383 timing question
Thread Starter
Safety Car
Joined: May 2004
Posts: 4,628
Likes: 397
From: Madison Wi
All the issues are corrected and it's ready to fire up. no leaks, vacuum gauge connected, etc.
I just cant do it now because I'd get in big trouble with the neighbors and my wife... lol
I'm really excited to finish up work and get home tomorrow!!
oh... and I was right. The throttle blades were not opening 100%... more like 75%. I fixed it, they open all the way now when the loud pedal is mashed.
I just cant do it now because I'd get in big trouble with the neighbors and my wife... lol
I'm really excited to finish up work and get home tomorrow!!
oh... and I was right. The throttle blades were not opening 100%... more like 75%. I fixed it, they open all the way now when the loud pedal is mashed.
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
Ok guys!! You ready for the news!!! You are NOT going to believe this.
I pulled the carb and disassembled it.
5 things. I'll save the best for last so don't read ahead and spoil it.
1) There was a thin 1/2" nylon disc on the carb flange that made a dent in the gasket, but didn't appear to be causing a vacuum leak as the gasket had formed to it. Someone must of dropped it there and whoever installed the carb missed it.
2) The throttle cable was in the big eyelet at the top of the throttle lever instead of the smaller one closer in. I'm suspecting the car never saw 100% open throttle. I will verify when re-installing the carb.
3) There is no power valve in the secondary metering block on this carb. the stock jetting is 69front-78rear. Someone put in 72s in the front and 73s in the rear. 73s without a powervalve should of been a problem. You are only supposed to put the same or nealy same jets in all 4 corners if there is a secondary power valve.
4) The secondary throttle blades were adjusted 100% closed. It is my understanding you are supposed to give them a little crack open. This would force it to pull all its idle air from the primaries, where the idle slots are lower and come in sooner. The idle slots on the secondaries are up higher so they can be cracked open without adding fuel to the idle.
and... drumroll....
5) It had a 2.5" power valve in the primaries. With the engine making 12.5" at idle, that power valve would of opened up and run the primaries at idle, resulting in the throat stinging eye watering idle I had.
I pulled the carb and disassembled it.
5 things. I'll save the best for last so don't read ahead and spoil it.
1) There was a thin 1/2" nylon disc on the carb flange that made a dent in the gasket, but didn't appear to be causing a vacuum leak as the gasket had formed to it. Someone must of dropped it there and whoever installed the carb missed it.
2) The throttle cable was in the big eyelet at the top of the throttle lever instead of the smaller one closer in. I'm suspecting the car never saw 100% open throttle. I will verify when re-installing the carb.
3) There is no power valve in the secondary metering block on this carb. the stock jetting is 69front-78rear. Someone put in 72s in the front and 73s in the rear. 73s without a powervalve should of been a problem. You are only supposed to put the same or nealy same jets in all 4 corners if there is a secondary power valve.
4) The secondary throttle blades were adjusted 100% closed. It is my understanding you are supposed to give them a little crack open. This would force it to pull all its idle air from the primaries, where the idle slots are lower and come in sooner. The idle slots on the secondaries are up higher so they can be cracked open without adding fuel to the idle.
and... drumroll....
5) It had a 2.5" power valve in the primaries. With the engine making 12.5" at idle, that power valve would of opened up and run the primaries at idle, resulting in the throat stinging eye watering idle I had.
You may be showing too much transfer slot in the primaries. Set the primary throttle blades so that only about .020" of the transfer slot is showing beneath the throttle blades, and use the secondaries to adjust the idle speed, instead of the idle speed screw.
Scott
Last edited by scottyp99; May 20, 2014 at 03:13 AM.
Thread Starter
Safety Car
Joined: May 2004
Posts: 4,628
Likes: 397
From: Madison Wi
Well, that's not really how a power valve works. A 2.5" power valve (I didn't even know they made them that low!) won't open until the vacuum gets down to 2.5". Anything above 2.5" of vacuum, the power valve should be closed. Also, the power valve really only has an effect on the main circuit, anyway. (unless it's blown, of course.) You're going to have to keep looking.
You may be showing too much transfer slot in the primaries. Set the primary throttle blades so that only about .020" of the transfer slot is showing beneath the throttle blades, and use the secondaries to adjust the idle speed, instead of the idle speed screw.
Scott
You may be showing too much transfer slot in the primaries. Set the primary throttle blades so that only about .020" of the transfer slot is showing beneath the throttle blades, and use the secondaries to adjust the idle speed, instead of the idle speed screw.
Scott
I'm still hopefull what I did will solve the issue. I put the carb back to stock configuration and cracked the secondaries open a little to allow some more air in the carb at idle.
