'65 300HP miss and bucking at steady speed

[Joe M.]

Re: '65 300HP miss and bucking at steady speed

the carb screws that hold the top to the body sometimes loosen. the intake manifold bolts always need a retorque. Obny takes a few minutes before you take the carb off.

Another thought is upsetting the carb when removing the intake may have dislodged some dirt into an internal orifice.

[Duke W.]

Re: '65 300HP miss and bucking at steady speed

It sounds like your engine doesn't have an OE 300 HP cam, and you don't know what the VAC specs are. You can verify the VAC specs with a Mity Vac and timing light. If it doesn't comply with the two inch rule, then get a ten dollar replacement that does. This has been discussed a zillion times.

It may just be lean. The '65 AFBs are lean relative to the '63 AFBs that were tuned to work with the high overlap Duntov cam. Oxygenated fuel can exacerbate a slight lean condition.

This is what happens when "engine builders" start swapping camshafts without giving any thought to the impact they have on the fuel and spark advance maps.

The fact that the dimple in the dist. gear was 180 out is clear evidence that Bubba has been in your engine.

Get the spark advance map squared away before you tear into the carb. What's the centrifugal curve? Where does it start? Where does it end and with how much advance?

Duke

[Stuart F.]

Re: '65 300HP miss and bucking at steady speed

Dave;

From your latest post it appears your well on your way to sorting this problem out, and you have a good approach.

Regarding the wetness on the SS plate, I have experienced the same phenom in playing around with my two AFB's attempting to sort out a crazy 3461S (original 63) and my standby 3721SB replacement carb. When I use a base stack of phenolic spacer and SS plate with my 3721SB, upon removal (to test changes on my 3461S), I will have some condensed fuel on the plate surface that the aluminum carb base sets on. With my 3461S this does occur. The only thing I see different between the two carbs is the 3461S has vapor vent holes just above the butterflies in each throttle bore. I have since plugged them to help reduce the smell in my garage and stop the staining on the front and back of the carb.

I trust your installation has a 3700 series AFB and, therefore, you will have that liquid film of condensed gas on the plate, and possibly some wetness in the manifold below the throttle butterflies. Seems to be the nature of the beast whether you have a cast iron intake or aluminum like mine, i.e. nothing to worry about.

I would look closely at just how well your base is sealing. You say you already discovered you had the phenolic spacer upside down. You may want to consider blocking off the exhaust heat ports in the manifold beneath the carb (if you have them). Be certain whatever gasket or plates you use are correct for your manifold. I have seen many AFB kits have the wrong base gaskets which can lead to vacuum leaks - real easy with AFB's. Check the pictures in "Doc Rebuild's" catalog (paper copy or go on-line). They show all the base gaskets/plates and what engine applications they are for.

Stu Fox

[Edward J.]

Re: '65 300HP miss and bucking at steady speed

Stu, do you use the 300hp plastic spacer on you 340hp engine? Thanks Ed

[Timothy B.]

Re: '65 300HP miss and bucking at steady speed

Dave,

Before you take the carburetor apart warm the engine and pull one wire at a time off the distributor cap to see if you can isolate the miss to a cylinder, you may have a bad spark plug.

Also, if you use the stock hot air choke be careful for a vacuum leak around the gasket surface where the choke cover bolts on the side, a leak here is sometimes hard to see.

[Stuart F.]

Re: '65 300HP miss and bucking at steady speed

Ed;

Yes, I use the 3/8" phenolic spacer from the 300hp L-75, but I currently sandwich it with base gaskets for my 340hp L-76. This arrangement effectively seals off the exhaust heat slot in the spacer, and fits the manifold and AFB bases properly. These gaskets I get from "Dr. Rebuild" which seem to be the only correct ones out there for the 340hp L-76(have small tab at front of gasket). In checking my notes from a few years past when I first made this change, it effectively accounts for a true 35 to 40 degree temperture reduction at the carb. This, of course, also includes the use of an electric choke and a fuel hose from the filter to the carb to isolate it from any heat conducted to it from the steel tubes. I will be running another test on the temps this week end to post my findings in Duke's thread about the effects of Ethanol laced gas. I currently run Non-Ethanol 90 octane with a boost from Max Lead 2000 to get it up to about 100 octane. As long as the non-laced stuff is available, I will be using it as it seems to contribute to the cool and stable running I am enjoying here in Florida.

Stu Fox

[Duke W.]

Re: '65 300HP miss and bucking at steady speed

I look forward to your temp data, but there is no way that a can of anything you can legally buy, will increase 90 PON to 100 PON, which is about 105 RON.

Try running without the over-hyped additive and see if it makes any difference. The "points" some off these guys advertise are 0.1, not 1.0.

Duke

[Larry M.]

