no power

[scott]

took it out for it's first drive in 11 months. you might remember my rebuild tale. well it was gutless. it stuggled to do 25 mph on flat road. been stuggling with timing but think i'm close. question, would the old plugs champion N5 be part of the problem? 7:1 head is supposed to run w/ N8, i've now an 8:1. could not having the recomended UN12Y make that much of a difference? the plugs showed i was running rich so i will lean it out.

[LaneRover]

Valves out of adjustment?

[scott]

i'll have to go check. i assumed the machine shop adjusted 'em. he's a good guy and he leases space to a guy that works on dicos and defenders

[LaneRover]

Too tight or too loose and you will lose power. They may have adjusted them to what they think is right - they may not have had the correct settings.

Brent

[SafeAirOne]

i'll have to go check. i assumed the machine shop adjusted 'em. he's a good guy and he leases space to a guy that works on dicos and defenders

Whenever I have had out-of vehicle top end machine shop work done, the shop has never adjusted valves for me. They get it in the ballpark so the engine will at least start. Usually valves are adjusted hot, so it must normally be done once the engine is reassembled.

[scott]

just check valves, one a little tight, two a little loose but really not that bad. timing by ear got it idling smooth at 9 degrees adv w/ the vacuum line d/c and plugged. i've the 2.5 cam and i'm at 5500 ft above sea level. also i've a petronix elec ign. when i hook up the vacum it adv to 12-14 degrees adv'd. when i tighten up dizzy it died and now it won't start. i'm tired, dirty and hot. maybe tomorrow i'll put the points back in.

[Sputnicker]

I can only think of a few things that will make a car run smooth (fire on all four cylinders), but have such low power:

1) Distributor timing off substantially
2) Cam timing off (did you also replace the cam?)
3) Vacuum leak
4) Carburetor blockage/fuel delivery problem
5) Major blockage in the exhaust (pack rat nest, or shop rag?)

If you replaced the cam, Id probably start with a compression check, which should reveal a valve timing problem (all cylinders equally low). It could also be that the distributor drive gear is not lined up as before.

If you're not sure its firing on all four, try removing or shorting one spark plug wire at a time and see if it makes a difference. Something as simple as crossing two plug wires could account for the low power and you would see gas on the two spark plugs that are mis-wired and not firing. That much power loss means more than one cylinder is affected. You could do better than 25 MPH on 3 cylinders.

Good luck and let us know what you find.

[scott]

i'm pretty sure the dizzy drive gear is in one cog from were it was originally. but as i understand that would only affect the way the dizzy lines up. before the rebuild the vac adv was towards the rear now it's outboard. i did get a new cam, a 2.5. i'm pretty sure no.1 is compressing just as the timing marks are aproaching the pointer but i will check this again. all 4 are firing. carb is clean and spaying it with cleaner while idling doesn't change the idle. the plugs are N5 and haynes manual says to use N8 for a 7:1 head. i've now an 8:1 head. do you think i putting in UY12N (i think that's what haynes says to use w/ an 8:1) woud make a difference? also they get all black sootied up pretty quickly. i've been attributing that to poor timing. i've also notice that the timing seems to retard initially when revving but then advances.

[Sputnicker]

I doubt if it's the spark plugs - there's something more fundamental going on. The cam being off just one or two teeth on the chain could cause all of your symptoms and it would still be getting some compression and able to run (albeit poorly). The distributor clocking being different also makes me suspect cam timing.

I'd suggest a compression check first. I would guess you would get something around 140 PSI on all four cylinders with the mods you've made if the cam timing is correct (others may have better numbers). As a point of reference, the stock 7:1 spec is 125 PSI at cranking speed. If compression is low, I'd start by reviewing the procedure for checking cam timing in the Green Bible. Basically, the number one exhaust valve should be fully open (highest point of the cam) when the "EP" mark on the flywheel lines up with the pointer. You'll need a dial indicator to figure out exactly where the highest point (peak) of that lobe is, but you might be able to detect a gross misalignment by eyeballing it.

By the way, there was a discussion in another thread about what the "EP" mark means and it looks like "Exhaust Peak" to me.

