I bet you don't. Though I'd wait until you have your buddies scan tool and just check the crank signal.
CK5
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'86 Jimmy 4in Lift, 40’s, tons, 8.1 Swap- 700r4 said PNNNNN
- Thread starter GWeakland620
- Start date
This is not a dedicated trail rig, but does trailer to the destination usually. I am currently in the planning phase of doing a 52/56" spring swap, and getting back to being more road worthy.
Ok so, on this episode of “Why did I do it that way when I was in here the first time?”
So with the scanner hooked up, we could see that the cam was not giving any values. Well long story short when I bought a timing cover due to the engine not having one when I purchased it, I snagged one from O’Reilly’s when I was putting this engine together. Little did I know, they sold me a cover from an older 8.1 and the sensor from the newer 8.1’s was not correct.
I swapped to the correct sensor for the cover, then re-pinned the plug for the correct layout. I then was able to get it to bark a bit with starting fluid, so I know I’m getting closer.
View attachment IMG_4311.mov
Next on the list is to open the fuel system back up and make sure everything is still good to go for some fresh fuel. Then I’ll see if I can get this thing to light off more than a couple burps.
So with the scanner hooked up, we could see that the cam was not giving any values. Well long story short when I bought a timing cover due to the engine not having one when I purchased it, I snagged one from O’Reilly’s when I was putting this engine together. Little did I know, they sold me a cover from an older 8.1 and the sensor from the newer 8.1’s was not correct.
I swapped to the correct sensor for the cover, then re-pinned the plug for the correct layout. I then was able to get it to bark a bit with starting fluid, so I know I’m getting closer.
View attachment IMG_4311.mov
Next on the list is to open the fuel system back up and make sure everything is still good to go for some fresh fuel. Then I’ll see if I can get this thing to light off more than a couple burps.
This thing is definitely not timed correctly. It’s backfiring through the TB, then tries to run for a couple rotations. I’m going to pull the timing cover to verify my timing marks.
Anything else I should look at?
Anything else I should look at?
Rocker arms could also be too tight, but best to verify the cam timing first.
Does an 8.1 have adjustable rocker arms?
Martin
Martin
That’s what it was on the bronco. Timed it a 100x and it was dead on but would just spin and cough. Finally gave in and took it to a shop and they said they had to break the rockers loose with a 3’ cheater bar. Apparently BIL set them a bit tight and when I primed the oil system it pumped the lifters up and hung open the valves just enough.
8.1’s don’t have adjustable rockers. Nor is timing adjustable unless you put the timing chain on wrong. The timing set should have gone on like any other big block with the marks “dot to dot”.
Though your earlier remark about the cam sensor does have me wondering something. You know they had two different sensors but that also goes with changes to the timing cover too.
Take a look at this link and compare to yours to make sure you have the right combo. My concern is you may have a mismatch.
Though your earlier remark about the cam sensor does have me wondering something. You know they had two different sensors but that also goes with changes to the timing cover too.
Take a look at this link and compare to yours to make sure you have the right combo. My concern is you may have a mismatch.
Vortec 8100 8.1L Chevy GM Camshaft Position Sensor Guide - 496cid Cam Gear Sensors - Raylar Engineering
Find the right camshaft position sensor and cam gear for your Vortec 8100 8.1L 496cid.
www.raylarengineering.com
Not to question Zoo, but is dot to dot or 12 o'clock for both?
I've never been this deep into an 8.1
I've never been this deep into an 8.1
I just did mine b4 BB and it was 12 and 12, you saw it run
Dot to dot.
So another dumb moment brought to light this evening. My buddy had fresh eyes on it and caught a very dumb mistake.
Not sure why, but I had the coil harnesses plugged into the wrong side of the truck.
Bank 1 was in bank 2 slot and so on. Not sure what I was doing, but a very silly oversight.
The computer is so far out of whack from trying to correct it, that it won’t start now.
It’s going to sit overnight with the battery unplugged and on the trickle charger. Tomorrow should yield much better results
Not sure why, but I had the coil harnesses plugged into the wrong side of the truck.
Bank 1 was in bank 2 slot and so on. Not sure what I was doing, but a very silly oversight.
The computer is so far out of whack from trying to correct it, that it won’t start now.
It’s going to sit overnight with the battery unplugged and on the trickle charger. Tomorrow should yield much better results
I guess it shouldn't mater 6 tdc or 1 tdc the crank sensor and cam sensor should know where there crank and cam are and fire the correct coil.
If the right bank and left bank leads are reversed the pcm won't have a snowball's chance in hell to firing the right coil.
Step 5 from the reinstall procedure on the 8.1 timing set:
yeah was just thinking all things being correct. and how the dots were aligned when the chain is installed. I can't find documented proof that a gen6 big block is same or different then a gen 1 big block, dot to dot is #6 tdc and 12 and 12 is #1 tdc
I found some procedures on line and read through, no mention of putting any cylinder at tdc, just as you say dot to dot. The computer does it all.
Aren't those two alignments the same? If you're dot to dot and rotate the crank 1 Rev, now they're both at 12:00. I more rev and you're back at dot to dot. The relationship is always 2:1.
Ok, more confusion today. Last night I had spark. It had spark before I unplugged the computer overnight. Now when I try to start it, there’s no spark anymore. I changed nothing.
