Starting to understand why building engines may be best left to the professional

[My427stang]

OK, so the vacuum is lower than I expected especially with the cam advance.  However, some questions

1 - Did you readjust idle a/f and idle or did you just put the carb on as is?  If you did not adjust, recommend adjusting

2 - Do you have any large vacuum demands that could be leaking?  I don't expect this, but asking anyway, really thinking something like a purge tank or power brake booster leaking

3 - Rattle and bog, two different reasons likely.  If you hear it rattling, you have too much timing and likely too lean under load based based on your PV and the fact they leaned you out.  Don't run it that way, it'll beat up parts or blow head gaskets. The bog is expected because you are too lean and your PV is too late. 

- I would return that carb to stock, as delivered, both jets and PV.  Even if it is a little rich, which I do not think it will be, at least it's safe to run while you dial in the timing
- As far as timing, you were off on the balancer slightly (I think) did you compensate for that when you set it?  If so, we need to get both rate and total under control, short term, if you are still waiting for a new distributor, you may be able to pull 4-6 degrees of initial out of it, but I lost track of where you are for rate and total.

4 - How did you adjust your accelerator pump? ...and does it squirt immediately engine off moving the throttle and looking inside, no sputters or delays?  There is a trend of guys doing it incorrectly, just checking

[Yellow Truck]

Ross,

I have not touched the carb, in fact never took it off. The timing yesterday was around 18-19, taking into consideration that the balancer is about 1.5 degrees off (it was showing 20 with the light on the timing marks). Timing maxed out at 33-34 degrees with the engine up around 3,000. I can only say "around" since I was alone and the tach is in the truck, but revving the engine it stopped moving around 34 degrees.

I have been all over this thing looking for vacuum issues, including the booster. I am assuming the video I provided doesn't show "bouncing" as Brent referred to it, in other words it isn't acting like I have hanging valves. I note again that I am at 3,500 feet and that is about 2 inches of mercury from what I have read. Maybe that is just this engine.

The rattle and bog appeared AFTER the carb adjustments, and are unchanged by the cam timing adjustment. I think I mentioned this before, but I expect that my current distributor is ok for what we are doing. The good news is it is REALLY easy to pull and reinstall the distributor now I have the oil drive shaft in the right position.

I can't buy carb parts on a Sunday since it the performance shops are closed, but I will get the two new gauges in and try to get a video of the A/F, vacuum and tach so you can see what it is doing. These are not tools I'm used to using so my interpretations may be invalid.

So, carb questions:

• I have the original specs for the carb, but I was running it two jet sizes down - this is what QFT recommended and it was quite rich at that. Do I go back to the jets they recommended or to the two sizes up? EDIT - the two sizes down were because of the altitude here.
• The QFT docs give Primary Pump Nozzle sizes of 33 and 35, the garage referred to the pump as a "3.5" but I don't see any thing in the specs that aligns with that. I don't know of any adjustment to the accelerator pump, but I will investigate it's behaviour today.
• I have a 5.5 PV, but I can trade it for a 6.5 (if they have one) when I pick up the jets. If I'm going to a shop for some parts, I can buy a kit for about $80, or since we know where we are (72 and 74) and where we were with QFT's recommendation (76 and78), perhaps there is a small assortment I may need?
• Since it has been suggested that the IFR is too large at .37, should I also pick up a different IFR - remembering that it is an hour minimum round trip to get parts and it kind of chews up the day.

The specs for the SS 830:
SS 830 Specs by Fred Snoyd, on Flickr

[comet2]

fred on page 10 you indicated your idle was 17afr  that is way too lean it has to be pretty rich at idle around 13afr the rest of what you had doesnt seem too bad except secondary jet may be  a bit fat  my car works best with 13.5 afr idle about 15afr cruise  12.5-13 wot. on a 750 vac secondary carb i had to go  to a 37 squirter and  orange or green pump cams blue will work but only in 1 position i could not slowly move from a stop sign without  running out of fuel i mean driving like a grandma  your carb is much bigger and i would think it has less signal and demands more fuel off idle from pumpshot and more fuel from the transfer slots to transition from idle transferslot then main jet i wouldnt  worry about ifr unless you cant get  to 13afr  your plug gap will take care of smog issues  i run mine at .048 gap  this is why new cars have emissions systems and smell like a dryer vent! also disconnect vacuum advance until you get other stuff sorted out!

