My 454 aparently was detonating it ran for for about 20 min after cam break in and then spun the #1 rod bearing.

It had forged pistons with small domes. The heads are oval port closed chambers. Any possible guess to the compression ratio? How high can you run on pump gas? (91 here in colorado 5280' elevation)

What sort of hydrolic cam would you run in a chevelle with a 3000 stall converter 4.10's and a 454 big block? I know the cam selection can change cyclender pressueres and cause detonation.

I'm not the best person to answer questions but since no one else has stepped up I'll give it try. I don't think detenation would cause bearing damage, I know it will damage your piston but if I'm wrong someone please correct me. Also, you would get a better repsonse if more information was provided. To compute static compression the following needs to be measured: bore, stroke, combustion chamber volume, dome volume, gasket thickness and deck height. I have an excel spreadsheet that will do the math for you, all you need to do is throw the data in it, so let me know what your email address is and I'll send it to you. Also, there is a guy on here named Pat Kelley that has a dynamic compression ratio program so you can plug in different cam specs to figure out which one would work out the best, just do a search on his name and follow the link in his sign. for the program. Good luck man, sorry to hear the engine had problems :sad: .

Did you or some one else just assemble your motor?
What were your indicators of thinking the motor was detonating?
What Kind of gas you had in it for break in?

All of these questions can help us out on helping your troubleshooting.

It sounds like you had a lack of oil pressure to that particualar crank journal. (The bluing color of the rod bearing can tell some of the story) The bearing clearnance may have been too tight or the worst case, trash may have made its way and blocked the oil passage in that area and caused the failure

I can't remember the part # of the heads, but my orginal ls6 setup had 11:1 domed pistons and I had some closed chamber 67 "pre" smog heads. I got by with 93 octane and a shot octane booster for years, messing around on the street. Of couse I had the timing pulled down to about 33 or so degrees total
for street cursing.

I hope that you can get it up and running soon, once the problem is found.

My 454 aparently was detonating it ran for for about 20 min after cam break in and then spun the #1 rod bearing.

It had forged pistons with small domes. The heads are oval port closed chambers. Any possible guess to the compression ratio? How high can you run on pump gas? (91 here in colorado 5280' elevation)

What sort of hydrolic cam would you run in a chevelle with a 3000 stall converter 4.10's and a 454 big block? I know the cam selection can change cyclender pressueres and cause detonation.I.M.O.,it spun the rod due oil starvation,ie wrong rod bearing clearance.Did you have the rods re-sized?What was your rod bearing clearence?Did you pre-oil the engine before you started it?

Detonation can absolutely beat the bearings out. You need to know the volume of the chambers and domes to accurately figure compression ratio. Look at the tops of the pistons and the spark plugs - signs of detonation are tiny spots/flecks of aluminum deposited on the plugs as well as tiny nicks/dings in the tops of the pistons. If you see no signs of this, I'd check your oil flow path. Was the block and crank thoroughly washed with soapy water and long brushes prior to assembly? I've seen more than one motor killed by dirt left in the oil passages. Were the bearing clearances checked, etc. at assembly?

The #1 rod is always the first to go when there is a lack of oil. When I first got my Nova it didn't even have the motor in it. Someone had already rebuilt it and it was ready to go in. I put it in and it ran for awhile but started to knock. It eventually locked up. Found out that whoever put the engine together put the rear main bearing in backwards.

Quick way to figure compression is to have your heads CC'ed then look up the number on your pistons. They usually give ratios for given head cc's

Ditto to all the above,but i feel it's not a detonation issue,its very likely a motor build and or mechanical issue of some kind.

As stated above detonation can break pistons & ruin bearings but i really dont think the motor was loaded down enough just during cam breakin (as you stated it barely made it through ) to wipe out a bearing even if comp is high and timing was advanced a fair amount IMHO.

If someone built that motor with such hi comp that it could detonate it's self to death just runing at 2k rpms with no load for 20 mins then someone really goofed up but thats not what i think happened becasue it's it very unlikely.

I have built many motors over the yrs and have also been witness to many rebuild startups with very high comp and never heard a motor detonate while running at high idle 2k rpms for cam break in. But,under a load on the road is a different story,could detoante easily at 2k rpm cruise under a load with vac advnace pulling too much advance but that was not your case.

Maybe if you were running domed pistons with 100cc closed chamber heads and a very mild cam with like 200-210 deg int dur @ .05 maybe that would create very high cyl pressure but other then that extreeme cond i cant see detonation as the culprit here not under any load durring cam breakin.



Scott

Our L78 Chevelle is stock, except for headers, and runs fine on the 91-93 octane gas. The cam, 4.10 gear, and 4 speed all help. If anything jet on the rich side and set up the distributor accordingly with no more than 34-36 degrees total. A heavier car, with 2.73 gears, and a mild cam might have some problems. Spun bearing during the first startup stages is often caused by dirt left in the oil passages. I've had blocks come back from hot tanking and machining and still have the oil passages full of the old crud. The hot tanking loosens the stuff and it moves right along until it hits the bearings. They will only embed so much before catastrophic damage occurs.

Can you even get detonation at a fast idle/no load situation?