I also verified the transfer slots on the primaries are .020 exposed (square... as much height exposed as their width)
If it needs to idle faster, I'll pull the carb and open the secondaries a little further.
Thread Starter
Safety Car
Joined: May 2004
Posts: 4,628
Likes: 397
From: Madison Wi
well, it's a bit better.... but still very rich at idle.
It feels stronger on the road, gets good rubber in 1st and squaks them very well going into second.
My Vette and Camaro both have over 300 hp at the rear wheels and they feel as fast or faster to me. My dad rode shotgun on the test drive and he said from his seat it felt very fast.
1st and 2nd gear should be all rubber in this thing geared the way it is with the power it's supposed to have.
Maybe it weighs more than I'm guessing it does?
Timing set at 18* base, 18* mechanical advance
no vacuum advance
jetted at 69F - 78R
6.5" power valve in primary metering block
No power valve in secondary metering block
mechanical secondaries
PCV valve stamped "F" connected to carb vacuum port
idle mixture screws produce max vacuum (12.5") at 1.5 turns out
Idles very nicely at 900 rpm
Engine runs good, idles well, feels ok
Idle exhaust smells too rich
If I turn the idle mixture screws in, vacuum drops and it starts getting choppy.
I've tried experimenting with the secondary idle stop screw and not had any success that way either.
It feels stronger on the road, gets good rubber in 1st and squaks them very well going into second.
My Vette and Camaro both have over 300 hp at the rear wheels and they feel as fast or faster to me. My dad rode shotgun on the test drive and he said from his seat it felt very fast.
1st and 2nd gear should be all rubber in this thing geared the way it is with the power it's supposed to have.
Maybe it weighs more than I'm guessing it does?
Timing set at 18* base, 18* mechanical advance
no vacuum advance
jetted at 69F - 78R
6.5" power valve in primary metering block
No power valve in secondary metering block
mechanical secondaries
PCV valve stamped "F" connected to carb vacuum port
idle mixture screws produce max vacuum (12.5") at 1.5 turns out
Idles very nicely at 900 rpm
Engine runs good, idles well, feels ok
Idle exhaust smells too rich
If I turn the idle mixture screws in, vacuum drops and it starts getting choppy.
I've tried experimenting with the secondary idle stop screw and not had any success that way either.
Safety Car
Joined: Jan 2009
Posts: 3,736
Likes: 56
From: anchorage ak
I don't know what size your cam is, but If you don't have a vacuum advance, then try 22-24 initial and limit your mechanical to the remainder from that and 36*. The more duration you have the initial timing you need. Mine always smells rich, even had dill holes say the exhaust smells like I'm running race fuel, it took a lot of tinkering to get it were it doesn't foul the plugs. Runs awesome, always has.
Last edited by bluedawg; May 20, 2014 at 11:16 PM.
Thread Starter
Safety Car
Joined: May 2004
Posts: 4,628
Likes: 397
From: Madison Wi
I don't know what size your cam is, but If you don't have a vacuum advance, then try 22-24 initial and limit your mechanical to the remainder from that and 36*. The more duration you have the initial timing you need. Mine always smells rich, even had dill holes say the exhaust smells like I'm running race fuel, it took a lot of tinkering to get it were it doesn't foul the plugs. Runs awesome, always has.
I'd need a 10* limit bushing for my MSD distributor. The lowest they make is 18*
Racer
Joined: Jul 2008
Posts: 258
Likes: 1
From: Gippsland, VIC Australia
fyi, msd have a tech forum as well, they may be able to point us in the right direction
I'm not trying to chase you away, but they might have a way around the bushing issue
I'm not trying to chase you away, but they might have a way around the bushing issue
Last edited by waljr; May 21, 2014 at 06:24 AM.
Had a 1976 L-82, 4-sp
Joined: Mar 2011
Posts: 5,338
Likes: 1,213
From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
Great info on "Limiting or locking the mechanical advance mechanism" found here:
http://www.crankshaftcoalition.com/w...ecommendations
I did this mod on my HEI using a screw. Worked perfect. You may be able to this or similar with a MSD.
http://www.crankshaftcoalition.com/w...ecommendations
I did this mod on my HEI using a screw. Worked perfect. You may be able to this or similar with a MSD.
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Safety Car
Joined: Jan 2009
Posts: 3,736
Likes: 56
From: anchorage ak
Alright. Try this as an experiment, lock it out at 32* and see if the fuel smell goes away. This would let us know that your not getting enough initial. If that works you could modify the advance mechanism to only allow 10* advance.
Last edited by bluedawg; May 21, 2014 at 11:56 AM.