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Speed top off
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Author:  Luthastro [ Sat Apr 01, 2006 9:27 pm ]
Post subject:  Speed top off
My newly built '65 226 purs like a kitten, but it hits a very distinct hot spot in the middle of the RPM range in any gear starting out. It's factory spec according to what I find. There are 3 things I'm thinking might improve the situation. I'd appreciate comments on them.

1. Advance the spark greater then the factory 2.5 degrees.

2. Put in 2bbl carburation.

3. Put in a 4 speed trans.

Are any of these on the mark? Would all 3 be good? I need a tranny. This 3 speed is very marginal.
Author:  slantvaliant [ Sat Apr 01, 2006 11:06 pm ]
Post subject: 
What do you mean by "hot spot"?
Author:  Luthastro [ Sun Apr 02, 2006 8:50 am ]
Post subject: 
Quote:
What do you mean by "hot spot"?
I mean that torque builds at the start of acceleration, holds a while, then suddenly drops off almost as if you took your foot off the accelerator.

I can't tell you what RPMs are involved, because I don't have a tach.
Author:  SlantSixDan [ Sun Apr 02, 2006 9:36 am ]
Post subject: 
You haven't got a "hot spot", you've got a flat spot. Or a bog. Advancing the timing beyond 2.5° may make the flat spot seem to go away. Changing to a different carburetor may improve or worsen it. A 4-speed transmission has no place in this conversation.

This flat spot may be due to an issue with the carburetor or with the distributor. What's required to fix it is a tachometer, a vacuum gauge and some time spent thinking about the symptoms to trace down the problem. In the meantime: Does this flat spot occur all the time at a certain engine speed? Only at full-throttle, only at part-throttle? Only when going uphill? Only when cold, only when hot? You've got which carburetor, the Holley 1920, the Carter BBS, something else? What distributor are you running?
Author:  Luthastro [ Mon Apr 03, 2006 8:57 pm ]
Post subject: 
Quote:
You haven't got a "hot spot", you've got a flat spot. Or a bog. Advancing the timing beyond 2.5° may make the flat spot seem to go away. Changing to a different carburetor may improve or worsen it. A 4-speed transmission has no place in this conversation.

This flat spot may be due to an issue with the carburetor or with the distributor. What's required to fix it is a tachometer, a vacuum gauge and some time spent thinking about the symptoms to trace down the problem. In the meantime: Does this flat spot occur all the time at a certain engine speed? Only at full-throttle, only at part-throttle? Only when going uphill? Only when cold, only when hot? You've got which carburetor, the Holley 1920, the Carter BBS, something else? What distributor are you running?
OK, I guess by flat spot you refer to the place on the "curve" past the rapid acceleration.

Seem to go away? I thought maybe it had too little spark advance for high RPMs. This is the only car I've ever had with such a low advance. But I guess maybe it's relative to something else.

Tracing symptoms? I understand why a tach is needed. I have no clue what I would do with a vacuum gage beyond setting the idle to max vacuum as I've already done.

Flat spot at a certain speed? I think that's the general nature of it. It gets up to a certain point and loses torque. That point seems to be a little short of where I would normally shift. Obviously engines are made with max torque at a certain speed range. But I'm surprised at the very obvious torque fall off.

Carb or distributor? The dist is a bit old and loose. I'm thinking about upgrading to electronic. Would a short dwell cause such a drop off? I seem to be finding conflicting dwell specs on the internet.

Full or part throttle? The more throttle I give it the more obvious it is.

I don't think grade effects it.

Cold or hot? I'll have to check on that.

Carburetor? It's "a" BBS. I see two different carbs called BBS. Mine looks like one of them.

The distributor is an auto supply replacement for the original point/condenser distributor, with lots of miles on it.
Author:  Jeb [ Tue Apr 04, 2006 6:11 pm ]
Post subject: 
Since it is a Carter, you might have a misadjusted metering rod.

Is your vacuum advance pod blown or leaking? Do the centrifugal weights in the distributor move freely? You can adjust the vacuum advance pod my inserting an allen wrench(not sure what size) into the vacuum fitting and turning it clockwise(I think)

The Vacuum gauge can be used to determine whether or not you have a low vacuum condition that you encounter while going down the road. A vacuum leak can lean out the mixture, causing the bog you are experiencing.

