New combo missing lots of hp

[fdicrasto]

Well that eliminates the idea of not enough timing assuming marks are accurate.

[mag2555]

How much bigger are they?
If your old combo was on the edge of having too high a port velocity somewhere in the whole Intake flow system then gaining 50 cfm and let's say that's a 25% flow gain , but only a 15% gain in Manifold area was had, then your air speed is 10% higher now on the new combo then the old one and that could be the perverbal straw!

[AMXstocker1]

i'm leaning toward ignition or trans/converter issue i called turbo action earlier and they want us to check a few things and if its still bad they will take a look at the converter and see if they got something wrong.

[Ken_Parkman]

106, 28", and 4.10 calculates to 5200 rpm, so 6000 rpm is 15% slippage, pretty bad. I once broke a converter stator and the stall dropped big time, but the car was a dog on the line, so that does not match your symptoms. If the converter was eating power big time - and some do - to the tune that yours should be with that engine combo it would burn the fluid in short order. Is the fluid still red? The above mentioned converter failure took me a few blasts in the yard to figure out, and at that point the fluid was burned so bad the dye settled out. And STINK!!!! Tranny was wrecked.

If it is the engine something is deeply wrong. That is half the hp you should have, so something is broken or not right. This is not a combo problem. Check all of the above, leak the engine, check the valvetrain, pull the oil filter and cut it open, check everything you can think of and then some. It is possible to check the cam degree in an assembled AMC, but a pain.

[jarmoyp]

I set out with Epoxy in hand and made the runner taper smaller and even picked up 40 cfm in air flow in the process , and I slapped myself on the back for a job well done, well two days latter the bad news came when this guy's car slowed down by a full 3 tenths, and this was on a better weather and track day then the last time the Car was run!

Long story short I knocked the Epoxy out and then due to the other motor work done the car picked up.

LESSON WELL LEARNED on my part!

Schyss, dont let your competitors know that, let they use epoxy to pick up cfm.
I have too seen this fenomy many times.

[amc fan]

Are you running an alternator? What is you voltage? Low voltage=fuel pump and ignition problems. It is looking like a bad converter if all other things like ignition,polarity of coil etc. are up to par.

[GARY C]

i'll admit we don't have data and i missed what it flashed too off the brake i guess i could stick it on the trans brake with out the two step and see what it does. the pistons are 0 deck flat tops with 52cc combustion chambers and a .040 head gasket the valve reliefs are about 10ccs and its 4.205 bore by 3.85 stroke

Did you raise the chip in your two step for your leave rpm to compensate for the bigger cam rpm? I think your going to need a 5.13 gear to get the engine in the rpm range it's built for.

[AMXstocker1]

Yes 4500 rpm on the 2 step works well. the car ran the 60ft just fine its the other end i'm concerned about.

[AMXstocker1]

it has a 100 amp alternator 14 volts going down the track.

[Casper393W]

I have a been there and done this....its the converter! I would also freshen the trans because it prolly has a ton of metal in the fluid

[John Wallace]

Did the car sit awhile waiting for the engine?

I'd check that the vent line or fuel tank vent is clear.

[AMXstocker1]

John yes the car has set for roughly a year with the fuel system installed if not a bit longer. so the vent tube/line will be checked and blown out this weekend.

Thanks For the input.

[Newold1]

Hate to say this again as some of us keep harping on this a bit but it does not seem to sink in very well with a few here. Here is a case where you don't know what your power is and this is not a good way to prove it?

If you're going to put this much effort, money and time into a race car engine and drive train, then budget a little more and break in and pull the engine on a dyno and work out any issues there that come up as much as possible and then put the engine in the car and do the rest of the running dial in there. If this had been done in this case you would pretty much know now if the converter or other fueling or tuning issue is there before the guessing games start. Dyno, Dyno, Dyno! Use a program before the build, use that to set a target horsepower, build the engine and then dyno to know what the real power is and then match up converters, gear ratios ,tire size, car weight ,suspension and dial the car in for the realistic target ET and MPH! JMO

[AMXstocker1]

I've already thought of ripping the motor out and taking it to a dyno,finding a dyno that has the stuff to hook up an amc isn't as easy as you would think.

[cpmotors]

I've already thought of ripping the motor out and taking it to a dyno,finding a dyno that has the stuff to hook up an amc isn't as easy as you would think.

The exact reasons to dyno an engine of this caliber. Had this happen with a 434 SBC about 7 years ago, customer skipped dyno and stuck engine in car and went to the track. Car ran 11.00 120-121 mph, and he tried shift points of 7200-6800 based off of what the cam he bought was suppose to turn. Pulled engine out following winter and found out it peaked at 6200! Cam change, oil pan, coonverter change and suspension work its gone 10.49 @ 129.
Adding your location may help others point your toward a dyno that is AMC compatible if thats an issue.