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  #16 (permalink)  
Old 09-03-2010, 05:49 PM
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Perfectly understandable! I'm pretty good at making things that are supposed to be round, not so!

Thanks!

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Old 09-03-2010, 07:34 PM
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F-Bird mentioned about the power valves in the carb should be 4.5, curious what you have in there now. You described that it has a dead spot in 3rd gear and also said how it spins the tires easily. That kinda sounds like a wrong powervalve which would give you a deadspot when you have a heavy load....and Im guessing that 1 and 2 gear the tires arent really pushing as hard as in 3rd when you're really hauling *** and they finally grab the road???
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Old 09-03-2010, 08:16 PM
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Bubba -

The flat spot that was recently mentioned came about from installing the short yellow springs - with the purple springs, it was fine -- just didn't seem like the secondaries weren't doing much. Tried the short yellows to see if it come alive, but it didn't do a thing in a positive way.

Still need to throw in the tall yellows and see if the flat spot goes away. If it doesn't, the purples will go back in as a control point.

In regards to the launch of the car, while I can smoke the tires, I do what I can to ease into the throttle so that I'm not losing time with wheel spin. Unless I just need to show off, burning off through first and second is only for that purpose.

Now, you wouldn't think that would translate into what I perceive as a doggy high end car, but once the traction takes hold, or I try to accelerate from a steady 50-60, it just seems to not want to climb up the RPM range. That gets back to where Eric was headed in possibly a lack of adequate fuel delivery under high load - something I need to confirm by relocating my fuel pressure gauge so that I can see it from inside the car.

The power valves that are currently installed are 35's. Well, below the ideal if I have 12" of vacuum at idle in gear - but certainly close to F-Bird's recommendation of a 45 to start with.

Back to the overall driveability of the car, it is perfect for the average drive around town. Easy to start. No bog off the line. Flat spots only when I go to too light of a spring. I can run the car as hard as I want now that the large 76 jets are in the car. If a prospective buyer were to jump in the car, they would be amazed as to how tame it is in term of driving the car around.

It's just getting into it at the higher speeds is where it disappoints.

Maybe the timing change will turn this into a high rpm screamer up to my cam's 5500 rpm limit, maybe not. Not sure what the higher base/max 38 really will do for performance. It certainly revs easily to over 6000 in first and almost mostly through second, but in 3rd, that is where the disappoinment ends.

Guess maybe I should post a video on You Tube to show you guys - if I can get someone in the front seat to hold the camera!!!

In fact, I just may do that!!!

Let me try it over the weekend.

A couple of photos showing the new tires that went on the car a few months ago. Much stickier than the old MT Sportsman Bias tires. Not slicks, but they should ride nicer than what I had.







Last days of my camera - sorry about the photo quality.
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Old 09-03-2010, 08:48 PM
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http://4secondsflat.com/MSD%20Distributor%20Tuning.htm

Apparently this guy sells special CNC machined 10 and 14 MSD distributors advance bushings.
Just for this purpose. If your want a high base timing without excessive max timing, these may work.
If you don;t need this now, you will later with a bigger racy cam.

Playing with the sec spring tension won;t do nothing good until you get the sec jetting corrected. If the primary side needed a big jump in jet over stock, the sec side will too. Start at a number 21 plate or drill your plates equally.big. or modify your sec plates to accept screw in jets.

That is a very nice T bucket.

Last edited by F-BIRD'88; 09-03-2010 at 08:58 PM.
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Old 09-03-2010, 08:52 PM
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I don't care whats wrong with the camera, thats a beauty,,,envy

Quote:
One of my questions is this: What is really happening with a tunnel ram in terms of vacuum vs. a lower plane manifold?
Just a thought with respect to your 3rd gear sluggishness,,, Have you tried flipping the air scoop around? At increased MPH the scoop produces a bigger effect on flow and may be messing with the natural aspiration of the tunnel ram/carb combo....yeah I know its out there but ideas are free
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Old 09-03-2010, 10:30 PM
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Hey guys - all of you...

I can't tell you how much I appreciate all of the comments. I have looked at other forums and watched the guys fight over who knows the most, and it is really irritating. This is just wonderful to read what you have to say and no one is all over someone else calling them an idiot.

What a refreshing site to be on!!!

F-Bird -
Have to say, I would have guessed you would have written the text for those bushings!!! And nice of you to say that possibly I may not need that type of advance strategy with the current cam. This is all easy stuff to try and very reversible. I try to log notes on everything I do, so I don't have to repeat lessons already learned.

