'83 FJ60- Dizzy Recurve- Can anyone demystify this process?

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John Staton

Oct 23, 2017
The Woodlands, TX
I have owned an '83 FJ60 for a couple months now and outside of maybe changing out the carpet and replacing exhaust, the two big things I would like to get done are a desmog and an H55 conversion. I have read a lot about the desmog on the various threads and will likely order a kit and do the desmog next. I was wondering if anyone could take the mystery out of the dizzy recurve for me. Give ma a brief overview of what it is and what it does. On top of that, my mechanic is a guy who restores hot rods, and can do anything. He has done some crazy engine swaps and even works on helicopters and builds gyrocopters. He told me he has desmoged vehicles before and we talked a bit about the recurve. He mentioned something about a recurve kit he got for a vehicle he did recently or having to work with the existing distributor in the past. Is there any type of guide, directions or specs for a recurve specifically for the FJ60? I have enough resources for removing and capping off for the desmog, but the recurve is still a bit of a mystery for me. I realize that I can take it and send it off to someone who knows these things backwards and forwards, and that maybe an option, but I want to understand it better...probably others do as well.

dizzy recurve kinda needs a dizzy machine. hence, why most just send em off. Jim C and TrollHole to mention a couple of the usual suspects... a lot of it has to do with rebushing the advance plate and the rest has to do with weights, springs, and actual rpm of the unit. one needs to have a firm understanding of the environment the dizzy will be working in to set the curve properly. the trick is getting the right rate of gain... and not overshooting the ceiling... Good looking rig, BTW.
There are plastic pieces on the pins that hold the advance weights that are ALWAYS broken and missing. They are NLA, but some have used brass bits to reproduce them. They effect the total advance about 5*... The point of the dissy recurve is to make the advance arc vs rpm optimal for performance, not emissions.

There are some threads on how to do it, but you won't spend a better $150 or so by sending it to the guys mentioned above. You really need an old obsolete (expensive) Sun distributor machine to do it right. Plus, you get the distributor cleaned, rebuilt and tested in the process.

But turn-around is slow, so be prepared to wait or buy a replacement dissy to have rebuilt/re-curved while you wait. Make sure the vac advancer is working, too.
I recommend doing the desmog yourself. It is not that hard but just takes some time. It's a great way to get to know your engine and understand the vacuum system.

I did a desmog and have not have the dizzy recurved. It doesn't seem to have any negative effects by not recurving it.
I just added the JimC distributor last week and went to 10* initial.

It really woke the truck up. Money well spent and certainly another piece of this worn out truck that is new.
One of my hangups, and I am sure I am no different than anyone else, is having the truck out of commission for so long waiting for the distributor to come back if I send it off. I wonder if I could buy a recurved dizzy from JimC and then send mine in to have an extra? Has anyone just bought one from him before??
I bought an extra one from the classifieds for $100 and now I’ve got an extra that I’ll loan out as a core to friends. Took about two months to get it back from Jim but it was worth it.

Due to all the advance from the smog curved distributor I was having detonation on 87, with the softer curve and more initial I’m doing great on run of the mill gas like I should be. Makes up for the lack of torque with the 33” tires.
He may have one to sell you, but I doubt it. You'd have to call. Best best is to ask in the wanted section.

You could call Mark at mark's off road. He's parted a few 60s lately. 818.953.9230

Jim C. -- www.tlcperformance.com
You don’t “need” a machine to do a recurve. There are some of us who followed another mudders detailed thread on how to curve their diz. It’s under $17 and quite easy.
I will say I have spoke w/ someone who had followed it and later had Jim recurve an extra. They did say it was quite different.
So depends on how far you want to go or how much $$ you’ve got to burn.
Nothing wrong w/ spending $17 and do it yourself initially. It’s just a matter of cleaning up the parts, swapping out the springs, adding an aluminum bushing and resetting the gap.
I did mine but I honestly haven’t driven much to be someone who can say for sure it was a bonus or not.
I can't remember which port needs to hold vac, but if buy one from someone check that out. Otherwise your buying something that isn't fully functional for vac advance if I remember correctly. If you getting rid of HAC it may not matter.

Worth the check. Let me know if you need more details I'll dig back thru the emails that Jim C sent me about what to verify.
You don’t “need” a machine to do a recurve. There are some of us who followed another mudders detailed thread on how to curve their diz. It’s under $17 and quite easy.
I will say I have spoke w/ someone who had followed it and later had Jim recurve an extra. They did say it was quite different.
So depends on how far you want to go or how much $$ you’ve got to burn.
Nothing wrong w/ spending $17 and do it yourself initially. It’s just a matter of cleaning up the parts, swapping out the springs, adding an aluminum bushing and resetting the gap.
I did mine but I honestly haven’t driven much to be someone who can say for sure it was a bonus or not.

Interesting. Any idea the title of the thread?...I will search around. The guy that works on my rig is quite talented and acted as though doing a recurve was no big deal, but I told him I would look around for some details.

I think it is common knowledge that desmogging an FJ60 and recurving the distributor go hand in hand. The distributor was set up to optimize performance based on a vehicle with the emissions equipment in place. Once all that stuff is removed the distributor provides too much advance and the advance comes in before you really need it and runs out when it is needed the most. Simply leaving the distributor and timing alone will, in most cases, cause pre-ignition or pinging when the truck is under load. There are a couple of band-aid fixes that will allow you to drive the truck but the results are far from optimal. One fix is to reduce the initial timing to the point that the pre-ignition goes away. This method can cause hard starts and stumbly idle and the truck will feel sluggish and under powered. The other band-aid fix is to leave the initial timing alone and run the truck with the primary advance from the carb connected to the secondary port on the distributor. The second method cured my pinging and allowed me to drive my truck for several months issue-free. It still felt sluggish though and I started to think hard about a dizzy recurve.

