Re: Need help on detination........
[Re: 64legacy]
#1027570
07/07/11 09:39 AM
07/07/11 09:39 AM
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Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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Need a baseline on what you have: get a cranking compression #. W vac adv plugged, set initial w vac gauge method then shorten slots to get 36 total then heavier spring(s) staying just under the pinging point at WOT up thru the gears on your hottest/driest day then hookup vac adv & want the fastest tip in it'll take at steady PART throttle (high vacuum) at a RPM at or above the RPM where your mech curve (slots) are maxed out. If your cranking # is too high you may need to proportion in a % of race or av gas as slowing timing from ideal severly hurts performance & in this case might not even touch the prob so feed it what it needs to b happy. In a nutshell your curve is too fast (& DCR may be too high for 94/proper curce)
live every 24 hour block of time like it's your last day on earth
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Re: Need help on detination........
[Re: RapidRobert]
#1027572
07/07/11 10:53 AM
07/07/11 10:53 AM
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Joined: Mar 2007
Posts: 49
Canada
64legacy
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OP
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Joined: Mar 2007
Posts: 49
Canada
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Quote:
Need a baseline on what you have: get a cranking compression #. W vac adv plugged, set initial w vac gauge method then shorten slots to get 36 total then heavier spring(s) staying just under the pinging point at WOT up thru the gears on your hottest/driest day then hookup vac adv & want the fastest tip in it'll take at steady PART throttle (high vacuum) at a RPM at or above the RPM where your mech curve (slots) are maxed out. If your cranking # is too high you may need to proportion in a % of race or av gas as slowing timing from ideal severly hurts performance & in this case might not even touch the prob so feed it what it needs to b happy. In a nutshell your curve is too fast (& DCR may be too high for 94/proper curce)
There is no vac advance on this dizzy. Cranking compression is 135 lbs. cold with throttle blades wide open.I have set engine running with vac gauge, started better, better throttle responce......but out on the road no more then part throttle and it rattled. Have been reducing timing back to stop, but not working at the moment.
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Re: Need help on detination........
[Re: Mr.Yuck]
#1027573
07/07/11 11:05 AM
07/07/11 11:05 AM
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Joined: Mar 2007
Posts: 49
Canada
64legacy
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Canada
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A stock 68 rebild even with 915/516 heads and steel shims should be maybe 10:1. I can't think of a reason that wouldn't work on pump gas. That is a small 430/455 cam. Are those domed pistons? Are you sure your carb is set up right? Is your timing advancing? You need a good timing light w/ an advance on it. If that were my engine I'd have it set at 16-18* initial and 36-38* total in full at 2200. I'd start with your carb. 1st if you don't have a carb spacer or thick insolated gasket do it, 2nd make sure your getting full open throttle. What 750 is it? What jets? what squirtters? what PV? I'd probably start w/ 74/82's 31 squirters and a 6.5PV.
Cam specs off of card say lift .474 duration 280 overlap 60 and centerline 110.Just flat top pistons.Carb is a Holly 750 List 4779-4 deul feed double pumper. Power valve has D5 on it and jets are #70 on front.Front metering block is #11180. Plugs are Bosch Platinum WR9FP R6865. I have a 4 hole spacer under the carb to stop the heat sink and have also insulated all feul line to the carb. This stopped the boil over in the carb after shutdown.After setting engine with vac method I did have about 18 degrees intial and did advance when revving. But it rattled badly. Have been adjusting ever since.
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Re: Need help on detination........
[Re: Mr.Yuck]
#1027575
07/07/11 11:42 AM
07/07/11 11:42 AM
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Joined: Mar 2007
Posts: 49
Canada
64legacy
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whoops sorry yeas that the 474 cam. 135 is not a ton of compression. So your problem is somewhere else. You have a good carb, I'd step up on the jetting and see how that works. 70 jets are pretty small if it has 70's in the front it probably has 74-76's rear and that's not enough. The squirters should be 31's if they are smaller you might need more. Also what thermostat are you running? How hot is your engine getting? Gas shouldn't be boiling with that tall intake, unless you didn't block off your crossovers. Bump up the jetting and see what happends.
Ok just checked and they are 31 squirters front and rear. Running a 180 degree thermostat,actual temp with thermal reader about 185 to 195. Crossovers are blocked. I;ve had this car 40 years and never had a problem untill this new gas with alcohol in it. The heat soak after shutdown was boiling it in the carb. As said the spacer and insulated feul lines fixed that. Got that info from this board. Anyways on the issues of sparkplugs....are the ones I have ok or not?? They look kinda black,like it's running rich. How much should I step up the front jets?
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Re: Need help on detination........
[Re: 64legacy]
#1027577
07/07/11 11:56 AM
07/07/11 11:56 AM
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Joined: Jan 2003
Posts: 24,562
Brookeville, Md
Mr.Yuck
Not enough dumb comments...yet
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Not enough dumb comments...yet
Joined: Jan 2003
Posts: 24,562
Brookeville, Md
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Quote:
Quote:
whoops sorry yeas that the 474 cam. 135 is not a ton of compression. So your problem is somewhere else. You have a good carb, I'd step up on the jetting and see how that works. 70 jets are pretty small if it has 70's in the front it probably has 74-76's rear and that's not enough. The squirters should be 31's if they are smaller you might need more. Also what thermostat are you running? How hot is your engine getting? Gas shouldn't be boiling with that tall intake, unless you didn't block off your crossovers. Bump up the jetting and see what happends.
