Idle too high on new engine break-in

[ozconv]

Well I finally got things back together for another try. Here is the latest. Exhaust is now installed but the engine still won't idle well below about 1200 rpm. The best vacuum I can get now is about 15 at 1500 rpm and ignition timing reading about 48 degrees of total advance. The vacuum advance is disconnected and plugged. The harmonic balancer is a rebuilt unit from Mike. The cam is a 264/274 112. If the balancer is right, even with some all of the mechanical advance in at 1500 wchich it shouldn't be, the timing shouldn't be more than about 32 degrees. Has anyone ever had an issue with these rebuilt balancers?

All along I have suspected the carb so I rebuilt a 1.14 and swapped it for the 1.02 today and other than less throttle response, nothing changed. I also readjusted the valves once again before this latest try, thinking again that they might be too tight. I pulled the distributer and ran the oil pump with a drill between every valve adjustment. I stopped as soon as I felt the slightest resistance to spinning the pushrods and then only went another 1/8 of a turn.

Since swapping carbs and re-adjusting the valves made no difference, I am now suspecting ignition issues. The dizzy is an early 70s, pre ds1 with both vacuum and mechanical advance with the vacuum hook ups on both sides of the vacuum canister. The vacuum advance has been disconnected and plugged at the carb every time I have started the engine and attempted to tune it. I installed a pertronix ignitor II, pertronix ignitor II coil, and new plug wires also from pertronix. The plug gaps are set at 0.040". When installing the ignitor II one thing I noticed is that it comes with a plastic gage to set the gap between the module and the pick ups that are attached to the shaft. One of the holes in the module base plate is oval in order to allow adjustment of this distance. With the module as close as I could get it it was still maybe a little farther away than the included plastic gage.

After I shut the engine down for good today, I checked the number one spark plug and while trying to disconnect the wire, it pulled apart with the crimped connector staying on the plug and the wire coming off in my hand. The plug looked a little sooty. I guess my question is, could inconsistent ignition cause an engine to have lower vacuum and run rough at lower rpms? Would it also require way more ignition advance than should be necessary? I am starting to think that I should go back to a stock cam as I am running out of ideas.

 

[bubba22349]

I pulled the distributer and ran the oil pump with a drill between every valve adjustment. I stopped as soon as I felt the slightest resistance to spinning the pushrods and then only went another 1/8 of a turn.

Is a hyd. Cam right? Any valve train noise? When you did your valve adjust did you have each cylinder at TDC on compression? If not you may be tight on a few. Is easy to set them with it running and is the most accurate way. Engine running and warmed up, back each one off until it click's than tighten just until it stops add a 1/4 to 1 turn. Personally I set mine at zero plus a 1/4 (will help them RPM a little more) they may click for a few seconds at start up after sitting over night.

1500 RPM and 48 degrees of total advance that would be way too much with vacuum advance disconnected and plugged. Have you checked to see if TDC mark is the actual TDC of no. 1? Back that timing down 8 to 10 BTDC if the balancer mark is right than make all you adjustments to valves and carb than you can add more timing after you get it to idle

 

[rbohm]

8) you might want to pull the break plate from your distributor and check to see if the advance springs are properly installed, and that the advance weights are also properly installed. sometimes people install the weights backwards, or the springs lose tension.

 

[Frankenstang]

Taking a tip from Rich, what are you using for fuel pump and do you have a fuel pressure regulator incorporated?
What float setting did you end up with on the 1.14 carb?
More for my own edification (so kinda directing this question to anyone reading along)...while 264/274-112 is not the most agressive cam, it's still considered in that 'performance' range, when you factor in the full roller 1.6 high ratio rockers you've got; what's a reasonable smooth idle range for that setup 800-900rpm?

