My latest happenings

[tylerrocks]

Well, I was going to go to a mustang shootout today but it's not likely now. Ive got a few problems (seems like I always do). I recently swapped a 9" from currie (minus ebay centersection) in my car and when I test drove it I was going slow at first but as I got on it, sometimes I would get a BANG and a jolt. At first I didn't know if it was the engine or the rear. I tried again and it became apparent it was the engine. It felt sometimes as if the engine were spuddering but it would come and go once or twice throughout the mid-upper RPM, sometimes accompanied by a backfire and jolt which is where i get off the gas.

Before I swapped the rear I replaced my leaking fuel pressure regulator with the only one I could find in town, it only went up to 5.5 psi the bowl level was right under the glass, but it drove around town fine and actually performed fine before I put the 9" in.

Foward.... I hooked up my Innovate wide band sensor and fired up my car. A/F was like 17-19 at warm idle, sometimes it would go leaner and die, I have a demon carb so I started messing with the four corner screws untill I got A/F down to 14 .5 or so (BTW I am a complete novice at carb tuning, Im only 19). I was checking the timing and I noticed every once and a while it would drop along with engine RPM, I went to the LM1 and it showed A/F going to 16 or so when the RPM dropped.

So by now I'm thinking vacume leak, I've had hell with vucume leaks comming from the front cork intake gasket. So I used straight silicon (sp?) instead of corks, let it dry overnight and the car ran better the next day, but I'm still getting that spudder and the car feels slow. I am a little bumed because with my 9" I went from 3:1 to 3.89 gears and the car feels slower. My buddy in a 04 Mach1 used to barley pull away from me in a race, now he pulls faster, and I was telling him that with my gears, i would pull from him.

I'm really hoping the pressure regulator is holding me back, I just got a new one in from summit that goes up to nine psi so I'll see. Oh now I have an oil leak out the back of the intake so now you know where I'm at. Care to comment?

Thanks
Tyler

 

[302 coupe]

the cork end seals will not cause a vacuum leak, just an oil leak. Though you may have a vacuum leak somewhere else. Seems kinda weird that it started when you did the axle swap. maybe you pinched a fuel line or something, maybe broke something loose????

 

[tylerrocks]

I didnt realize the cork gaskets wern't exposed to vaccume, I feel dumb. I dont think I pinched a fuel line, I just wonder if the gears, causing my engine to spool up quicker, are sucking up the fuel in the bowls faster than it is being supplied?

 

[rebel65]

well the 9" will have a parasitic loss greater than whatever you had in there before, coupled with high A/F readings, i would focus on getting your vaccum and carb tuned correctly. and then figure out why you are going slower

 

[mustangman1974]

Do you have electronic ignition?
Did you weld to fit the 9in?

If you answered yes to both and did not disconnect the ignition you may have an ignition problem from welding. I fried a Mallory MBI from welding an exhaust brasket with a mig.

 

[tylerrocks]

Sorry for the slow response. Well I put my new fuel pressure regulator in and that helped some. Now I can keep my bowl levels correct. The car feels better but I still get that stumbeling feeling when I go WOT. I think the carb needs a tune but I lack that skill. I know where jets and power valves are but thats it. So I geuss I'll do some research on that. When I replaced the intake gaskets I felt really confident that I had done a good job; everything was really clean, gaskets didn't move, had a good dab of silocon where they met, let sit for 24 hrs. Still, I have an oil leak out the front. But you know, Iv'e always had a little oil sitting on top of my timing cover. I bought my heads and intake used and the shortblock from a machine shop, I was told the block was 0 decked. Could something be off with alignment to cause the oil leak?

Oh and I have a Mallory HEI but I didn't do any welding on my car.

Tyler

 

[67Dylan]

Is the oil leak evidently from the intake? Reason I ask, if you use enough silicon, torque the bolts down in the correct order/sequence you shouldn't have any probs. What kind of sealant used?

If you want to learn to tune a carb, IMO, purhcase a How to Tune Holley Carb book. It includes pics and will help you a looong way! When you are tuning the carb it's nice to refer to the book if needed and of course this website as well... just an idea.

First off, how much fuel pressure under WOT?
How about around town driving; does she drive fine w/no sputtering/stumbling?
What color are the plugs and what do they look like?
Probs only at WOT?

BTW, this is a good site to get you started: http://www.jason.fletcher.net/tech/carbtuning/carbtuning.htm It was VERY useful when I jumped to a carb in my 90 mustang.