Good luck - I hope it's something simple and easy to fix.

[scott]

i'll do a compression check tonight. if all cylinders are equal but significantly low then i should suspect the cam and crank aren't timed given that i already adjust the valves? i have a dial indicator, bought it to set up a dif, figured i'd probly never use it again, i was wrong again. if i can't find the EP mark could i use the TDC? which valvel should be doing what then?

[scott]

compression, all 4 are at 133 psi. oes this rule out cam timing off?

i've an 8:1 head and shaved a bit off the top of the block when it was rebuilt.

[Sputnicker]

I would defer to others who know how many PSI an 8:1 head and 2.5L cam should put out, but it sounds pretty good to me. I would have anticipated something lower if the cam timing was off enough to make it run that badly. So, you are probably okay, but to completely cross this off the list, it would still be good to verify cam timing IAW the Green Bible. Your level of confidence that the cam was installed correctly is another factor.

By the way, the EP mark (located on the flywheel, not the front pulley) is 95 degrees from TDC, so I can't think of an easy way to use TDC to verify cam timing.

Another thing to add to the list of possible causes is no advance from the distributor. Unlikely, but possible, if something is seized or broken.

[scott]

i've ruled out the coil. it tested using petronix directions to be compatable w/ the electronic ignition. next is the dizzy adv mechanism. it was working before the rebuid but i did tear it all apart so maybe i hosed it up.

[scott]

spoke w/ pertronix paul yesterday. after doing their test on the coil he suggested that i jump the positive wire of the electronic ign straight from the battery and see it that helps

the volt test on the coil was to ground the neg side of the coil and read the pos side with the ignition switch on. i got 8.54 v which was no surprize given the resisters but it wasn't holding at 8.54, it dropped pretty quickly down to less that 2 v.

tonight or tomorrow i'll be checking to see if this resisters or coil are shorting. i'll start by checking the ign wire and see it it holds 12 v. any thoughts on this?

bottom line i'm praying for an ign issue and not a cam timing problem

[kevkon]

You said the truck was struggling to get up to 25mph. How did the motor sound? If it didn't backfire or sound really rough you might want to check a couple simple things; exhaust blockage and fuel supply to the carb. Also, as simple as it sounds, make sure the accelerator cable /linkage is allowing for full throttle on the carb ( I've seen this happen and get overlooked many times on re-builds).

[scott]

... make sure the accelerator cable /linkage is allowing for full throttle on the carb ( I've seen this happen and get overlooked many times on re-builds).



linkage is good. peddle moves throttle linkage through it's full range smoothly. exhaust blockage is a slight possibility, i covered a leaky gasket with an exhaust repair paste, covered it with aluminum foil (to keep it from sticking to the flanges) then tighten it down. paste may have oozed inward. i'll chck that today. i could get it to idle and rev smooth but when trying to drive it was popp'n back through the carb.

[kevkon]

li could get it to idle and rev smooth but when trying to drive it was popp'n back through the carb.

That sounds like a typical improper cam/ignition timing issue. Valve lash adjustment effects the engine timing as well.

[Sputnicker]

Fuel delivery problems and exhaust could easily cause the low power, but probably not the "popp'n back through the carb." That requires combustion at the wrong time, so I agree it's probably timing. With a timing light you can (or already have) verified the distributor is positioned correctly and advancing as you raise engine speed. That leaves cam timing, unfortunately.

I'm not sure what it takes to remove the access plate on the bell housing and view the EP mark on the flywheel (I've never done it and my Land Rover is 700 miles away), but if you can get to it, here's what I suggest. It's a slight variation to the procedure in the Green Bible taking into account that your engine is fully assembled.

Take off the valve cover, remove the spark Plugs and turn the engine by hand (or by pushing the car while it's in gear) so that the number 1 exhaust valve is fully open. Use your dial indicator (see illustration in the Green Bible) to find the point at which the valve is fully open and zero out the dial indicator. Then turn the engine until the dial indicator reads .025" from the peak and make a mark on the front crankshaft pulley. Turn the engine the opposite direction, past the peak, until you get the same .025 reading and make another mark. Then turn the engine so that it's half-way between the two marks. Now you are at the "exhaust peak" and the EP mark on the flywheel should line up with the pointer, as illustrated in the Green Bible.