[My427stang]

So, carb questions:

• I have the original specs for the carb, but I was running it two jet sizes down - this is what QFT recommended and it was quite rich at that. Do I go back to the jets they recommended or to the two sizes up? EDIT - the two sizes down were because of the altitude here.
• The QFT docs give Primary Pump Nozzle sizes of 33 and 35, the garage referred to the pump as a "3.5" but I don't see any thing in the specs that aligns with that. I don't know of any adjustment to the accelerator pump, but I will investigate it's behaviour today.
• I have a 5.5 PV, but I can trade it for a 6.5 (if they have one) when I pick up the jets. If I'm going to a shop for some parts, I can buy a kit for about $80, or since we know where we are (72 and 74) and where we were with QFT's recommendation (76 and78), perhaps there is a small assortment I may need?
• Since it has been suggested that the IFR is too large at .37, should I also pick up a different IFR - remembering that it is an hour minimum round trip to get parts and it kind of chews up the day.

If it was in my garage

1 - I would ignore anything you think the carb told you before, because again, I will say with the utmost certainty, your jet re-size and incorrect PV did NOT fix the rich running issue.  I would bet agaist all odds that you had a bad PV from the backfire.  There is no way swapping a good PV and a couple of jet sizes would make it run leaner that you could notice. 

HOWEVER, as I said, your behavior of bog and rattle acts like a lean condition, easily explained by the PV and to a lesser extent jets.  If it was mine, I would run the original jets if you have them, if it was 2 sizes down, and that is what you have, good enough, but to me a primary main jet of 78 for an 830 is just about perfect, 76 is likely OK, but man o man is 72 lean.  That's a 750 jet (it's not exact science, but it's too lean)

However, I would not buy jets, run whatever biggest set you have already paid for, then put a PV in.  I think your 5.5 PV may be OK if you want to go with it.  It depends what your vacuum really at cruise, but 5.5 or 6.5 should work

In the end though, EVERY thing you are experiencing matches a lean condition, stop trying to lean out until we have it running well.

2 - Check your accel pump and let us know.  However I do NOT think you should touch the IFR.  You have to fix the "knowns" before you start screwing with hunches. 

3 - Let me reiterate, what you think is data from the carb before IS NOT DATA, that carb IMHO was being flooded with a bad PV and you need to delete it from your logic.  We are starting over, and the carb as close as delivered originally is the smartest place to be

4 - Whichever jet/PV combo you change to, always start by readjusting idle speed and idle a/f before you do anything else.  Jets and PV don't affect idle, but any time you look at vacuum, you need to make sure the carb is adjusted and the timing is where you want it

5 - Timing - you have sort of verified initial and total, but you still have not verified rate.  If it is rattling, and rate and total are good, you likely have too quick of a curve, which requires a spring swap, but let's get the carb with the right jets and PV in first

Again, forget the old carb stuff, the engine is setup differently, AND every single bit of carb data is pointing to first a bad PV then a carb asssembled with the wrong PV

Let me add one more thing about the IFR as well, it's not too large, period.  If an IFR is too large, you might have a little rich mixture at transition, but idle air/fuel screws will clean up the idle itself.  It is a large IFR compared to some, but it's based on a lot of factors and if you start changing multiple things, I won't be able to keep up with you.  Please, leave the IFR alone and get it out of your head for a while.  ALL the issues I see point to 1 - PV, 2 - timing curve, 3 - accel pump (maybe), 4 - jets (least but I hate guys going to lean)

[Yellow Truck]

Ross,

I am paying VERY close attention. Let me assure you that I am making NO assumptions about the carb are based on how it ran with what was in it before, or is in it now. My only assumption is it is suspect in all aspects.