There is a vendor on this site who recurves dizzys, rebuilds carbs and sells de-smog components. He does excellent work. I've used him before and I always recommend him to others. I have a trip coming up and I wanted to get the Turdle ready. The vendor was not responding to my emails so I decided to go it alone using information gleaned from MUD. Here's what I did:

Remove the plug wires/vent hose from the distributor cap. Unclip the electrical connector on the side of the dizzy. Remove the cap. Take pics and mark the location of the rotor button in relationship to the engine (mine was pointing directly at the #1 wire position on the cap). Mark the position of the distributor housing. I used a dot of red paint on the distributor and marked a dot on the engine block directly behind. This is not super critical. You do want it close so that the truck will actually start once the distributor goes back in. You will tweak the timing later. Remove the hold-down bolt and pull the dizzy out. With the dizzy now on the work bench, gently remove the plastic cover over the electronic trigger. Remove the two screws that hold the trigger in place (consult the FSM when you re-install to set the gap properly). Remove the vacuum advance clip. Pop the advance rod off of the pin. Remove the vacuum advance hold-down screw from the side of the distributor. Gently wiggle and remove the vacuum advance canister from the distributor. Remove the two screws and the hold-down tabs that locate the advance mechanism. Pop out the vacuum advance mechanism to access the springs, weights and stop pin.

The first issue with the FJ60 distributor is the common problem of the advance stop pin bushing. Inside the dizzy is a pin that keeps the advance in check. Mr. T used a little plastic bushing on this pin. The bushings always crack and fall off leaving only the thin pin to limit the advance. The thickness of this little bushing equates to 3-4 degrees of advance so if your bushing is gone (it probably is) your distributor is advancing more than it should. To remedy this issue I found a replacement aluminum bushing at Lowes for 78 cents.
View attachment 1279395
The aluminum bushing just barely fits over the distributor pin. I drilled the bushing out just a hair and tapped it over the pin. It holds nice and tight and should provide years of service.

The second issue with the FJ60 distributor is the advance springs. The primary advance spring is soft and thin and the secondary advance spring is thick and quite rigid. They work fine on a truck with the emissions intact but being de-smogged, I knew I needed something different. I picked up an MSD recurve kit (PN 8464) and used the springs in that kit. The kit was $16 at Pep Boys.

View attachment 1279400 The kit comes with a pair of hard, medium and soft springs. I replaced Mr. T's primary spring with the blue (medium) spring from the MSD kit and Mr. T's secondary spring was replaced with the silver (light) spring from the MSD kit. Here is a pic of the factory springs next to the springs that replaced them.
View attachment 1279399

Once the MSD springs were installed I reassembled the dizzy and re-installed it. I re-installed the vacuum lines with primary to primary and secondary to secondary as they were intended. I played around with the timing and I found that this set-up likes more initial advance than the original set-up. The timing light I have is a cheapo so I don't know my exact setting but it has to be around 15-17 degrees advanced. The BB is down below the sight window about 1/4". It seems like a lot of advance but the truck starts right up and runs great. I drove the truck hard with several pulls all the way up to redline. The truck pulls much stronger throughout the RPM range. Overall the truck just feels peppy. There was no pinging whatsoever and the advance curve seems very linear. My butt meter tells me I have a new truck now! I know I don't but the drivability is night and day compared to before. I will continue to drive the truck and tweak things as needed but for now I am very happy with my set-up.

I am sure that a professional recurve would improve even more on what I have done here but for $17 and a couple hours of time this set-up is hard to beat!
If you do nothing but replace the (almost guaranteed to-be) broken nylon bushing on the stop pin with the aluminum one in the thread above, you will have made a significant improvement.
And really our engines aren’t so significant that a specialised machine is needed to map out all the points on the curve.
If your advance pot holds (can be checked while diz is still installed) from a mityvac and you recurve, you will be way ahead and have only spent $17.
I know I’m all for a cheap and easy mod I did myself way over shipping and waiting.
I posted pics of when I did mine on my thread but I’d have to skim through to find the page.
Reinstalling the diz can be tricky but if you follow the fsm it’s easy enough. Or as Dave from above would say as well, if you do nothing but pull the diz out, mark on its housing where the rotor tip was pointing w/ a sharpie and then drop it back in exactly at that spot then you ‘should’ have no trouble. I’ve had mine put a few times but have chosen the fsm directions moreso Now seeing as it is more precise.

Thanks for the info....I have been noodling how to best do the desmog without farming out the work. Even if I don't do it myself, I want my local mechanic to be able to do the work so I am not having to reach out to someone far away. Question- I plan to order a desmog kit from JimC...I see you can get them from ManFre, but his looks beefier on a couple of the parts. I asked Jim if a carb rebuild was absolutely necc at the time of the desmog and he said it wasn't , but eluded to things that could be done to optimize. Mine was rebuilt not that long ago when they rebuilt the engine. Did you do anything to yours at the time you desmogged your engine?? and are you still running good using the recurve procedure described above??
I went with a Trollhole carb just to clean things up and because I had one on the shelf. I am still running my $17 DIY recurve. No issues.

If you don't want to do the re-curve right now, just go ahead and de-smog but swap the hoses on the dizzy so that the main vacuum from the carb goes to the secondary port on the dizzy. That will limit your vacuum advance and prevent pinging. Doing it this way it is likely that you will not even have to mess with engine timing at all. Just leave it and see how it does. I did this after my install and had no pinging whatsoever. I did the DIY recurve later to pick up a little more power, but it wasn't required at all.

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