RPM drop in 1st under load (FJ60) (1 Viewer)

[vszUnclear]

Slow Left,
Last test was over 5 months ago. Dammit, I'm reviewing my notes and it looks like in my haste I forgot to open the choke all the way before testing. I'll post new results when I have a chance to test again.

But even if the scale of my botched results are wrong, the fact that 3 & 4 are showing nearly no compression is probably indicative.

 

[Slow Left]

Yeah, I was wondering why there was such a big discrepancy (...big word...hard to spell...).

I bet you're right (I hope you're right, too) that you might have botched the second test by doing something different.

By the way, good on you for continuing to work the problem and not let it work you.

And good judgment call on the whole misfire thing. You should be able to measure the resistance for each individual spark plug wire (and the coil to dizzy wire, too) to test to make sure they are within spec (if you know what the manufacturer spec for resistance per foot is supposed to be). Just remove each one, one at a time, and put a mulitmeter probe at each end of the wire, measuring continuity (should be 1/ohms, where ohms is resistance, or maybe just straight up ohms...i guess it depends on the mulitmeter you've got).

Then with your good spark plugs, see if that misfire symptom you saw on 3/4 goes away or not.

Also, before I forget, did you check to make sure that the vac line that goes from the vac advance port on the carb goes directly (no BVSV or check valve inline) to the primary vac advance port on the dizzy? I guess when you guys do the desmog, the only BVSV you keep using is the one for the charcoal canister...I think that's what Jim was talking about in a post above. The check valve is going to slow down the vac advance response at the dizzy. And the BVSV is supposed to only allow vac advance above certain engine operating temps, but in reality only serves as a headache...

 

[FJ40Jim]

No problem. Head gasket is blown between #3 & #4.
Doing it in your garage at home, it's still only a day to disassemble and a day to reassemble.

 

[vszUnclear]

Jim,
Thank you for your diagnosis! I can live with HG leak, at least it's not something more sinister involving the bottom end of the engine. I will definitely tackle this at home and get my head into a shop for machining while it's off.

Slow Left,
I feel pretty dumb for posting those results too fast, but at least I'm getting credit for effort - thanks! Sounds like we have the culprit, but to answer your questions I was going to pick up a cheapie in-line spark tester. But if cylinders 3 & 4 have super low compression, then it seemed to rule out an electrical issue. FWIW, BVSV(2) is removed and replaced with a plug, so yes I have a direct vac tube between carb port and vac advance. I only have BVSV(1) to deal with canister/evap.

I can't thank you guys enough. In all sincerity, this forum is an amazing community. As I learn more I look forward to contributing back to help others. I'll post follow up in my build thread.

 

[Slow Left]

Nice. Sounds like you've got the problem identified!

I think I'm going to go double check my compression this weekend...I wonder if I've got a similar problem I've been blaming on ignition...

Your rig's gonna run like a champ when you get it all sorted out! Be sure to post updates/road blocks...

 

[vszUnclear]

I will definitely post updates and pics, Slow Left.

Could use some advise on parts:
Head gasket kit: it sounds like OEM is preferred, but any experience with the (cheaper) Ishino W0133-1620842 gasket kit? I've seen positive comments on Ishino gaskets.

Replace or re-use the head bolts?

 

[gregnash]

Think that concensus is that you should go with OEM which is made by FelPro (if memory serves me). Think that on head bolts it depends on what shape they are in but normally most replace them.

 

[FJ40Jim]

I have plenty of experience changing out the cheap Ishino or Stone gasket kits. Go with the OEM NHK or Pillar graphite gasket.

Headbolts are lifetime.

 

[vszUnclear]

Update:
Pulled the head yesterday and took some pics to share.

Survey says...

Looks clearly blown between 3/4. Nicely diagnosed, Jim!

I'm posting some pics of my cylinders and valves too, hoping you guys can help me identify any problems. Cylinder 1-3 are posted here, others to follow in next post.

After I took these pics I cleaned the block up with brake cleaner and a putty knife. I cleaned the junk off the piston rings as well. The cylinders look OK to me, there are some light marks, but nothing deep.

 

[vszUnclear]

Cylinders 4-6,
Valves for cylinders 1 & 2.

 

[vszUnclear]

And valves for cylinders 3-6

Would love to get some feedback. I did oil the block and cover with plastic before calling it a night. All in all, I'm feeling a lot more confident in my skills and it was fascinating to get a peek under the head.

Head is now at a local machine shop... hope they don't botch it up. I gave them new OEM seals I got in the HG kit from Beno (thanks man!) and printed out Jim's SBC instructions in case I need to swap out parts.

Going to re-assemble next weekend, can't wait to fire her up!

 

[FJ40Jim]

Looks pretty good inside.
Thoroughly clean the block in the failed HG spot, then check with a straightedge to see if there is erosion in that spot. If it is flat, it should seal fine.

 

[Spike Strip]

Go with ... or Pillar graphite gasket.

Is that the Fel-Pro Grafoil ?

 

[FJ40Jim]

No, Felpro makes the good manifold gasket, but their HG is not as good as the NHK/Pillar brand.

 

[vszUnclear]

Thanks for spot check, Jim. Machine shop says the head is in good condition, no cracks, and that the guides looked "perfect".

My piston heads have a modest layer of carbon. I've read conflicting things about cleaning them while in the cylinder. Some people say it's not recommended because grime and bits of carbon will fall down the cylinder walls in the process. Is there a big performance or longevity impact to leaving the carbon layer there?

Any sage advice on cleaning piston heads?

 

[FJ40Jim]

Clean the deck first. Then bring each pair of pistons to TDC to wipe off with brakleen and use the blow gun to try getting the loose carbon off the top of the rings and outta the headbolt holes. It's not gonna be perfect, but it'll be better than when you took it apart.

 

[vszUnclear]

Just to close the loop on this thread. I got the rebuilt head back on with the new head gasket and fired it up. First and foremost, the dreaded stumble in first under load is gone. In fact, this is really the first time I've experienced the full power of this rig. You can imagine how exciting it's been. Vacuum is a steady 19" at idle (even with a new intake leak at the EGR inlet... someone lost the new gasket).

Thanks to all those who weighed in with advice and help, Jim C and SlowLeft in particular, thank you guys a million. I'm finally enjoying my 60.

 

[Slow Left]

Sweet, glad it worked out! Your problem solving skills are exemplary. That's gotta be a good feeling!...all that 2F power...

 

[gregnash]

Glad to hear that it all worked out!!

 

[gregnash]

Bringing this around for my own notes and posterity! Going through this shortly.