[Roverlab]

Any idea how much material was removed from the head by the machine shop? Can you back the adjusters on the valves off to be way loose? I don't know 2.25 and 2.5 cam compatability that well, but I would think that the 2.5 doesn't have huge lift and the valves are closing fully to get 133psi. per cylinder, so coil bind is also unlikely.
Pulling the front cover isn't the worst job and I'd agree that cam timing seems off. Especially with dist drive also being off. Compounding the error?
Does the engine rev to 2500-3500rpm easily no-load?
Caveat: I'd check with the engine builder before opening up "their" work or running a fresh engine really high on rpm!
My .02!

Trevor

[scott]

good news, bad news. i pulled off the valve cover and set the EP at the pointer. no.1 valve is not openned. no. 8 is! i can believe this thing even starts. my time is set at at least 28 degrees btdc. looks like my machinist is going to have to make a house call. he had my green bible. i wish he had called me and asked for the fly wheel cause it's kind of of needed to set the cam timing.

[kevkon]

That's what I suspected. Do yourself a favor, when you have the machinist come by to correct the issue make sure that he verifies the timing marks are correct. Factory timing marks are often inaccurate and while you have the opportunity it would be wise to accurately zero it in for precise timing.

[scott]

i'll be putt'n a dial indicator to it today. and i figure that since 1 & 4 are opposit each other their exhst cycles would be close to opposite and maybe no. 8 is open on one revolution and no. 1 on the next.

speaking of factory timing marks being off what do your pointers look like? mine is way up high in the viewing port and barely vissible. no at all like the pictures in the manuals showing the pointer nearer the middle.

[Sputnicker]

Your hunch is correct - since the crank is spinning twice as fast as the cam, the EP mark will appear for cylinders 1 and 4.

[scott]

power upped! i called and talked w/ my machinist. he was certain that the cam timing was not my issue. he pointed the fingure at the carb or ignition. he seem very confident so i redirected my thinking. the carb was torn apart and cleaned while the motor was being rebuilt but it wasn't really changed. the ignition was changed by dropping in a pertronix electranic system. but my understanding is that electronic ignition either work or don't, no middle ground. but for the heck of it i dropped the points/condensor back in and the old truck screams! well it works. now to start bolting down the loose ends and gett'n out to the trails!

and i don't if this had anything to do with it or if it was just a coquindence but i purchased and drank my first six of guienness since putting the motor back in. mmm, maybe it was just the head clearing i needed

[badvibes]

Scott-

Hey that's great news. Shows how difficult it can be to diagnose a problem when more than one thing has been changed. Man you'll be out breaking things again in no time now.....

[scott]

well i got my rear loom in and work'n. i've now have break lights. i say break cuz now that the brake lights work i can take it out of the driveway and break something new

[jac04]

Any idea what was wrong with the Pertronix unit? I assume it was brand new.

[scott]

Any idea what was wrong with the Pertronix unit? I assume it was brand new.

not a clue. it was new. bought it last fall when the motor was in the shop. no receipt now and the box is long gone. i would be happy if they just sent me another but the money would be good to.

went out wipp'n around the hood. the truck has some giddie up in it now.

[SafeAirOne]

Leaving the ignition switch in the "on" position for even a few minutes without the engine running can fry the pertronix units...

[scott]

Leaving the ignition switch in the "on" position for even a few minutes without the engine running can fry the pertronix units...


it's crappy performance was from the get go. and i thought when they go they go. no middle ground. this one made sparks just not enough and or at the right time.

[badvibes]

Scott-

So you just going to run a points dizzy or will you try to trouble shoot the Petronix and use it?

[scott]

well alls well that roves well...w/ the old ign system back in i am finally rov'n w/ a degree of confidence that i'll make it back. to play it safe i put the bumper back on with it's tow bar, i hate being drug by a strap. it may not have been the pertronix ign. it may be that my spark plug wires are the solid type and i understand that they interfer w/ the ignitor.