i208.photobucket.com/albums/b...r/IMG_1321.jpg And here's what we have left for the rest of the pistons.... http://i208.photobucket.com/albums/b...r/IMG_1316.jpg http://i208.photobucket.com/albums/b...r/IMG_1317.jpg http://i208.photobucket.com/albums/b...r/IMG_1320.jpg http://i208.photobucket.com/albums/b...r/IMG_1319.jpg So, Obviously the valves have been dancing with the pistons for about 400 miles due to insufficient valve clearance. My builder says it was caused by valve float?? I find that hard to believe when the motor hasn't exceeded 6500rpm while in my possession. Comments? Suggestions? The motor let go while in traffic with rpm's between 3500 - 4000 (It was between 2 -3 shift). |
Was the engine setup to run a lower ratio rocker arm maybe?
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Huh?
Valve float? With solid lifters? If it is, then he assembled with the WRONG springs in those heads; AFR is good stuff, as long as you tell them what you're using. Think maybe you need to sit him down for a little talk - with all the exhaust valves making contact I'm of the opinion that either he never checked valve clearance or the cam timing was never checked.
A crying shame; truly feel for you. |
Looks like somebody whipped the motor together and never bothered to check clearances.
You are lucky only one went bad. Looks like a few more weren't too far behind. Let me guess...being it was a "race" motor, the builder won't warranty anything? |
Dont suppose you checked the cam timing before you pulled it to bits. If you have not stripped it down that far yet, do that now and then refit one head and check the valve to piston clearance. Then & only then can you stand there with confidence and argue your case if both or one of those scenarios is correct. You owe it to yourself & the engine builder to do at least that much.
Jac Mac |
Jac Mac,
You are so correct. I do plan on checking the clearance... The motor is intact other than the heads and offending piston so no problem verifying. I have a video of this motor being built, the cam timing and the clearancing with the valves/pistons. I do need to watch it again and pay particular attention to the clearance section to see if he illustrated both intake and exhaust. |
If it was valve clearance, either floating or not checked, then clearly the motor was not 'blue printed'. Blue printing is simply checking and double checking everything, and 'clearance' is a HUGE part of that. As is valve spring tension that matches the cam, and degreeing the cam is as well.
Heres a pic where I'm using modeling clay on top of the piston to check for valve clearance with the cam all ready 'degreed' and the valve lash set. The valve opens, leaves a mark in the clay, you then measure the depth of the indentation in the clay and THATS your valve clearance. Only way to be sure... I 'dry assembled' my engine numerous times during the blue printing process before I did the 'final assembly'. This is very labor intensive and would cost a fortune if you were building motors commercially. SO, you offer 'package' motors with known specs and known parts so you don't have to double check everything. The problem is, sometimes that works and sometimes it doesn't. 'Blue printing', it's one reason why you pay BIG bucks for a custom built engine and then wonder how apparently the SAME spec engine from another guy is way cheaper. It's all about the 'final assembly'. Now it's also possible you simply had a defective valve, stuff happens. http://www.clubcobra.com/photopost/d...lay-Piston.jpg |
meant "or" n.c.
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Jac Mac,
I just got done watching the video of him degreeing in the cam and checking the valve clearance... Degree was done correct and right on... The clearancing is another issue... He used Play Dough, The CC checker springs and torqued the head to 10lbs!! After running through the cycle he pulls the head and I can see how the valve has pushed the play dough out and I can see the piston top right where the damage is on the pistons. I'm assuming with the correct torque of the head and heat expansion would account for the rest!!! In my book, it FAILED and was not correctly clearanced |
Does he say how much clearance there was?
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His gauge registered .2100, however that was in the center of the piston, the piston relief is where the valve was hitting and is showing through the Play Dow on the video
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I have a video I can post if someone will tellme how to do it. The dvd is over 2 1/2 hours long, how do I pull the 30 seconds of the clearancing in order to post?
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Damn iphone ... Was the engine built in nj? Or nc?
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So he was using a dial indicator and checking springs? That's actually a good way of doing it.
You can either bolt the head on, leave the valve springs on, and run it through a few cycles....or you can put checking springs on, put a dial indicator on the retainer and check the clearance at different degrees by pushing the valve down until it contacts the piston and noting it. The method of doing it with the checking springs is great and easy.....but you can't tell how much radial clearance you have unless you clay it up. When I assemble, I usually just use clay and run it through the cycles. If it's a hydraulic cam, I'll usually pop a solid lifter in it, or tighten the rocker up until it bottoms the plunger out on the hydraulic one. If you have good springs, you won't have any valve float with a solid roller cam. |
Built by Wayne Partridge in KS
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How much lift does the cam have by the way? Usually a good aftermarket JE/Diamond/Probe, etc piston will have PLENTY of clearance for a high lift cam.
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Int= .696 Ex= .683
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Well I can't imagine it having .210" of clearance with that much lift. When I built my 428, I had .060/.100 of clearance with a .685" cam and Probe pistons. That was not counting head gasket thickness or valve lash.
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Quote:
The 0.210" you mention is irrelevant as it would be in a non critical area, the exhaust valve should have in the region of 0.100"+ clearance in the now 'marked' area of the pistons. Rather than plasticine I prefer to do this check without head gaskets fitted & with a dial gauge against the valve retainer & light checking springs. It is then quite simple to turn the crank thru 5° at a time and check the +/- readings on the dialgauge by pushing the valve into piston contact via the rocker arm.---by doing it sans head gasket you also assure radial clearance of the valve head to pocket sidewall due to the valve inclination. One further thing--you can see that the valves are not concentric in the valve notches , so no attempt has been made to recut the pockets to address the problem, all of those exh valves will be bent. Jac Mac |
Quote:
Ask your builder if he used the AFR springs or replaced them with a quality "made in America" spring. That may be the answer to your problem. |
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