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).