OK. I give up!!! Need help I decided to do a cam swap/roller conversion on the Mav a month ago and am experiencing some interesting issues. After putting it back together and getting the firing order corrected, I now have issues getting the motor to idle or even to maintain any consistent RPM level. I have to keep hitting the gas to keep it running and even then it eventually dies. Even holding the throttle in will not keep it going. I have to pump the throttle to make it stay running. Also there is an odd whirring noise coming from the motor. It sounds like it has an 8-71 blower on it. (it does'nt btw) What could the problem be? It ran just fine before I tore it down. Items changed are: Comp 270H cam swapped for FMS X303 351W heads swapped for AFR 185 Flat tappet lifter swapped for FMS retro-fit roller lifters Scorpion 1.6 rockers Others items: Flat top pistons with valve reliefs 670 Holley carb stock fuel pump T-5 tranny running alt. and water pump only Things I have checked already: starter is disengaging properly clutch cable is connected back already removed belts to ensure accessories were not making the noise replaced carb gasket adjusted idle mixture screws checked new plugs they are black from running rich. had not changed anything from previous setup which ran rich but still ran. Thanks. Any help would be appreciated. I really want to make it to the Mini-meets in the coming weeks.
Cam change usually equates to power valve change, that may be the reason you have no idle. Different vacuum. If I remember right. The whirring noise,, I dont know. Dan
Well, you gained lift, but duration change was nil. You should have more vacuum now, I doubt the powervalve is a problem. Other than lightening your wallet, you really didn't gain much in cam specs other than reduced friction. I'd also look for vacuum leaks first. Check the float levels too, might be too high or have stuck floats. What did you set the initial timing at? Set timing, then idle speed, then adjust mixture screws and floats.
Oh,,,an afterthought! Make sure pistons are installed correctly,, or may be banging valves. Bummer of a deal,,,looking on the good side,,,it'll never happe3n again! Good luck ps,,just had to edit Cam gear, fuel pump eccentric, oil slinger rubbing? Assuming you did install push rod guides. Does seem to have vacuum leak. Does the new carb have all the ports plugged or used? Good luck
I did the same thing...I forgot to plug one of the vacuum lines on the carb...simple fix for me. Hope it is something simple like that for you... By the way, it took me 3 days and removing the intake a second time before I found this...
Ditto the vacuum leak theory.Time to get the squirt bottle of water out and start fishing for leaks.Good luck.
And of course the roller cam has a different firing order than the old cam, 13726548 vs. the old cam's 15426378. And you used to proper distributor drive gear for the roller?
Firing order is a good place to look. Carb float is also a good place to look. Vac leak is likely. Do the afr heads use a different push rod length? Do the new rockers or the new lifters use a different push rod length? Whirring could be cam/dist gears clashing or cam thrust forcing the timing chain against the timing cover.
Alright. Here is what I've got. Firing order is correct. I had it wrong to begin with but quickly found that it needed to be changed. This got the car to where it is now. Checked for vacuum leaks using carb cleaner the best I could. I had to shoot it down the carb to keep it running so hard to tell if I did find a leaking area. Squirt bottle of water method??? Checked thermactor ports on back of heads. they are plugged. Carb is not new. Same carb as previous setup with same settings. All ports are plugged or used. Should have same power valve as shipped and should prob be sufficient. Not sure about what noises are normal anymore. I never paid attention to them so now I am hearing soo many things and I dont know what is normal and what isnt. Perhaps the whirring noise is normal and I usually just dont hear it because I have a fan hooked up. No fan now so I can hear the noise. I am trying to listen for the sound by turning the crank manually. I hear nothing coming from the timing cover area but a creaking from the area of the balancer. Perhaps balancer runbbing against the new crank seal. Got correct length pushrods with heads, lifters, and cam as a group. I checked them by looking at the pattern the rockers left on the valve stem. Cam and dist gear, per the FMS tech line as well as Jegs tech line did not need to be changed. I pulled all the plugs while searching for the source of the sound and below are pictures of what I see. I have not cleaned them since correcting the firing order so that may be part of the reason for discoloration. Plugs 4 and 5 appear to be very lightly colored. Almost clean. Plugs 3, 6, and 8 have lots of black on them. Plugs 1, 7, and 2 are somewhere in-between.
Ok. When you adjusted the lifter pre-load did you over adjust them?? The wet plug either isnt working at all or its getting washed with fuel.The others look rich.I use water to search for vacuum leaks becuase it isnt flammable and will make the engine run bad when it finds a vac leak and gets sucked in.I have experienced fire balls with starting fluid and other flammable substances searching for vacuum leaks and finding instead bad plug wires.It only takes one good spark to ignite that stuff.I think you may have a fuel delivery problem with the carb.Check the power valve,make sure the floats arent stuck open allowing fuel to just pump into the intake.If it aint fuel its an ignition problem.If all else fails pull the valve covers and make sure you dont have rockers hangin the valves open due to improper adjustment.Does it backfire or pop out the exhaust or intake??Good luck man,let us know how you make out.
I assume the wet plug is the clean one??? Its not completely clean so I assume it is firing. Fuel delivery problem? How do I check these items: power valve, floats. Already checked valve adjustment. Initially they may have been too tight but now if anything they are loose with zero lash. when it backfires it is through the carb. Have put out a couple fires already coming up through the carb after backfire.
Pull your valve covers and check to make sure you dont have any valves stuck open.I would assume with fire out the carb it would be an intake valve issue.If they are good then you have a mechanicle timing issue.Cam/cranck not phased properly.Its possible the key on the crank is bent or broken causing the crank gear to move from its correct position.This could be very bad for the valves and pistons.I would check cam/cranck phasing before running it again.Might explain the strange sounds you hear coming from the engine.As for the carb,Pull the sight plugs(its a holley right?)If fuel pours out then the floats are stuck or adjusted too high.As for the PV you need to take the carb apart and visually inspect it.Look for holes cracks or rips in the rubber diaphragm.If it looks ok try to manipulate the piston on it by blowing on or applying vacuum to the diaphragm.If you get no result after this the diaphragm is probbably popped.Lemme know.
I don't know about the others, but the plug readings don't jive to me #'s 2, 4, 5 & 7 look to be running leaner than the others, but they're on different planes of the intake, therefore different carb throats. It is a dual plane intake, right? Try a fresh set of plugs and see what happens. Overly fowled plugs oftentimes just don't perform up to snuff, even after cleaning.
