Beautiful car, but you can see in this picture that he posted in his other thread that the PVC hose is hooked up to a breather. But, it's fixed, and it's why we are here !!
318 Motor, please help
- Thread starter insidegroove
- Start date
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That's pretty good but you can do better.
As Rick mentioned idle in neutral is not the same as idle turning the toque converter and pump.
Turn in until you notice a drop in rpm or vacuum, then turn out (richer) about 1/4 turn.
No feeler gage at idle to off idle. The pump should move as soon as the throttle moves.
The clearance check is a way to insure the spring is not fully compressed at wide open throttle and is done at wide open throttle.
Looks like 7 or 8 BTDC to me. That would be about right for a stock '69 UNLESS the RPMs are too high.
It will take several iterations of reducing the throttle stop postion, adjusting the idle mix, and then adjusting the timing a little.
You should be able to get the timing down so it 5-8* at 750 rpm or so.
When the transmission is placed in gear, it should not drop much more than 50 rpm. (stock engine)
Why rpm is important when setting timing.
Let's assume the the timing is set at 8* BTDC at 1200 rpm using original distributor.
But if we measured timing at some other engine speeds the timing might look like the dashed gray line.
See how the timing at 700 rpm (the intended idle rpm) is much too late?
In contrast 8* BTDC at 1000 rpm with that same distributor might be OK.
That distributor was intended to be used with an initial of TDC.
The distributor you have may be different, but it will still have an rapide advance above the intended idle rpm. So when you slow the engine down, take another reading.
Let's assume the the timing is set at 8* BTDC at 1200 rpm using original distributor.
But if we measured timing at some other engine speeds the timing might look like the dashed gray line.
See how the timing at 700 rpm (the intended idle rpm) is much too late?
In contrast 8* BTDC at 1000 rpm with that same distributor might be OK.
That distributor was intended to be used with an initial of TDC.
The distributor you have may be different, but it will still have an rapide advance above the intended idle rpm. So when you slow the engine down, take another reading.
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insidegroove
Member
it had a 6.5 power valve on it. i watched a few youtube videos and one said to take the vacuum reading you get when you have the car in drive and divide it in half and if its an even number drop down .5 so for me my reading was 10, so i installed a 4.5. but now i need to start all over since we found the vacuum leak. so i think your right and the number is going to increase, maybe back to an 8.5. im loving my Holley carb and im determined to get it dialed in correctly. thank you very much
Dartswinger70
Well-Known Member
Out of curiosity, whats the vacuum reading at idle now?
Only thing I have to say about Holley is the gas needle drops pretty quick other than that I have no issues with Holley or Eddy or carter etc.
insidegroove
Member
totally bonehead move on my part. now i have to ask this......can i just plug the hole on the back of the carb since i dont have power brakes, and just use a standard breather.......or do i need to order the PVC valve and connect it to the carb?
insidegroove
Member
do you recommend i take the vacuum reading from the ported side (spout up near the top on the passengers side) or the manifold side (bottom of the carb on the passengers side near the spacer)? last time i took the reading from the manifold sideOut of curiosity, whats the vacuum reading at idle now?
Only thing I have to say about Holley is the gas needle drops pretty quick other than that I have no issues with Holley or Eddy or carter etc.
Dartswinger70
Well-Known Member
manifold vaccum at idle in park...I am still thinking 10 is low.
run a PVC. Use the hole in the back of the carb for the PVC. You need to ventilate the crank case. Usually, power brakes run off the intake manifold.
insidegroove
Member
keep in mind now that i found the vacuum leak, nothing is in tune anymore and i wont have time until the weekend, but i just hooked up the vacuum gauge quickly. at idle it's reading 16, then when i put it in drive it drops to 11....definately needs some tuning and timing BUT the good news is the RPMs barely dropped this time when i put the car in drive. i dont have a tach yet but it was very noticable how smooth it tansitioned this time verses before. once i get it all tuned back up this weekend i will know what power valve to put into it.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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The PCV HAS to be routed to the underside of the PRIMARY throttle valves.
If you route it to the Secondary side, on an engine with a high idle vacuum, the rear cylinders will idle lean. This usually causes a tip-in sag, once the idle speed is back to normal.
At WOT it it does not matter.
If your carb does not have a port on the front,and does not route the PCV into the vicinity of the idle discharge ports and if it was mine, I would either put one there or shelf it.
If you route it to the Secondary side, on an engine with a high idle vacuum, the rear cylinders will idle lean. This usually causes a tip-in sag, once the idle speed is back to normal.
At WOT it it does not matter.
If your carb does not have a port on the front,and does not route the PCV into the vicinity of the idle discharge ports and if it was mine, I would either put one there or shelf it.
These guys are just regurgitating what they heard someone else say. When its repeated enough it becomes beleiveable. But its pseudo-science.
The real engineering is this. The enrichment is needed when the engine is approaching its maximum power for that rpm. An engine with good fuel and air distribution to all cylinders at part throttle and full throttle, and good combustion characteristics under those conditions, can go deeper in the throttle before needing enrichment.
Engines that are focused more on full power, high rpm performance, etc, tend to need enrichment at less throttle. So a those engines tend need PV in the 8.5 to 10.5 opening.
