if i remember correctly, the pre 71 sets have 3 notches for the crankgear, +4, 0, -4.......0 being straight up......... the timinggear i installed (by mistake) is for a 78 460 (factory retarded) and would only go on one way....hope that helps....im sure someone will correct me if im wrong....

 

You are going to have to drill holes in the throttle plates and check the idle transfer slot relationship to the throttle blade. tIMED PORT VACUUM SHOULD BE 0. Never been much on the secondary opening adjustment method it sometimes starts the secondary "idle" circut up to soon sucks more gas too.

 

turbo2256d-

You have really got me scratching my head. I can't understand why there would be a need to drill the throttle plate. I understand that there is a transfer slot, and I think that it helps the carb come off of the idle circuit. I also think that the transfer slot is very close to the throttle plates when at idle. When the throttle plate is closed the transfer slot doesn't see vacuum. As the plates open, the transfer slot sees more vacuum and begins to flow. I understand that if the throttle plates are too far off the closed position, they expose the transfer slot to vacuum. Drilling the holes would make less vacuum and prevent the transfer slot from seeing as much vacuum.
Could it be that an idle air bleed is plugged or undersized?
I'm not calling you out but I really want to understand why this will help the problem. There's a lot in this world that I haven't seen, and drilling throttle plates is one of them.
I agree with you that timed ( port ) vacuum should be at zero at idle.
I also believe that manifold vacuum is too low for a cam of this size.
To make more vacuum I would think that you would want to close the plates, but drilling them would have the effect of opening the plates, with the exception of the transfer slot relationship to the plates.
I don't understand why this motor won't run on the idle circuit as Holley intended.
If my assumptions are wrong please tell me. I'm trying to learn something here and help a fellow FTE member.

 

First some Holleys have these holes from the factory. It is a fix usually needed with hot cams. If you look at a Holley out of the box from underneath the Curb Idle Hole is exposed and about 1/4 of the Idle Transfer Slot. This should be measured before installing the carb. It is were the blade needs to be in relation to the idle curcuit for proper idle curcuit operation determined by Holley engineering. If after istalling and start up the idle speed needs increased by turning in the Idle Speed Screw so that 1/3 or more of the slot is uncovered or far enough that it uncovers the Timed Spark Port, adjustments need to be made. Small adjustments can be made turning in the secondary stop screw. Larger adjustments can be made by drilling a hole in each of the primary throttle plates near the opening edge. Usally 1/8 of an inch diameter to start. Since air is being added the Idle Speed Screw can be backed out and more of the slot can be covered up. Ideal would be back to the factory set position. If you go to far it can be filled in with solder or JB Weld is what I use most often and redrilled to a smaller size.

Sometimes the opposite happens usually if the carbs to big. and the Idle Speed Screw is backed out covering too much of the Idle Transfer Slot and Curb Idle Bleed. Then the throttle plate must be champhered beveled at the edge over the slot to expose more of the Idle Transfer Slot. Please get the book I dont like texting all this carple tunnel is making my arms go numb.

 

If your speaking double roller. Dont rember the breaking point of new and old. Both sets have three positions. The old set 0 and plus or minus 4*. The smog newer engine double rollers have 7* retard with plus or minus 4*. The guy that orignaaly set up my 86 had the 7* retard sprocket set to 4* advance. Good move but puzzled me as to why he bought the retarded sprocket set. I put the 0 set in over the winter.

 

also if the carb is too small the holes in the throttle plates might need to be drilled. Hot cams are usally the issue. Other things like idle air bleeds and or Idle Feed restrictions need modified. Not for the novice.

 

Thanks for taking the time to reply. I do have the book but a friend of mine currently has it. Belive me it's killing me not to have it for a reference right now. That all seems to make sense now. I was not taking into consideration that this is a special procedure for big cams. I probably had the same problem on my 429, but since everything was mechanical I never knew it. Yet another thing I learned today.

 

The Holley book does mention two different options, the first being to adjust the secondary stop 1/4 of a turn in, the second is the drilling of an 1/16 or 1/8 hole in the primary butterflies. I know we have talked about a lot here but could the fact that I cant get my initial timing below 18 added to the low manifold vacuum be the result of incorrect valve timing?

 

yes i could...if the valves arent opening at the right time the pistons wont be pulling all the air in that they can, and the vacuum would suffer...and not being able to get the timing below 18 is definitely because the timing chain is off, or at least i cant think of any other reason why it would be like that, even if the advances where both stuck you would still be able to turn the dizzy back far enough to get a lower number than that....

 

Thanks, that will be my next test.

 

Ok it's just me but I would do the check on the valve timing before doing a bunch of mods to your carb. You can alwas do it latter if needed.
Good luck
Bill

 

What would cause low manifold vacuum with regard to cam timing- cam too advanced or too retarded? I would guess retarded would give less time to draw in the fuel/air mixture on the intake stroke. That would make less manifold vacuum. That's just a guess though.. Your thoughts?
Also it might pay to take the time to check the basics, such as timing pointer installed correctly, balancer has not twisted or missing a key, etc..
I don't doubt that these carb mods could have an affect, but if it was me I would save those things for last. Can you borrow a carb for test purposes and see if it fixes the problem?
I just keep going over my motor and although my setup is different, it is similar and the biggest tuning issue I had was selecting the right jets and advance springs. What do you guys think the limit is on a cam where you need to switch from vacuum advance and secondaries to mechanical advance and secondaries? Or do you ever need to?
Learning alot here, hope others are too...

 

Hey guys, I pulled the timing cover off tonight. The lower sprocket has three markings. Facing the front of the engine the mark on the left is a triangle, the mark on the top is a small o, the mark on the right is a rectangle. Can anyone help me out with this? The small o on the top is ligned up with the circular indention in the top gear. Does this mean my timing is retarded or advanced? The top gear has a 3 in the face along with a GL and a number 1142B. The bottom gear has the markings 11-02 143B if this means anything. Please let me know as soon as you can in case I need to get parts tomorrow. Thanks again. I am also learning a lot. Thanks for the patience.

 

It looks like you are at top center on the cam timing or 0, the triangle to the left would be the retard and the rectangle to the right would be the advanced settings. The 11-02 on the bottom gear probably means that the set was manufactured in Nov of 2002. The 1142B probably is the model number of the chain set or the hardness. So far I haven't found the manufacturer, so I don't know what the advance or retard degrees are but they are commonly 4 degrees. This should give you enough info to get started, good luck, Gary

 

Thanks, I just got back from picking up a new Ford Motorsports timing chain set. It gives me the option of advance or retard in 2 degree increments. I was going to install at 0 degrees. Any suggestions?