I broke in my rebuilt engine a couple of weeks ago. I ran Brad Penn Oil break in oil for my flat tappet cam. Ran it at 2000-2500 for 25 minutes.
The problem I am having is setting the timing. I can't the engine down to 750 rpm. I've set the static timing at 10deg BTDC but I can't get the rpms down. The engine is running at 1100. When I tried to set the timing 5deg BTDC it was way way down on power its like I was starting 3rd gear..it felt like I could walk faster than this car could go. And it way hot too at idel.
I have the choke open. I set 0 tdc by turning the engine over by hand using a stop. I did this a few times.
The only thing I can think of is a vacuum leak. That's my next step. Could be the base of my new carb/intake (both summit brands)? Or maybe the PCV valve is leaking? ...
So you can't turn the carb idle screw down after setting to 10 BTDC? I guess confused since it sounds like you can set the timing to 10deg but then you should be able to turn down the idle screw on the carb to the RPMs you want. Or is it shutting off on you?
Ditto, what was stated.......are the throttle blades closed when you back out the throttle idle screw all the way? Check your throttle linkage is free.
Its a 289 rebuilt heads block is .40 over. 9.8 comp. It has a mild/moderate cam -Melling MTF-5. Valve lift is .450 intake/.474 exhaust. 107/117 overlap.
I'm using the spacer that comes with the carb (500). It might be binding I'll have to check. The plugs look good all light brown, the oil pressure is 60 cold/50 hot. But it can't run - its so soft my old six cylinder could walk it,
Here is a video on how to adjust the secondary idle screw. It is for Holley but the same for Summit. I think for your application it should be completely closed. The best way is to remove the carb turn the screw until you see the secondary throttle plates are closed.
The secondary idle screw is always cracked open slightly so that fuel is used from the secondary bowl to keep it from going stale. On Autolite's it's adjusted one turn from first contact with the stop. On Holley's I've seen them state both 1/4 and 1/2 turn from first contact but the transition slot must remain covered.
You said you're using the spacer that came with the carb... do you mean the thick base gasket or is it an actual spacer?
As has been said you probably have a vac leak. However, it looks like your cam has a fairly tight LSA which would leave it with quite a bit of overlap. If so you might not get it to idle at 750 and it might want more initial timing. I would worry more about total timing (initial plus mechanical plus vac) than initial with an aftermarket camshaft. It might idle rich and fairly high. I felt pretty good that I got mine to idle at 950 hot which I arrived at with work with the vac gauge and timing light. I only have a 110 lsa which would have less overlap than yours.
Thanks for the insight - I thought the overlap wasn't too radical but you might have point. I'm going to go over the timing again and run the car without the linkage attached. I have another carb (holley 650) - runs rich but just to see if the idle will tone down as an experiment.
Yep that's going to be my first step. New manifold and carb. I used it on the old engine it was fine. Can there be a leak from the intake? I'll be a bit unhappy if that's the case. I dont think the heads were milled at all at the machine shop. I'll find out today if I get a chance
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
Vintage Mustang Forums
4M posts
89.2K members
Since 2001
A forum community dedicated to vintage Ford Mustang owners and enthusiasts. Come join the discussion about restoration, modifications, NOS parts, troubleshooting, VIN codes, and more!