On a real efficient engine like a factory 318 that might just be wasted fuel and less part throttle power. A 5.5 or 6.5 would probably be fine.
Slightly too rich is harder to notice than slightly too lean, especially Seat of Pants.
One observation that will provide a clue as to engine efficiency is the vacuum while cruising.
As you press the throttle (going up hill or accelerating) the vacuum will drop and the car should pull harder.
What is happening as the throttle opens is the fuel mixture is getting leaner and the car is making more power.
There is a point in throttle opening (under load, not in neutral) when the AFR needs to get richer for the engine to continue to make more power.
That's the power valve opening point, or step up, or enrichment vacuum.
racingfuelsystems-Desired Carburetor AFR Characteristics At Different % Load
The clue here is rich idle, lean cruise, leaner (leanest, actually) part-throttle acceleration and rich WOT. The leanest is at mid-load, half-thrott
www.tapatalk.com
Low port.
Manifold vacuum is the low pressure under the throttle.
The high port is the spark port. Goes to the distributor.
At idle that should be at atmospheric pressure (no vacuum or close to no vacuum)
From Chrysler
The Master Technicians Conference has a lot of good info like this.
Master Technician Service Conference - Chrysler's Training for Mechanics
The Imperial Mailing List Online Car Club is dedicated to the preservation, appreciation and restoration of Imperials and Chrysler Imperials of all years, models and body-styles.
www.web.imperialclub.info
or if you prefer pdf format go to www.mymopar.com
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1971swinger
Well-Known Member
Glad you got it fixed,my 318 2 barrel rochester with pcv valve, upgraded to electronic ignition
1971swinger
Well-Known Member
Glad you got it fixed,my 318 2 barrel rochester with pcv valve, upgraded to electronic ignition
insidegroove
Member
beautiful!!! i am considering upgrading to electronic ignition
1971swinger
Well-Known Member
Glad you got it fixed,my 318 2 barrel rochester with pcv valve, upgraded to electronic ignition
insidegroove
Member
UPDATE: Great news!!! Finally had time today to get tuning on my 318 since that vacuum leak was found. the timing and settings were so out of wack that i had a heck of a time even getting the car to start and stay running so i could get started. after a bunch of tweaking on the timing, and starting all over with the air fuel mixtures and adjusting the throttle pumps AND the idle and transition circuits......HOLY COW my motor has never run so good since i got it a year ago. my vacuum at idle now is 22 and when i drop it into gear it smoothly drops to 17 but no sign at all of wanting to stall. i now have instant response when i stab the gas (so much fun!). im sure i have alot more tweaking to do but im thrilled at the difference already. i still have the 4.5 power valve in there, the store near me that sells them isnt open today so im going tomorrow. do you guys still recommend an 8.5 power valve? im also going to buy a tach tomorrow but by ear i CAN say that the idle now sounds MUCH closer to wear it should be. before it was idling way too high, if i had to guess about 1200rpm and i couldnt get it to come down any more. now i would say its idling about 700rpm (should be around 800 i believe) and the motor looks so smooth, not shaking and running like a turd. Damn I'm excited......and P.S. im loving the Holley and would never switch to an Edelbrock.
Glad you made several big steps forward.
Doesn't always go that smooth. LOL So this is good.
Your call on the PV. 8.5 would be a good bet.
Here's why. We're going to cheat a little. We don't know what the step up vacuum is for the original carbs (BBD). But we do know the situations when vacuum advance is not needed or desired. Remember what vacuum advance is for? So the two work hand and glove.
At 10.5" this engine had little bit of vacuum advance, 2 to 8 crankshaft degrees.
So below 10.5" vacuum, it was probably getting enrichment on the original carbs.
Based on this.
8.5 is a reasonable guess. If they only have a 9.5 or 10.5 in stock, either would also be OK as a starting point,
and 4.5 seems way too far into the throttle before enrichment.
Doesn't always go that smooth. LOL So this is good.
Your call on the PV. 8.5 would be a good bet.
Here's why. We're going to cheat a little. We don't know what the step up vacuum is for the original carbs (BBD). But we do know the situations when vacuum advance is not needed or desired. Remember what vacuum advance is for? So the two work hand and glove.
At 10.5" this engine had little bit of vacuum advance, 2 to 8 crankshaft degrees.
So below 10.5" vacuum, it was probably getting enrichment on the original carbs.
Based on this.
8.5 is a reasonable guess. If they only have a 9.5 or 10.5 in stock, either would also be OK as a starting point,
and 4.5 seems way too far into the throttle before enrichment.
iScamp
Well-Known Member
Hey, we've all been there at one time or another. Not an idiot.
However, I question your sanity with this statement: "practically ran my wife over to head out to the garage...". That'll cost you in the long run.
insidegroove
Member
Followup just for you guys.....thanks again everyone!
Beautiful engine bay... whos cutouts did you go with? I'm planning a single 3" exhaust for non annoying driving and granetelli cutouts to be annoying
P.S. please take some polish to that shifter
P.S. please take some polish to that shifter
1971swinger
Well-Known Member
Sounds awesome, like your copilot
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