New Carb

Everything to do with the 425, 472, and 500 inch Cadillac engines.

Re: New Carb

Postby baxternick » Fri May 19, 2017 8:29 am

I have the similar car and have posted in your other thread. My 54 Chevrolet has a 500 in it that has been bored 30 over. I am using a MTS15 cam, edlebrock intake, DUI Dizzy, rebuilt Quadrajet, and my compression is 9-1. My suspension is soft with my air ride. I still have the stock converter in mine with 3.27 gears on a 6.70 29" Ply bias tire. My car won't snap the tires loose from a roll. It just kind of squats and goes. From a dead stop if I floor it, it will smoke the tires through 1st and a portion of second. This is with a tire that has a 5.5" contact patch. I don't know about how much HP I make but I do know the instantaneous torque through out the entire RPM band is amazing. If I could do it over again I feel I would have run a new converter and some serious head work (new valves etc). I honestly feel like the Caddi converter is WAY to soft for my driving style and it kills my performance. One day I will pull it all apart and change it. I know I chased timing and fuel issues forever on mine. I had to use the upgraded RobbMc pump because I had fuel starvation issues. I also had to spend alot of time watching my A/F Ratio to get my carb just right. The needles and hanger on the secondary makes a huge difference. I also had issues where my secondaries were not opening all the say at first. Until I broke down and bought the DUI dizzy I was had alot of issues getting my timing curve correct as well. I whole heartedly understand your fustration. My first engine was a whore and spun a rod bearing after 700 miles. Local machine shop screwed me on the bottom end. This current engine took a couple weeks to to get right. Still feel like it has alot more in it, but I am not skilled enough to risk finding it.
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Re: New Carb

Postby one finger john » Fri May 19, 2017 8:42 am

O.K., here we go.
Get a non-adjustable timing light or dial your light to 0*, put a piece of tape on it to hold the dial at 0* and do not touch it again.
Which amount of timing is built into the distributor ? 16* or 18* ?
You realize that below 1000 rpms the distributor should not be advancing on it's own (mechanical advance).
SO get the engine to idle comfortably below 1000 rpms, say 750 rpms, and set INITIAL TIMING at 18*. DO NOT TOUCH THE TIMING LIGHT DIAL.LEAVE IT TAPED AT 0*
Now set your timing at 18* BTDC. LOCK IT DOWN. Adjust carb mixture. The engine should now be idling at approx. 750 rpms with the INITIAL TIMING SET AT 18* BTDC. If need be raise or lower idle by adjusting idle speed screw on carb. Recheck idle mixture and adjust for highest & smoothest idle. Lower idle to comfortable level (again approx. 750 rpms) recheck mixture adjustment and re-adjust. You might have to do this two or three times to get the engine to idle properly at a rock solid pace (be it 750 rpms or 900 rpms, whatever idle rpm the engine is comfortable with, with the INITIAL TIMING SET AT 18* BTDC.
Do not dial up, dial back, dial around, dial through. with the timing light. Throw it in the back of your tool box and NEVER LOOK AT IT AGAIN.
GET A NON-ADJUSTABLE TIMING LIGHT AND LEARN HOW TO USE IT.
The engine should now be idling beautifully.
Hook up the vacuum advance to the carb, not the brake vacuum line.
You want constant manifold vacuum from the carb.
Now check the timing again with the timing light. DO NOT TOUCH THAT DIAL LEAVE IT AT 0*
IT will have gained approx. 10* to 15* and it will be idling higher.
Go through the re-adjustment process til the engine idles comfortably again. BELOW 1000 rpms so the mechanical advance is not yet activated.
Make a note of how many degrees are now indicated while idling (comfortably)
Don't worry about what it SEEMS to be doing.
If it is not over heating and running approx. 180* temp, go for a drive.How does it run ?

John
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Re: New Carb

Postby 8ad-f85 » Fri May 19, 2017 9:19 am

Timing curve seems ok by description, other than not to trust dial back lights.
I make a mark on the dampener BTDC equal to 10% of the circumference (36* being 10% of 360*) and use whatever the engine's tab is. It's OK to lightly stamp it in.
Put your light to zero, use another verified, or trust the shop's readings to be certain.

So if the choke linkage/secondary lockout isn't fully operable the lower blades can open but the top doesn't or some partial version if things are bent or incorrect...but more likely I'm leaning towards looking over the tension spring and secondary metering, esp. the hanger type and rod tips.
Those are the first things I look at with timing and carb issues, anyways.

What I meant by not looking good for a performance tuning shop is that it wasn't verified, talked about or explained to you if or what they did to adjust the secondary spring tension or any other workings, including metering.
That stuff is kind of paramount to performance.
If so, then you haven't shared that info.
I can picture a scenario where they might adjust the tension too tight to avoid the infamous q jet bog, esp. during seasonal transitions. That might make it kind of a turd all the time...but with no bog.
You can loosen the tension until a bog is induced and then back up some.
How much tension and other tuning methods are up to you and your research.
It takes me longer to think about, describe and type out than to do in person.
If you make some kind of change that drastically affects where you are at then it is your own accomplishment that you can refine from then on.
This whole hobby is one giant learning curve, or you write a check for results.

(I haven't read the above reply yet)
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Re: New Carb

Postby mrconcdid » Fri May 19, 2017 9:24 am

Thanks, Baxter and One finger John.
Question my timing tab only goes to 10?

I have another timing tab on my 368 I think it goes to 25. may be I could swap them?

MrC.
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Re: New Carb

Postby 8ad-f85 » Fri May 19, 2017 9:40 am

I know you were typing your response same time as mine and as a reminder, I addressed the timing mark limitation near the top of my response.
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Re: New Carb

Postby mrconcdid » Fri May 19, 2017 9:58 am

ha ha
yes i was, thanks for the info

MrC.
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Re: New Carb

Postby one finger john » Fri May 19, 2017 10:26 am

That's o.k., approximate 18* or 16* or drag out the dial-back and utilize that. Just don't use it to accurately set initial timing.
If the 25* tab bolts on in the same position and the hubs ( 368 balancer ? pulley ? are the same diameter with the TDC mark the same go for it.)
Did you get a piece of paper that showed what the advance progress was with the springs and weights that were supplied with the distributor ?
Could you shoot a photo of it and show us ? (you know, how many degrees of mechanical advance per 100 rpms til fully advanced. Should be like a chart.
Who made this distributor ?

John

PM sent or on the way.
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Re: New Carb

Postby frankenregal84 » Fri May 19, 2017 10:48 am

Your more detailed description of the timing on page 1 seems ok to me as well.

But 8:1 or not you should have explosive torque off line. Like i said my Buick 350 with 217 hp would blaze the 275/60/15 tires with a 2.73 rear gear off the line.

Your description of how it runs up top indicates a very healthy engine.v
-Azeem K.
Ottawa, ON
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Re: New Carb

Postby Darius » Fri May 19, 2017 10:57 am

mrconcdid wrote:Thanks, Baxter and One finger John.
Question my timing tab only goes to 10?

I have another timing tab on my 368 I think it goes to 25. may be I could swap them?

MrC.


NO! Do not swap the timing tab from the 368 to this engine. The timing tabs are "keyed", "linked" with a particular crankshaft and pulley depending on a host of variables. They are not all the same and therefore not ALL timing tabs will give a true reflection of top dead center - if not with it's original setup.

I have checked several different pulleys with different tabs and some match up to TDC and others don't.

Best,

d
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Re: New Carb

Postby one finger john » Fri May 19, 2017 11:12 am

D. IF the pulley diameters are the same, if the TDC marks are in the same place on the pulley and the tab is in the same place.

Well, shouldn't the tabs be interchangeable ? Are the front covers different ?

Or MR.C go to MTS or CadCo and get an adjustable timing tab.

Darius I will always defer to your obvious superior wisdom, good looks, charm and ...................................... age.

John
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Re: New Carb

Postby Darius » Fri May 19, 2017 3:20 pm

one finger john wrote:D. IF the pulley diameters are the same, if the TDC marks are in the same place on the pulley and the tab is in the same place.

Well, shouldn't the tabs be interchangeable ? Are the front covers different ?

Or MR.C go to MTS or CadCo and get an adjustable timing tab.

Darius I will always defer to your obvious superior wisdom, good looks, charm and ...................................... age.

John


All right now, Son. You could have left that last one off the list ... because it is the only FACTUAL one given. :yes: LOL. Wait just a dog-gone minute. What am I saying? No, ALL of those lovely things are lies, I tell you, LIES!!

Johnny and All,

My comments come from a little experiment I undertook while building my engine and had everything open and available to check pulleys and timing tabs with the engine at top dead center. You are right to ASSUME that the same sized pulleys should work - and in fact they may. What I found was that: WITHOUT measuring the diameters but just by bolting the pulleys onto the crank and using different timing tabs some were smack on TDC and others were not.

I didn't bother to measure as most folks aren't likely to have a sewing (flexible) tape or micrometers large enough to be precise. I do have both of those but the point was to see what MIGHT happen IF someone just grabbed a Caddy pulley or timing tab thinking all would be well.

Best (and I do smile pretty!), lol

bro. d
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Re: New Carb

Postby one finger john » Fri May 19, 2017 3:47 pm

So ummmm ........ which ones worked in harmony and which ones did not ?
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Re: New Carb

Postby Darius » Fri May 19, 2017 5:22 pm

one finger john wrote:So ummmm ........ which ones worked in harmony and which ones did not ?


The ones I mounted? ;) :yes:

Actually, several sets worked together but since my goal was to have the shortest engine possible due to the extreme tightness, front to rear, I went that direction. The units with multiple belt grooves were non starters.
There's a box in the garage with four or five crank pulleys and a shelf with a couple of timing tabs. That's all I know.

d
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Re: New Carb

Postby one finger john » Fri May 19, 2017 5:47 pm

Now go to the garage, find the timing tab that has the most indicated degrees on it and fit it to the front of your engine and see if everything lines up.

Go on, I'm waiting. No snow on the ground stoppin' you. I'll look at Mr.Cs pulley set up and see if it is a single or double pulley deal. Take a picture of the tab and show it here. Appears to be a double pulley. Still should work.
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Re: New Carb

Postby Darius » Fri May 19, 2017 5:53 pm

one finger john wrote:Now go to the garage, find the timing tab that has the most indicated degrees on it and fit it to the front of your engine and see if everything lines up.

Go on, I'm waiting. No snow on the ground stoppin' you. I'll look at Mr.Cs pulley set up and see if it is a single or double pulley deal. Take a picture of the tab and show it here. Appears to be a double pulley. Still should work.


You talkin to me?? By the way, it did snow here two days ago! Nothing like springtime in the Rockies.

DANG! The forum is quiet. Doesn’t anybody have lies they want to tell?

As the years go by and memories get older, things get blurred. But the symptoms that both MrC and Baxter have cited remind me of my first Cadillac engine build. Doc, here on the forum, knows the engine and my ‘79 Olds Toronado it was in. His junkyard 472 in a Dodge pickup could jump up and down on my 500 with its re-ground cam.

In some old threads here I’ve told about the details, which are now lost in time, but the bottom line is how “soft” the big Cadillac 507 was. It just didn’t have the suds you would have expected from a large engine. My build and tune were way off. Too much cam for too little compression, cam installed straight-up with no advance. In fact, the “ground in” advance was purposely taken out because of plans for the engine (turbos) that never developed. The final straw was the lean jetted Quadrajet (17 MPG), matted to 2.73 gears.

Guys, the power IS THERE in your engines. Just make sure the tune is right and that you’ve got the right mix of parts.

Best,

bro. d
Last edited by Darius on Fri May 19, 2017 8:06 pm, edited 1 time in total.
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Re: New Carb

Postby pila78 » Fri May 19, 2017 6:40 pm

I know exactly what you refer to D. !! The rocking chair is chasing me ! And CRS is setting in ! And my engine sucks ! My supercharged Buick V6 would keep up without a problem !
I finished two airplanes today, and simple carbs and fixed magneto timing makes things easy :D
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Re: New Carb

Postby one finger john » Fri May 19, 2017 7:23 pm

D. Sorry, I got carried away.

John
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Re: New Carb

Postby mrconcdid » Wed May 24, 2017 10:10 am

Hey guys,

So I set my adjustable light to zero and measured out what should be 20 degrees (my tab only goes to 10) set the timing to 16 degrees BTDC.
That did seem to help. It did start even when hot. It did run strong up to 4,200 rpms, then it just kind of stopped accelerating and leveled off (power), I shifted at 4800 from second to drive and rode out.
I did receive my McRobb fuel pump Q. do I really need 1/2 fuel line? or will my 3/8 be enough using the quadrajet?

I am beginning to think my valve springs are floating, I cant hear anything but it stops pulling at about 4200 and up. So with that said, I am looking at a cam, springs and lifters (keeping my carb).
looking at the MTS15 with lifters and springs?

I did not have a chance to do a compression test, my neighbor is out of town and I normally borrow his tester.
As for timing tabs, the 368 is held on by one bolt not two and is different, I also have a peanut piston 472 but it has the same timing tab as the one I have.
So I measured over the distance needed from my tab and marked the block, and set the timing that way.

I still have a long way to go, but thank you all
I really appreciate all the advice.
MrC.
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Re: New Carb

Postby one finger john » Wed May 24, 2017 12:20 pm

If you do not have a vacuum gauge get one and mount it at eye level. Or easily observable.
At what rpm was the engine idling when you set the initial timing ? Must be below 1000 rpms.
Did it get a full 34* at full advance ?
Do you still have the Herbert 270H in the engine ?

John
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