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Thanks this thing really run good. Lots of power between 2 and 5 thousand rpms
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Jerry McAbee
1967 912
1968 912
2002 Tundra 4x4
Old 10-03-2010, 11:49 AM
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1966 - 912 - SOLD
 
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i like how you mesure deck hight wish i knew that 3 months ago when i did my top end. next time.
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Old 10-03-2010, 12:10 PM
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I had an issue with the right carb, The throttle lever was not closing all the way and was making it hard to tune. After removing the carb I noticed the accelerator pump was binding up. After adjusting and resetting the idle jets what a difference. This car is has so much power. I hope to get the engine on a dyno soon I will post the results if I do.

I just want to say thanks to Walt at Comp Engineering I don't take credit for any of this build. Ever thing I know or posted is because Walt took the time to teach me or show me. I feel blessed to have had the opportunity work with this master Porsche engine expert.

Thanks again
Jerry
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Jerry McAbee
1967 912
1968 912
2002 Tundra 4x4
Old 10-04-2010, 08:54 PM
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Hi Jerry,

I remember your carbs were rough prior to rebuild, grooves in the body made by the butterflies and other issues. How did the carb rebuild go?

Thanks,

Steve
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Steve
'65 912 project
'66 912 rusty
'84 944 NA
'88 911 Cabrio
Old 10-05-2010, 08:11 AM
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Hi Steve Walt had some carbs in the shop we swapped my old ones for his rebuilt set. I am still having trouble with one side. The idle mixture screw would not make any changes in the idle. So I tore it down and cleaned it. It had some crud in the float bowl blow out all the jets and passages with brake cleaner. Reinstalled but its like the one side is not firing on idle. I wonder if I fouled the plugs or if the carb has more crap in it. It will have to wait till tomorrow. Any ideas?
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Jerry McAbee
1967 912
1968 912
2002 Tundra 4x4
Old 10-05-2010, 08:22 PM
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It's been a long time since I messed with carbs, but make sure your crossbar linkage isn't preventing a change in idle on the one side. Disconnect the crossbar linkage completely until you get it setup on both sides equally.

After that, I usually just blamed all other problems on the age of the carbs. The only time I ever had a dramatic change in the ability to adjust dual carbs was when I added a brand new set of Webers on any old 914. It was like magic.
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1968 912
1974 914-6 3.2 conversion (gone, but never forgotten)
2012 Mustang
Old 10-06-2010, 03:27 AM
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i would check the idle jet again. remove it from the carrier. there is probably some debris in it again. also remove the mixture screw. that might be partially clogged as well.
Old 10-06-2010, 04:46 AM
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What seems weird is neither 1 or 2 will adjust with the idle screws, and the intakes are cold like it is getting fuel. Maybe weak spark bad coil. I am using bosch wr-6-sc spark plugs should I try wr-7-cr. I need to see if I have spark out of the distributor. I am going to pick up a timing light tonight. But how would I check for weak spark. Can I take the spark plug out and check visually I have done that on my motorcycle.
Give me an old rusty bucket to sand any thing but this.
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Jerry McAbee
1967 912
1968 912
2002 Tundra 4x4
Old 10-06-2010, 04:09 PM
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i haven't heard this plug used on a 616 before. w6bc would be typical. i use wr7bp which are the same dimensions as a w#bc, but are the platinum variety.
that is something to look at. just look to see if they are fuel fouled. or if the dimensions aren't correct, maybe the pistons tapped the electrodes shut. (i wasn't able to find any info about them)
if they're just fuel fouled, you may just have the mixture too rich.
Old 10-06-2010, 04:57 PM
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Jerry, your engine rebuild effort has been fantastic to follow and admire so I hope I do not offend you with making some simple suggestions.
To check spark from distributor I would pull off all 4 plug leads, crank engine with ignition on and hold the end of each lead in turn near a good solid earthed part of the engine. You should get a good spark across a gap of about 2.5mm (tenth of an inch in your terms). Wear rubber gloves and make sure that the metal connectors on the end of the leads are not shielded by the boots.
Removing/replacing rear plugs is a pain (I've got Webers and they may make it worse) but you can test the spark at the plugs in the same way if you wish. Remove plug, attach its lead (leave all others off) and place outer electrode of plug on an earthed bit of engine, crank engine.
Re carbs, idling jet, idle air bleed, idle mixture passageways and, particularly, the main hole where the idle mixture enters the carb throat (the hole that the idle mixture screw closes when it is fully screwed in) have to be clean.
I note that when talking idle adjustment you tend to talk about the mixture screw. What about the idle speed screw(s). Does it have an affect? As a start I would disconnect throttle rods from both carbs (essential), screw idle mixture screws in till they seat (don't use force), then screw them back out one and a half turns (all as per book).
Don't touch idle speed screws on either side at this stage as your engine has apparently been running. With ignition system back together, start the engine. If it runs reasonably let it warm up a bit. Now turn idle speed screw on RH (problem) side one turn in. Does idle speed change? If no, try another turn. Don't go too far or you will transition on to the main jet.
Old 10-06-2010, 05:28 PM
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Thanks Richard I took the carb off today and noticed not very much fuel in the float bowl and found a pick of something blocking the float jet. Put everything back together and it tuned perfectly all the idle screws adjusted like they are suppose to. Started out at about 1000 rpms adjusted the first screw to achieve the highest rpm. Did this to all 4, readjusted the rpms back to 1000 rpms and did it again. brought the idle down to 800 rpms and drove it. The engine would not stay running coming to a stop. If I pushed in the clutch and ebraked to a stop to keep it running after I stopped it would idle fine. I am not sure I am getting full hp. I don't really like this set up any suggestions.
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Jerry McAbee
1967 912
1968 912
2002 Tundra 4x4
Old 10-07-2010, 07:31 PM
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My car has Webers and so I am not familiar with the Solexs. However, if I understand it, your problem now seems to be that the carbie(s) are not handling a rapid closing of the throttle butterflies. That is, not handling the transition from the main jet back to the idle jet.

