70 dart 470 ci drag car build.

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92b said:
This is from Jere Stahl's (of stahl headers) website. I don’t know if the site still exist. There was lots of helpful information about dynoing on his site. I copied it into my dyno book when researchinghow to build my dyno. Here is what he had to say about dyno exhaust. For what it's worth.

View attachment 1716148084
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We did some testing today again and besides having to find 40 HP that was lost, it was found again at 14 ° initial timing. We backed it up 2 degrees per test from 22. We made back to back 660 HP runs then before we made any changes we unhooked the Dyno exhaust and it picked up 15 HP and 10 ft lbs.
The Dyno exhaust is 5 inch by 12 feet long and big 5 inch semi truck mufflers ..
 
Also did a big change after getting the curve corrected . Changed jets, 74s rear & 66 front blocked off 2 pv's and went from 1 to 1 to progressive. I really don't believe the o2 sensors now because it was reading rich before these changes but the plugs looked great. Now they're black. More to come
 
I bet if you put the timing back in it the plugs would cleanup.
 
MMT isn't known for keeping plugs clean, it can be a little harsh on them.
 
I hate leaving with set backs.
Tim's going to drill the butterflies tommorow morning see it we can lean the fat pig out .
 
fishmens67 said:
MMT isn't known for keeping plugs clean, it can be a little harsh on them.
Click to expand...
Yeah we ran into that on my engine last year but it was running so clean at 1 to 1 linkage. There was absolutely 0 orange this time and just a little grey , porcelain was white basically a perfect plug too me and it was reading rich, so I don't know what to think.
 
fishmens67 said:
MMT isn't known for keeping plugs clean, it can be a little harsh on them.
Click to expand...
Oh I forgot, the t- slots were completely exposed so I think that's why the plugs are black. And as I said because drilling holes in the throttle blades
That should clean it up.
 
So I just watched my video again.
New highs 664 torque 4900 rpm
675 HP 5800 rpm.
 
MOPARMAGA said:
We did some testing today again and besides having to find 40 HP that was lost, it was found again at 14 ° initial timing. We backed it up 2 degrees per test from 22. We made back to back 660 HP runs then before we made any changes we unhooked the Dyno exhaust and it picked up 15 HP and 10 ft lbs.
The Dyno exhaust is 5 inch by 12 feet long and big 5 inch semi truck mufflers ..
Click to expand...
The exhaust test is Interesting.
When speaking about timing numbers I have found that it is helpful if you include the rpm that the timing was measured at and if the distributor is locked or unlocked. I'm not trying to tell you how you should do it but I'll give you my 2 cents on how I do it. I'm probably telling you what you already know.
When dynoing with locked distributors I noticed that often the timing doesn't stay the same throughout the rpm range. They back up with rpm, some worse than others. If for example you set the timing on a locked distributor at 2000 rpm to 34 degrees, when the motor is revved to 6000rpm the timing might back up to 28 degrees. So when the customer ask me what he should set his timing at do I tell him 34 or 28? Most customers think that a locked distributor doesn't change with rpm.
What I thought would work best for me and my customers is to specify at what rpm the timing should be set at. I was doing alot of 602 crate motors for circle track customers so I'll use these as an example. The first thing was to figure out the rpm range that was most important to have the timing correct. I figured these motor spend most of there time in about a 2200 rpm range. These motors are chipped at 6200 rpm so that sets the top of the working range. That makes the bottom 4000. So I round the middle of the opperating range to 5000 rpm. This means that I use 5000rpm as my timing rpm. I will sweep the timing on the motor to find best average power in the working range from 4000 to 6200 using 5000 rpm as my timing rpm. When I find the number that makes the best average power I tell my customer to set his timing to 35 degrees @ 5000 rpm, as an example. Doing it this way minimizes the effects of the timing variation through the rpm range. Even if the distributor is unlocked this method works pretty good for me. I'm not saying that timing at other rpms should be ignored but this keeps it simple for my customers.
Before I start I will also check tdc and correct the mark if necessary on each motor. Then I will mark the balancer in degrees. After I do the timing sweep I will mark the zero on the tab and the balancer with a paint marker and write the number next to the line so it cant be confused with tdc. I tell my customer if he has a dial back light to set it to zero. With the motor warmed up rev it to 5000 rpm and make sure the paint marks are lined up. When I mark the balancer I extend the line across the front crossing the elastomer strip to the center hub. This makes it easy to verify that the balancer has not slipped when setting timing.
Crap! I made this way too long. Sorry.
 
