How bad is a rebuild supposed to run at start up?
08-10-04, 07:31 PM
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How bad is a rebuild supposed to run at start up?
I ran the engine another 10 minutes this afternoon before discovering a fuel leak and having to kill it. The fuel leak is fixed and I'm done out there for the night. I'm gonna try to start and run it again tomorrow morning again. My question is though, how bad for how long is the engine gonna run? While I had it goin it was shaking and popping like crazy. The shaking was almost as bad as when I blew the apex seal on the previous engine. Is this normal? If so, how long is it gonna last for before it settles down? I know its supposed to run rough, but is that normal? This may be a dumb question, but I'd rather err on the side of caution. Thanks!
08-10-04, 08:07 PM
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I don't think shaking and popping is normal, or maybe my rebuild just acted more tame when I first got it going. It should be hard to start, smoke a little, misfire a little, all for about 30 minutes to a few hours of run time. If urs is misfiring a lot, that could cause the shaking. Double check crank angle sensor position, plugs, vacuum leaks, and grounds would be my suggestion. 
08-10-04, 10:29 PM
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Yes, sounds like another problem to me...perhaps your timing is off, perhaps a plug is fouled, etc.
They usually run a bit rough, but nothing like a blown motor...more like one that hasn't been started in a long time...rough idle, weak power, misfiring here and there, etc. IT gets much better after a few hundred miles are put on...mostly it depends on teh quality of housings used. New housings, or nearly new ones, will have very little breakin to wory with, and will run great from day one.
They usually run a bit rough, but nothing like a blown motor...more like one that hasn't been started in a long time...rough idle, weak power, misfiring here and there, etc. IT gets much better after a few hundred miles are put on...mostly it depends on teh quality of housings used. New housings, or nearly new ones, will have very little breakin to wory with, and will run great from day one.
08-10-04, 10:36 PM
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So if I had one new and one used housing, I would have some discrepency (sp?) in compression that could result in the vibration? I may have exaggerated in its severity a bit as well. Also, I pulled and cleaned the plugs, and there was indeed some crap on them, so I'm hoping that will help as well.
08-10-04, 10:43 PM
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Nope, no discrepancy of compression (within a reasonable degree, like 20psi per the fsm) will affect vibration or anything. Low compression means the engine will not fully burn the fuel/air intake charge it ingests, so it runs rich and misfires until compression comes up. Thus, a bit of rough idle and sputtering at idle is pretty much normal for a used housing rebuild.
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08-10-04, 11:27 PM
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Thanks for the input. I'm gonna try it tomorrow morning again, and hopefully I'll be able to report some progress, and hopefully it won't grenade.
08-11-04, 01:12 PM
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Alright, I had it goin for about 20 minutes, and it definately started to smooth out and it held very steady at about 2000 rpm. I am starting to think that the CAS is out of alignment though, as it developed a rather regular popping as I ran it. I'm gonna dive into that now, since I'm not 100% sure that its aligned corrected since my pulleys lacked the yellow marks that they were supposed to have. Is there some trick I can use to check it without having the markson the pulleys?
08-11-04, 02:12 PM
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Nevermind, I just found the screw on the other side of the TB that I missed, it is now idling happily at 1500!
Last edited by jdmsuper7; 08-11-04 at 02:14 PM.
08-11-04, 08:03 PM
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Ports with more overlap (later exhaust closing and earlier intake opening) cause the idle quality to get rough and emissions to get ugly. Ports can still have a lot more duration than stock (later closing intake) but idle and get gas mileage like stock ports . . with a good boost in power . .
08-11-04, 08:15 PM
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My streetport isn't real aggresive, but you really answered my question. In other news: after two more hours idling tonight, everything has become quite stable. The only minor problem with the quality is my 8 month old gas, hopefully it will use it all up tomorrow when I run it all day, then i can get some new gas and things will get even better. Thanks for the input everyone!
Last edited by jdmsuper7; 08-11-04 at 08:16 PM. Reason: edited for spelling
08-11-04, 11:48 PM
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As soon as i get some money to buy tools, ill get an engine stand and porting drills to make my t2 street ported.. another question.. Do u have the porting templates? if u do... pm me with info on what can i do to obtain them.. thanks..
"Good Luck! and best happy Piston killing"
"Good Luck! and best happy Piston killing"
08-12-04, 01:23 AM
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It's dependent on who builds the engine and their tolerances.
I've never had an engine idle real badly unless it floods initially which can foul spark plugs.
It might not idle at the stock 750RPM spec, but I like to keep initial idle speeds around 1,000RPM or a little higher to aid break-in and prevent the engine from dying from the low compression.
The engine should be stable enough to idle at Mazda spec and crank and start reliably within the first 100 to 200 miles of break-in.
-Ted
I've never had an engine idle real badly unless it floods initially which can foul spark plugs.
It might not idle at the stock 750RPM spec, but I like to keep initial idle speeds around 1,000RPM or a little higher to aid break-in and prevent the engine from dying from the low compression.
The engine should be stable enough to idle at Mazda spec and crank and start reliably within the first 100 to 200 miles of break-in.
-Ted
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