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Discussion Starter · #1 ·
Hello everyone I am needing a little help with a 460 that is in a 1976 Ford T bird. The engine was just rebuilt and is being used as a daily driver in the mentioned t bird. The issue is that i can't get this engine to idle smoothly to save my life. Now I do have 460's in two other cars and they idle perfect no issues. please any suggestions would be helpful.
The engine is question has had the following done to try and locate the reasons for not idling smooth.
1) checked compression. All right around 155-160
2) went over ignition system plugs ,wires, distributor, cap and rotor spark box replaced coil checked all good
3) carb installed Holley warrior brand new 650 cfm (replaced an older carter AFB) Made no difference.
4) timing set at 14 BTDC ( increasing timing would not smooth out idle)
5) checked for vacuum leaks none found
6) engine runs great right off idle at any speed plenty of power.
7) cam is a stage II trailer towing
8) 9.0:1 compression
9) 1970 timing chain set
 

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Discussion Starter · #3 ·
Engine idles @700 RPM with about 17 inches of vacuum. I assembled the upper half. The shop did the lower half including installing the timing chain. timing chain is a stock single keyway 1970 unit. They did degree the unit and he told me it was perfect. I installed the distributor Timing @ 14 BTDC (again stock type) and the unit when in without any issues.
 

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Discussion Starter · #11 ·
If you find no line related vacuum leaks remove the pcv valve and plug it.
Stuff a rag into the oil fill on the drivers side valve cover. Start engine and check for vacuum at the other valve cover.
There should be none.

Here is what we have done:
1) disconnected all vacuum lines hooked up vacuum gauge - no change same 17 inches of vacuum with needle slightly wavering
2) while lines were disconnected removed PCV from engine capped off carb and one valve cover - good news no vacuum at other valve cover engine RPM slowed a bit but continue to run rough.










Scotty J. "AKA" The "Mad Porter"
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Ported BBF iron head specialist & Aluminum heads from all sources.
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Discussion Starter · #13 ·
This problem has been consistent since the engine refresh? YES AND BEFORE AS WELL (WANT TO ADD SWAPPING CARB MADE NO DIFFERENCE)

How did the spark plugs look when you had them out for the comp check? AT 1000 MILES PLUG ELECTRODE CLEAN SLIGHT TAN/WHITISH COLOR. CENTER INSULATOR BRIGHT WHITE.

Is it possible the rockers are improperly adjusted without affecting the comp check? POSITIVE STOP NO ADJUSTMENT
 

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Discussion Starter · #15 ·
Gas is fresh 93 oct and carb is new 650 warrior series. There was a 750 carter AFB on the engine before and it acted the same way. So at this point I don't want to blame a carburetor. Thanks for the suggestion.
 

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Discussion Starter · #21 ·
Check spark plug wire resistance, coil resistance, spark quality/color-of course blue/white is better than orange, magnetic pickup resistance, if using a Duraspark module-try swapping it out for a known "good" unit, also check the resistance between the distributor cap's outside coil terminal and the inside center spring loaded "button" that touches the rotor, I've personally seen big ohm reading differences on different manufacturer caps. Hope this helps
Replaced distributor today. One that was in engine had bad side to side clearance. This seems to help a lot. Changed the entire way the engine runs. Now timing is set at 10 BTDC. We will see how it runs in the morning while warming up. That will be the big test.
 

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Discussion Starter · #24 ·
Proper curve set up is critical.

As delivered the curve is awful.






Scotty J. "AKA" The "Mad Porter"
"EMC 2006" 3rd place finisher
Ported BBF iron head specialist & Aluminum heads from all sources.
Custom ground cams
See our products in the Vendor for sale section
Customized crate engines
ParklandAutoMachine.com
R-H-P.biz
"Parkland Performance Auto Machine" Formerly RHP
(253)-988-6648
Parkland Auto Machine
Right now with vacuum advance capped off and only using centrifugal advance at 10 BTDC it's all in at 34 BTDC at 1800 RPM.
 

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Discussion Starter · #25 ·
It sounds like you’ve made some headway but did you measure for the correct length pushrods during engine assembly?
To be honest.....no. I reused the old pushrods. The engine made no noise before the rebuild. It was a very low mileage engine that was unfortunately overheated buy the original owner and had cylinder damage. That is why it was rebuilt.
 

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Discussion Starter · #34 ·
OK folks Good news! The beast is running great! This issue was a bad distributor. The shaft bushing had way to much play and was causing all kinds of issues. I did not suspect it at first because the unit is new with less than 10K . So after discovering it there were a couple of other units laying around here that I tried. The original problem went away but new ones popped up (excessive pinging and stumbling issues. So I did what i had to do. Used three different distributors to build one really decent one. Now with initial timing set @ 16 BTDC centrifugal timing all in at 3000 RPM (instead of 1800 RPM) and with the vacuum advance all in at 2500 RPM the car runs great. No pinging no trembling and no stumbling! Can burn the tires down to the rims now and runs smooth! I want to take the time now to thanks all of you for your suggestions and help! It's great to have a place to go and get help. Take care and peace, Dan the Ranchero man
 
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