New motor's killin me...
#2537493
08/17/18 04:10 AM
08/17/18 04:10 AM
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Joined: Nov 2003
Posts: 4,027 Dearborn Hts, MI
Sledge_57
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Dearborn Hts, MI
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Had a new motor built, 500" 400 block, 10.8 compression, .629 lift, 263@.050, my Bulldog heads from old motor, MP M1 single plane, Holley HP 950, MSD Pro billet Dist and 6al and TTI step headers 2" - 2 1/8". It runs but not well. We're pretty sure it's a vacuum leak at the intake. First we found one of the extra four carb mounting holes for AVS style carbs (I guess) was drilled all the through to the plenum. We fixed that but still seem to have a sizable vacuum leak. We suspect the intake's not sealing to the heads well, looking at the gasket after pulling intake could see indents along top of gasket where manifold was sealed but nothing along the bottom. Used intake of course but it looked as if it was never on a motor before. Cylinders on even side seem to have the issue based on temps at header tubes. Odd side was showing ~200* (didn't run it long) even side (#2 specifically) ~85* We checked and we know we're getting spark btw... Tried thicker gaskets and used a little sealer, better but still not right. Looking for a way to track it down, other than spraying carb cleaner trick, we tried that and found nothing. Might put old Performer RPM on tomorrow I think to see if it makes a difference but would like to try to get the M1 to work Thanks
Last edited by Sledge_57; 08/17/18 04:16 AM.
Doug
1967 "Pedal Car" 500" low deck , TF 727, 4.30 Locker Best to Date: 11.67 @ 114.9 1.64 60ft
"Kids in cars cause accidents. Accidents in cars cause kids..."
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Re: New motor's killin me...
[Re: Sledge_57]
#2537529
08/17/18 08:56 AM
08/17/18 08:56 AM
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Joined: Jan 2005
Posts: 4,243 Charlotte, North Carolina
sgcuda
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I cheated and brought home the smoke machine from work for checking evap leaks. Showed me a lot of my issues from start up. You can put the intake on without the gaskets to check mating surfaces and angles. I think that .003" gap would be max before clean milling the intake to match the heads.
[image][/image]
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Re: New motor's killin me...
[Re: Sledge_57]
#2537614
08/17/18 01:28 PM
08/17/18 01:28 PM
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Joined: Aug 2003
Posts: 43,719 Bend,OR USA
Cab_Burge
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I have sat the intake on the heads, make sure all the flat surfaces are clean and ding free, to check the alignment and then used a feeler gauge to measure all four corners with a feeler gauge at the top and bottom of the intake to head mating surfaces. don't be surprise to see some at zero and some as bad as .015+ Write the clearances down for each corner and then take that manifold to a good machine shop and have them surface it to cure the machining differences, if the bolt holes in the manifold are above the ones in the heads you may need to have additional material removed to get the port alignment better, if below then add gaskets (stack them if needed ) to raise the intake up to align the manifold
Last edited by Cab_Burge; 08/17/18 01:30 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: New motor's killin me...
[Re: Sledge_57]
#2538001
08/18/18 03:38 AM
08/18/18 03:38 AM
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Joined: Nov 2003
Posts: 4,027 Dearborn Hts, MI
Sledge_57
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Thanks for the replies and suggestions.
We tried my Performer RPM intake that had been used with these heads before and had the same issue, also tried another carb I used on my old 470. Still the same.
After all was said and done we discovered it wasn't a vacuum leak at all.
It was the power valves. My HP 950 came jetted square with 79 mains and 6.5 PV's. We knew 6.5 wouldn't work, we dropped them to 3.5 and that's what was in when we thought it was a vac leak.
Finally realized 3.5 wasn't low enough and installed PV block off plugs.
Ran perfect, idling right at 1000 rpm.
Now, how much to increase jetting without PV's?
Doug
1967 "Pedal Car" 500" low deck , TF 727, 4.30 Locker Best to Date: 11.67 @ 114.9 1.64 60ft
"Kids in cars cause accidents. Accidents in cars cause kids..."
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Re: New motor's killin me...
[Re: Sledge_57]
#2538060
08/18/18 11:44 AM
08/18/18 11:44 AM
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Joined: Nov 2003
Posts: 4,027 Dearborn Hts, MI
Sledge_57
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OK one more thing I remembered from last night and I think this may have been the culprit.
When I pulled the secondary PV it had 2 gaskets, can this cause it to dump fuel?