92b said:
The exhaust test is Interesting.
When speaking about timing numbers I have found that it is helpful if you include the rpm that the timing was measured at and if the distributor is locked or unlocked. I'm not trying to tell you how you should do it but I'll give you my 2 cents on how I do it. I'm probably telling you what you already know.
When dynoing with locked distributors I noticed that often the timing doesn't stay the same throughout the rpm range. They back up with rpm, some worse than others. If for example you set the timing on a locked distributor at 2000 rpm to 34 degrees, when the motor is revved to 6000rpm the timing might back up to 28 degrees. So when the customer ask me what he should set his timing at do I tell him 34 or 28? Most customers think that a locked distributor doesn't change with rpm.
What I thought would work best for me and my customers is to specify at what rpm the timing should be set at. I was doing alot of 602 crate motors for circle track customers so I'll use these as an example. The first thing was to figure out the rpm range that was most important to have the timing correct. I figured these motor spend most of there time in about a 2200 rpm range. These motors are chipped at 6200 rpm so that sets the top of the working range. That makes the bottom 4000. So I round the middle of the opperating range to 5000 rpm. This means that I use 5000rpm as my timing rpm. I will sweep the timing on the motor to find best average power in the working range from 4000 to 6200 using 5000 rpm as my timing rpm. When I find the number that makes the best average power I tell my customer to set his timing to 35 degrees @ 5000 rpm, as an example. Doing it this way minimizes the effects of the timing variation through the rpm range. Even if the distributor is unlocked this method works pretty good for me. I'm not saying that timing at other rpms should be ignored but this keeps it simple for my customers.
Before I start I will also check tdc and correct the mark if necessary on each motor. Then I will mark the balancer in degrees. After I do the timing sweep I will mark the zero on the tab and the balancer with a paint marker and write the number next to the line so it cant be confused with tdc. I tell my customer if he has a dial back light to set it to zero. With the motor warmed up rev it to 5000 rpm and make sure the paint marks are lined up. When I mark the balancer I extend the line across the front crossing the elastomer strip to the center hub. This makes it easy to verify that the balancer has not slipped when setting timing.
Crap! I made this way too long. Sorry.
Click to expand...
Thanks, that's a great reply with a lot of good information. The 14° was at 1000 rpm. Yes we have done timing sweeps. We did find out one of the timing lights was giving us fits to set it so we used the timing light on the scope, oh by the way we were actually just reading the vacuum and found out my power valves were opening way to soon. I will go through and verify tdc and my mark too just because it's good to make sure nothing is going wrong with parts
I think I'll try setting the timing to what it likes up around peak torque 5000 rpm tommorow. We should have that number written down.
Hey thanks a lot, your posts and info have already helped make a substantial difference.
I appreciate this stuff as I am just learning all this stuff, Dyno isn't mine but it is my friends and this kind of stuff is what really makes me get out of bed. Plus this is my 1st real build of this power level, I know it's not a world beater but it puts me at or very near my goal for my dart 10.00 1/4 mile
 
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92b said:
The exhaust test is Interesting.
When speaking about timing numbers I have found that it is helpful if you include the rpm that the timing was measured at and if the distributor is locked or unlocked. I'm not trying to tell you how you should do it but I'll give you my 2 cents on how I do it. I'm probably telling you what you already know.
When dynoing with locked distributors I noticed that often the timing doesn't stay the same throughout the rpm range. They back up with rpm, some worse than others. If for example you set the timing on a locked distributor at 2000 rpm to 34 degrees, when the motor is revved to 6000rpm the timing might back up to 28 degrees. So when the customer ask me what he should set his timing at do I tell him 34 or 28? Most customers think that a locked distributor doesn't change with rpm.
What I thought would work best for me and my customers is to specify at what rpm the timing should be set at. I was doing alot of 602 crate motors for circle track customers so I'll use these as an example. The first thing was to figure out the rpm range that was most important to have the timing correct. I figured these motor spend most of there time in about a 2200 rpm range. These motors are chipped at 6200 rpm so that sets the top of the working range. That makes the bottom 4000. So I round the middle of the opperating range to 5000 rpm. This means that I use 5000rpm as my timing rpm. I will sweep the timing on the motor to find best average power in the working range from 4000 to 6200 using 5000 rpm as my timing rpm. When I find the number that makes the best average power I tell my customer to set his timing to 35 degrees @ 5000 rpm, as an example. Doing it this way minimizes the effects of the timing variation through the rpm range. Even if the distributor is unlocked this method works pretty good for me. I'm not saying that timing at other rpms should be ignored but this keeps it simple for my customers.
Before I start I will also check tdc and correct the mark if necessary on each motor. Then I will mark the balancer in degrees. After I do the timing sweep I will mark the zero on the tab and the balancer with a paint marker and write the number next to the line so it cant be confused with tdc. I tell my customer if he has a dial back light to set it to zero. With the motor warmed up rev it to 5000 rpm and make sure the paint marks are lined up. When I mark the balancer I extend the line across the front crossing the elastomer strip to the center hub. This makes it easy to verify that the balancer has not slipped when setting timing.
Crap! I made this way too long. Sorry.
Click to expand...


Posting this for a friend.



 
Here's the today's totals.
We're going to try a set of open spacers & also what it does with no spacers.
Pk Tq 661.02 @ 4900
Pk HP 682.52 @ 5700

IMG_20231008_155150511_HDR.jpg
 
Tomorrow before we do any changes on the spacers we're going to try 2 degrees of timing up and down. It's at 21 initial and around 27 at 4500.
Tim really got the fuel curve dialed in perfect in my book, the plugs look excellent.
I bet theres 8 more hp.
 
Today, we just bumped up the timing 1 degree and it picked up more power 2 HP and 11 on torque. Then for s&g we turned the super sucker tapered spacer upside down and it only lost a 10th of a HP, and 1/2 a foot pound torque at the peaks but a couple numbers throughout the pull.
I think it's getting close to it's best.
 
As far as timing is concerned, have you reached the point where the motor is losing power anywhere in the curve yet from too much?
 
What I find fairly often, when running the timing locked out, is that when you’re hovering around whatever timing is giving the best results, is that slightly retarded will often make the peak TQ numbers better than the setting which yields the best HP number.

And then there’s the combos that are almost impervious to the timing unless you make a fairly big change.
 
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