Still scared to death to try starting the car without an ignition cut off switch at 20 plus degrees, but nothing is going to break once. If I need to throw the switch I can and act like a real racer. We'll see if I fool anyone after they hear the tame idle after it starts.

Really curious to try this.

I think I'm going to call these guys Tuesday and talk to them. I want to ask them about Eric's thought that they won't fit without alteration. They look perfectly round to me. Now, I can't believe I'm going to pay $29 for $2 worth of parts, but they take the guess work out of the dimensions. Certainly worth some labor savings there. Bet they won't release the inner and outer diameter specs!!!

In regards to the secondary side of the carbs, everyone seems to be on board with going bigger. I just had always thought that since I was over carbed I didn't need to do anything back there, but it certainly seems to be consistent that what little it may open, needs to be correctly jetted for proper air flow.

What I currently have is a 34R9716-6. Equivalent to a 69 jet. I believe you want me to install a 134-21 which correlates to a 75. Or I can do the plate from Quick Fuel 34-3 for a few dollars more and then purchase jets as needed. Seems like that might be the least expensive way to go over the long haul.

Could this be the area that I'm missing the kick or turbo coming in feel because the overall mixture is leaning out when the secondaries are opening?

Would trying 79 jets just be another experiment or is there some logic to apply after the 75's are installed. How do I really know which way to go without going too far? Now, don't call me lazy, but changing jets with two carbs takes some time! I know I asked for it...

I'm really anxious to hear your response on this one. It just seems like something isn't right and after 12 years of wondering what it has been, this would really be an amazing solution.

Appreciate the compliment on the car. Thanks!!! Too bad you live so far away, we could go cruise the beach! It's a kick!

Custom -
We'll get some new photos once the pipes are recoated. Jet Hot is going to redo them for free - love those guys - and once they are back on, I'll have some nice photos to share. Thanks!!!

Now I hate to show this next photo, because you are catching me with a dirty part on my hands!!!

The hood scoop design is pretty much a fake. It is not sealed on the bottom so that air can enter between the two carbs probably easier than they do through the wire mesh screen with the foam behind it - the main reason why it is dirty. If I try to clean the screen, the foam deteriorates.



I really don't think that turning it around would make a difference in this case because of the open bottom, but possibly it would be a good idea to remove the foam so the air gets a straight shot coming in from the front. Let's see what the other guys think. I know from my days in the auto biz, that it didn't take much in front of a radiator to effectively block the air flow at high speeds and maybe this is doing the same. It might not look as nice seeing the K & N filter back there, but if the foam is part of the issue, I'm ready to try it out.

Let me throw out something new to everyone who is reading this post.

One of the weak parts of the engine cosmetics is the throttle linkage between the two carbs. I'm thinking of using some chrome heim joints (like what is on there) with offsetting spacers to dress this up and threaded stainless. Any ideas of commercially available products from a manufacturer that deals in this area of the car?



And finally, since Custom brought up the intake situation with the scoop, let me ask your opinions on the exhaust extensions. They don't have a muffler inside but a welded insert that you can see in the photo. I have thought about opening this up, and would need to do so before the pipes get recoated.

Aside from the fact it would make the car louder, could the back pressure from the insert be a major blockage in the engine being able to breathe at high rpm in high second/third gear???



Note how small the opening is in relation to the extension diameter. Not sure that we measured it, but it is probably 2". That seems awfully restricted to me, but maybe backpressure is better for the engine.

I have not run the car without the extensions to see how it performs at high rpm in 3rd gear. No place for me to really try that around where I live.

Welcome comments on the exhaust system. Curious to hear what everyone thinks.

Thanks!!!!!
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  #22 (permalink)  
Old 09-03-2010, 10:53 PM
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The exhaust baffles are very restrictive and will limit top end power a lot.
A engine has to breathe deep to make power. The engine any engine does not want or need "back pressure" But it does need collector length.

"back pressure" slows you down.

The baffles in your pipes are made to make it quiet primarily by pure restriction.
You will not make any horsepower with those things in the pipes.
Show car stuff.

You need a large see thru core muffler design that works on absorption and sonic phasing separation/deflection.

if you are willing you can make better baffles than you can buy.

i suggest a 2.75" to 3" inner core "perforated tube" A big diameter long tube with holes drilled in it, wrapped with steel wool or some kind of fiber glass wrap.
Borla, Magnaflow, Dynomax. muffler designs for inspiration.
ya it may be a bit louder but doesn't have to be crazy loud.