Might want to check your fuel filter and float level also. When was the last time this carb had a rebuild?
Author:  SlantSixDan [ Tue Apr 04, 2006 6:44 pm ]
Post subject: 
Quote:
OK, I guess by flat spot you refer to the place on the "curve" past the rapid acceleration.
That's one way to think of it, yeah.
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I thought maybe it had too little spark advance for high RPMs
You might have better results with a little more spark lead. Try 5°BTDC and see how that runs for you.
Quote:
I understand why a tach is needed. I have no clue what I would do with a vacuum gage
Watch what it does when you encounter the flat spot, then see if you can cause the flat spot to occur reliably at different road speeds by driving so as to attain that same vacuum reading (as for instance by keeping the car in 2nd gear or revving in Neutral). This will help narrow in on what's causing the flat spot.
Quote:
Carb or distributor? The dist is a bit old and loose.
Well, old and loose points-condenser distributors are notorious for causing tough-to-trace driveability problems, because when they wear and get loose, it's impossible to get anything like consistent dwell at low and high RPM.
Quote:
I'm thinking about upgrading to electronic.
Not a bad idea, see here.
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I seem to be finding conflicting dwell specs on the internet.
Uh-oh, sounds like you haven't got the factory service manual for your car! Following the advice in this post will pay for itself very quickly.
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Full or part throttle? The more throttle I give it the more obvious it is.
OK, that suggests a potentially sticking step-up rod piston in your Carter BBS carburetor. Have you been through the carb to rebuild it?
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Carburetor? It's "a" BBS. I see two different carbs called BBS.
H'mm. Where do you see two? There's only one basic BBS design, though it got draped with different accessories and linkages for various year vehicles between '60 and '74.
Author:  SlantSixDan [ Tue Apr 04, 2006 6:46 pm ]
Post subject: 
Quote:
Since it is a Carter, you might have a misadjusted metering rod.
Step-up ("metering") rod is nonadjustable in the BBS.
Quote:
You can adjust the vacuum advance pod my inserting an allen wrench(not sure what size) into the vacuum fitting and turning it clockwise(I think)
The vacuum advances on the points-type distributors are nonadjustable. The adjustable ones found on some electronic distributors are adjusted by turning the allen key either direction, depending on which direction you want to adjust the unit (more advance or less).
Quote:
Might want to check your fuel filter and float level also. When was the last time this carb had a rebuild?
Good advice.
Author:  Luthastro [ Sun Apr 09, 2006 10:36 am ]
Post subject: 
Quote:
The Vacuum gauge can be used to determine whether or not you have a low vacuum condition that you encounter while going down the road. A vacuum leak can lean out the mixture, causing the bog you are experiencing.
Hm. I guess I can get a longer rubber hose for the guage so I can watch it while driving.
Quote:
Might want to check your fuel filter and float level also. When was the last time this carb had a rebuild?
New fuel filter. New carb - with a note not to mess with the float. But I guess I can check it.
Author:  Luthastro [ Sun Apr 09, 2006 11:15 am ]
Post subject: 
Quote:
Watch what it does when you encounter the flat spot, then see if you can cause the flat spot to occur reliably at different road speeds by driving so as to attain that same vacuum reading (as for instance by keeping the car in 2nd gear or revving in Neutral). This will help narrow in on what's causing the flat spot.
Thanks. I'll look into that. (After I put the rear cam bearing in right. It now occurs to me that having the rockers not oiling right might interfere with RPM's too)
Quote:
Uh-oh, sounds like you haven't got the factory service manual for your car! Following the advice in this post will pay for itself very quickly.
I've had one on order for weeks. :-(
Quote:
OK, that suggests a potentially sticking step-up rod piston in your Carter BBS carburetor. Have you been through the carb to rebuild it?
New carb. Couldn't find a kit.
Quote:
H'mm. Where do you see two? There's only one basic BBS design, though it got draped with different accessories and linkages for various year vehicles between '60 and '74.
Well.... I have a Walker PDF that shows one. It shows a sort of "box" covering part of the bowl. Both my last and current one (Advance Auto replacements for almost all 225's, part # 14-612) are like the BBS except that the bowl is open topped right to the barrel. It definitely doesn't have that side mounted, rectangular thing (bowl I suppose).

I suppose it could be something other then BBS, but it is a Carter and I can't find anything else that looks even remotely like it.
Author:  Luthastro [ Sun Apr 09, 2006 12:36 pm ]
Post subject: 
Quote:
There's only one basic BBS design, though it got draped with different accessories and linkages for various year vehicles between '60 and '74.
Here's mine, except mine doesn't have the dash pot.

http://users.isp.com/lifedata/bbs2.jpg
Author:  SlantSixDan [ Sun Apr 09, 2006 1:17 pm ]
Post subject: 
Quote:
I've had one on order for weeks.
Cancel the order and buy it somewhere else. This isn't a 6-week-delay kind of book. Where'd you order from?
Quote:
New carb.
I'm guessing by this you mean you went into a parts store and got a replacement carburetor, which was not "new", it was "remanufactured", and is almost certainly causing your problems. As is discussed on this board almost constantly, parts-store "remanufactured" carburetors are trash.
Quote:
Couldn't find a kit.
Oh, now come on. If you didn't find a kit, it's because you didn't look very hard and/or you didn't ask on here. Carburetor kits for any carb used on any slant-6 are not a hard item to find.
Quote:
I have a Walker PDF
Walker is a Johnny-come-lately marketer of mostly offshore trash parts (=Chinese), trading on a long-established and reputable name of an exhaust components maker. As such, the quality of the information they provide is maybe not as trustworthy as we'd like.
Quote:
It shows a sort of "box" covering part of the bowl.
Y'mean like this?

