427 down on power

[FatBoy]

I have a 750cfm Holley on my 427, which was built by Southern Automotive and something isn't quite right with the engine. Although everything appears OK and it sounds fine, it just doesn't have the "go" that it should have and it's reluctant to rev.
I've checked the plugs and they are very clean and pale, maybe a little too pale. Fuel pressure is fine.
How do I know if the secondaries on my Holley are working OK?
I've removed the choke assemby and I'm running a K&N filter.
Any ideas ?

BTW, it has only run for a couple of very gentle hours.

Paul

[blykins]

Can you clarify your statement about not wanting to rev? Will it not pull past a certain point?

Is your carb mechanical or vacuum secondaries?

[Ron61]

Also is the Holly a double pumper or not. If it has mechanical secondaries you can check to see if they open with the engine not running. Just pull the throttle back and watch to see if they open when it gets to the point the cam is set at. If it is a double pumper you will see gas squirt in the secondary end as well as the primary. And do you have the specs that tell what RPM the engine should make peak power and torque?

Ron

[FatBoy]

I'm sorry, I should have said, the secondaries are vacuum.

[patrickt]

Originally Posted by FatBoy

I'm sorry, I should have said, the secondaries are vacuum.

Do what I suggested. Wire the secondaries with a little string, wire, or twine so they won't open (just as if you had a very heavy spring controlling them so they never opened) and take it for a ride; get on the throttle hard, and see if it behaves exactly the same as before. If so, your secondaries are not opening.

[patrickt]

Originally Posted by FatBoy

How do I know if the secondaries on my Holley are working OK?

A very simple method is to disconnect/fasten-shut the secondaries and then take the car for a quick hard ride. If you don't notice a big difference, then you've found the problem. Has your car ever run better than it is running now, meaning is the lackluster performance a recent event? EDIT, oh I see it's only run for a couple of hours. You might want to give it a little more break in time before you get too involved.

[strictlypersonl]

Check the timing. If is retarded or erratic, pull the distributor and check whether you're losing the distributor drive gear.

[My427stang]

Try to take it very scientifically, at first especially

- Verify with someone else on the throttle (not running) that the throttle is opening all the way
- Check the initial and total timing to ensure it is where you want it, and that it is advancing
- Review the firing order and make sure you have it correct
- Readjust the valves if you have solids
- Check how close the air cleaner lid is to the top of the carb

Dont ever discount bringing a good mechanic in for his ear as a backup plan, even if you only pay him to listen. Often it can go a long way

[Excaliber]

Cam shaft is retarded, like strictlypersonal alluded to...

[Bobcat]

Another suggestion to check if your secondaries are opening is a trick I learned years ago when racing . Take a piece of vacuum line slightly smaller in diameter than the secondary vacuum shaft ... about 1/8 " long and split it lengthwise and then put it on the shaft up as far up as it will go . Drive the car wide open and then look at the tubing . This will tell you not only if the secondaries are opening , but how far . Think of this as a travel indicator like is on a shock .
I also like all the other suggestions .... something like this can drive you crazy ... or in my case , crazier !!

[4pipes]

Originally Posted by Bobcat

Another suggestion to check if your secondaries are opening is a trick I learned years ago when racing . Take a piece of vacuum line slightly smaller in diameter than the secondary vacuum shaft ... about 1/8 " long and split it lengthwise and then put it on the shaft up as far up as it will go . Drive the car wide open and then look at the tubing . This will tell you not only if the secondaries are opening , but how far . Think of this as a travel indicator like is on a shock .
I also like all the other suggestions .... something like this can drive you crazy ... or in my case , crazier !!

A paper clip can be used the same way.

[patrickt]

Originally Posted by 4pipes

A paper clip can be used the same way.

Before:


After (if your secondaries are opening, that is...)

[Johan]

Why not call Southern Automotive and ask them ? Did they build the carb ? What compression ratio ? Sounds more like a timing issue to me. What grade of gasoline are you running in it ?

[767Jockey]

If you want to try the disconnect the secondaries method, it's only a "c" clip that holds the vacuum linkage to the secondary shaft. Just pop it off.

[patrickt]

FB -- How much throttle pedal travel do you have from when your foot is just touching the pedal to when you have it pushed all the way to the floor (in inches)?

[jhv48]

I bet it's a timing issue.

Check your initial setting first.

Then check to see if you are getting full advance at WOT.

[FatBoy]

Originally Posted by jhv48

I bet it's a timing issue.

Check your initial setting first.

Then check to see if you are getting full advance at WOT.

I've checked the timing and the advance and both are as they should be.
Resetting the float levels hasn't fixed it either.
I'm running out of things to check. I've just changed the spring in the vacuum secondaries for a lighter one, but I don't really expect that to make big difference.

Paul

[Ron61]

Paul,

Does the engine pull well up to 3,000 and then just flatten out and start to miss, or is it sluggish getting up to 3,000 under load? Also when you are just running it under no load. does it act the same way? That # 3 plug really looks as if it isn't firing at all and if they just ran the engine to break in the cam and not under any load, then it must have came from them the way it is unless you have added or changed something. I believe in an earlier post someone asked you if you had checked the valve springs as some engine builders use a light set to do the break in run with and then put the heavy ones in for the dyno and testing.

Ron

[Naumoff]

Originally Posted by Johan

Why not call Southern Automotive and ask them ? Did they build the carb ? What compression ratio ? Sounds more like a timing issue to me. What grade of gasoline are you running in it ?

Fatboy,

Have you done this yet? Please do so if you haven't. They will be very helpful.

I would check through everything twice. Did you get an owner's manual with the engine?
Have you checked the power timing? Should be 36-38

have you check the fuel filter?

[FatBoy]

Hi,

I pulled the carb this morning and took the float bowls off. Everythinbg was very clean as you'd expect from a brand new carb with no signs of debris. I checked the diaphram for the vacuum secondaries, which again, was fine.
I've checked the distributor cap and that is OK with no signs of burning.
The advance is mechanical and that is nice and free with no sign of binding.
I have good fuel pressure (around 7psi) at the carb. I'm running a Holley electrical pump with a Carter mechanical pump, as recommended by KMS.
The MSD has a 6,000rpm limiter fitted.
The plug wires are Accel Hi-Temp Super Stock Spiral Wound with separators fitted.
I'm still inclined to think it is fuel starvation, but I don't know where the restriction is.
Here is a picture of the plugs. There is a pretty wide variation of colours with 5,7 & 8 looking almost unused and 3 looking pretty sooty.



Thanks again for your input, it is appreciated.

One more point, I have a manul on rebuilding Big Block Fords and it recommends separating plug leads 7 & 8 to prevent induced firing. Do I need to take this into account with the plugs leads I have? The leads have been run adjacent to each other as suppled by SA, but they are in clips and don't actually touch.

Paul