Seriously the car wouldn't even run until we blocked the PV's. I'm going to check vacuum today to see where it is and try PV's again.
It was impossible to check it before had to keep it over 1500 to stay lit and was missing badly.
Kathy, I'm hoping to...
Doug
1967 "Pedal Car" 500" low deck , TF 727, 4.30 Locker Best to Date: 11.67 @ 114.9 1.64 60ft
"Kids in cars cause accidents. Accidents in cars cause kids..."
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Re: New motor's killin me...
[Re: Sledge_57]
#2538069
08/18/18 12:13 PM
08/18/18 12:13 PM
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Joined: Jul 2004
Posts: 19,318 State of confusion
Thumperdart
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Thanks for the replies and suggestions.
We tried my Performer RPM intake that had been used with these heads before and had the same issue, also tried another carb I used on my old 470. Still the same.
After all was said and done we discovered it wasn't a vacuum leak at all.
It was the power valves. My HP 950 came jetted square with 79 mains and 6.5 PV's. We knew 6.5 wouldn't work, we dropped them to 3.5 and that's what was in when we thought it was a vac leak.
Finally realized 3.5 wasn't low enough and installed PV block off plugs.
Ran perfect, idling right at 1000 rpm.
Now, how much to increase jetting without PV's? The jet spread depends on the size of the pvcr's but a 2.5 or 3.5 rarely belongs in ANYTHING so you need to clean up the idle/transition circuits first then start tuning again. Cruise is where/why the p/v's work or not NOT idle and my Dart has 5 in. of vacuum at idle and I run a 6.5 but cruise at 12 in so when I crowd the throttle under load, it opens up giving me the enrichment I need accordingly..........That carb needs work and not just jetting but a complete make over and if u call me I can help ya out if u'd like.........
72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....
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Re: New motor's killin me...
[Re: Thumperdart]
#2538280
08/18/18 10:50 PM
08/18/18 10:50 PM
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Joined: Jan 2004
Posts: 13,247 Mt. Vernon, Ohio
dartman366
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I Live Here
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Posts: 13,247
Mt. Vernon, Ohio
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make the call,,,,you will be glad you did.
Light travels faster than the speed of sound,,,this is why some people seem bright untill you hear them speak.
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Re: New motor's killin me...
[Re: Sledge_57]
#2538359
08/19/18 12:51 AM
08/19/18 12:51 AM
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Joined: Nov 2003
Posts: 4,027 Dearborn Hts, MI
Sledge_57
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Dearborn Hts, MI
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Put a vacuum gage on it today and has a steady 9in at idle with PV's blocked so at least I have a starting point. I have to assume that second gasket on the PV that we didn't know was there was the original problem
Doug
1967 "Pedal Car" 500" low deck , TF 727, 4.30 Locker Best to Date: 11.67 @ 114.9 1.64 60ft
"Kids in cars cause accidents. Accidents in cars cause kids..."
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Re: New motor's killin me...
[Re: Thumperdart]
#2538825
08/20/18 02:19 AM
08/20/18 02:19 AM
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Joined: Nov 2003
Posts: 4,027 Dearborn Hts, MI
Sledge_57
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If you run a plugged p/v on the street you are doing nothing towards fixing the issues and creating more nasty oil fouling richness......... I have no intention of leaving this way Dom, but it was the only way it'd run. Like I said, based on the amount of vacuum I have it must have been the extra gasket I accidentally put under the PV, other than changing the PV's this carb is just as it came from Holley. Nothing else makes sense to me, unfortunately working out of town next week so it'll have to wait till next weekend, gonna start with a 4.5 PV in the primary and go from there. Here's a small vid https://youtu.be/qkr0uWS2gcE
Doug
1967 "Pedal Car" 500" low deck , TF 727, 4.30 Locker Best to Date: 11.67 @ 114.9 1.64 60ft
"Kids in cars cause accidents. Accidents in cars cause kids..."
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Re: New motor's killin me...
[Re: Sledge_57]
#2538873
08/20/18 08:39 AM
08/20/18 08:39 AM
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Joined: Jan 2003
Posts: 18,025 S.E. Michigan
ZIPPY
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S.E. Michigan
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The car sure looks great, Doug. I'm sure you'll figure it out soon. These kind of issues are part of what led me down the path to air/fuel ratio gauges. I bet if you could grab one it'd give helpful directional info. Just a thought. Good luck.
Rich H.
Esse Quam Videri
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