new combo missing a bunch of power?
 

So after a major overhaul, our car starts and ideals and does everything well its just way down on power. and i was wondering if you guys could give some ideas on where to look. the car is 1969 amx with a 427inch amc stroker 13.1 compression .740 and .760 lift solid roller duration is 278 and 284 @ .050 108 lobe separation installed at 104.5. Hemi Adkins did the heads they flow 305 @ .700 on a stingy bench. it weighs 3264 with me in it its got 727 torque flight with a brake and a turbo action 8 inch converter that should stall at 5900 and 28 inch tires and 4.10 gears and spool. the rear suspension is all calvert stuff. i don't think the lack is in the chassis or transmission because the car is ok in the 60ft if it was down 300hp becuase it went 12.00 at 106 with 1.51 60ft lifting the wheels about 6 inches. i've thought it could be in the converter. it just does not pull like it should, the motor hasn't been dynoed but i would think it should make 600hp. when its right i wondered about valve springs but if that was the case it would hit a rpm wall right? i'm open to any and all ideas. The things i've considered that could be wrong are.

The plug wires are over 5 years old those will be changed soon.
I'm curious about our digital 6 thinking about having it tested
its 1000cfm e85 carb we have a gas dominator we intend to test in its place. the timing is locked at 38 and has been checked repeatedly. that setting might be a little soft alot of amc's like 40 but it shouldn't make 2 seconds worth of difference. the fuel system is overkill magnafuel 500 pump and regulator and -10 line holds 6.5psi with out flinching. i'm kinda at a loss any help is appreciated

Thank you
Patrick Ford

Re: new combo missing a bunch of power?
 

My only question is what is different from before.
Be real you know it's not identical from before what
have you change, so we can get a handle it and
maybe of some help you with.

Re: new combo missing a bunch of power?
 

what do the plugs look like?

Re: new combo missing a bunch of power?
 

whats different? the old motor was 9.5 to 1 stock stroke 390 with a 238@.050 hydraulic flat tappet with some iron heads that flowed about 260@.700 a torker and a 850 holley behind it was a 904 and 8inch 3800 stall converter and 4.10 gears car ran 11.50s at 115 at the time the car had all stock suspenion except caltracks and some 90/10's and almost wieghted the exact same took out a 6 point steel bar added 10 point molly cage. out side of that the car has been completely rewired and re plumbed fuel and brakes have been redone the whole front end has been gone through. its basicly a new car theres not much to compare from the old combo the heads flow 40 cfm better its got a much bigger solid roller, 3.5 points more compression and 30 cubes on the old combo but somehow it is slower. the only similarity is the 4.10 gear and 28 inch tires although we went from a bias ply to a probracket radial.

Re: new combo missing a bunch of power?
 

oh and the plugs look good for a gas motor but i'm not as schooled in reading e85 plugs i sent a few photos to the carb builder and he said they looked a little rich, but i don't think a little rich is causing this kind of power loss.

Re: new combo missing a bunch of power?
 

Having built many similar AMC engines ,I have to say , you could pour fuel thru the manifold out of a coffee can and it would run faster than that !
I would be very suspicious of the converter sprag .
That combo should run hi 9's lo10's with ease .

Re: new combo missing a bunch of power?
 

Do 2 quick diagnostic checks,Cylinder leakage test and cranking compression test.If good go directly to a well instrumented engine dyno ,That will save you many dollars in track testing and parts changing.One obsveration if static compression ratio is as stated ,cam durations are to big.Bill C.

Re: new combo missing a bunch of power?
 

305 CFMs will support over 730Hp.Were heads flowed with manifold attached?.Bill C.

Re: new combo missing a bunch of power?
 

no they were not, the intake is a modified edelbrock torker, we have a better manifold that will be going on but i don't think the the manifold is a 300hp problem will do a leak down and compression test and the converter is going back to tci which is funny because they had it and put a new hub in it about 3 weeks ago that actually might make it more suspect. its maddening to know you have a combo thats a solid 2 seconds slower than it should be without an obvious reason.

Re: new combo missing a bunch of power?
 

What's the scoop with the e85 carb ? Are you running e85 fuel ? Certainly the jetting would be way off if you were running a carb jetted for e85 , but were running race gas .

Re: new combo missing a bunch of power?
 

convertor....nothing will make a turd out of a stout combo like the wrong or damaged convertor can.

just a guess.... but what worked before is not getting it near the powerband now

Re: new combo missing a bunch of power?
 

the car runs on e85 the carb was built for this combo. not saying its perfect but hopefully better than a coffee can purring gas down the intake.

Re: new combo missing a bunch of power?
 

Re: new combo missing a bunch of power?
 

We have discussed cam timing. haven't checked it yet its on the list of things to go over this weekend.

Re: new combo missing a bunch of power?
 

Not the converter.
With NO stator ,it would run about 12.0h @ about 125 !


Put it in manual 3rd gear, and flash the converter.Not going to hurt anything at that power level.

