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Topic Review (Newest First)
02-25-2014 02:01 PM
64nailhead 28 degrees of initial timing? Better be a Found On Road Dead or you have about .070" quench.
02-21-2014 11:30 AM
clwhoops44 wait, just re-read and saw he said "initial timing at 28"

i was talking about total timing.
02-21-2014 11:28 AM
clwhoops44 hogg,

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 11:16 AM
Hogg
Quote:
Originally Posted by clwhoops44 View Post
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
Name a GEN 1 head that has a more efficient chamber.

The Vortec head doesnt need as much timing as other heads, as they are that efficient. GM got the chamber right on the Vortec.

peace
Hog
02-21-2014 11:14 AM
bygddy
Quote:
Originally Posted by 92hotrodhalfton View Post
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
If you run your initial at 32 then were going to be reading about your blown up motor as well. Initial can be 32, assuming its locked with no mechanical advance. More likely your cam choice will dictate an 18*-20* curve, in which case your initial timing may be 14*, add in your 20* mechanical for a total of 34* (where i find vortec heads happiest)
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 09:11 AM
clwhoops44 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 08:55 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 10:47 AM
machine shop tom
Quote:
Originally Posted by jeffp View Post
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.
Those Speed Pro pistons pictured are hypereutectic, not forged.

tom
02-16-2014 06:24 AM
KeithDyer
Quote:
Originally Posted by 68NovaSS View Post
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.
Pistons are most times the biggest diameter at the bottom of the skirt, but are usually measured at the pin height and 90 degrees to the pin to size the piston with the bore. Some piston mfgs have different places they want you to measure it but that seems to be the norm.

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 06:49 PM
64nailhead
Quote:
Originally Posted by 68NovaSS View Post
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.
This may be an old thread, but it's a good one.

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 06:14 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 05:50 PM
jeffp
Piston

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 09:51 AM
cdminter59
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.
12-12-2012 05:43 AM
maxdudy
Quote:
Originally Posted by brad33478 View Post
fuel was fresh so it must of been timing when i screwed with it. can anyone think of other reasons for this?
I just want to run through all possible causes so it doesnt happen again

thanks for the quick responses
10to 1 compresson would demand premium fule in todays world.
Engine must have been singing to you (pinging/knock).

head design makes alot of difference also. Newer Vortec heads may help because of chamber design but looks like detonnation as stated. Lots of fuel wash indecated by carbon deposits but todays world fuel is very inadiquet for this type of compression. Fuel additives state they may raise octain rating 6 points but in reality it is maybe 1 point at best.
11-07-2012 05:17 PM
1Gary You guys did see the O/P's post date pf 3/12.
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