Take the inserts out remove the little air cleaners in the scoop.

jet 76 pri 75 sec ( or drill your plates to approx .076"(75jet)
92+++octane gas 38deg timing
it will be a whole different deal Don't kill yourself when you road test it.

You will need to use a AFR gauge/02sensor to fine tune the idle, part throttle cruise and WOT jetting further beyond my base recomendation.
even a cheap narrow band type is very informative.
I made one for under $100. (gauge, 12v lighter plug, 4wire heated narrow 02 sensor, wireing harness with 4 pin trailer plug.) A multimeter with PC serial interface allow you to datalog.
allows a very accurate carb tune up.

Last edited by F-BIRD'88; 09-03-2010 at 11:08 PM.
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  #23 (permalink)  
Old 09-03-2010, 11:17 PM
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Your 270 magnum cam is fairly mild as cams go. the car is very light with a ton of gear. You can retard the cam to good effect to improve top end power.
You need to degree the cam first to determine its present installed timing using a degree wheel and reading off the push rod tip with a dial indcator, then move it to 'straight up" as required using cam offset bushings in the cam timing gear.
The timing cover has to come off.
Allows more top end without going to a bigger cam.
The cam now is normally "advanced" You can afford to give up some bottom end grunt for top end. I'd move it back by 4 to 6deg from its natural installed position.

What is the compression ratio of this motor? If the fact that you could not get to 38deg without detonation is caused by excesiive compression ratio, moving the cam back a bit will help tame the cylinder pressure.
A simple engine compression test will tell the tale.
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Old 09-03-2010, 11:20 PM
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F-Bird

I thought the same thing about the restrictors when I saw them a few months back when we had the extensions off. They are fully welded in, so they aren't coming out without detroying the outer surface. I could punch out the centers, but I don't think that would really get the job done.

Not sure what to do about them at this point. Definitely no budget available for new headers from another company - and I don't know if another brand would be less restrictive. I'm sure I'm just skirting on sound pressure laws the way they are.

If the engine can wind freely through 6,000 rpm with my current cam in first gear, does something change about air flow in 3rd with more load on the engine?

And look what I just found on EBAY - 3.42 gears from a company in Texas. No budget for those either, but at least I know where to go if I decide to head in that direction. Guess I need to decide on the total package before buying the next cam.

Plenty of other things to play with first. Maybe this cam will be just fine once I make the changes you have recommended.

Are you saying you want me to run the engine without air filters - just the foam protection up front? The design of the scoop needs some type of plate on top of some spacer (currently the filter) to hold the mounting plates to the scoop itself.



Maybe farbicate some type of open spacer that still utlizes a plate on top to secure everything?

I don't always drive in that clean of an environment to be too excited about running without filters.

Let me know what you think after you take a look at the photo above.
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Old 09-03-2010, 11:39 PM
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Took a while to find the compression test results from a few years back.

Range was 230-245. Speed shop had calculated it would be around 10.3 during the engine build. Not sure how consistent that sounds next to these readings.


No problem in degreeing the cam. I need to replace the water pump and find a better looking timing cover, so that can all be done at once. Thanks for the suggestion.

I can do a compression test after the cam location is changed and see where it moves to.

In regards to the dyno test and detonation, the pro's noticed it, not me. It's not like the clanging noise you would hear in a passenger car under load in high gear. They cut the test because of it.

Forgot I had the thre runs they made on You Tube. You should be able to hear the test here: http://www.youtube.com/user/Yegstert.../3/Ux_auP96X8I

If I recall the highest hp reading was 282. At that time, I don't think the secondaries opened at all. I only use 92 octane - doesn't cost that much more in my small tank.

Hear anything of note in the video or from what you see in the exhaust puffs at high rpm? The test was run with 64 jets and 25 squirters.
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Old 09-03-2010, 11:42 PM
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Quote:
Appreciate the compliment on the car. Thanks!!! Too bad you live so far away, we could go cruise the beach! It's a kick!
Or you could come up my way,,, its dear hunting season, I got guns and lots of irish wiskey, yeah bad combo I know but so far so good:

http://www.whitetaileddeer.ca/world-...ilo-hansen.htm

Comment on the linkage; looks are'nt everything and some more chrome may suit you fine but that lokar linkage weak link looks to be in the set screw holding the cable, mine let go frayed the cable and like a dumb **** I stuck it back in the hole and tightened it up some more, fray/broke again. You got 4 springs to deal with and the linkage friction, lots riding there, get something with more grab/metal.

