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Discussion Starter · #1 ·
Engine specs:

289 Standard bore. 10.1:1 compression. 93 Octane pump gas
Holley 600cfm 4160, stock jets (#66 primary).
Ford Motorsport Dual Plane High Rise Intake (same as the old COBRA intakes, I think)
Stock distributor with Petronix I, 40 kv FMS coil, FMS wires, big cap on distributor
AFR 165 cc Aluminum Heads (58 cc combustion Chambers)

Comp Xtreme Energy Cam XE262H 1300 - 5600 RPM
ADVERTISED - - - - @.050 LIFT
IN - - - - EX - - - - - - - IN - - - - EX
262 / 270 - - - - - - - 218 / 224

Lift with 1.6:1 Ratio Roller rockers is .493 intake .500 exhaust
Dual Roller timing chain set
initial Timing is 10 degrees BTDC
Stock C4 with Stock T/C. 2.79:1 8" rear

The car runs fine and is has excellent throttle response down low. However, when I wind it out above about 4800 rpm, at WOT it feels like the engine hits a wall. It doesn't stumble really. It just doesn't want to rev any more at WOT. I can ease back on the throttle and actually feel the car surge ahead. Then it will upshift and I'm back in business at WOT with lower the lower revs in the next gear. This is a consistent problem. It doesn't come and go...it always happens as I've said.

This isn't something new. It's been around since I rebuilt my engine during Project More Power a year and a half ago. It's not awful, it's just not as good as it could be, if you know what I mean.

What would you guys do to fix this?

Phil
 

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It sounds like it is running out of something. Whether it be air, fuel, or spark, something isn't as plentiful as it should be at higher rpms. Does it knock or ping at all? That would cause a huge power loss when that occurs, but you would have probably heard it long ago if it did it bad enough.

For some reason I am thinking timing advance issues with the distributor. Hopefully others more intune with your problem can be of more help. My .02
 

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I've still got mostly stock heads (Ported A code with stiffer springs) and intake, "better" cam - Crane, and its balanced and machined to perfection, but mine will very quickly wind up over 6,500 RPM without any problems (lots of low end power also). This is on pump gas with a lead substitutue additive.

Might it be a carb problem?

John Harvey
 

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Did you degree the cam when you installed it? Is it advanced, retarded or straight-up? Some of the timing chain sets will retard the timing 4 degrees if you just line up the dots without checking cam timing and I think you might have it retarded.
 

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Perhaps it is a simple as a kink in you fuel line somewhere restricting the amount of fuel.
 

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How new is the motor? If the motor is to new it will do what you are talking about. it may need to be broken in.
 

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Sounds like a great motor. I'm sure you have enough cam to breath at the higher RPMs. You did not say but what kind of exhaust are you running? I had a rusty muffler and killer my upper RPM band. After going over a railroad track too fast, my car got very load and much faster! Also, read you spark plugs after a hard run. Either too led or too rich will kill power. Also, too lean can lead to motor damage. A fun tool to install is an air/fuel ratio gauge and vacuum gauge.
 

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Since the car runs fine down low and I assume thru the transaction to WOT, I would leave the carb alone for second and look at the following after you check the timing issues mentioned by others:

Dual Plane manifolds are great for the low end, but lack up top. try putting a 1" open spacer between the carb and manifold and see if this helps the top end without significant effects to the low/mid range. If the top end is "fixed" but you lose too much down low, you can try putting small notches in the intake divided until you find the right compromise.

Are you still run that small air fitler pictures on your website. As you rev up you need air and the setup pictured may be a restriction. I run a K&N stub stack with a 3" wide K&N fitler (drop based) with the filter top.

How is you fuel flow. Again at the top end, you need more fuel and air. I had a lean condition at the top end do to fuel flow. I had to replace the 5/16" fuel hard line with a new 3/8" line and 3/8" fuel hose from cell to carb. I also upgraded the pump. Make sure your fuel fitlers flow good too.

Is you exhaust system larger than 2 1/8" and are the bends mandrel bent. If not, the exhaust could be somewhat restrictive. I run 2 1/2, but feel that something just slightly smaller might be better.

I don't know much about the Petronix system and it's effect up top. Usually at higher rev's, ignition is more important. Can you run an MSD box or similiar with it? Is the distributor in good shape (no wobbles in the shaft)?

Lastly, what rpm/speed does this occur? The nose of are cars kinda become a brick wall at speed.

Good luck, Bob.
 

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Discussion Starter · #9 ·
Additional information.