Re: '65 300HP miss and bucking at steady speed

I look forward to your temp data, but there is no way that a can of anything you can legally buy, will increase 90 PON to 100 PON, which is about 105 RON.

Try running without the over-hyped additive and see if it makes any difference. The "points" some off these guys advertise are 0.1, not 1.0.

Duke

The octane booster that Stu refers to is really tetraethyl lead fluid (TEL with EDC/EDB scavengers or TEF) in a toluene or Jet fuel A diluent. There were originally the two diluents offered, but I believe today that only the toluene diluent remains. It is the real deal. It is also sold for "off road use only". It is hazardeous and it is poisonous. You need to use and handle with care.

Adding various amounts TEL can and will boost the PON by as much as 10 full octane numbers. This is not advertising hype, but is from data from technical articles on the effect of TEL on gasoline octane numbers from the 1960's -1990's hydrocarbon and gasoline publications of this time period. These articles state that a TEL (or TEF) content of 1.05 grams lead per liter (g Pb/l) will boost the octane of unleaded gasoline stock by approximately ten (10) control octane numbers. ie. 93 PON to 103 PON.

Not certain anymore where the tetraethyl lead fluid (TEF) comes from. It used to be left over from old USA inventory......and it still may be. There is only one major tetraethyl lead manufacturer left in the (western industrialized) world and they are in Great Britain. They supply the TEF for all of the 100LL Av Gas and for all of our leaded racing fuels.

This particular octane booster was discontinued about 2-3 years ago when that chemical company went under, but has resurfaced under a new name.

FWIW..........Larry

[Duke W.]

Re: '65 300HP miss and bucking at steady speed

I'd like to see those references, but given their age... Can you provide specific publication names?

The octane increase for a given amount of TEL varies with the fuel blend, but the 1.05 gPB/l is about 4 cc TEL per gallon, which is about double the typical TEL content of sixties vintage gasolines. I may have some data on how much this raised the RON of sixties vintage gasolines, but I doubt if it was close to ten points. ASTM D910, which contains the specs for 100LL avgas specifies a maximum of 0.56 gPb/l, so the volume concentration of TEL is about 2.0 cc/gal.


The old 115/145 avgas blends had as much as 7-8 cc/gal TEL. Modern 100LL avgas is 100 MON and is effectively the equivalent of the old 100/130, but it no longer carries the 130 Performance Number for high boost with a very rich mixture.

Diluting TEL with jet fuel is a good way to reduce octane, but toluene is well over 100 RON.

Also, TEL is considered a hazardous substance by the EPA and I believe there are regulatory requirements on its manufacture and handling.

To any that use this substance, assuming it actually has a meaningful amount of TEL, use disposable gloves when you handle it. TEL can be absorbed directly through the skin and takes up residence in fatty tissues forever. One should be very careful when handling TEL.

So, until I can review some real data from reputable sources, I remain skeptical.

Duke

[Stuart F.]

Re: '65 300HP miss and bucking at steady speed

Duke;

It is never easy to conclude the exact octane one arrives at when using and having any faith in what the provider states. I have been using the Max Lead 2000 for nearly 20 years now, buying it by the case from Jack Podell's booth at the winter meets of late. Their source has dried up so I don't know how long my shelf supply will keep me, hopefully till they put me in the ground.

Their label charts the following with the notation that it is based on 1970 octane ratings:

- 12 oz. in 20 Gals. = .28g TEL/Gal. = 99.5 octane
- 18 oz. in 20 Gals. = .37g TEL/Gal. = 100.3 octane
- 24 oz. in 20 Gals. = .56g TEL/Gal. = 101 octane
- 48 oz. in 20 Gals. = 1.12g/ TEL/Gal. = 103 octane

Now it is true that they base that on "93 octane unleaded", so my calculations would be off some now that I've found a source for, and adopted use of, 90 octane Non-Ethanol gas. You all can call it "snake oil" or whatever you like, but I do know it works for me and it is not all psychological. I've lived with this car since new and have endured the 70's and 80's when trying to make it run on pump gas was a challenge, i.e. retarding my mechanical advance curve and initial timing, using a B20 VAC, and dropping back to a 160 degree thermostat, etc. The engine has never been apart, save for dropping the pan once to remove a dent and repair the drain fitting (replaced the rear main seal as part of a 36,000 mile P.M.). Since using the TEL, I've been able to return to my aggressive timing MAP with 12 initial, using a B28 VAC with my Dyna-Flite plate, and go back to a 180 degree thermostat. Everything had been roses until Ethanol came along and the wife said "get that stinky car outa our garage". Now that too has been resolved and we have peace once again. I'm lovin it! Zero to redline everytime out of the garage in 1st, 2nd and 3rd, and the temp gauge rarely peaks above 180 - no stumbles, no hesitations, no engine stalls - even on our mid 90 degree days - providing I'm using my 3721SB (the 3461S is another matter). Current odometer reading is just shy of 46k.

