|10-25-2014 08:49 AM|
|wildman1932||From here it looks like you detonated it. A 10-1 motor needs 91 oct gas. Iron head motors do it worse. Aluminum heads will go about one point higher on compression, before det. You HAVE to limit the timing to a max of 34 degs @ 2500 RPM. No vac advance. If you don't have a timing light with a dial, get one! Looks like you hammered on it with 50-55 degs. Bummer.|
|05-15-2014 11:50 AM|
|compje||I have very similar pistons in a 383 . A bit more cam. The engine does not like a lot of timing under 3,000rpm. On the first test drive, had some pinging with "light" springs. Switched to the middle springs with about 10 degrees at idle with vacuum advance disconnected and it was much much better. Still some tuning to do when the tranny is back in.|
|02-25-2014 03:01 PM|
|64nailhead||28 degrees of initial timing? Better be a Found On Road Dead or you have about .070" quench.|
|02-21-2014 12:30 PM|
wait, just re-read and saw he said "initial timing at 28"
i was talking about total timing.
|02-21-2014 12:28 PM|
im sure that vortec heads are the best stock head on the market. but id say new dart iron eagle platinum castings are more efficient.
there is no reason to limit your timing to 28deg just because you have vortec heads??
|02-21-2014 12:16 PM|
The Vortec head doesnt need as much timing as other heads, as they are that efficient. GM got the chamber right on the Vortec.
|02-21-2014 12:14 PM|
Or if a larger duration cam you may want 16* initial with 18* mechanical bringing you to the same 34* total.
If you find it hard to start with a higher initial timing then after you have confirmed good grounds and cables, you can look at an ignition interrupt switch which is a simple and cost effective solution.
|02-21-2014 10:11 AM|
dont think thats true. i think any iron headed sbc likes 32-36.
the stock vortec certainly isnt the most efficient iron head on the market.
my 355 with dart iron eagle heads has 34 deg total timing and could probably take a little more but at 16 initial it starts to kick back on the starter
|02-21-2014 09:55 AM|
|92hotrodhalfton||I haven't run my vortecs yet but I read where the combustion was so efficiant initial timing was to be around 28 vs like 32 on older lower performance stock based heads|
|02-17-2014 11:47 AM|
|machine shop tom||
|02-16-2014 07:24 AM|
They have an oval or "cam" grind to the diameter so that when they get to temp, they are round.
Or course, this all changes when the pistons see detonation as that will shrink a piston (not sure why) then it REALLY rattles in the bore . . . . .
THEN, you get oil contamination in the combustion process that will bring the octane down even further so that is knocks harder, etc . . .
You get the idea. Big damage at that point . . .
Take care, K
|02-15-2014 07:49 PM|
I think the original poster must have been deaf not to hear the detonation to cause that damage in less than 100 miles
FWIW, when I hear/read about guys saying they want to throw out their fuel injected computer controlled setup, either TBI or multiport, for a carb setup because it is 'easier' to tune, I wonder if they realize that the knock sensor isn't just a plug in a coolant port? But I have to admit that I have broke ring lands on hyper pistons due to too much timing/detonation, but I didn't try to blame someone else. I wonder how the OP made out.
|02-15-2014 07:14 PM|
|68NovaSS||This thread is over a year old, but please explain why a forged piston, specifically, will be oval out of the box, and if that's the case, where is the narrowest point and what will make it round again...I don't have a spare/new piston on the shelf to measure.|
|02-15-2014 06:50 PM|
Im sure, speed pro is a forged piston if so it would be ovil shaped till it got warmed up , bur too much timing for sure,and poor gas.
|12-12-2012 10:51 AM|
Fresh 383 burns up pistons
A classic case of putting a tool in someone hands that don't know his ^#% from a hole in the ground. If you don't know what you are doing ask somebody first. I am sure the machinist explained the build to him and told him what fuel he would have to use. Being cheap he fills it up with 87 octane gas. Unless he was running an open exhaust he must have heard it pinging. Probably with the brand new Holley bolted it on with no tuning so it was probably running lean. There is no way that the spark plugs would have read normal with that much damage.
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