I am still using the 14" X 2" air cleaner. It would be easy enough to take a test drive and leave it in the garage. That wouldn't be ideal, but would eliminate it as a possible bottleneck. I've considered this myself, and even a possible fix of installing a 14" K&N "filter lid", or a larger drop base air cleaner. I don't have loads of hood clearance. I should probably clay it up and check how much I do have. I'm guessing 1/2" or less.

Fuel delivery is accomplished through a brand new (but stock size) hard line feeding a brand new holley mechanical fuel pump. I also just replaced the fuel sender and intank filter. I guess I don't think that's the issue. The fuel bowl feeds the engine, not the pump. There aren't any kinks of any kind in the fuel lines, in any case.

The exhaust is a set of no name long tube headers into a 2 1/2" exhaust (with H-pipe) feeding Delta 3 chamber Flowmasters before necking down into STOCK GT TIPS. Problem...Maybe. Those tips are 1.875". By the time the exhaust gets there, it should have cooled considerably and since PV=MRT...I figure I can get by with the smaller tips. Since it's all welded together, this might be hard to check. I GUESS I could loosen up the collector bolts, and make a run with open headers...but the car is so frickin loud with open headers that I don't think I'd have the guts to do it.

Ignition...something I don't completely understand...which makes me wonder if it's not at the bottom of all this. Specifically, I'm wondering if my stock vacumm advance might be the issue. But I just don't know.

Phil
 

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Sorry but what it WOT, w/Over drive? What about the kick down linkage? Does the kick down linkage work? It sound to me that it is a C4 trans. I would say you have something stuck in your valve body if it doesn't want to shift higher and is sluggish. It doesn't sound like an engine problem. Your torque falls off at that high of an RPM.
 

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Can you rev it up to 6500 in park or neutral? If so than it's your trans. You mentioned that you only notice it when you are driving and letting off of the gas to make it shift.
 

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Discussion Starter · #12 ·
Even more information.

The Cam is installed straight up. I did degree it, and it checked dead on with the cam card (106 degrees IIRC).

WOT is the common term for Wide Open Throttle.

The key point may be that the car will rev past 4800, but NOT UNTIL I let off the gas a bit (like 20% maybe). I guess that's why I'm thinking a change in vacuum may be affecting the timing and allowing it to rev on out, but I don't know.

The tranny is a C4...and it does have problems...but this ain't one of them.

Phil
 

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Take the distributor cap off and see if you can turn the rotor to the advanced position manually. If it won't budge than it's the distributor. If it does move check the vacuum going to the distributor. Where is the vacuum coming from? Is it coming from under the carb or from a sensor on the manifold? Does the car act the same when it is cold as to when it is hot?
 

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Two things,

First, I'm thinking timing is the problem. Maybe your vacuum advance is sticking, and freeing up when you let off the gas.

Second, those jets are likely WAY too big for that engine. I was running 54's in my 289, very similar setup to yours. I'm not sure of your carb specifics, and it does sound like your low end power is OK, but something to consider. Speaking of, make sure your secondaries are opening. If you are running vacuum secondaries, have you tried a lighter spring?
 

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Two things I can think of that do this.

Lack of fuel flow.
Excessive backpressure.

Put a vacuum/pressure gage on the pressure side of the fuel pump and make sure you get at least 5 psi.
Also, put the gauge on the inlet side of the fuel pump (tank side). You should see no significant vacuum or else you have an obstruction. You should also disconnect the fuel pressure side and make sure you have enough volume. About a quart in 15 sec/idle.

To check backpressure put a vacuum gauge on the intake manifold (make sure it not ported vacuum).
If you cannot get farily close to 0 at WOT you may have a restriction.
It's easier on cars with O2 sensors, but if you can plumb into the exhaust at the collectors, you should not see anything above 3-5 psi at WOT. Never more than 1 psi at idle.
Usually a vehicle with excessive backpressure sounds 'wheezy' or 'hissy' at the tail pipe.

BossBill
 

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Speaking of your secondaries... are they controlled by vacuum or not? The gasket might be blocking the vacuum port holes on the side of the carb.
 

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As you know we have similar setups, same heads, similar cams. I have sightly more lift, durations is almost
the same. I'm not sure what your problem is, I'll share my setup (from the dyno tune) timing is 16 initial, 34 total. I run headers with 2 1/2 pipes all the way out. Big K&N air filter, 650 DB, 66 font, 56 rear (from memory). My power is REALLY coming on after 4500rpms (your missing the best part). My rev limiter is set
at 6200rpms, and it hits it with authority. If you have a dyno tuning shop in your area, a strongly recomend it. I would still be goofy around with it!!
 

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There is no mention of the total advance the distributor is attaining.

I suspect your not getting to 32 - 34 degress at WOT. Check it with a timing tape and light.
 
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