My main question was, and remains, do you think I should take it back to QFT factory set up for sea level operation, or what they told me (and is the standard procedure) for running at 3,500 feet of elevation - namely take it down to jet sizes. This is how it was run from day one, and it was rich.

I hear you on the PV - I am going to get a 6.5. No discussion, just can't until tomorrow.

I DON'T have any jets. My buddy swapped me the original jets for the sizes that QFT recommended, and the garage kept the others. Not a big deal to buy new ones. My only question here is, assuming I'd rather have a few parts on hand I never use rather than run back and forth to the shop, what other jet sizes would it make sense to keep in my tool box?

The garage said they changed the pump to a 3.5 - any idea what he meant by that? I don't see anything with a 3.5 value in the specs.

I had the distributor re-curved by a local specialist with a machine to spin and check it, and I'm pretty confident he did it right, however is there a way to confirm the timing is coming in as expected? I can have someone manage the throttle/rpm and check timing at different engine speeds. If there is I'll check the new one too.

I have not had a chance to put the gauges in yet, had some coolant leaks that needed cleaning up after the re-assembly. Will start on gauges next, that way we can get better AF/vacuum info for any tuning.

Last, from what you are saying, we DON'T need any more info about the current carb setup since it is just plain wrong, so I won't fire it today and gather more info.

[My427stang]

Good readback, appreciate your patience as well

If I was in your shoes, I would read timing at idle, vac disconnected.  Then I would go 250 rpm increments and note the timing at each increment until it stops changing.  You are looking for 3 things, 1 - Initial is correct, 2 - total (max) is correct, and 3 - when it reaches max.  Find that out and post it, all vac advance disconnected.  Let's see what it is, my hunch it isn't what you think

Once we have that, we'll decide on the next move

With the carb,  I'd be OK with the QFT recommended 76/84, I'd even be OK with a 5.5 PV,  it's not that far off what I think you will need, but realize what you just typed was 72/74, that is WAY too lean on both the primaries and the secondaries.  Stock QFT is 78/86, don't go under 76/84.  Your 5.5 PV you bought is likely fine, don't lose money if they won't take it back, use it.

In the end what I am telling you 76/84 is so close to 76/86 (from your spec sheet) that is is close enough, pick one, QFT recommendation is fine, but what you have now is detonation waiting to happen, especially with that 3.5 PV

My hunch on the 3.5 discussion with the accel pump is that they meant .035 or 35, and had the PV value in their head.  That will be fine for now, assuming it is adjusted correctly and working, but let's get the timing mapped first

[Yellow Truck]

Ok, I'll map the timing when a friend comes over. I'll do it in increments of 500 rpm because the throttle is a little hard to manage to 250. I'll also check the pump behaviour, haven't had time yet.

I asked and I can swap the 5.5 for a 6.5. I will go back to the QFT altitude adjusted sizes - 76/84. I will not bother to pick up a IFR, but I'll probably grab a set of the metering block gaskets.

I drove it around the block to see that my new gauges are working correctly. They look nicer that the cheap oil pressure gauge I took out, and the vacuum is showing the values as the under hood gauge but I should be able to get some info on vacuum, AF, and RPM now.

IMG_3430 by Fred Snoyd, on Flickr

I'll also bend the secondary link a little more as has been suggested to snap the secondary closed, and will take the carb back to stock mixture positions before starting it with the new jets and PV. That is for tomorrow.

[Yellow Truck]

Timing test:
1,000 (idle) 20 degrees
1,500 30 degrees
2,000 33.5 degrees
2,500 35 degrees.

These are as per the marks, true TDC is at 1.5 on the marks.

How do those stack up?

