[68birdfreak]

The bird went on the Mustang Chassis dyno the other day and has not been right since. The goal was to tune on it but time did not allow for it...was mostly interested making sure A/F ratio was ok after making several jet changes earlier in the year at the track. Hard to explain but I know my car well enough to know when something is up. It almost acts as if its limping or hurt. Its definately down on power feels somewhat slower to rev. Still pulls hard just not as responsive almost lazy. I did notice that it was not interested in being held at a steady rpm..not really a surge but kind of??? hard to explain...definately not right tho. Where do I start? comes at a difficult time as I have the car on Ebay...just my luck. Trying not to freak out but its been so reliable I fear the worst.

[J.C.you]

if you think you hurt the motor, pull the plugs, take a torque wrench and turn it over by hand. If you have bearing issues, you should be able to hear the flattened bearing making noise on the crank journal or there should be a big difference on torque as you turn it over.

[aaronman]

If ever in doubt, pull the valve covers and pull the oil filter and cut it open.

[68birdfreak]

JC...does it sound like bottom end the way I described it or more like a top end issue? pulling the plugs and valve covers now...to be continued...

[71firebird400]

Sounds like topend to me, but could be anything. I'd be checking for bent pushrods, also put a timing light on in and make sure everything's good there. Lastly, double check your carb linkage. Don't overlook the simple things!

What's oil pressure doin?

[68birdfreak]

Well, pulled the valve covers and 10 out of the 16 rocker arms are sloppy loose... carb linkage looked okay but needs to be tightened up...found out that when the car was put on the dyno he did adjust the idle circuit a touch...That wouldnt cause it to be bucky when you're trying to maintane a steady rpm would it? it feels almost like its down a cylinder. Oh...and I found out that one of my RAII heads has an insert for the spark plug on the passengers side closest to the firewall..came out when i pulled the plug...bummer...should be fixable tho...What next? Plugs and wires appear to be fine... Does not smoke when running or when you get on it
Thanks for all the help

[62fatcat]

it wouldn't hurt to do a compression test and a leak down test also.

[screamingchief]

I pretty much give the same answers to this question everytime I see such.

There are four mandatory things that must be known from the time the engine is "fresh",and these are also what you reference anytime there are issues of possible concern.

Timing: Base/initial setting,mechanical/centrifugal advance,total timing,and vacuum (if used).

Vacuum readings:In both neutral and in gear.

Compression test results: Both dry and wet tests.

Leakdown test results: The final word on the subject.

Those are the basic diagnostics one needs to use,and you baseline the engine while you know it's in a "healthy" state so you can tell if anything is wrong when you re-test later on.

And agree,cutting open the oil filters is SOP too,another good idea is to run a magnetic oil drain plug,and a filter mag as well,both can help track ferrous debris in the engine,but are no good for stuff like bearing materials (aluminum or copper,both are non-ferrous metals),so that's why we still cut open filters for closer inspection.

Then there are the other "basic" items one should always try to monitor:
Oil pressure:
Water temperature:
Engine oil temperatures:

But alas I digress,,,in the end,,,it might not even be the engine,,,could easily be in the driveline...

And check to make sure the E-brake was'nt left on by accident too.

[68birdfreak]

Not sure what to think...everything is checking out..time to road test tomorrow...

[Jagtec1]

Originally Posted by 68birdfreak

Well, pulled the valve covers and 10 out of the 16 rocker arms are sloppy loose... carb linkage looked okay but needs to be tightened up...found out that when the car was put on the dyno he did adjust the idle circuit a touch...That wouldnt cause it to be bucky when you're trying to maintane a steady rpm would it? it feels almost like its down a cylinder. Oh...and I found out that one of my RAII heads has an insert for the spark plug on the passengers side closest to the firewall..came out when i pulled the plug...bummer...should be fixable tho...What next? Plugs and wires appear to be fine... Does not smoke when running or when you get on it
Thanks for all the help

Flat tappet cam??

[71 Ventura II]

The last time my car felt flat and lost that powerfull feeling was when the tranmission went bad. Just brainstorming... Good Luck! JD

[68birdfreak]

Originally Posted by Jagtec1

Flat tappet cam??

Yes!....insight please!

[silver68]

10 out of 16 rocker arms loose sounds like another wasted flat tappet cam. Adjust the valves and if quickly loosen again start pulling lifters. should also cut open the oil filter. reusing old stock adjusting nuts can loosen up though. poly locks are preferred.

[Jagtec1]

Poss. wiped cam lobes based on info you provided. I'd cut the filter.

[screamingchief]

Check the spring pressures too,get yourself an on-car spring pressure tester.

That is another item that should have a baseline established when the engine is "fresh",and gets checked anytime there are any suspected issues,as well getting checked as part of the routine maintainance of an engine.

So I guess I should have said there are five mandatory things to know and monitor...



Hope it is'nt the cam going south.

Checking lobe lift is pretty easy to do with the engine still together,with the right equipement of course.

Visual inspection is another possibility too.

Good luck.

Bret P.

[68birdfreak]

Okay...feelin stupid for not goin with my gut and my first initial diagnosis... pulled distributor, plugs, checked coil, did compression test...TWICE...checked lash after pulling valve covers, pulled carb off and tore that down...turns out...power valve had a slight leak...checked it by blowing thru it with my mouth...couldnt blow thru the new ones in my kit so went and bought a new one....runs like a million bucks...thanks for all the help...was much appreciated