Does sound like something out of whack on timing, especially given the total advance you're measuring@rpm (is that with a dial back timing light?)...good idea to thoroughly examine condition of your dizzy, and the petronix have been know to have some issues with magnet locations and them staying in the proper place...just throwing some ideas out...sounds like one helluva build. Bummer to hear about the pertronix plug wire coming apart on you...have had that happen on very high end ACCEl and more recently Mallory $$ wires...took to testing new wires on a spare plug. Good luck

 

[JackFish]

I have the same cam.
In gear, with an automatic transmission it like to idle about 750-800rpm.
About 900-1000 in neutral.
It will idle lower than that, but it starts to get really thumpy. 8)

 

[ozconv]

Right now I am running a standard fuel pump without a regulator. Different carbs had no discernable effect so I am starting to look elsewhere. From what I have been researching, in order for the engine to run best and have the highest vacuum with that much advance (assuming the rebuilt balancer is right and it appeared to be when I assembled the engine and degreed the cam), it is likely that the cylinders or a cylinder is being leaned out either by a vacuum leak or that an intake and/or exhaust valve(s) are closing too late since the leaner mixture will take longer to burn.

The four upper threaded holes on the OZ 250 manifold are not in the greatest shape so I have ordered steel inserts that I plan to install. The manifold gaskets are not available so I made my own and consequently had to reuse it after having the head back off recently. The material is from a local gasket manufacturer and is about 0.070" thick and able to take the temp and gas. I did not use any sealer either time but my vacuum was slightly higher (16-17 instead of 15) during initial breakin before removing the head for a freeze plug leak. In addition to the inserts, I have ordered some Permatex No. 3 aviation sealant that is approved for use in higher temperature and with gasoline. I plan to use it between the carb adaptor and manifold as well as the manifold and head. Not sure if I should use it with the gaskets or without???

As far as the valves, I plan to do them once again. Not quite ready to do them with the engine running but it may come to that. I plan to check the thread pitch on the adjusters to see how much of a turn will equal 0.020"-0.030". Then I plan to readjust but this time one cylinder at a time, again priming the lifters with a drill inbetween each valve adjustment. I have read to adjust the intake valve on a cylinder as soon as that cylinders exhaust valve starts to open and to adjust the exhaust valve as soon as that cylinders intake valve has reached full lift and is starting to close. Does this sound right?? Since the engine won't be that warm, I'll err towards 0.020".

Right now the PCV valve is going into the manifold vacuum port rather than the carb base but has been disconnected while testing so that I can hook my vacuum gage directly to the manifold. I have a 1/2" carb spacer that I made into an adaptor while I was waiting on Mike's. I think I will modify it to accept the PCV hose and use it instead. It also has a hole for each throttle plate rather than the oval hole that Mike's adaptor has. I don't know if this makes any difference to the airflow coming out of the carb or not. Just wondering.

I plan to re-examing the dizzy noting the advice above. What it the best way to tell if each cylinder is actually getting a decent spark??

Lastly, the gas is from last year adn although I put Stabil in it, I am thinking that I will drain it and put fresh gas in just in case.

If I can get it to idle well in drive without the idle in park being more than about 800-900 rpm, I( think I can live with it. What concerns me the most is the timing needing to be advanced so far and the low vacuum. If I pull the timing back to around 12, the vacuum drops in the 5-10 range and the engine will barely run. Everything seems to point to a vacuum leak but I sprayed around the carb and manifold to head (top side only due to access) and it had no effect. One thing I thought of is that maybe the manifold has an internal crack where the coolant is supposed to circulate under the carb. I don't have the heater hose hooked into this so if there is a crack, it would let air in. I guess I could check with my air hose or fill it with water and see if any leaks out into the runners.

 

[chad]

the same cam.
In gear, with an automatic transmission it like to idle about 750-800rpm.
About 900-1000 in neutral.
It will idle lower than that, but it starts to get really thumpy

If I can get it to idle well in drive without the idle in park being more than about 800-900 rpm, I( think I can live with it. .[/quote]

:
May B U got it already? It's in the car, not on a stand? (sorry, got dial up - have not looked @ the pic). U got an auto, no?