[My427stang]

Nice work, but I may send you back to do it again LOL

At 2500 you were at 35 degrees, did you go to 3000?  The reason I ask is we need to make sure it doesn't go any higher.  If you did, we are good

Regardless, your timing curve is too quick for a 4x4 truck.  We know it's at 35 degrees at 2500, but it could be actually a bit earlier too as you did the test in 500 rpm increments.  I like to see total timing all in by closer to 2800-3000 (for a truck). 

Additionally, running so much initial flattens the curve, so you have a lot more timing along the slope than a traditional 20-ish degree curve.  You can see that if you graphed 2 curves, one that starts at 10 and gets to 35 all by 2500 and one that starts at 20, the early part of the curve has more even though they get to the same place. 

This is not your bog or hesitation, but it is almost certainly why it's rattling.  How is the new distributor going to be setup?  I'd love to see a little less initial, even with the low-ish vacuum, and then all in by 2800.

Be sure you don't run it in the rattle, the pressures inside, depending how bad it is, can quickly take out a head gasket and in severe cases can take out a piston

[Yellow Truck]

Ross,

Didn't report 3,000 because it had stopped moving at 2,500. For now are you suggesting a little less initial timing?

My plan didn't include changes to this distributor, but I can back the initial off if it makes sense. I don't really know how the new one will be set up. I'll ask but I have noticed Faron has gone a little silent since he is late delivering.

I can try the test again in 250 RPM increments, but will need a different assistant, this one was a friend who came over for dinner and she was a little scared of the truck (and my wife hates it).

At present the most I'm driving it is once around the block, and have to have a reason at that. Off to pick up carb parts this morning.

[My427stang]

So, we start running into competing fixes

First, I'd pull 4 degrees of initial out of it for now if you plan to drive it after the carb repair. Make the timing change and the carb parts swap and then adjust idle a/f mixture and idle speed, but realize it won't be 100% until you get the correct timing curve in.  Really, your timing should be resolved and the carb done last, but it won't hurt anything to get the carb closer to stock as we discussed.

I don't really think you need to do it again if it is difficult, we know it's too quick of a curve, the question would only be how bad is it?

Faron knows his stuff and I cannot imagine he would have that quick of a curve in a truck, but I would email him and see what he had in mind, even if he is late delivering.  My hunch is it could be delayed to as long as 3000, depending on weight of the vehicle and use.

Another question, do you run vacuum advance too?  If so, I would leave it disconnected and plugged for now.

[Yellow Truck]

Ross,

No vacuum advance - took it off a while back at your advice (or Drew's - can't remember).

I'll pull out some initial vacuum, write to Faron, and get the carb back to stock for now.

The truck is not really used. It is purely a toy. Learned to drive in one in the bush in Northern Quebec working at a sawmill when I was 16. Always wanted a 4WD F100 from the period and picked it up about 14 years ago and it has been a hobby ever since. This is the third engine. I had the 360 rebuilt, didn't like it so bought a 410 for it, dropped that in and it was ok, finally scratched the itch to build my own. Cruising around town, odd trip to the dump, and more WOT time than is sensible is what it sees.

[Tobbemek]

I dont know why i got the impression of that you have a 750 cfm carb Paul when it states clearly in every post ( when one looks )that it is a bigger venturi 830. The size of a carbs venturi is whats  most demands the size of the jets. And like Ross seas the 72-76 jetting is way to small for a 830.
I think you will do great if you follow Ross recommendations he has have you covered all the time in this very long tread and putt in a good job off effort in it, just stay with him and you will be fine.

[scott foxwell]

Shouldn't you guys be talking on the phone? I appreciate all the information being shared here but this is long past the title of the thread...

[Tobbemek]

I believe there are many people following this thread with a lot of interest to see how it will turn out for Paul. Another thing when you is taking on new technical information, if it is in writing one can go back and check "hmmm what was it again" that one cant do over the phone. 
Of cause just mine thoughts