Tuning 12A Streetport
05-13-09, 06:23 PM
#1
Tuning 12A Streetport
I just dropped a 12A street port into my 82 and got her started up, but there are a couple things that still need to be hammered out. First, the car starts, but it has to turn over quite a bit and seems to sort of just sputter for a few seconds and then catch, it doesn't just fire right up. Secondly, when it is running, it backfires a lot and sounds really choppy. It also doesn't keep idle even after i warm it up.
I've tried changing the ignition timing by moving the dizzy using a timing light, but it never really seems to line up all the way. Any suggestions would be greatly appreciated.
I've tried changing the ignition timing by moving the dizzy using a timing light, but it never really seems to line up all the way. Any suggestions would be greatly appreciated.
05-13-09, 06:35 PM
#2
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What supporting mods do you have done? Judging from the pics your engine is stock aside from the streetport. The larger porting is going to try to suck more air and the stock carb and fuel pump won't be able to provide enough fuel and the stock exhaust is just a huge restriction. The exhaust is the first thing you should have changed out, then the carb and fuel delivery. If your not sure how to tune your carb's idle check out the tuning instructions at www.sterlingmetalworks.com. Alot of good carb info there. If your local laws allow you should remove all the emissions related components. That way you can seriously clean up the engine bay and reduce the number of components that can fail. Theres a tutorial at www.mazspeed.com.
05-13-09, 06:44 PM
#3
yeah, I know I sound like a noob for just buying a streetport without any supporting mods, but I really needed a motor fast and this one was a really good deal. I'm going to do the emissions removal this weekend, but I'm going to take it to a shop first and see if I missed anything.
05-13-09, 07:13 PM
#4
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Take the emissions off and get a block off plate for the intake manifold. Try to get a header b/c the streetport requires a header. I have run streetports before with a holley and the stock fuel pump with no problem. I think your backfiring has to do with the timing.
05-13-09, 08:37 PM
#6
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Stock fuel pump wouldn't even keep up with my stock carb. Sure as hell wouldn't keep up with my Sterling carb. You been smoking those funny cigarettes again Joey? But I guess that technically it would run, but run well?
To the OP, I would start by getting a timing light and some instructions on how to set the timing. There are instructions on this site, or in the Haynes manual. This is most likely your issue, as long as you haven't lost your leading ignition. You have checked for spark, right?
To the OP, I would start by getting a timing light and some instructions on how to set the timing. There are instructions on this site, or in the Haynes manual. This is most likely your issue, as long as you haven't lost your leading ignition. You have checked for spark, right?
05-13-09, 09:41 PM
#7
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Stock fuel pump wouldn't even keep up with my stock carb. Sure as hell wouldn't keep up with my Sterling carb. You been smoking those funny cigarettes again Joey? But I guess that technically it would run, but run well?
To the OP, I would start by getting a timing light and some instructions on how to set the timing. There are instructions on this site, or in the Haynes manual. This is most likely your issue, as long as you haven't lost your leading ignition. You have checked for spark, right?
To the OP, I would start by getting a timing light and some instructions on how to set the timing. There are instructions on this site, or in the Haynes manual. This is most likely your issue, as long as you haven't lost your leading ignition. You have checked for spark, right?
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05-13-09, 10:58 PM
#8
yeah, I checked for spark, and all plugs are firing. I started working on the timing, but I had to get back to college before I could finish. I think I might have set the distributor in a tooth late or something because I could only seem to get it 20 degrees back from the mark. I'll sort that **** out this weekend and get back to you guys.
05-14-09, 03:11 AM
#9
I thought i missed the right tooth at one point also, then i turned it one tooth forward and one tooth back and both times it wouldn't even run. You really gotta get a bigger carb or something man cause I have a street port and i got a 600 holley with 66 jets and it doesn't even like to run (well) at times, I'm waiting for my bigger jets i ordered to arrive. 
05-14-09, 12:21 PM
#11
Somebody put the dizzy drive gear on backwards. I've ran across a few rebuilt engines with this mistake. The newer gears don't have an F mark but they do have a beveled edge. Easy to overlook.
What is the quick fix? I'm not sure as I've torn down all of them so far because they were in need of a rebuild anyway.
What is the quick fix? I'm not sure as I've torn down all of them so far because they were in need of a rebuild anyway.
05-14-09, 04:12 PM
#13
Yeah, I'm going to get a bigger carb in about a month. I'm going to go with either a 45DCOE or 48IDA setup. It depends on what kind of deal I can get on either. Also, holley fuel pump/regulator, and possibly gilmer pulleys if I end up ditching my AC. Any thoughts of alternatives?
05-14-09, 04:18 PM
#15
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Actually he wouldn't be surprised about that. Why do you think he's constantly telling people such as yourself that your carb is too damn big. There are people running 465CFM carbs on bridgeport engines with good results, so maybe not a good idea to tell people they have to have such a big carb on a streetport when it's not necessary. And the 13B might be 0.1L bigger than the 12A, but that doesn't really mean anything in the rotary world. Stock it comes with 35 HP more than the 12A.
