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Discussion Starter #1
I sprayed my car with a 225 shot and I had 36* of timing in my engine it went 10.20 @ 135 mph and ran flawless .I have read and heard everyone talking about dropping all this timing out of there engines .Would my car go faster with the same amount of spray if I pulled out more timing or have I got it running as efficient as I can expect ?? The plugs looked perfect at the end of the trac and the ground strap was still there .I've pulled the engine apart for it's winter inspection and it all looks great .I have even tried it at 38* for a short shot but not a full 1/4 mile pass I'm just a bit scared about that much timing .Maybe for a good reason .
 

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That really sounds like too much timing. Have you checked TDC to verify your timing pointer?
I only ran 15 with a 350 shot.
 

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What do you consider perfect on the plugs? what made you try running the nitrous with out pulling any timming at all?
 

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i always thought you wanted as much timing as you could get away with with out detonation... i run my motor at 42* and run it at 38* on 225, 30* on 400.
 

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Matt,
We too have been all over the board on retard and have found what you are saying
is correct. Run as much as you can with out detonation. I think you are right on target. Our 388" SBC likes 38* with a 150hit. We have pulled alot of timing out in the past only to find very poor performance. We like to pull 1* out for each 50hp and we run good race gas. No detonation problems. Say Matt, did you see the Newport Wheelstand that we had the bad luck of experiecing?
Mooreboys
 

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matt mcarthur said:
i always thought you wanted as much timing as you could get away with with out detonation... i run my motor at 42* and run it at 38* on 225, 30* on 400.
This is correct as much timing with out detonation. A lot fo guys will tell you flirting with timing can be dangerous so it all depend on how much you want to lean on it. Start low and work you way back up
 

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Discussion Starter #9
well to answer some of the questions I had a race on the street and I wasn't going to spay the car but after we had started I found out I had to use it. The car at that time had 38* timing in it (not knowing ) but thank god I didn't blow it up after that it raised some thought and I tried it at the track with 36* and low and behold it rocked but I haven't had that much experience with it and I didn't know if it would work better with less timing I don't run any race fuel 94 octane pump gas only , but it only has just under 10.1 compression normally I run as much as 41* timing for staight motor it's a 406 in a full weight stock leaf spring 80 Z28 with a 10.5 ET street through 3' exhaust . 60ft are off (1.47 on spray) but I'll work with it .Thanks guy's I 'll be waching for any more info .

P.S hey Pat (bigblock chev) what did you get that big block doing last season on spray "Hum" :smt015
 

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Mooreboys said:
Matt,
We too have been all over the board on retard and have found what you are saying
is correct. Run as much as you can with out detonation. I think you are right on target. Our 388" SBC likes 38* with a 150hit. We have pulled alot of timing out in the past only to find very poor performance. We like to pull 1* out for each 50hp and we run good race gas. No detonation problems. Say Matt, did you see the Newport Wheelstand that we had the bad luck of experiecing?
Mooreboys
no, never did... ya'll gonna put some 10.5's on that thing and come tp prescott this year?
 

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the more timing you have the more inefficent your cylinderheads are.. Remember running more timing means you are giving the gas more time to burn. A motor that can run with 42* of timing has a lot of room for improvement in the cylinderhead department.. Typical SBC motors that are doing rather well in the performance department run around 28-32* of timing.

The post stating to run as much timing without buring plugs or slugs is 100% correct. Remember this.. you need to pump in as much fuel as possible, burn all of it and get it all out to make power. The less timing the less time the fuel has to burn.. The only way to know if you have the correct amount of fuel and timing is to read plugs.. Someone who reads plugs carefully sits down with each plug for a minute or so for each and every plug. Just looking to see if the ground strap is still there or if its not black is not the correct method..

Remove 1 degree of timing for every 25 HP of nitrous as a baseline. Step down to a colder plug for every 100 HP of nitrous as a baseline. Use good fuel and make 1/8 test hits.. Never lift and get back into the throttle when on nitrous.. take is slow and easy and things will be fine..
 

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Matt, We are still trying to recover from two wheelstands at Newport in Nov. Lost the oil pan, flexplate, tranny, converter as well as some damage to the frame and body. A little girl took this shot on the way down.....it was verticle at launch. The last one was at about 8PM and that is the one that did the damage. We should have stopped racing after the first one, but we were winning rounds.

http://www.z28.com/gallery/showphoto.php?photo=6821&sort=1&cat=500&page=1

Mabye you can copy and paste this link to see it. I would like to try Prescott some time next season. Be seeing you.
 

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aww come on... i've been there before on the radials. :-D sure tears shit up huh? ya'll come down and catch a race this year... your allways welcome in my pit.
 

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Monty Mikho said:
Never lift and get back into the throttle when on nitrous.. take is slow and easy and things will be fine..
Why? What happens when you do this. I have had to do this on some big wheelies.
 

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Monty Mikho said:
the more timing you have the more inefficent your cylinderheads are.. Remember running more timing means you are giving the gas more time to burn. A motor that can run with 42* of timing has a lot of room for improvement in the cylinderhead department.. Typical SBC motors that are doing rather well in the performance department run around 28-32* of timing.

Will having a more appropriate size head for my motor & rpm band help me to need less timing :smt017 I'm going from AFR 190'S(street) to 210 Comp ported on a 383 :-D
 

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Mark, nitrous, fuel and timing all get to the cylinder at different times when activated. Since electricity is the quickest of all 3 it will be the one that hits the cylinder first. Nitrous at 950 PSI being second and fuel being 3rd. When you let off the throttle timing is removed first with the gas and nitrous still in the intake being ingested by your motor. Being in and out of the throttle you should be able to see there is a risk of blowing the intake off the car. The more nitrous/gas and timing removed from the motor.. more prone to happen.. Will it happen? Maybe or maybe not.. but I have never seen any record set doing this.. If its during a race and some money is up for grabs then you will have to justify the possibilities of this happening..

A more efficient head on your motor will push you to need less timing. Like stated above timing is the amount of time needed to burn the fuel. The more time needed the less efficient the head design is in burning it. There are other variables to this as well but 42* is pretty far off for a race motor at WOT..
 

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Timing requirements as monty stated are related to cylinder head/combustion efficiency.

Typically for a 23 degree style chevrolet head(worst cast scenario)... it could need a lot of timing... a typical chamber is just way inefficient... poor charge motion, port flame propogation, from the resultant piston dome, and depth of the chamber, and spark plug position.... all that spells bad for a nitrous motor so it's more sensitive to detonate when you lean on it.... Even more is that with more timing, you have more pumping losses.... the earlier you bring the spark on while the piston is on its way up, the more the engien has to work, to overcome that combustion WHILE the piston closes in on TDC.... so less timing in and of itself, is more efficient....
 

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OK, so my bigger 23 degree heads aren't going to make my motor any more efficient, would a 6" con rod vs my 5.7 w/more dwell time be more efficient & as a rule require less timing :smt017

A friend of mine is runnin a 6" rod w/the size of heads & cam I want to go to, & he's only runnin 34 deg of timing vs 38 to 39 that I was runnin :(
 

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In theory,

The longer dwell resultant of the longer rod will help keep detonation down.... in theory... whether we see that in the real world is another story.
 
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