Stu Fox

[Larry M.]

Re: '65 300HP miss and bucking at steady speed

Here is one technical article from my files. I will post a few others others as I find them. A lot of this info was developed and printed way before the internet, so it is not that easy to find anymore. I could scan a few paper copies.



Pages 240-244 are shown. http://www1.ifc.org/wps/wcm/connect/...fcd36a6515bb18


This second reference is simply an outstanding technical reference for gasoline in general. This is Part 1. You can also read Parts 2-3-4 for more than anyone needs or wants to know about gasoline for our cars. It is by Bruce Hamilton of the Department of Information and Computing Sciences, with references to about everywhere and everyone in the industry. See Section 4.6 for the TEL stuff. http://www.faqs.org/faqs/autos/gasoline-faq/part1/

This third reference is actually all four parts of the Gasoline FAQ above, INCLUDING the actual listing of all references and authors cited by Bruce Hamilton. This way folks can do more/further research on their own if they desire. http://blizzard.rwic.und.edu/~nordli.../gasoline.html


Larry

[Stuart F.]

Re: '65 300HP miss and bucking at steady speed

Larry;

Thanks for the information. I'll keep it handy so I don't sound like a bumbling idiot when someone challenges my reasoning in the future. I admit I've lost a lot of brain cells since retiring from Senior Techwriter on EMD Locomotives, thanks to age and health issues. Wish I could have retained my "edge" like Duke and John Hinckley, but guess I got too good at compartmentalizing the periods in my past that weren't too much fun - like SEA and working (never was much of a "foamer" about locomotives).

Stu Fox

[Chuck M.]

Re: '65 300HP miss and bucking at steady speed

Dave,

Before you take the carburetor apart warm the engine and pull one wire at a time off the distributor cap to see if you can isolate the miss to a cylinder, you may have a bad spark plug.

Also, if you use the stock hot air choke be careful for a vacuum leak around the gasket surface where the choke cover bolts on the side, a leak here is sometimes hard to see.

Dave,

I would agree with Timothy. We experienced a very similar problem last summer with our '67 L79. We had just had the carb rebuilt and once we put it on had very bad bucking under load. We conducted almost all of the tests you have and decided to change the plugs out before going further. This is pretty easy to do and is a cheap check. We have not had one issue since then. Check your plugs if you havent already done so.

Good Luck!!
Chuck

[Larry M.]

Re: '65 300HP miss and bucking at steady speed

Stu:

If you run out of your MAX LEAD, you can still buy it......but in a toluene diluent instead of the Jet A fuel diluent. Don't know how much longer it will be available, and whether Jack P. will try to sell it anymore. But I can provide the contact information if you need/want.

FWIW: As a young chemical engineer just out of school, I worked for a company the made TEL (or TEF) along with other chemicals. There were only three (3) companies in the USA that produced TEL at this time. I worked this process as both an engineer and occasionally as an operator (as the OCAW union frequently went out on strike). I have since moved on, and the plant is no longer there, but I still keep up with what is happening.

Larry

[Joe C.]

Re: '65 300HP miss and bucking at steady speed

Here is one technical article from my files. I will post a few others others as I find them. A lot of this info was developed and printed way before the internet, so it is not that easy to find anymore. I could scan a few paper copies.



Pages 240-244 are shown. http://www1.ifc.org/wps/wcm/connect/...fcd36a6515bb18


This second reference is simply an outstanding technical reference for gasoline in general. This is Part 1. You can also read Parts 2-3-4 for more than anyone needs or wants to know about gasoline for our cars. It is by Bruce Hamilton of the Department of Information and Computing Sciences, with references to about everywhere and everyone in the industry. See Section 4.6 for the TEL stuff. http://www.faqs.org/faqs/autos/gasoline-faq/part1/

This third reference is actually all four parts of the Gasoline FAQ above, INCLUDING the actual listing of all references and authors cited by Bruce Hamilton. This way folks can do more/further research on their own if they desire. http://blizzard.rwic.und.edu/~nordli.../gasoline.html


Larry

One of the most important facts from the first referenced article is the following:
"Lead addition is subject to decreasing returns to scale: each increment of lead added to a gasoline blend provides a smaller octane boost than the previous increment"
I have used a very similar product, manufactured by Kemco, called "Octane Supreme 130" and have found that the law of diminishing returns makes it uneconomical to increase PON rating beyond about 97. For boosts beyond this point, it is cheaper to dope with 100LL.
I had a detonation problem at the time, and the Kemco TEL (in a Toulene base, which is in itself a mild octane booster) quelled it. I have not had a need for the stuff for the last 4-5 years.