05-14-09, 10:04 PM
#16
Actually he wouldn't be surprised about that. Why do you think he's constantly telling people such as yourself that your carb is too damn big. There are people running 465CFM carbs on bridgeport engines with good results, so maybe not a good idea to tell people they have to have such a big carb on a streetport when it's not necessary. And the 13B might be 0.1L bigger than the 12A, but that doesn't really mean anything in the rotary world. Stock it comes with 35 HP more than the 12A.
05-15-09, 12:03 AM
#17
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12a is 1146cc and the 13b is 1308cc. Its over a 10% difference in displacement, so thats about the difference between a 350 and a 383. I'm not sure what the actual difference in power is though, the 35 extra horse that the 13b came with could very well be from the more advanced design and fuel injection.
05-15-09, 12:10 AM
#19
LOL! true! Oh boy.... it's been a long night at work and not a good one.......... i think we all know how that is.....
Anyways, a 465 on a bridge 12a may work pretty good but since racing beat themselves use 650's on 12a bridgys I don't feel a 600 on a street is too overkill........ Thats just how i look at it.
And I didn't mean to step on any toes, just frusterated right now.
Anyways, a 465 on a bridge 12a may work pretty good but since racing beat themselves use 650's on 12a bridgys I don't feel a 600 on a street is too overkill........ Thats just how i look at it.
And I didn't mean to step on any toes, just frusterated right now.
05-15-09, 12:32 AM
#20
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No worries, I certainly understand a long day at work. But now I am going to insist you go to Sterlings website if you already haven't. www.sterlingmetalworks.com. Lots of info there you should be reading. I am starting to think I am beating a dead horse, but you really aren't getting it, no offence. The 12A engine will not ingest 600CFM in naturally aspirated form. EVER!!! The most a stockport will ingest at ridiculous, unrealisticly high VE numbers is just over 400. The only reason Sterling even builds his carbs to flow 465 is because everyone thinks big carb CFM numbers means more HP and his RB Holley competitor flows that much. It just doesn't work that way, but very few people will listen to reason or after being given proof. Racing Beat is not the be all end all anymore. Maybe 15 years ago they knew everything, but things have changed, and if you owned many of their parts, you'd see their design and build philosophy hasn't. Example: Their front sway bars are solid and heavy. I find that strange since it's been proven on race cars that hollow, lighter bars are more effective. So can you really trust all the guidelines they have on their webpage? I know they aren't stupid, and in some cases even pioneered certain aspects of the rotary world, but there is more out there than RB.
End rant.
End rant.
05-15-09, 12:42 AM
#21
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No worries, I certainly understand a long day at work. But now I am going to insist you go to Sterlings website if you already haven't. www.sterlingmetalworks.com. Lots of info there you should be reading. I am starting to think I am beating a dead horse, but you really aren't getting it, no offence. The 12A engine will not ingest 600CFM in naturally aspirated form. EVER!!! The most a stockport will ingest at ridiculous, unrealisticly high VE numbers is just over 400. The only reason Sterling even builds his carbs to flow 465 is because everyone thinks big carb CFM numbers means more HP and his RB Holley competitor flows that much. It just doesn't work that way, but very few people will listen to reason or after being given proof. Racing Beat is not the be all end all anymore. Maybe 15 years ago they knew everything, but things have changed, and if you owned many of their parts, you'd see their design and build philosophy hasn't. Example: Their front sway bars are solid and heavy. I find that strange since it's been proven on race cars that hollow, lighter bars are more effective. So can you really trust all the guidelines they have on their webpage? I know they aren't stupid, and in some cases even pioneered certain aspects of the rotary world, but there is more out there than RB.
End rant.
End rant.
05-15-09, 02:22 AM
#22
Alright.
And I'm not argueing here but i really do wanna know..... how is it a huge carb like a 600 doesn't flood the poor little rotary? Now that i know those figures I'm suprised it even runs with a 600 on it! lol But if it's properly tuned won't a 600 work pretty well? I've found a few people with great results from a 600.... How is that?
And I'm not argueing here but i really do wanna know..... how is it a huge carb like a 600 doesn't flood the poor little rotary? Now that i know those figures I'm suprised it even runs with a 600 on it! lol But if it's properly tuned won't a 600 work pretty well? I've found a few people with great results from a 600.... How is that?
05-15-09, 02:49 AM
#23
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I don't think its a matter of a big carb flooding your motor, but rather it has to do with the velocity of the airflow. A monster carb on a small motor is only going to flow at a portion of what it is designed to. As a result, response suffers, as does part throttle control and cruising. It won't matter a whole lot at wide open throttle, but everything else suffers. So, unless you are drag racing, your overall performance will suffer when compared to a "properly sized" carb.
And I totally agree with Orion. Just because Racing Beat does something a certain way does not mean that it is the best way. I think that, just like a Doctor who doesn't keep up on the medical journals, they have fallen behind and atrophied a bit.
And I totally agree with Orion. Just because Racing Beat does something a certain way does not mean that it is the best way. I think that, just like a Doctor who doesn't keep up on the medical journals, they have fallen behind and atrophied a bit.
05-15-09, 03:06 AM
#25
haha, thread jack apology accepted. I think I'm going to get the timing set right, do the rats nest removal and convert to mechanical secondaries for the time being. Then when I have the money, I'll convert to a Dellorto side draft intake and RB exhaust. I really appreciate all your help you guys. I'll bring the thread up again with some pics of the rats nest removal.