Yeah motor is a big air pump and garbage in makes for garbage out and vice versa, exhaust looks like a big choke, great pics. Try and run it without the scoop and then maybe open headers,,, you'd be rock'n
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Old 09-03-2010, 11:48 PM
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If the engine can wind freely through 6,000 rpm with my current cam in first gear, does something change about air flow in 3rd with more load on the engine?

ya its called horsepower required to gain more speed. Does not take a lot of power to move a light car with a lot of gear at first, but as speed goes up, power required to maintain the same rate of acceleration goes up exponentially.

yaking the cork out of the pipes will help a lot, retarding the cam and moving the torque curve up in rpm ( this is what you feel) you don;t feel horswepower.
A ;pw restriction air cleaner will help. Correct gearing to spread the power band out so its not all concentrated on the low end of the trip will help.
You'll put more down to the ground and burn the tires up less.
The car is very light. A 3.42 is a much better match to the car weight/engine power curve. You'll get to the end of the 1/4 mile without overreving the motor.

4.30's would be good if you had a huge high rpm cam or a mcuh heavier car or a much smaller CID motor like a 283

You could make your self a custom made collector/muffler with larger diameter and a large high flow efficient muffler insert. and then get it chromed or ...

You have to realize the show car stuff like the chrome pipes and air scoop were made to look pretty, not make horsepower.
I would not drive far without air cleaners either. You will ahve to A-B road test to see how restrictive they are. A big difference in jetting required on or off is a good clue. Drag MPH is a really good clue.

If you primarily cruise with this car you probabily won;t enjoy a big honkin race cam. But your cam moved to a better position along with the other changes mentioned will wake up the top end.

We all ave to work within our budget and pay for the stuff we buy.
While you got the carb off, look at the throttle blade/idle transfer slot position at idle. pri and sec. needs to show about .020" of transfer slot.
should be even pri and sec on both carbs. how much exposure is yours at now? post a pic of possible.
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Old 09-03-2010, 11:53 PM
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Custom!!!

You crack me up but my wife and kids would be all over me if you came after some of the deer that visit our backyard!!! Now, the whisky they could live with!!!



I better keep on topic though.

Interesting comment about the linkage. Has never been a problem. Probably installed in 1999-2000. Works for me!!! Now, watch it let loose tomorrow...

Just ran it with the scoop the other day, filters in place - no real differenc that I could tell. Purple spring day if anyone is keeping track!!!
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Old 09-04-2010, 12:00 AM
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Took a while to find the compression test results from a few years back.

Range was 230-245. Speed shop had calculated it would be around 10.3 during the engine build. Not sure how consistent that sounds next to these readings.

this amount of cranking cylinder pressure is way to high for pump gas.
Why did you dragt use all thru this with pages and pages of post when the problem is obvious.
You need 110+ octane gtas or methanol. You will never get a good tune on 92 even with dialed back timing.

Your compression ratio is way too high aprox 13:1 not 10:1.
Moving this little street cam is not going to fix it.

You need to low the compression ratio. On a BBC with steel heads 10:1 measured honest cr is a lot for 92 octane gas.

Change pistons, change heads, change fuel. pick one before you damage this motor.
What heads and pistons are in this motor?

You will damage this motor if you push it on 92 gas.
You need to stop and figure out exactly what you got there and start from scratch.

You want approx 170 to 190psi on the cranking test for pump gas.

No **** it was over heating, the cr is way to high for pump gas.

Last edited by F-BIRD'88; 09-04-2010 at 12:05 AM.
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Old 09-04-2010, 12:06 AM
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F Bird

That pic was taken a week ago when the squirters and larger jets went in. No plan to remove them this weekend as I have to take off on a trip in couple of days and won't be back for a week. Need to leave the car together so my son can cruise around in it. Now, that my 16 year old daughter is starting to drive it - with me along so far, things are really getting scary!

I do face a lot of compromises in this being a street, never raced car. But I always remember my brother's 68 GTO flying through the qtr, and mine - well, it would be an interesting match to see if he could have caught me on the top end with the launch I have. Even he is impressed when we go out on a drive.

As far as the quarter mile goes, I'm way too chicken for that in this car. Too many old parts that can fail, no head protection if something goes wrong etc. Just want it fast to 75 and I'm happy.

Guess I could drill out the restrictors to open them up to 3" or so, but have a feeling the sound would be a killer next to my ear for hour long drives. Much less be ticket causing. I only get once chance with the recoat, so this just may have to stay the way it is, and then once in a while head out somewhere and try it with the mufflers off.

I'm sure it would be a real kick!!!
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