HI Guys,
Some time since I visited the site. I recently installed a set of aussie cleveland heads on my 1978 F250 400 motor. I have some bugs that are driving me nuts and I cannot work out as of yet. I can tell you this that I was blown away by the difference in throttle response and midrange power.(dead stop and stomp on it the rearend is letting loose)I got my heads from Power heads in stockton California. They were put together very well and there communication with me has been excellent. Although they are at a loss as to my problem. All research indicated that I had a measly 8 to 1 compression and that these heads woulds take me to somewhere in the neighborhood of about 9.4 to 1. And I could live with that on pump gas and as a daily driver. Although it is usually a weekend driver and hauls a camper and motorcycles on any given weekend. The fact that it would not haul my camper over our local Mt.Hood prompted me to search for a good performance change and a blown head gasket prompted the move.I installed a edelbrock performer manifold and a 600 cfm carb #1400 which was emmissions legal. The first problem is that I have a chatter in the rockers. Everything I have read or been told is that there is no change to the push rod length. These are non adjustable rockers and they are taken up all the way as should be from 0 lash. I have read several items in rebuild books that Ford offered a .60 thousands + or - for variations in milled heads or valve stems. I have went on this assumption and odered the .60 oversize push rods. The thought here is that maybe the previous owner milled the heads and shortened the push rods to compensate. I hope I am in the right direction on this.

The second problem is that at low to midrange loading on the motor I am pinging. My base timing is 12 degree's BTC and I thought not a problem. Started working it back by driving it and changing it. It is all the way down to 4 degree's BTC and the ping is there slightly with a slight increase in temperature. It is not right as it should be. I next proceeded to a octane booster and more octane booster to calm down the pinging. Nothing has changed. The pinging is slight through the midrange to knocking at 3/4 throttle then going away at higher throttle.

Through inquiry I have found that many think I am to lean in the fuel delivery. I contacted Edelbrock techs They told me I am not allowed any setting changes with this emmisions carb. After I begged and pleaded and assured him I was not in a DEQ zone he gave me a suggestion for changing my metering rods and springs and also is sending a performer carb hand book for fine tuning. He suggested using the # 1406 for reference. I made the changes he suggested and all to no avail. The change was definetly for a richer power and cruise mode. But nonetheless it still has a ping and the temperature is warmer (10 degree's above normal)

The questions I am seeking are; Is it possible that the chatter in my rockers indicates my valves are not opening all the way? That might explain the pinging (lack of fuel) and it could explain the temperature rise (not completely exhausting) And if not the case could my carb be to lean still? It is a emissions carb. Could this be rectified by continually upsizing my main jet and metering rods to get to a mixture that is right.Scary thought would be that this carb wont let me get the needed fuel volume to stop that pinging. Anyway your expertese is surely needed at this point

Thanks very much Patricka

 

I don't have any experience with those heads but,
You can get the push rods shorter or longer from Ford. You can also get shims from Crane to effectively make the push rod shorter. You need to find out which way to go. With a cylinder at top dead center (both valves closed) you can loosen a rocker and then tighten it slowly while turning a push rod with your fingers. When you feel all the slack is gone you should turn it about 3/4 turn (approx.)more before it gets tight. If you get less the push rod is too long, more it's too short. This is a way of checking the preload on the lifter.
As for the carb, richer is better for preignition. It should not run hotter when you make it richer. I suspect that carb is set up quite lean and would consider a Holley 750cfm.
Have you checked your static compression? It would be a good clue to your compression ratio. What cam?

Good Luck!

 

The part throttle spark knock could be your vacuum advance setting. If it's adjustable try backing it out a turn at a time until it stop knocking.
Clint

 

Check overall advance on the distributor. You ought to have somewhere in the neighborhood of 11* of mechanical and 11* of vacuum. On a small block anyway, seems to me the book says do not go over 28* total advance. I have seen the mechanical part get loose and end up with about 50* total advance.

 

"Torge1st" has some good comments on this particular page, about timing. Gear timing set retarded from ford, not spark timing. Sorry I don't know how to make this page a dirrect reference.
[https://www.ford-trucks.com/dcforum/DCForumID91/10956.html]

 

hi guy,

Thanks for your input. The carb is brand new and I do not want to go to another new. I feel that if it is in the carb I should be able to tune it right in with enough trial and error. I was hoping someone good with edelbrock would join in. As far as the shims we tried that first thing seems like the .30 which was smallest in the assortment make it worse. Taking them out eased up on the clanking. The camshaft is not known for sure. I know that it has a rv cam in it and it has a very slight lope when idling nothing radical. It has the stock dish pan pistons. I am sure it is somewhere close just need to find it.

Patricka

 

I am not sure what my advance is but I recall my mechanic getting about 32 degree's total. The distributor is a brand new ford part some two months ago so I do not feel the distributor is worn. But the advance could be worth looking at. I am not even sure that it is adjustable.

 

Try installing the orange springs and the metering rods with the smallest number in the tuning kit. It fixed my 750 on my 460.

 

have you tried switching it to manifold vacuum instead of ported? or swapping which vacuum port feeds the distributor, smaller chambers but no change in deck clearance wont help either though

 

If the heads were milled at all, wouldn't you need shorter pushrods, not longer? I would go with the .060 shorter Ford service rods. When valves wear into the seats, or if valve machining involved 'sinking' the seats some, that would also require shorter pushrods. Otherwise, the valves will no longer close all the way.
Just a suggestion!
Mark



https://www.ford-trucks.com/user_gallery/displaythumbnail.php?&photoid=5362&.jpg
Ford started it; Ford will finish it!

 

Mark,
Your thoughts are well taken.The new aussie heads are not milled confirmed with Power heads. But the thought here is that the old heads were milled to bring up compression and now that I have installed the new heads (unmilled) that the push rods would now be short. That is the thought anyway and I am hoping that the Longer push rods are going to solve the problem and in turn stop the pinging with a little carb tuning and definetly verifying the advance on the distibutor.

Patrick

 

[updated:LAST EDITED ON 04-Oct-02 AT 12:44 PM (EST)]You should be able to run 38degrees total timeing (without any vacuum involved) unless you have real high compression. i actually run 18 initial, 20 centrifugal and 6 vacuum with 170 pounds static compression But I do have custom dished pistons. Probably 10:1

Don't try this at home folks unless you know what you are doing. Heh, heh.

 

[updated:LAST EDITED ON 04-Oct-02 AT 05:20 PM (EST)]Bear Tracks,
Thanks for your input. I am totally out of the loop when it comes to the total timing, coupled with mechanical/centrifigal and vaccum advancing. I need to get educated for sure and intend to do so in short order. Is there any good reference material that you know of that gives a good education in the distributor curves and advances and the formulas that apply? I would really appreciate the information.I would like to understand static compression a whole lot better as well.I am told that I should be at 9.4 or 5 to 1 for compression although I have not verified for a fact.

Thank you Patrick

 

Here's a good article on timing.

http://www.fordmuscle.com/archives/2000/03/timing/index.shtml

Clint