Looking for some help in trouble shooting

[carolina440racer]

I have a friend with a 68 road-runner. This car used to run in the 7's in an 1/8th, but is running very poorly. Here is what I know.
Engine specs - Carb=750 Dominator, cam=Mopar.557 lift, pistons 30 over Ross 12:1, MSD ignition and Distributor with light springs. 5.13 gear in a Dana 60 with big tires, coil overs. 2 inch headers, automatic trans. This motor just will not wind up well. It seems to be bogging down at full throttle. It is currently jetted at 88, 89. I think the timing is between 36-38. New plugs gapped to .45 and new wires. Fuel pressure set to 8 lbs. Two things are clues here for me.
#1 When we went to the staging lanes the distributor and intake, both aluminum, were hotter than the headers 20 minutes after the car was running.
#2 The car does not want to start. The starter turns over very easily, but it has to crank and crank before it fires. Once it fires, it seems to run ok.

The car does not bogg on the line, (it was, but we jetted it up, and that seems to have helped that).

Any ideas?

[amxauto-x]

Broken weak valve springs?

[dwc43]

I agree. I watched the lap times fall off on a dirt car lap after lap and the valve springs had went south. Idled decent but no power at all.

[Slant Cecil]

May first thought was weak valve springs, if it is laying down in the upper RPMs. The Mopar cams seem to be easy on springs so there may be another problem. The hard start may say something. Have you done a plug reading? It may be over rich. You jetted it up to get rid of a bog, the usual thing to do is increase the accelerator pump shot, this will give more fuel off the line while allowing correct mixture down track. Most 1050 Dominator set ups use 88-94 jets, you may be too rich. If 750 and 1050 Dominators use the same size jets, then the difference is made up with the power valve channel restricions. Jet for best MPH and adjust the pump shot to eliminate bog. Hard start may also be from too much fuel pressure, 8 lbs is pushing it if there is a large orifice needle and seat. Are you shutting off fuel pump a few seconds before shutting motor down and turning it on after motor is fired? Try that and/or back pressure down 1 lb. Another thing is double check timing. Make sure timing mark hasn't moved and giving a bad reading. Keep looking, sometimes gremlins are hard to find.

Cecil

[nhdriver]

Check the timing. ( the dist. might have accidentally been moved) (turned)

[451Mopar]

Double check the spark plug wires and make sure the #5 and #7 are correct as it is easy to accidently switch those two wires.

[holshotbb]

Go back too the MSD and try the stock dodge electronic.Weve had a rash of bad boxes latley show up.Poor electrical connections that are not soldered will also show up as a fading away in performance,grounds must be proper ,clean,and a new 10 gauge wire from alternator to battery in all old mopars will aid the electrical cercuit.Get a volt meter and test battery,alternator and delivery voltage to MSD.

[cuda66273]

1st thing I would do is check fuel volume....12 second car requires 1 gal jug to be filled in 30 seconds.

Pressure is only a measurement of restriction, you probably have a pump going bad and you keep cranking down on the regulator to increase pressure and your really just decreasing the flow and running out of gas at the top end.

look at #5 and 7 plugs they'll tell you allot.

[carolina440racer]

Thanks folks. You have given me a lot to look at. I will keep you updated.