I would first try moving the idle speed up to about 1,200 rpm. Again, make sure that you have the accelerator levers disconnected from both carbies while you are doing this. After adjusting the levers to match the new butterfly positions try blipping the throttle. Does the engine speed recover reasonably back to the 1,200 rpm? Does it come back OK but a little slowly? Or does it tend to die on you? Slowish drop back is common in my experience. I think it is related to the timing change that is also going on as the revs drop. If not dieing, try a test drive.

Interested to hear what happens if you try this. Another comment/question. You seem to be finding a lot of crud in the carbies. I should go and check out your other thread on the body restoration to see what you did but are you sure that the fuel tank, pipes etc. are clean - no old oxidised fuel remnants or other nasties. Low fuel level in float chamber will make the transition back to idle more difficult.
Old 10-08-2010, 05:06 AM
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My plan is to take both carbs off clean and check again. Note all jet sizes. I think the junk I am getting is from the rebuild I may not have got the fuel lines cleaned out of the old junk. I have 2 filters on the fuel system one at the fuel tank and one in the engine compartment. New fuel and the fuel tank has been cleaned. I need to do this I am just fighting it. This is my school of hard knocks this is how I learn. Thanks for your help I will let you know what I find
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Jerry McAbee
1967 912
1968 912
2002 Tundra 4x4
Old 10-08-2010, 05:40 AM
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i've watched most of your build, but i can't remember; did you clean out your gas tank?
sounds like a float issue. the needle/seat meters the float level(assuming the levels are set properly) if the needle/seat gets clogged the flow won't be metered properly and could be causing raw fuel to spill into the carbs when you slow to a stop.
Old 10-08-2010, 05:41 AM
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Jerry,

You have overcome a hundred problems that would stump most of us. Reading your posts on how you overcame is one of the highlights of my day. Here is lots of Solex tuning lore:

356Talk ::

Looking forward to your next solution!

Steve
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'65 912 project
'66 912 rusty
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Old 10-09-2010, 06:06 AM
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Thanks for the confidence I have surprised myself at times. Well I have one thing to say. Don't bead blast your fuels you will be sorry. I thought I had clean the fuel lines good enough. I should have ran the fuel pump and flushed the lines before hooking the lines to the carbs. Now that I have take the carbs off and cleaned them 2 times now I feel a little more comfortable about working on them. I have this deep fear of dropping something down the intakes. I am not sure if I have the right jets it seems to run better but the main jet is a 115 and stock is 120. Probably need to keep an eye on my spark plugs make sure I am not running to lean.

I made a couple of videos

YouTube - Jerry's Porsche 912 tuning

YouTube - Jerry's Porsche 912 test drive
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Jerry McAbee
1967 912
1968 912
2002 Tundra 4x4
Old 10-09-2010, 10:04 AM
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we've all had those brain farts. i'd bet you needle/seats are clogged. you might have luck with a sonic cleaner. there are small cheap ones at harbor freight for $30. check their function first of course. remove them from the inside of the carb tops. inspect the inlet side; there is probably some media in there. the shaft should move up and down. to check the function blow into the inlet side. you should hear air passing through. push the shaft close with you finger as you blow, the airflow should stop as you push. don't use the ones in rebuild kits, they're worthless as teets on a boar hog.
i had this problem with mine, except it was rust dust from a dirty tank. i gave up on them and put dells on b/c i couldn't find a a replacement for the needle/seats. i eventually cleaned them with the sonic cleaner(took about 3 days), and they work now. the carbs are still on the shelf though.
Old 10-10-2010, 06:00 AM
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Question about Idle

Hi all I have been working on the jetting for my engine. The Main jet that I started with was a 115 which I figured was to small. Stock according to the Porsche manual is a 120. With the bigger pistons and advanced cam I figured I need to be a little bigger than stock. I tried the 120 it ran better but the 122 really gives you low growl and lots of power. The problem I am having is coming off the mains to the idle. The engine dies coming to a stop. If I bring it down slowly it will idle sometimes. It was really bad with the 115s but it is still there. The timing is 0 to 28 degs. I am running the 022 stock distributor rebuilt. Any ideas


Thanks Jerry
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Jerry McAbee
1967 912
1968 912
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Old 10-25-2010, 09:14 PM
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What are the idle jet sizes ? mains. Timing is normally set 32 or 33 BTDC @ 3000 for the 912.....35 is spec. but the fuels of today have changed that or so I've read.....
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Last edited by C. Clark; 10-26-2010 at 08:39 PM..
Old 10-26-2010, 04:05 PM
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I was told my air volume was set to low. It was about 3psi and need to be at 5 to 7 but that put my idle up to 1200 1300 rpms I could retard the timing to make the idle come down but the engine didn't like that.

Jetting is as followed

Main 122
air correction 180
idle metering 57.5
idle air bleed 1.8
float needle valve 175

Do you think maybe a bigger idle jet would help.

I need to check the timing at 3000 rpms at 2200 its 20 degrees.

Thanks for your input
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Jerry McAbee
1967 912
1968 912
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Old 10-26-2010, 10:05 PM
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