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  #61 (permalink)  
Old 04-15-2010, 09:00 PM
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Thanks a ton for the explanation, all the off road engines I worked with used Webber carbs using single runner/ throat per cyll. arrangements so there's a lot here for me to learn. MB only used a 4 barrel for 3-4 years and then went exclusively to FI. All the big motors always used FI, the earlier ones were all mechanical FI hence the dyno. experience on my part. You would or perhaps not be amazed at the differences between domestic and European engines from the past.
Bill

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  #62 (permalink)  
Old 04-15-2010, 09:13 PM
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I run cams with plenty of overlap, open the secondary blades like cobalt says
to allow closing the primary side to gain control of the idle circuits. Lately I
have been converting all my carbs. to 4 corner idle and drilling the blades with
a 0.100" hole to close the throttle blades further.

Another benefit from cracking open the secondary blades is to "activate" the
transition circuit when the secondary is closed; this way when the blades open, fuel is
already flowing to eliminate a lean spike. Tuning this way allows a smaller
fuel enrichment shooter size.
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  #63 (permalink)  
Old 04-15-2010, 09:30 PM
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Quote:
Originally Posted by Bill Adkins
You would or perhaps not be amazed at the differences between domestic and European engines from the past.
Bill
Bill, I'm SURE I'd be boggled w/the current crop of Euro-engine tech.

I used to keep up w/motorcycling AFA the engine technology went (owned Ducatis w/desmodromic valve train. Old, odd, but interesting), and even to this day enjoy an occasional foray into F1 automobile tech, just to stay humble (I'm sure you're aware M. Schumacher is back w/ Mercedes again).

The technology that 90% of the engines here are still dealing with hearken from the 50's, as you know- with the occasional LS-type engine exception (that is still dinosaur era).

But to this day, nothing has given me the visceral thrill of a ground-pounding large displacement iron block V8, American style...
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  #64 (permalink)  
Old 04-15-2010, 10:18 PM
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I had the pleasure of attending the Long Beach grand pre for several years as well as attending a race program in Mexico City a number of years ago on Mercedes Benz as a part of an award for being ranked highly as an MB tech. I retired two years ago and the technology is mind boggling. There is a web site you might enjoy, it's benzworld.org . I play answer man there from time to time. Anyway I was involved in a USAC midget race team for a number of years and I found that a lot more exciting.
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  #65 (permalink)  
Old 04-16-2010, 03:53 AM
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Used to go to the Sebring race. When Chaparral was doing well, I was there in '65 (11 at the time) for a rain-soaked event that they won- after sitting in the pits for about 15 minutes because the track was basically under water in places. Had no idea what had happened- other than the (OUR!) car wasn't on the track! Nail biting, until we realized what had 'happened'.

To this day I never had the occasion to see a F1 race, we did get to go as a guest of Jaguar to the Daytona 24 hour event, I was friends w/a mechanic who got me passes and was able to hang around to watch.

I just don't see IR Weber set-ups that much. Sometimes a Weber/Inglese or clones on a Ford engine.

I'd have to say that here, an IR intake set-up is rare almost to the point of nonexistent, AFA carbed street engines goes- unless it's motorcycles being discussed. One member has mentioned toying w/the idea, but I haven't heard anything about it recently. You could probably lend him a hand if the occasion presents itself.

Last edited by cobalt327; 04-16-2010 at 04:00 AM.
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  #66 (permalink)  
Old 04-16-2010, 05:52 AM
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eric,
it is because it is all new info to you that it's IMPERATIVE that you are aware of any "cautions" before you do a change!!!

turned to the full on position a adjustable vac unit can/will add 30*+ to the mechanical!!!

when you were test driving it in the full on position hooked to manifold your idle timing was about 46*'s and cruise timing was about 64*'s...

darn good way to destroy a motor!!!!

only for the "idea" to study,,, here is a (accel unit) chart example that shows what the relationships are for Hg and degrees added and screw turns...
(different brands units have different curves and total added)

the degrees listed on the chart is distributor degrees,,,you multiply by 2 to know how many crankshaft degrees will be added,,, which is how you read timing with your light...
example from this vac model unit:
with 14Hg idle and turned full on 8 turns it will add 26* to the mechanical base timing (13 dist degrees x 2 = 26)...
so your idle timing would be 16+26=42=WAY TO MUCH!!!

your cruise Hg is more than 17Hg (we will prove that later) so turned full on the unit will add 28*'s (14 dist degrees x 2=28 crankshaft degrees)...

16b +18c =34T+ 28v=68*'s TT = WAY TO MUCH!!!

PS: pretty doubtful that you can hear ping at WOT with just cherry bombs for mufflers...
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Last edited by red65mustang; 04-16-2010 at 06:17 AM.
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  #67 (permalink)  
Old 04-16-2010, 06:52 AM
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Red, if he had either a segmented or marked degree wheel on the engine or an indicating light can't he just monitor the advance at idle with and then without vacuum and do the math. The idle vacuum signal will be bettered a slight amount at say 2500- 3300 cruise or light throttle and will diminish beyond that . Thats how I did it on the MB's wayyyyy back when quite effectively. During the hay day of dyno work I averaged 10 cars a day on my rollers.
Bill
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  #68 (permalink)  
Old 04-16-2010, 07:18 AM
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Quote:
Originally Posted by automotive breath
...
How much initial advance do you have?
What is your total advance?
How much advance is in the vacuum canister?...
Red, on page one of this thread I asked Eric these questions and explained
how to gather this information, I agree its dangerous to make ignition
advance adjustments with out knowing exactly where you are first.

