Hi together, once upon a time in 2017, I reported a rough idle and then some more under this thread http://v8buick.com/index.php?threads/spark-plugs-on-455-compressed.324320/ Basically it was either an overrevving or an overheating situation back then that caused the engine to give me a rough idle afterwards, mostly gone beyond 1800 rpm tough. A little loss in power came with it, but then, 455 ci, street driven...hard to tell sometimes if it really doesn`t pull that strong anymore (still fast enough to take down a Maserati Quattroporte at the stoplight ) After realizing it not getting better by itself I checked the pressure on all cylinders, and found them all in the 160-180 psi range except for cyl. 7, which yielded a mere 25 psi. Putting air into the cylinder rewared me with it coming out of the carb...intake valve, I suggested. I then had my mechanic disassemble the head last week to find what you see in the pictures (check out the area in 9 to 11 o`clock position). Big chunk of the pistion missing, right? Up till now, the missing part couldn`t be found, I`m quite sure it got smashed and when out through the exhaust side. The mechanic said that by checking the valves closed in the head you can see a little light shining through...valve(s) slightly bend, hmm? And now I need your opinion and help on our conclusion: Though the damage is scary, the engine lived happily after the incident 2 years ago, a little more oil but not really much. Pressure in all other cylinders seems good so we would like to go down the easy route for now, just fixing the cylinder 7 piston. Engine is a mild build 455 Stage 1, 466 ci (overbore) with cast dish pistons (they look stock-ish to me), 517lb-ft and 425 hp, Stage 1 head conversion, it`s one of AM&Ps last mules. Compresion is 9.23:1 Tried to get in touch with Mike, he`s usually right there with advices even though he`s retired, but this time I couldn`t reach him via email...hope he`s ok. I`ve read that piston weight might differ as far as 5% without even noticing, some sources say even 30-50 g is nearly undetectable. Can I more or less safley just go for that no. 7 cylinder and what kind of piston should be used? Stage 1 conversion valves, can I get a single one, and not just a whole set? I know you can do a lot to an engine at this point but I`m on a budget and would like to get by with not too much fuzz. Thanks for your help Jens
Hi Joe, thanks for the offer....what`s the weight of the forged pistons? I`ll have to match more or less to the cast ones I have in right now as I wouldn`t (right now) like to change all pistons. Jens
You would definitely need to change all 8. I think at your power level you'd be much better off with forged pistons anyway.
Are you sure your engine is 466 cubic inch displacement? That would mean you have .050" over size pistons. I never seen any make offer .050" over pistons, for some reason that oversize is always skipped.
I chipped a #7 in mine years ago. Not as bad as yours, I didnt have any real noticable wall damage, I just replaced it......luckily I have the build sheet and knew each piston weight b4 the chip and just matched it. I had no issues. Mike, at least 2 weeks, ago was ok as I spoke with him via email. Here is his email, it's how he prefers to be contacted, ampmike@aol.com But I see no harm in repair the damage by just replacing that piston and valve and moving on. As long as your willing to live with the cylinder wall as it is........and as compare to a the price of a full reset that wall would have to have some real issue. I would check everything out real close to try to figure out what happened.......did the top ring touch, or detonate or what to pull that ring land off.
@ Derek: The dyno sheet reads 466 Buick, unfortunatly I cannot get in touch with Mike to clarify this at this Point, so it would be just guessing right now.We`ll have to pull the piston, measure /weigh it an go from there. @Ben: Sounds exactly like I`m trying to pull it off. The mechanic said the wall looks good, no visible damage done...as far as the cause, hmm, don`t know, my guess is heat and/or overrevving (went on the Autobahn in the summer heat, full throttle, my TH2004R shifted back 4th into 3rd, that`s quit a drop backwards, and I noticed a "bang", two plugs in two different cylinders had their contacts pressed to the plug itself, no spark anymore, went back home to Switzerland 260 miles on 6 cylinders that way... Jens
Yeah....that`s a good thing, thanks, Matt, good info when the estimated 0.50 overbore becomes a reality...and they might even sell my needed Stage 1 valves. Jens
They definitely sell valves too, individually or as a set. I'm not sure about individual pistons though. I think it's easier to find parts if you download a pdf of their catalog http://www.taperformance.com/
Hey Matt, had it a few years ago (2011 or so), time to update it and get their catalog again. Thanks for the info. Jens
Get the part number off that piston and determine the oversize diameter. Match it if possible. Replace the bent valve. That is the cheapest option. Other pistons can be shorter, taller, heavier, lighter, and have improper clearance to the bore.$
If mike knew how the motor was going to be used u cant believe he would use cast pistons unless it was requested....... .050 is slot of over bore
I'm experiencing an extremely similar issue. I believe the pre-ignition or, perhaps more likely, detonation events were triggered by the change in dynamic compression ratio when I installed aluminum heads. I'm not nearly as knowledgeable or experienced as anybody else on this board, but if I end up going the same route to replace only the affected piston, I believe that I'm potentially going to introduce other failure modes and would still be susceptible to the original cause occurring again. What I'm trying to say is that without knowing and addressing the cause, you may be spending more money in the future to fix it again instead of spending more now to check clearances and get more robust parts (forged pistons)
Hey everybody, thanks for your input so far, as usual I find it extremly helpful to get your opinions, leads and infos on the subjects being asked. Just to clarify this: I`m 100% satisfied, and always have been, with the way Mike did the engine, I ordered his "mule 455" and that`s what I paid for and got...I think you can still see the ad on his old homepage giving you the infos on the specs. Even years after the purchase he was there, answering questions and helping along when he could. I`m sure the piston failure was either age or my driving...if he`d still be in business I`d turn to him again, great workmanship and somebody who stands behind his work. Jens
Mike still does work, but he is retired so things go slower, some work he has to sublet out as he doesnt have all the equipment that he used to have. If he doesn't get ahold of you let me know and I will pass the information to him, I have his number but he prefers email
Normally, aluminum heads make the engine more octane tolerant. My engine runs great with street driving on 93 octane pump fuel with 10.5:1 SCR, 7.84 DCR, and 35* of timing. Having said that, I always mix in some 110 leaded fuel at the track as I don't trust 93 pump at sustained WOT through all 3 gears and maximum load.
The smaller volume chamber of TA's heads (62.6 cc vs. whatever '72 non-stage I heads are) increased the scr to 9.88 and put the dcr at 8.35. While that should still be on the upper end of okay, I think having too high of a quench distance made the combination more sensitive to detonation. I'm not sure if the damage happened before backing the timing down to 32* from 36* a long time ago or the one time I was recently forced to use 87 octane because we were in the middle of nowhere after shooting a video for a song for a friends band. If you like bluegrass-y/country/folk-y music, you might enjoy their song. They mistakenly believe the video was for their song but when I watch it, all I see is my Riv:
