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German Guy needs Help to tune Engine properly. THANKS

1K views 12 replies 11 participants last post by  oldcutlass 
#1 ·
Hey Folks,
I have much trouble to get my engine running properly....
Biggest problem is, that there are not many pros over here in Germany (especially in my area)to help me out, with that kind of problems....


So here we go.... ( i hope i can describe as good as possible:))
It starts right away, but i need to hold it with my foot for about 20 seconds to run for itself....
other than that ... when i put it in gear, it stalls....
It gets better when the engine warms up....
But this makes me not happy... ive tried a lot of timing and carb tuning but i am not satisfied....


Some facts to the engine and Car Setup :
1966 Chevelle Malibu
396 Block 0.030 over
3904390 Heads with 2.19 / 1.88 Valves
domed Pistons - CR should be in the 9.5 - 10:1
Elgin 929 Cam: 231/231 at .050 290/290 duration .544/.544 Lift 109 lobe sep. Angle
Holley 600 cfm Double Pumper Carburetor (fresh rebuilt)
MSD 8362 HEI Streetfire Distributor with 8mm Taylor Streethunder Wires
Hedman Headers 1 3/4 in. with 2,5 inch Flowmaster H- Pipe complete dual exhaust system
TCI Streetfighter TH350 Transmission with 2400 Holeshot Converter
3.73 Auburn Limited Slip Differential


I had it at 22 degrees initial and 44 total and it stumbled at very light throttle when driving around so ive took some readjusting...


Now I´ve timed it initial to 18 degrees with vacuum plugged... (ive ran full manifold vacuum from beginning ... but now ive added the vacuum limiter plate to the distributor setting now is between 8-11 degrees ) (seems to get better ?!?)


it pulls just between 8 and 10 inches of vacuum it idles at around 850 to 900...
Throttle response is very well, but when i put in in Gear.... it almost stalls to 250 to 300 and then come back to around 750 rpm...


I really don´t know where or how to move on / or start new ....?!?!


I´ve also checked for vacuum leaks with brake cleaner around the intake and carb gaskets, but this seems to be ok.....
My buddy told me also my 600 cfm double pumper is waaaaaay to small... but for normal street driving conditions, it should be work fine, right?!!?


I have no idea, at this moment



Please help me out, and let me know if you need any more Information
THANK YOU !!!!!!!!!!!!!!!!!!!!!!
Best regards from Germany

Torsten
 
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#2 ·
My amateur opinion is, one thing to check is the carb jets and mixture screws and all that related to the holley carb. they're not hard to get in the ballpark, fine tuning is a little more difficult.
You should find out what the factory settings are, and start there.
 
#3 ·
Set the timing to 36 degrees total. That carb is too small. The smallest double pumper that I know of is a 650. Is it a 650 double pumper or a 600 dual feed vacuum secondary? If it doesn't have a choke, then the cold manners are normal. How does it run after it is up to temp? I wouldn't run anything smaller than a 750. If you are going to buy one, get a 850.
 
#4 ·
Here is what I would do:

1. Get a dial back timing light.
2. Disconnect the vacuum advance
3. With Iron heads, set initial timing at 18 to 20.
4. Rev. engine to 3K RPM and check timing with dial back timing light. You want an additional 16-18 degrees timing to come in from the distributor for all in at 38 degrees total. If it is a lot more than that, then, you have to re-curve your distributor by changing the springs and cams.
5. Get a vacuum advance that is all in at idle - ie. all in 6 or 7 in hg. -- with somewhere between 12 - 18 degrees depending.... Use manifold vacuum

On item 4 above, if you find your distributor gives you too much timing at 3K rpm, ie. 42 or 44 degrees, then, just dial back your initial timing appropriately and rely on your all-in vacuum advance to get you the good advance at idle --- until you can find the time to recurve your distributor.

Also, search my ID, I posted lots of stuff about tuning with Vacuum advance.
Good Luck.
 
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#7 ·
NO DIAL BACK TIMING LIGHT WILL WORK. Dial back is for timing compensation for electronic ignition timing done in a computer, that has lag time to compute the timing from all the various sensors, and an HEI does not have a lag time in timing, nor delivery, so, DO NOT USE A DIAL BACK FEATURE ON A TIMING LIGHT FOR AN HEI, MARK THE BALANCER, AND READ IT STRAIGHT ON.

The ONLY adjustable vacuum advances that will work down to the lower vacuum levels are the Crane units, for a large HEI, the p/n is 99600-1. They come with a degrees stop plate, but their info tells how to install the plate completely incorrectly, on the WRONG side of the pull pin.

If you want the correct stop plate mounting info, just email and ask for it, the info is free for the asking. Simple to do, one drilled and tapped hole, one screw and flat washer, fixed and tunable.

gmvacuumadvancemodifications@gmail.com

18 to 20 degrees of initial timing is way, way too much, 12 to 14 is where it needs to be, with 10 to 12 more degrees added by vacuum advance sourced from full manifold vacuum, for 22 to 24 IDLE degrees.

NEVER just "set the total to 36 and let the initial fall where it will", that isn't the way to do it right.

With an analog HEI, DO NOT USE A DIAL BACK FEATURE ON A TIMING LIGHT, there is no "computation lag" in an analog HEI ignition system. Mark the balancer, and read the degrees on the balancer, not the computer lag from the dial back that ISN'T THERE.
 
#8 ·
One of the things that I would like to know is, what year is the block? If it is a 66 block, was the rear cam journal grooved for oiling? Carry on....
 
#9 ·
First of all, thank you for all of your replys!!!


Nice to get some help from overseas!!!!!!!!!!!

@glend123: Ive rebuildet the holley (first time ive ever did a carburetor) and know how this this works, but tuning this thing is the process i am learning right now...

The biggest thing for me is that this engine ( i wanted to leave it like it was, because it was rebuilded totally 10 years ago with only 2500 miles on it) and is totally mixed up .... If it was stock block stock heads stock cam etc.... it would be much easier...:frown2:

@69SS454: i´ve expected that answer ....:laugh: i am looking for a 770 cfm Street Avenger (not sure if the vac. secondaries will work?!?) or a 750 cfm double pumper....
First try next will be a 850 Quick fuel double pumper from my buddies 694HP SBC, to see if there are any major differences (and i am sure there will be some difference.....>:)) then lets see......:grin2::grin2::grin2:



And yes it gets better and better, the more the engine warms up..!

@hjdca: Thanks for your detailed explenation!!!!
We have a timing light that we can switch to advanced, what i think is what you mentioned..
ive advanced it to 38° then revd the engine to almost 3950 rpm.. .(that scared me:eek:) MSD said 22° mechanical all in at 4000 rpm) and still had 4° on the balancer so should be 42° total timing ...
I´m a little confused right now, so please excuse me!!!!


I have a vacuum setting with a maximum of 5-8°, should i go with that ???
What do you mean exactly with recurve?!?

Yes ive read a lot of your posts and still will do that !!!!:thumbsup::thumbsup:

@Pioneer4x4: Yes, of course !!! Sorry for that !!! :thumbsup: Now attached

@Malibu ss 64:It has manual choke ....

Ive attached a picture from it ..


Yes ive tried but not much difference in rpm and vacuum... it is best at 1-3/4 turns out....
 

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#10 · (Edited)
Go with what Dave Ray says above. You have iron heads, so, he is correct on the initial timing. I am using an MSD Digital 6 plus ignition with an HEI coil in cap MSD distributor, so, it is not fully analog like yours, so, the dial back timing light may not be accurate. Like Dave Ray says above, get the MSD tape and tape up your Crank pulley. Note: On my digital ignition, I have tested my dial back timing light with the tape on my crank and it is accurate.

Go with what Dave Ray says on total timing -- 36 degrees all in -- vacuum advance off.

Note: regarding vacuum advance, my distributor requires the HEI type (longer) vacuum advance-- yours is probably the original shorter vacuum advance. Personally, I have had luck using the adjustable vacuum advance, turning the adjustment all the way clockwise (all in very early 5 or 6 in hg.), then, using the vacuum advance limiter bracket to limit the overall timing at idle.

Once you get everything set without vacuum advance, then, hook up your vacuum advance and check your timing at idle. It should shoot up into the 30's... This will tell you that you vacuum advance is working at idle. This additional timing should give you more hp at idle to hold your rpm when you go into gear. If you have a big cam, you may also need to add a little more fuel by richening your mixture screws.
With a big cam, the more you lean your idle, the more your idle will drop under load.
 
#12 ·
Based on the Price of Gas in Europe and here I would think this Carb would be a good chose for your 396

https://www.jegs.com/i/Demon-Carburetion/333/1904/10002/-1?parentProductId=2075515

https://www.jegs.com/i/Earls/361/991942K/10002/-1?parentProductId=2075515

some more info and Videos on them/it
https://www.jegs.com/p/Demon-Carburetion/Demon-Carburetion-Street-Demon-Carburetors/2075515/10002/-1

Other TCers on here have bought the 625 or 750 one and found they work great right out of the Box
and the Echoke would solve your Cold Start issue
 
#13 ·
I would disconnect and cap the vac advance until you get your initial timing dialed in. I have a similar setup, I run 16 initial as the only fuel around here available is 91 MON octane rating. Your Octane rating is in RON, in order run the timing numbers posted above you need a minimum of 98.
 
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