 

[ozconv]

It has been in the car since just before Christmas but I have only run it a few times (I took the head back off because of a leaky freeze plug and had the machine shop pressure test it for cracks. It also took me a while to get the exhaust installed and fab up the x-pipe. The car is an automatic but I was under the impression that it would be ok with the 112 lobe center 264/274 hydraulic cam.

 

[bubba22349]

(assuming the rebuilt balancer is right and it appeared to be when I assembled the engine and degreed the cam)

Shine a light into no. 1 cyl. To see if the piston is at TDC or use a piece of welding rod / coat hanger into it and watch for highest point as you turn eng. it back and forth by hand. Then check your balancer mark and you will know if it’s right or not. If it isn’t than make a new mark at TDC.

 

[ozconv]

UPDATE

Finally decided to do a compression check. Lowest cylinder (no.1) was 160, highest (no.3) was 180. All the others were around 165 -168. The car was hard to start and was backfiring through the carb so I decided to go back and adjust the cam timing. Went from +2 on the crank sprocket to 0 (retarded the timing 2 degrees). This is where I originally got an intake centerline of 108 when degreeing the cam during the build. If the cam is a 264/274 112 as marked it should be advanced +4 at this setting. My thinking was that I had it advanced +6 and the backfiring was due to the intake valve opening too early.

After this I did another compression check. My expectation was that the compression would go down since the intake valve would be closing later but the numbers actually went up. No.1 was 170. No.3 was 195 and the others were 172-178. When CCing the chambers during the build, they ranged between 50-51.5 CCs. I don't think this should be enough to explain a 20-25 psi difference. The engine is a 200 bored +0.030" with 6.5 CC dished pistons and the corteco +0.050" head gasket. Block was 0 decked. I calculated a SCR of approximately 9.3:1 and a DCR of around 7.7:1. Does this seem right?

After all this the engine wouldn't start. I put in another set of new plugs (gapped 0.045") and went back to points. It turned out that I must have fried the coil while doing the compression check. As soon as I swapped back to my old coil, the engine started right up (no backfiring through the carb). The engine ran at +12 deg ignition advance but the vacuum is only about 10". The max I can get the vacuum to is 14-15" and that is at 1500 rpm and about +20 deg of initial ignition advance. I disconnected the PCV at the carb spacer and that seemed to help initially until the engine warmed up. Once the engine warmed up, it seemed to need more initial advance to run smooth and maintain vacuum.

If I didn't know anything about the engine mods, I would be thinking late valve timing or too much lifter preload, but retarding(not advancing) the cam seemed to help and I have adjusted the lifters multiple times. Concerning the lifters, adjusted them one cylinder at a time (intake as exhaust begins to open, and exhaust as intake reaches full lift and begins to close). I primed the the oil pump inbetween each adjustment and only went an eighth turn past 0 lash. Since the lifter was pressurized with oil, this caused the valve to open slightly, however, I would think that the lifter should bleed down after a few rotations of the cam and would work itself out. Is this correct, or should I not pressurize the lifter before adjusting?

 

[JackFish]

I have the same cam installed straight up, and you're doing very well with the vacuum readings.
If anyone is getting any better I'd like to know. My numbers are a little lower but I still have some tuning and mods to do. My timing is at 8 or 10 degrees, can't remember which.
My idle is high, 1100rpm or so, especially after the engine has been run for a while, but it chugs at about 750rpm in gear with the foot on the brake. Stock converter.

Seems to want to settle in around 1000rpm for an idle speed.

 

[MPGmustang]

both of yours are very close to mine, I'm running the 264/274 but at 110*, I too have 15-16 max vac but 12 at idle.
with my LOM and Pertronix I had it settled @ 9* timing, idle was very easy to adjust and set,
I've found that it likes to be rich at idle and possible my bigger jet helped too, I can usually get a lower rpm this way.
with the DUI it likes 900rpm and kicks it down to 600~450 with a very distinct lope
keep going, it's all fine tunning from here