For sure...I got the TA 284-88H cam (223*/230* and only 0.460" lift) for the iron heads. Even though my heads don't flow quite as well (326 cfm at 0.6"), I'm using your motor as inspiration for the rebuild I'm still in the planning stage of. With all the research I've done in camshaft tech so far, I believe I'll need a hydraulic roller (custom ground of course) to get the lift I need (0.575ish?) but still be able to have lower duration (235ish/???ish) to keep the torque lower for the heavy Riv. I have TSP's big car 9.5" converter that I think flashes a little higher than 2,500 rpm and 3.42 posi rear end, but will gladly see if Jim can have it re-stalled higher if that's what it takes to make the Riv fast enough to beat my buddy's '99 Viper (12 second car with a good driver so I could finish at 12.5 and win). I'm not sure how much lighter my car is than the stock 4,500 lbs with a SP1 intake, aluminum heads, and removed a/c compressor
I don't claim to be an expert at this. Someone may want to verify: When I see detonation damage, I expect the piston top to be eroded--"scoured"--and a hole melted into it. You don't have any of that. You have a broken top ring land; which suggests not enough top ring gap. The ring butted from insufficient clearance, (or over-temperature) popped the land off the piston. IF (big IF) this is detonation damage, the rod bearing is going to be beat-up, too. (Although, if the piston broke apart, got jammed between the remainder of the piston and the cylinder head combustion chamber, the bearing could also be hammered even without detonation--beat-up by impact either way. I don't know if there's a way to separate mechanical impact damage from detonation impact damage.) I would be VERY suspicious of the second cylinder that had the plug gap smashed-shut. I'd at least pull the second piston out for closer inspection. You know the broken piston piece got pushed through the intake valve--which bent it--and then migrated through the intake manifold to the other cylinder. Then that piston crammed it into the spark plug. MAYBE the only damage is the smacked plug. MAYBE in the process, that piston got hammered and is now bent into the top ring, or cracked. I'd pull the valves out of whichever cylinder also got the plug smacked, to verify that the valves and seats still seal properly and aren't otherwise damaged. Make sure the guide(s) for the bent valve(s) are still in good condition.
I would agree if the engine was detonating over a long period of time, the piston top would have a sandblasted appearance, and the plug porcelain would probably have small round melted aluminum "balls". And yes, the rod bearings would be pounded from that as well. There is the possibility that this could be severe detonation at WOT that happened once from too much ignition timing, or extreme lean mixtures, maybe a singular event. I'm no expert either. Not sure how we could ever be sure.
@Ben: Thanks for the offer, I`m trying to get in touch with him again in the next few days, used your aforementioned email, but up till now no luck. If I can`t solve it myself then I`ll gladly let you know to contact him ,ok? @Larry and Schurkey: Detonation, hmm? Never played with the timing, had it where Mike put it from the beginning but it would be a good idea to double-check it....but it`s nothing that`s been occuring regularly, engine runs superfine usually, great street-combo. Jens
I would say, hit the throttle if you have: * 180 degrees maximum water temp * 32-34 degrees advance timing maximum * Cold air intake, at all times * Fuel/air ratio a hair on the rich side under a pull * Fuel pressure/volume verified adequate under full throttle * Gears/converter which will never allow luging the engine * Well insulated, or isolated fuel lines from tank to carb.
I just had to replace my 28 year old motor with hyperutectic pistons because an early spring run with old fuel and cold air. Smokey burnout and finally hooked in 3rd gear pulling the motor down. Heard a rattle and lifted. Pull up to the stop sign and the motor died. Took a while but restarted but was missing on one cylinder. Pulled the heads and found a broke piston. A piece was missing above the top ring land. I had heard spark knock over the years but I think it was a perfect storm scenario that finally cracked it. This has been a consistant low 12 sec motor in a 4000lb GS. Mike
Hyperutectic pistons are the least tolerant of detonation. The only time I would use them is in a build that will never see ANY sustained WOT.
Yeah, with their microprocessor controlled engine management, fuel injection, ignition timing, and knock sensors. I should have said small and big block, carburetor engines with a distributor with old school advance mechanisms.
I knew you were going to say that. I also think that with the smaller bore size the LS engines have makes the hyper pistons a bit stronger than a coffee can sized piston! Kind of like trying to break a brand new pencil in half compared to trying to break a stubby pencil in 2 pieces, that's my theory anyway. To make them as strong as the smaller bore sized pistons would make them WAY heavy which IIRC they are one of the heaviest piston choices already available. But maybe the old school TRW forged would be a close call to which one would be the heavier 455 piston?
Don't really know that much about piston weights, but the Diamond pistons in my engine weigh 641 g each, the pin is 153 g each.
Hi , thanks for your infos and opinions, very helpful. Even though the forged pistons would be an insurance, I might skip them for now and replace just that one cast piston if I can get a proper one to fit in. Same goes for the valves if the seat is still ok, we`ll have to check on it. I feel safe not to open to much of the engine as it has zero pressure loss in all the other cylinders, even the second affected one years ago that had the spark contaced flattened...and it has been good for 2.5 years now, no flattening again, no pressure loss, Nothing, as with the rest of the 7 cylinders... When time comes for a bigger rebuild with aluminum heads there will be forged pistons for sure, I`ve got your message to not go up with power on those cast pistons…. Jens
When I first read your initial thread I suspected a broken piston. Had the same issue on a 327 back in the day and simply replaced the broken one with a stock junkyard take out. reassembled everything and had no further issues.
You are assuming that everyone knows how to set total timing. I still get questions on how to do this (questions I am always willing to answer), but I can tell by the way the questions are asked that they don't understand the very BASICS AND FUNCTION of advance mechanisms. I still see too many guys simply revving the engine to 2500 RPM, setting what they think is the total advance, and then wondering why the engine sounds like a diesel every time they nail it. They don't understand that the timing could be advancing beyond that. Add the fact that with headers or loud exhaust, you may not hear engine damaging detonation, and this becomes even more unpredictable. That isn't even considering that the engine could be going super lean at WOT which will also induce detonation even if timing is correct. That's why my car never goes down the track without some leaded Race Fuel mixed in, it's cheap insurance.
Hey Briz, hope this works for me too We`ll see soon...well, you live you learn... Timing of the engine was never altered by me, but at least checked twice within the last 2 years (not by me), it`s 34°....seriously, I couldn`t set it straight myself, so I believe there`s quite some truth to Larrys point. Jens
Very good point. it is totally possible depending what spring are in there and stuff to gain another 5 or 10 degrees. The all in by 2500 can only happen accurately with very light springs. But without checking timing at 3000, 35000, or 4000 you cant know it's not done advancing. Or have a dist that has the options of limits
There used to be speed shops with distributor machines. I took one in and I thought all advance was in at 2500 but turned out at like 4500 another 4 degrees came in. So if I thought I had 30-32 it was 34-36....enough to cause damage (iron head motor) especially if hot, high barometer weather or a batch of crap gas. I was driving my 10sec GS to Bolling Green and tanked up in middle of nowhere....definately not 92 or 93 octane.....likely 87....severe rattling just cruising...had to pull off and retard distributor until I got some better gas...if I had gotten into it I'm sure it would have hurt it.
Hmmm, in the last couple of summers I experienced something like a "hickup" when we had hot weather and I was standing on it, I always thought it might be "boiling" gas not reaching the carb in a sufficent amount when being floored. Car started bogging, like starving....as soon as it cooled down, less outside temperatures, it never was a problem...maybe I`ll retard the distributor a tad, just to be on the safe side, 34° right now.
