Valve/Compression/Fuel/spark questions (HELP!)

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Nov 27, 2018
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Location
Campbell, Ca
Hi all,
I finally got around to checking my compression and wanted to get the forum's advice on how things looked...

1974 FJ40 with 1.5F
Engine seems like it has ~90k miles (speedo was broken when I got it, but it was from original owner and looked like it sat a bunch)
It has Sniper EFI 2300 installed
It has an Offenhauser 4 barrel intake that I have an adapter plate (HVH Super Sucker Carb Spacer)
Non-US distributor from City Racer

The compression numbers are

Cylinder #1​
Cylinder #2​
Cylinder #3​
Cylinder #4​
Cylinder #5​
Cylinder #6​
Dry​
145​
130​
125​
125​
125​
130​
Wet​
135​
128​
133​
133​
134​
190​

When I pulled the plugs, some looked good... others not so much.
Plugs 1-6.JPG


One observation when turning the engine over with no plugs, is that cylinder #6 seemed like fuel sprayed out, but no other cylinder seemed to do so.

I would love some help in understanding how these look to the experts...
1) Do the plugs look normal? 2, 4 and 5 seem to much darker. #2 looks the worst of the bunch (close up below)
2) Should the head be looked into for the compression numbers? I may have misread #1 Dry (first reading taken and with a new gauge, but I think I did it right), and #6 Wet is way above the others.

Any feedback or general advice is welcomed. I appreciate the support/help.

Thank you.
Craig

Plug #2.
Plug 2 close.JPG
 
Joined
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Messages
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Hi all,
One thing I noticed back in May 2021 (Rocker Arm 'play' question - https://forum.ih8mud.com/threads/rocker-arm-play-question.1253173/) when I adjusted the valves, is some of the rocker arms were not free floating (when setting the clearance, they wouldn't click/float. They were hanging up slightly). Last night I tore down the rocker arm assembly and cleaned all the grime/residue off of the main shaft (don't know the technical name) and rebuilt it using all the original parts (checked all the weep holes on the rockers). It got me wondering if the valves for cylinders 2, 4 and 5 were not fully closing and causing the strange burn cycles which resulted in the discoloration of the plugs. Time will tell I guess. I will run it for a bit, swap the plugs out and then check back on them in a few months of run time.

Rocker Arm assembly appart.JPG


Rocker Arm assembly out of head.JPG


Rocker Arm reassembled.JPG
 

EWheeler

4 Cruisers, No Garage !
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Hi all,
One thing I noticed back in May 2021 (Rocker Arm 'play' question - https://forum.ih8mud.com/threads/rocker-arm-play-question.1253173/) when I adjusted the valves, is some of the rocker arms were not free floating (when setting the clearance, they wouldn't click/float. They were hanging up slightly). Last night I tore down the rocker arm assembly and cleaned all the grime/residue off of the main shaft (don't know the technical name) and rebuilt it using all the original parts (checked all the weep holes on the rockers). It got me wondering if the valves for cylinders 2, 4 and 5 were not fully closing and causing the strange burn cycles which resulted in the discoloration of the plugs. Time will tell I guess. I will run it for a bit, swap the plugs out and then check back on them in a few months of run time.

View attachment 2886791

View attachment 2886792

View attachment 2886793
All of our 50 year old F engines could probably use this same spa treatment for the valvetrain! I've had it on my list, but it hasn't made it up high enough. Another member did similar work recently when he didn't see oil getting to the valvetrain upon priming the engine before a start on a truck that had been sitting for a long time. After cleaning all the oil passages, showed good flow and everything worked as it should upon re-assembly. Let us know if it makes a difference in how your plugs look. Does it seem to run OK?
 
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@EWheeler : I gave it a short drive last night after I wrapped up and it seemed great (peppy, valves sounded good, and exhaust/engine sounded great). I need to pull the valve cover and inspect that oil is flowing out as I hope/want, but I think 'all is well'. I need to find my spare plugs and after some run time with them installed, I will repost with an update. Again, the inconsistency is what I am most interested in. I have had trouble with the Sniper set up, so I know it isn't running perfect (would expect some black on the plugs), but the way 2, 4 and 5 look bad vs the others is most interesting. The compression numbers don't align with the plug condition.
 
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Does anyone have those bolts and hardware PNs handy? Mine were extractable, but they were a struggle to remove. Lots of resistance from the threads.
 
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Indiana
Your compression numbers look good enough, so no major worries there. Steamer is correct, the old plastic umbrella style valve stem seals will be likely cracked by now and allowing oil to seep down into the cylinders. The newer style seals with metal body should be usable on your engine. They worked fine on my '76 2F anyway. They can be swapped with the head on, or just run it until you feel like it is using more oil than you like. At that point, I would pull the head and give it a refresh.
 
Joined
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@Steamer : good point. I picked up a set of the newer valve seals and have watched a few videos of the 'rope, ziptie, socket with magnet' valve seal replacement trick. Something I think I will make time for in a bit.. trying to build the nerve on that one. Good advice. Thank you!

I am not familiar to the leak down test. Let me start looking into that. Thanks again!
 

EWheeler

4 Cruisers, No Garage !
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A word of advice to those doing this work. The bolts in our engines are old, heat cycled and may have been over torqued by a prior owner. Replace if possible so you can avoid my recent experience:
View attachment 2886861 View attachment 2886862
Where did you buy these bolts from? I searched all over online today and couldnt find anything based on Toyota part #’s for my year of engine.
 
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They, like so many other things, are discontinued by Toyota. Fortunately they are 70mm M8x1.25 (please verify as I’m not totally sure of my memory). Point being is that you can go to any specialty bolt supplier and get some high quality replacements. I think they only torque to something like 22lbs? So they don’t need to be some crazy expensive high strength bolt. Good luck.
 

EWheeler

4 Cruisers, No Garage !
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They, like so many other things, are discontinued by Toyota. Fortunately they are 70mm M8x1.25 (please verify as I’m not totally sure of my memory). Point being is that you can go to any specialty bolt supplier and get some high quality replacements. I think they only torque to something like 22lbs? So they don’t need to be some crazy expensive high strength bolt. Good luck.
Based on the part number and toyota's numbering decoder (@OGBeno ) the bolt is as you said, M8 and 70mm below the head. Part # 91112-70875. Tensile series 7, I will have to figure out what that equates to.
 
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A word of advice to those doing this work. The bolts in our engines are old, heat cycled and may have been over torqued by a prior owner. Replace if possible so you can avoid my recent experience:
View attachment 2886861 View attachment 2886862
I always give them a smack on the head with a hammer, then tighten just a smidgen before trying to remove them. That sucken heart feeling you get when pulling a head bolt or the like and you feel it begin to twist off is not fun.
 

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