alsil Posted September 6, 2001 Share Posted September 6, 2001 Ok guys, I got my engine back in. Went through it big time, cleaned it all up. Got it started, the damn thing does exactly the same thing as it did before I pulled it apart: -When I start it cold, it runs even and idles OK. -As is warms up, it begins to miss. Sounds like a vaccuum leak. -When it gets up to operating temp, is starts to surge worse and worse until it stalls. -the warmer it gets, the more it hesitates off idle until you have to keep it over 2000rpm for it not to try and stall. -pulling a vacuum plug does very little to the idle speed. Usually it should surge. Now I have built a FEW small blocks and never have I seen this happen. I have a few theories: -craked head on an intake port -plugs on the back of the head defective or not sealed. So my question is really your opinion. I am frustrated that I can't get this thing to run right. I have spent lots of money and time on this car and am getting tired of getting nowhere. For the guys who have used them, those threaded plugs that go in the back of the head to block the smog pipe openings, they are attached to the intake side, right? They let exhaust gas back into the intake track to burn unused fuel, right? That was my understanding. How far are those supposed to be installed into the head? mine are sticking out about 1"-1.5", which might not be all the way in. I was thinking about it last night and thought that if these were really on the intake side, that if it was leaking past them, that could explain it. Any other ideas or possibilities are welcome. I really want to drive my car. It's been sitting almost the whole time I've had it done. Thanks Guys. AL Quote Link to comment Share on other sites More sharing options...
pparaska Posted September 6, 2001 Share Posted September 6, 2001 Al, How about loosening all the rocker arms sealing off the TB and the vacuum ports in the intake and pressurizing the intake tract while you listen for air escaping? Quote Link to comment Share on other sites More sharing options...
alsil Posted September 6, 2001 Author Share Posted September 6, 2001 That's a good idea, except I don't have a way to do it. Besides, not sure that would work with a carb. My brother's got a compressor, maybe I can try that out. thanks! AL Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted September 6, 2001 Share Posted September 6, 2001 Those air injection holes in the back of the heads are connected to the air pump. Not the intake side. They are plugged off so that you won't have an exhaust leak. No way should they be connected to anything on the intake side of the motor. You may be thinking about EGR systems, but they run off ports cast in the head which are visible with the intake manifold off the engine. Sounds like a massive air leak or uncontrolled EGR. GrinZ Quote Link to comment Share on other sites More sharing options...
alsil Posted September 6, 2001 Author Share Posted September 6, 2001 Since I have no EGR on my engine (using a Performer 289 intake and Edelbrock 1406 carb), I'm pretty convinced it's a HUGE vacuum leak, too. Besides the intake gaskets, carb gaskets, and valve seal, I dont' know what to check next. The carb is new, the intake is new. The gaskets are new. I thought about swapping carbs with my truck (I have a 1406 on that, too) and seeing if maybe the carb is defective (although I can't imagine how it could be THAT messed up being brand new and showing no signs of defects). Who knows? Al Quote Link to comment Share on other sites More sharing options...
Guest scca Posted September 6, 2001 Share Posted September 6, 2001 try a vacuum guage first and see what it is. to detect a leak....... buy some carb cleaner. get it running and spray the stuff around the suspected area. IF its leaking it will run faster(depending on the brand of carb cleaner)you can use ether too(quick start) anything that you can spray will help detect the leak.. this is the far easiest way to tell. spray it in the carb first to see how it affects the motor and then spray it elsewhere - it will be noticeable easily... Quote Link to comment Share on other sites More sharing options...
pparaska Posted September 6, 2001 Share Posted September 6, 2001 I've used the carb cleaner trick too - but it takes paint off of stuff . Heck, even a spray bottle with water will help find leaks - if you can get to them. But if it's an intake manifold to head leak at the bottom of the intake port opening, or some other weird thing like a cracked port, this won't help much. Quote Link to comment Share on other sites More sharing options...
alsil Posted September 6, 2001 Author Share Posted September 6, 2001 Did that when I first started having the problem. Didn't find anything. That's what led me to suspect a cracked head, or something else. Are there any other areas that I might have missed? I mean, how many places can affect the intake track? I'll probably throw the vacuum guage on again tonight to try it again, because I was so frustrated last night I just gave up and went to rehearsal. But I KNOW that all the gaskets and seals are good. I was EXTREMELY careful to make sure not so much as dust got on those gaskets. ARGH!!!! Al Quote Link to comment Share on other sites More sharing options...
alsil Posted September 6, 2001 Author Share Posted September 6, 2001 I did check the casting to find out if there were any cracks or anything weird - I saw nothing. Like I said, I went over this thing. I did NOT want to have to pull it again. Quote Link to comment Share on other sites More sharing options...
Guest scca Posted September 6, 2001 Share Posted September 6, 2001 isnt the 289 intake different from the 5.0? do the egr runners line up ? i just changed my intake gasket on the 5.0 and it looked different from the 289's that i have worked on in the past... the early 289 intake gaskets i had here looked different as i recall???? i cant see a intake port cracking in the head-- it IS possible but pretty unlikely. it does sound like a huge vacuum leak... Quote Link to comment Share on other sites More sharing options...