Image

That's not a different carburetor, just a '70-up variant of the airhorn casting of the BBS.
Quote:
Both my last and current one (Advance Auto replacements for almost all 225's, part # 14-612)
Uh-huh, thought so. Parts store "remanufactured" junk. I believe we've ID'd the major cause of your problem.
Author:  Luthastro [ Tue Apr 11, 2006 9:04 am ]
Post subject: 
Quote:
Quote:
I've had one on order for weeks.
Cancel the order and buy it somewhere else. This isn't a 6-week-delay kind of book. Where'd you order from?
Ebay, already paid for.
Quote:
Quote:
Couldn't find a kit.
Oh, now come on. If you didn't find a kit, it's because you didn't look very hard and/or you didn't ask on here. Carburetor kits for any carb used on any slant-6 are not a hard item to find.
Once again, it's easy when you know how.
You're right, I asked on Allpar. What's more, I posted looking for the wrong carb, since I gave a number I found on the carb. Darn stupid thing to do. "My bad." Oddly enough, the number WAS a valid carburetor number, but I never saw an answer. At any rate since my stroke I'm lucky to remember theres a carb in a car. So maybe some of you guys who eat automobile parts for breakfast could lighten up a little bit.
Quote:
Quote:
It shows a sort of "box" covering part of the bowl.
Y'mean like this?
Image
Yeah, like that. That's the one Walker shows as a BBS.
Quote:
That's not a different carburetor, just a '70-up variant of the airhorn casting of the BBS.
I'm glad you cleared that up. Just remember, dummies like me have to search far and wide just to get a clue what a given carb IS, let alone know all about variants. All I had to go on was pictures I could find. If carbs don't look the same how in ___ am I supposed to know they ARE the same?
Quote:
Uh-huh, thought so. Parts store "remanufactured" junk. I believe we've ID'd the major cause of your problem.
How are non-experts supposed to know a good one from a bad one? I, for one, buy parts where I can (and get information where I can).

I found a place last night on the web that had a remanufactured BBS for $173. Would that be an acceptable one? But it doesn't matter, because I can't afford that kind of pricing on everything I buy. And just so you know, this isn't a restoration. It is my only transportation, which happens to be dead in the water at the moment, because I didn't notice when I rebuilt it that the rear cam bearing can go in upside down - that being because the oil holes aren't quite straight across from each other. But you already knew that.
Author:  Reed [ Tue Apr 11, 2006 9:53 am ]
Post subject: 
There areseveral problems with buying a "remanufactured" carb.

First, many "remanufacturers" do veyr little besides the mass disassembly, cleaning, and reassembly of carbs. Carburetors are reassembled by people who do not know or care what the specifications or adjustents on the carb are supposed to be. This leads to a carb that is completely misadjusted, often has mismatched pieces, and very often has the wrong size metering jets. If you do get a remanufactured carb you should be prepared to disassemble it, re-adjust all the settings, and swap out the main metering jet.

Second, they are really expensive. A good carb rebuild kit shouldn't cost more than $20, and all the tools you need (including a "dip tank" for cleaning) shouldn't cost more than $30.

i can appreciate not knowing a bunch about cars. I am a mostly self-taught mechanic. However, I do believe that you will have better luck if you rebuild the original carburetor for your car and don't use the remanufactured one.
Author:  SlantSixDan [ Tue Apr 11, 2006 2:09 pm ]
Post subject: 
Quote:
Ebay, already paid for.
Arrrgh. Report your seller for nonreceipt of the item. A 6-week delay is definitely against eBay policy.
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Once again, it's easy when you know how.
You don't have to know how, you just have to know www.slantsix.org . I don't mean to sound like I'm rubbing your nose in it or taking delight in your misfortune or anything, but asking your questions on here before you buy parts (rather than after) will save you a great deal of grief and money.
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I asked on Allpar
Much more consistently high-quality info here than there.
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Just remember, dummies like me have to search far and wide just to get a clue what a given carb IS
Again, that's just not true. All you have to do is ask on here...before making a purchase decision.
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How are non-experts supposed to know a good one from a bad one? I, for one, buy parts where I can (and get information where I can).
Answer to the first part, again, is "Ask here first". Answer to the second part is "Ask here first". This is a community of people who know about these particular cars and the parts that go into them, what works well and what doesn't, where to get stuff and where to avoid.
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I found a place last night on the web that had a remanufactured BBS for $173. Would that be an acceptable one?
Probably not. "Remanufactured" carbs are almost always junk.
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