Re: new combo missing a bunch of power?
 

At least a tooth off then.

Re: new combo missing a bunch of power?
 

I think a big cam a tooth off would cause the valves to hit the pistons.

Re: new combo missing a bunch of power?
 

Back in the early 70s I broke a B + M convertor and my Cuda lost about 3 tenths, it wouldn't stall much past idle.

Re: new combo missing a bunch of power?
 

Maybe, but this a bracket motor.
Maybe they already hit?

Re: new combo missing a bunch of power?
 

i can check stall on the transbrake right? and i can tell you it will go to 4500 easily on the brake because thats where the 2 step is but it drops a ton of rpm inbetween gears. could line pressure or trans being over full cause this type of issue? the fact that it still leaves is what makes me think the sprag is ok. i was considering raising the 2 step to 6500 and seeing where the converter stopped it. could a bad msd box cause this type of problem? the only things that aren't new are the box and plug wires. so they're pretested but 6-7 years old when everything else is relatively new.

Re: new combo missing a bunch of power?
 

You may have a converter issue, but if you only went 106 MPH you have a problem with power.

Re: new combo missing a bunch of power?
 

Yes, you can check it with the t-brake....on jackstands! You'll be auditioning for Super /Gas.
Your interval times are all within reason, as far as being correct. But still seems like it would go faster than that, if the secondaries weren't working at all.

Re: new combo missing a bunch of power?
 

Maybe a silly suggestion but in situations like this nothing is silly, maybe a couple plugs wires crossed.
And yes the reason I suggested it is because I done it recently and it cost me over a second in the 1/8 mile!

Re: new combo missing a bunch of power?
 

Check to make sure that carb linkage is opening all the way.....

Re: new combo missing a bunch of power?
 

god i could only dream its something as simple as some crossed plug wires.

Re: new combo missing a bunch of power?
 

With that cam timing you should have pumped up about 210lbs of compression. That would be where I would have started. If not then you either don't have the compression you thought you did or the cam timing is way off.........somehow.
And as you may have already guessed , if the PTV was checked it would have been checked AFTER the cam was "phased" the way you want it.....so that was check point 1 for correct cam install. If the PTV is where it should be , you would have very little "wiggle" room to move it around and definitely no room to be a "tooth" off.

Re: new combo missing a bunch of power?
 

Was this engine dyno tested? That would be the first thing done to eliminate what kind of power it makes.If engine is good then look at the rest of the car.

Re: new combo missing a bunch of power?
 

Along these lines, are you getting full throttle? Sorry if that's too obvious. Just hate to see you start pulling it all apart for nothing.

Re: new combo missing a bunch of power?
 

The msd either runs, or it don't. Just my experience. I take it you don't have a crank trigger? The pickup will lose that much if bad, and still run.

Re: new combo missing a bunch of power?
 

Old batteries ? I know at least one prominent stock Eliminator racer that freshened his motor and later found that a weak battery was the culprit.....

Re: new combo missing a bunch of power?
 

I had this happen to me with the pickup. The car slowed down and was laboring. I thought I hurt the engine. Pulled it down and did a freshen up. The engine was perfect when we took it apart. When I went to start the car after the engine was back in and it would not start. Turned out the pick up was bad on the crank trigger. Changed that out and the car started right up.

Re: new combo missing a bunch of power?
 

We had the same thing happen on our 705, motor would not run like it should it was laboring and it was a crank trigger.

Re: new combo missing a bunch of power?
 

NO crank trigger, the battery is pretty old now that i think of it um something else to try would that cause an issue even with a alternator putting out the required voltage? the Distributor is dated could the pick up in it be getting weak?

Re: new combo missing a bunch of power?
 

To save time,parts, and money I would pull the engine and put it on the dyno. You will find out real quick if its the engine or the car.

Re: new combo missing a bunch of power?
 

You have a PM

Jim Mantle

Re: new combo missing a bunch of power?
 

you have a reply.

thank you.

Re: new combo missing a bunch of power?
 

REREAD POST # 7 and #34.Go directly to an ENGINE DYNO and you will SAVE a lot of MONEY misspent on changing parts and trips to the race track.Bill C.

Re: new combo missing a bunch of power?
 

And post #27

Re: new combo missing a bunch of power?
 

Guys, I would imagine you don't walk into any dyno facility with an AMC motor, and everything hooks right up. Block, headers, etc.
Also ,this is a bracket deal, and he's already spent a bunch on it.
It may turn out that dyno-ing it would have saved him money in the long run, but maybe he prefers to spend it in smaller increments.
That's why he's here, asking questions, I would guess.

Re: new combo missing a bunch of power?
 

Mark is right at this point were going to try exchanging some parts we already have and see what it does if nothing changes. the engine will probably come back out and well find a dyno that can accommodate an amc somewhere. i still haven't rulled out the converter hopefully well get some answers this weekend. I do have access to a hub dyno but that still leaves alot of variable since the car would be part of the equation.