Guest scca Posted September 6, 2001 Share Posted September 6, 2001 did you use silicone on the intake gasket too or not? i use permatex ultra blue on all gaskets (except the high heat red on the exhaust... and i didnt even use header gaskets from header to block. just high temp silicone and it sealed up perfect.. no gasket to blow out there... on stuff small i use motorcycle case assembly sealer (semi hardening) it works great..thermostat housings etc.... if you put the intake on dry i would do it over... Quote Link to comment Share on other sites More sharing options...
alsil Posted September 6, 2001 Author Share Posted September 6, 2001 I'm using the '95 5.0 gaskets. the intake has no provision for EGR. It's just flat where the crossover would normally be. I dunno. I'm kind of confused, unless there is a PHYSICAL problem with one fo the castings, I don't know what to think. Kind of makes me realize why the guys sold this engine. Maybe they told him what was wrong and he decided to get rid of the engine instead of fixing it. Mike, what was the difference? It think the crossover holes are a different size on the older ones, smaller I think. Quote Link to comment Share on other sites More sharing options...
alsil Posted September 6, 2001 Author Share Posted September 6, 2001 I ALWAYS use sealer around the water passages on both sides of the head. I used to pull intakes on my old Mustang all the time, because I had 3 intakes, depending on where I was racing. I had a stock 4v, a Performer RPM, and a Torker II. Like I said, I've buila quite a few of these, and never had a problem remotely like this. Quote Link to comment Share on other sites More sharing options...
Guest scca Posted September 6, 2001 Share Posted September 6, 2001 i would start by calling edelbrock and ask if there are any issues with installing the early intake on a later 5.0. seems stupid but eliminate all possibilities first.. it is either a defective carb, warped intake at a port - or intake not compatible. at least those are my top 3 guess'...assuming you have it sealed ... if you take it off again you may be able to see if a port wasnt sealing on the gasket surface. the obvious like the timing is correct , valves are set is done....one tooth off on the distributor .. Quote Link to comment Share on other sites More sharing options...
alsil Posted September 6, 2001 Author Share Posted September 6, 2001 Yea, the usual suspects. This is how it's setup from memory - -12 degrees advanced -I have a Pertronix so no points to set carb is pretty close to dialed in, have not been able to get it to run well enough to really "fine tune" it, but jetting (unless it's WAY off) on Edelbrock's doesn't affect the idle. -Plugs are at .045", Accel plugs -Ford MS 8mm wires -All Vacuum ports on carb blocked That's pretty much the stats. Like I said, it seems like everything is right. I'll give Edelbrock a call. Thanks for the tip. Quote Link to comment Share on other sites More sharing options...
74_5.0L_Z Posted September 6, 2001 Share Posted September 6, 2001 I'm sure you've checked, but what is the condition of your PCV valve and hose. A bad PCV valve will produce a bad vacuum leak. Have you tried plugging the PCV line at the carb? Another possibility is that you have a leak under the intake in the lifter gallery. This can happen if the intake and or heads have been milled. Have you checked the vacuum with the engine running. The engine should make 15-18 in H20 of vaccuum on the engine side of the closed throttle plates at idle. The vacuum indication should be steady. One other thing that came to mind. Make certain the valves are adjusted properly. If sufficient clearance is not provided the valves will not seal properly, and the engine will act as if it has a vacuum leak. Further, the problem will get worse as the engine warmes up. I nearly ended up in that situation when I installed 1.7 rollers on my engine. I tightened the rockers down on their pedestals, and noticed that the valves were opening with the cam on the base circle. (Not good) To fix this I installed shim under the pedestals to correct the geometry. The shims come in a prepackaged kit from Crane. The kit includes two set of shims at different thicknesses and cost $13.00. I would almost bet that this is your problem, especially if the heads have been milled at all. Quote Link to comment Share on other sites More sharing options...
alsil Posted September 6, 2001 Author Share Posted September 6, 2001 Well, as far as I know (and can tell) the engine has never been apart until I pulled it apart. So I don't know about that, but you know what, I will check that too. this is a completely stock motor, with stock parts. The rockers are stock, with the stock cam and lifters. This should just work, since it's all stock. in fact, before I pulled it apart I had this same problem, so I know I didn't cause this. Who knows, maybe it is the intake. I guess anything's possible! Quote Link to comment Share on other sites More sharing options...
alsil Posted September 6, 2001 Author Share Posted September 6, 2001 Oh, and (because of a past experience, and because it's a good idea) I checked how the valves seat, and they were all straight. I don't know about while tightened down, but maybe I should check that. Who knows what has been done to this engine really. I don't have a PCV valve on this car yet. Haven't got that far, started the engine up, and had this problem. Barely driven it. I am going to throw the compression guage and vacuum guage on it tonight! Quote Link to comment Share on other sites More sharing options...
blueovalz Posted September 6, 2001 Share Posted September 6, 2001 The first thing that came to mind on this was "Is he using a choke?". If this engine is running real rich (power valve diaphram broke, etc) then a cold engine may run fine until it starts warming up, and then the over-rich condition rears it's ugly head (Like a choke left closed). An open (vacuume leak) port would make it tough just to keep the engine running when cold. Quote Link to comment Share on other sites More sharing options...
blueovalz Posted September 6, 2001 Share Posted September 6, 2001 Also, if it is truely a vacuum leak, cup your hands over the choke horn, just enough to cut off the air to the carb. If the engine picks up speed, then it's a good bet you have a vacuum leak, if it dies before you even get close to a good seal with your hands, then it may be running too rich. Good quick and easy way to check the carbs A/F mixture at idle. Quote Link to comment Share on other sites More sharing options...
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