 

[fasttback]

Sorry for the slow response. Well I put my new fuel pressure regulator in and that helped some. Now I can keep my bowl levels correct. The car feels better but I still get that stumbeling feeling when I go WOT. I think the carb needs a tune but I lack that skill. I know where jets and power valves are but thats it. So I geuss I'll do some research on that. When I replaced the intake gaskets I felt really confident that I had done a good job; everything was really clean, gaskets didn't move, had a good dab of silocon where they met, let sit for 24 hrs. Still, I have an oil leak out the front. But you know, Iv'e always had a little oil sitting on top of my timing cover. I bought my heads and intake used and the shortblock from a machine shop, I was told the block was 0 decked. Could something be off with alignment to cause the oil leak?

Oh and I have a Mallory HEI but I didn't do any welding on my car.

Tyler

Might be carb issues (the Holley book is a good purchase). When I switch my 8" 3.00 rearend to a 9" 3.50 I actually had to detune my carb to prevent WOT stumble. Your might try playing with the cam profiles and squirters on the carb, before metering jets.

 

[tylerrocks]

Well, I finally fixed my oil leak. Sixth times a charm . Every time I tried before the gasket would "suck" in right behind the distributor. So I finally just removed the distributor, made sure the gasket was in place and tourqued her down. Looking back, I should have removed the dizzy the first or second time. Oh well thats one lesson I wont soon forget. Still having carb trouble but I ordered Supertuning Holleys from Summit. I'll let you know how that turns out.

Tyler

 

[302 coupe]

In the future, use a felpro 1250 or 1262 manifold set, they have adhesive on the end seals so they won't slide around. The parts store felpro sets don't have that feature for some reason.

 

[SoCalCruising]

I wonder why no one mentioned that there is atuning book specific to Demons? I got one at Barnes and Noble.

Just a note: silicone is not recommended for garkets in contact with gasoline. If you used silicone to seal your intake ports, this might be a source of vacuum leak(s). Use a Felpro 1250 intake gasket. Use Gaskacinch on the back side of the gasket and head surface to seal it against the head, a little silicone around the water jackets, and then nothing on the intake port side of the gasket. The 1250 is self sealing.

I strongly recommend The Right Stuff for sealing up your end rails, too, rather than silicone. Also, check the gap between the intake manifold and block end rails. If the gap is small, discard the cork garkets and just use The Right Stuff. If it is larger than the cork gasket, use it and The Right Stuff to seal it up good. I had only about 0.020-0.030" gap on mine. Had I used the cork, the intake would NEVER had sealed against the head because the intake manifold would bottom out against the end rail before it would seal against the head. If this is the case for you, it would also be a source of vacuum leaks. Hope you get it sorted out.

 

[tylerrocks]

Noted 302, thanks.

Socal, I put the head/intake gaskets on clean. only silicon I used was at the corners. It seems to hold oil fine.

I ran it the other day, got her warmed up then went WOT through 3rd gear, killed the engine, coasted to a stop and pulled a plug. The tips of the grounds(2) were a light grey and the rest was black, the white electrode in the middle had just a hint of red to it. I'm pretty sure the carb is out of tune, however I dont know what fuel pressure is under loaded WOT. The gauge it under the hood, but when I rev it by hand pressure stays constant. I'm also going to take a vacume gage out to the shop today to see what I can find out there. Thank for all yalls help, I know I can fix this.

Tyler

 

[SoCalCruising]

Great attitude. Keep plugging away. You'll get it, plus learn some things along the way.

 

[tylerrocks]

I'm back and I may have found the culprit.



Rocker arm pedestal...... What do ya think?

BTW symptoms are: Going 2-6 full AFR points lean--I can't recall if it was intermittently or in rythm--while idleing along with RPM drop. Also, a stumbeling feeling at WOT and last time I drove it I got some backfire (exhaust).

 

[tylerrocks]

TTT

 

[65ShelbyClone]

Rocker arm pedestal...... What do ya think?

BTW symptoms are: Going 2-6 full AFR points lean--I can't recall if it was intermittently or in rythm--while idleing along with RPM drop. Also, a stumbeling feeling at WOT and last time I drove it I got some backfire (exhaust).

I think that pedestal looks broken.

Do you have datalogs from the WB 02? The AFR should go fairly lean under high vacuum like when the throttle is shut, but not really any more than 17:1. What is the AFR doing during the WOT stumbling?

 

[tylerrocks]

I think that pedestal looks broken.

Do you have datalogs from the WB 02? The AFR should go fairly lean under high vacuum like when the throttle is shut, but not really any more than 17:1. What is the AFR doing during the WOT stumbling?

No datalogs. Idle tuned in the 14.5 range but goes lean (16-18 AFR) and RPMs drop everyonce and a while. At WOT it runs around 12.5 I belive not sure about afr during the stumbeling. That pedestal was on an exhaust valve BTW.