Ok just checked and they are 31 squirters front and rear. Running a 180 degree thermostat,actual temp with thermal reader about 185 to 195. Crossovers are blocked. I;ve had this car 40 years and never had a problem untill this new gas with alcohol in it. The heat soak after shutdown was boiling it in the carb. As said the spacer and insulated feul lines fixed that. Got that info from this board. Anyways on the issues of sparkplugs....are the ones I have ok or not?? They look kinda black,like it's running rich. How much should I step up the front jets?
could you be sucking oil? doesn't take much to rupture the intake seal and you will start sucking oil and that can cause detonation. I had a 440 in a 67 coronet I had no idea it was sucking but when I swapped intakes I noticed on jug was pulling oil. I'd try 74 front 82 rear jets. If this motor ran fine before then it might be something as simple as your fuel pump starting to fail, clogged filter. I ran Autolite 85's in many mild 440's w/ no problems. If it was running rich you'd get a good wiff of gas as you drive and idle.
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Re: Need help on detination........
[Re: 1972challenger]
#1027578
07/07/11 12:15 PM
07/07/11 12:15 PM
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Joined: Mar 2007
Posts: 49
Canada
64legacy
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Quote:
I've had to enrich every car that comes into the shop. Go up 2 to 4 jet sizes reset your idle mixtures and it should do the trick. Also you may want to de-carbonize the combustion chambers too.
Ok thanks. I'll go and get some larger jet sizes and give it a try. AS far as de-carbonizing the chambers, when I get it back together a little H2O down the carb will fix that.
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Re: Need help on detination........
[Re: Mr.Yuck]
#1027579
07/07/11 12:21 PM
07/07/11 12:21 PM
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Joined: Mar 2007
Posts: 49
Canada
64legacy
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whoops sorry yeas that the 474 cam. 135 is not a ton of compression. So your problem is somewhere else. You have a good carb, I'd step up on the jetting and see how that works. 70 jets are pretty small if it has 70's in the front it probably has 74-76's rear and that's not enough. The squirters should be 31's if they are smaller you might need more. Also what thermostat are you running? How hot is your engine getting? Gas shouldn't be boiling with that tall intake, unless you didn't block off your crossovers. Bump up the jetting and see what happends.
Ok just checked and they are 31 squirters front and rear. Running a 180 degree thermostat,actual temp with thermal reader about 185 to 195. Crossovers are blocked. I;ve had this car 40 years and never had a problem untill this new gas with alcohol in it. The heat soak after shutdown was boiling it in the carb. As said the spacer and insulated feul lines fixed that. Got that info from this board. Anyways on the issues of sparkplugs....are the ones I have ok or not?? They look kinda black,like it's running rich. How much should I step up the front jets?
could you be sucking oil? doesn't take much to rupture the intake seal and you will start sucking oil and that can cause detonation. I had a 440 in a 67 coronet I had no idea it was sucking but when I swapped intakes I noticed on jug was pulling oil. I'd try 74 front 82 rear jets. If this motor ran fine before then it might be something as simple as your fuel pump starting to fail, clogged filter. I ran Autolite 85's in many mild 440's w/ no problems. If it was running rich you'd get a good wiff of gas as you drive and idle.
Never thought of that. Oil consumption is ok, no oil in valley pan, but I'll check anyways. Feul pump and filter are all new. I'll also try some new plugs as you stated. The only time I get a strong gas smell is when it's idling. Brings tears to the eyes. Only smoking issue I've noticed is when it rattles is a bluey black haze out the tailpipes. Stops when I let off of the peddle.
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Re: Need help on detination........
[Re: 64legacy]
#1027581
07/07/11 02:02 PM
07/07/11 02:02 PM
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Joined: Mar 2008
Posts: 5,746
Ontario, Canada
Dodgem
master
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master
Joined: Mar 2008
Posts: 5,746
Ontario, Canada
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I would put RJ12YC in and 74 jets in the front! check your in gear idle vacuum and get a power valve that is 1.5 to 2.5 below that. If idling in gear is 9 get a 7.5 if its 10.5 get an 8.5 and so on!  You sure your timing mark/ outer ring on the balancer is correct and has not moved?
Last edited by Dodgem; 07/07/11 02:03 PM.
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Re: Need help on detination........
[Re: Mr.Yuck]
#1027582
07/07/11 02:09 PM
07/07/11 02:09 PM
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Joined: Mar 2007
Posts: 49
Canada
64legacy
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Quote:
wonder if you PV is blown???
Just went and bought new one. 6.5 for now.
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Re: Need help on detination........
[Re: Dodgem]
#1027583
07/07/11 02:12 PM
07/07/11 02:12 PM
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Joined: Mar 2007
Posts: 49
Canada
64legacy
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Quote:
I would put RJ12YC in and 74 jets in the front! check your in gear idle vacuum and get a power valve that is 1.5 to 2.5 below that. If idling in gear is 9 get a 7.5 if its 10.5 get an 8.5 and so on!
You sure your timing mark/ outer ring on the balancer is correct and has not moved?
Have purchased 74 jets for front and are gunna check balancer marks. Mine has two lines on it about 3/4 inch apart. I have a balancer of the original 383 that was in it before. Looks identical, but will check them out.
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