If Eric had more static compression, he may have learned this the hard
way, many people do!
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  #69 (permalink)  
Old 04-16-2010, 12:24 PM
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Bill,
for now,,,all I can say is it would be a very slim chance of a problem if done as you described,, set to add only 10* at 14Hg idle plugged into manifold as a tuning start point on a healthy motor...

he hasn't responded yet to tell me what the brand and model dist is on the motor so I can look up the settings and dist spec's to answer absolute...
(heck, some dist's are designed for timed port only operation)
(he says his cent is 18 {16b+18c=34wot} but most are shipped with 20 or 22 so I'm not even sure he is reading the timing correct)

especially for ign timing my rule is "no guessing allowed"..
it only takes one "BANG" for "good by" motor...
(bad plan to add timing without first knowing the chambers are clean and the whole motor is healthy which are the reasons for all my post questions so far)

LOL,,,how about we prove it is a healthy motor first and fix the miss problem then discuss tuning it....

Last edited by red65mustang; 04-16-2010 at 12:56 PM.
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  #70 (permalink)  
Old 04-16-2010, 03:47 PM
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Hello guys ok Redmustang 64 thanks so much for the info. I was going to check things with my timing light and not leave it like it is I know better then that. I just had a preidea about the vacuum advance canister. I read an article about them and it said they only provide about 14 inches of vacuum at most. Wow I put my timing light on and they all must not be the same. I used some blue model paint to mark 16 degrees for my initial timing and red for 34 degrees. I am running 18 degrees vacuum advance right now as it stands so I need to take several turns out of it.

Now that being said I put my new plug wires on and still have the off and on miss but I guess i will have to live with that. Perhaps that is just the effect of the overlap of the cam. It happens on my other truck too. So what would you guys say I should put the vacuum advance at? I am thinking around 12-14. As the math goes 16+20+14 = 50 degrees total. Or should I play it safe and do just 12 degrees of vacuum? Where almost done here guys and thanks a bunch for helping me out here. Thanks again redmustang for taking your time and getting that chart for me its very much appreciated You the man and the other guys are too.
Thanks
Eric
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  #71 (permalink)  
Old 04-16-2010, 04:11 PM
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Quote:
Originally Posted by eric32
...I put my new plug wires on and still have the off and on miss but I guess
i will have to live with that. Perhaps that is just the effect of the overlap
of the cam...
If it's truly a miss, it's not caused by the camshaft overlap, something else
is causing the problem.
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  #72 (permalink)  
Old 04-16-2010, 04:25 PM
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Well I don't know about the stupid miss I have. All new plug wires have been put on distributor is brand new along with all the parts on it. Everything has been replaced with all new stuff for this motor. But anyways I will wait for other feedback on the vacuum advance setting. I am thinking around 12-14 degrees since I have all of my mechanical timing in by 3000 rpm.
Thanks guys I am done for today but when I get my truck home tomorrow I will readjust my vacuum canister.
Thanks
Eric
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  #73 (permalink)  
Old 04-16-2010, 04:36 PM
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Ok sorry for another post but looking at the chart if I am looking at it correct the bottom is how many inches of vacuum your engine is making and you follow the line and match it up with the line you want for degrees of advance in which I am wanting 7 turns to get 12 degrees correct? I guess I will have to turn so many times and recheck with my timing light till I get 12 to 14 extra degrees of timing with the vacuum advance connected. I really appreciate your guys help I am learning a lot about tuning vacuum advance here and am getting a nice lesson on it.
cheers
Eric
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  #74 (permalink)  
Old 04-16-2010, 08:29 PM
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Eric,

You could very well be having a lean miss(with the secondary's being open a bit). This would be aggravated when the engine is completely warmed up, and the choke is fully open, and the engine is at idle. A occasional miss on slight acceleration would be from the accelerator pump cam, or lever adjustment being too little too late.

My gut feeling is, your timing is NOT your problem. Your 'tune' sounds real close to being right on the money.

Your camshaft, and final compression ratio, are going to determine how much initial/base timing, and how much additional timing advance is needed. Every 'modified' engine is going to react differently. What works for me in SO CAL, may be different for your location. (altitude, barometric pressure.....etc)

There is a 'ton' of valuable information on this thread, from very knowledgeable contributors. As previously stated, 'each one of us can say the same thing, but with using different words'. So much so, that I felt my input is/was not needed.

Stephen
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  #75 (permalink)  
Old 04-16-2010, 08:46 PM
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I feel I'm learning from most everyone here with the different views and explanations. I can say that my background is extensive and well developed but from a different angle so to speak so don't hold back.... carp it may something I for one never thought about
Bill
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