 96MM Cylinder and Piston Install, Running real bad after install |
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| DanPMan |
 Aug 7 2005, 06:40 PM
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#1
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Newbie  Group: Members Posts: 7 Joined: 3-June 05 From: Las Vegas, NV Member No.: 4,192  |
Just installed a 96MM piston and cylinder set into our 75 914-2.0. Fuel injection has been removed and replaced with a 32/26 DFV. Upon restart, there's a lot of backfiring both through the intake and exhaust. Runs like #$$#@%!!! with no power whatsoever. So far we've reset the carb per Weber initial set-up procedures and performed some initial timing. It idles, but hydrocarbons read at well over 8000 and the CO% was at 5 to 7%. So we're probably real rich. Probably should be rejetted...
Question.... when we installed the piston and cylinder sets, we also performed a valve seat rework (with a Neway by hand). All valves were verified to seat. Do you think the backfiring and no power condition is due to any other cause besides the carb and timing set-up????? |
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Replies(1 - 18)
| bd1308 |
Aug 7 2005, 06:45 PM
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#2
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Sir Post-a-lot Group: Members Posts: 8,020 Joined: 24-January 05 From: Louisville,KY Member No.: 3,501 |
check your dwell..my car did the same thing right before my point block wore down to zero and caused my engine to do all sorts of crazy stuff.....
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| DanPMan |
Aug 7 2005, 06:55 PM
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#3
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Newbie Group: Members Posts: 7 Joined: 3-June 05 From: Las Vegas, NV Member No.: 4,192 |
Will do! I didn't have my dwell meter or timing light with me when we were attempting (key word!) to time it the other day...
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| bd1308 |
Aug 7 2005, 07:01 PM
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#4
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Sir Post-a-lot Group: Members Posts: 8,020 Joined: 24-January 05 From: Louisville,KY Member No.: 3,501 |
what sucks is that i actually lost my nice digital dwell meter, which was also a multimeter.
sigh.... point gap should be close to .012.... |
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| MattR |
Aug 7 2005, 07:03 PM
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#5
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Advanced Member Group: Members Posts: 3,279 Joined: 23-January 04 From: SF Bay Area Member No.: 1,589 Region Association: Northern California |
Did you set timing? You could be off. Loosen the distributor cap, start the car up, and rotate the distributor at idle to see if that changes anything. You should be rotating like 30-40 degrees each direction max.
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| Al Meredith |
Aug 7 2005, 07:04 PM
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#6
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Senior Member Group: Members Posts: 960 Joined: 4-November 04 From: Atlanta, ga Member No.: 3,061 |
My experience tells me that backfireing means lean mixture or exhaust leaks. I always rejet the idle jet (inside the brass screw on the upper side of the carb) with a "55" jet. I think they come jetted for a 1600CC VW
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| seanery |
Aug 7 2005, 07:08 PM
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#7
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waiting to rebuild whitey! Group: Retired Admin Posts: 15,854 Joined: 7-January 03 From: Indy Member No.: 100 Region Association: None |
what about the cam? You've got nice pic pistons, did you upgrade the cam? I think your carb is probably a wee bit tiny for this application, too. I'm sure other more experienced teeners will correct me if I'm wrong. (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)
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| bd1308 |
Aug 7 2005, 07:08 PM
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#8
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Sir Post-a-lot Group: Members Posts: 8,020 Joined: 24-January 05 From: Louisville,KY Member No.: 3,501 |
backfire from carb=lean
backfire from exhaust=rich running after being turned off=rich |
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| Jake Raby |
Aug 7 2005, 07:34 PM
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#9
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Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
Remove that carb
Grab the biggest hammer you can find..... Beat the carb into a million pieces and throw it in the trash.. (this is to keep another soul from the same BS later) Install a set of dual carbs, or go back with EFI. The single Weber with its long runners and piss poor CFM rating will create all sorts of issues- I consider them absolutely untunable and throw them away weekly. Making the engine larger has further increased the issues- the carb simply can't keep up with the engine. All your symptoms of backfiring lead to running lean- Working with that carb is like pissing into the wind, but I think I'd rather piss into the wind as install or work with one! |
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| bd1308 |
Aug 7 2005, 07:44 PM
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#10
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Sir Post-a-lot Group: Members Posts: 8,020 Joined: 24-January 05 From: Louisville,KY Member No.: 3,501 |
i enjoy my single carb setup......i know another 9fourteener with one too.
it's good. i'll pay shipping if you send those my way, jake. |
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| lapuwali |
Aug 7 2005, 08:37 PM
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#11
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Not another one! Group: Benefactors Posts: 4,526 Joined: 1-March 04 From: San Mateo, CA Member No.: 1,743  |
running on is usually lean, actually. backfires can also be caused by incorrect timing. |
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| bd1308 |
Aug 7 2005, 08:40 PM
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#12
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Sir Post-a-lot Group: Members Posts: 8,020 Joined: 24-January 05 From: Louisville,KY Member No.: 3,501 |
i dont understand....
why would the system run-on without any fuel to run-on with......... |
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| Bleyseng |
Aug 7 2005, 09:19 PM
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#13
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Aircooled Baby! Group: Members Posts: 13,035 Joined: 27-December 02 From: Seattle, Washington (for now) Member No.: 24 Region Association: Pacific Northwest |
Takes Jakes,DD,Brads and everyone else and chuck that POS carb.
FI or duals are the way to go. (IMG:http://www.914world.com/bbs2/html/emoticons/idea.gif) |
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| SLITS |
Aug 7 2005, 09:21 PM
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#14
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"This Utah shit is HARSH!" Group: Benefactors Posts: 13,602 Joined: 22-February 04 From: SoCal Mountains ... Member No.: 1,696 Region Association: None |
Ok budding M.E........hot spots in the cylinder head (preignition) from being to lean. If the engine still continues to turn, it still draws fuel and air 'cause a carb don't have no fuel cutoff.
Are the valves to tight also? |
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| Bleyseng |
Aug 7 2005, 09:24 PM
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#15
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Aircooled Baby! Group: Members Posts: 13,035 Joined: 27-December 02 From: Seattle, Washington (for now) Member No.: 24 Region Association: Pacific Northwest |
Thats my bet! |
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| bd1308 |
Aug 7 2005, 09:49 PM
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#16
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Sir Post-a-lot Group: Members Posts: 8,020 Joined: 24-January 05 From: Louisville,KY Member No.: 3,501 |
that was my other therory.
It just worked out both ways in my head. |
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| redshift |
Aug 7 2005, 10:00 PM
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#17
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Bless the Hell out of you! Group: Members Posts: 10,926 Joined: 29-June 03 Member No.: 869 |
popping.. i&o... and..
Yeah, valves.. may even take a sweet spot adjustment, with a lil carb, and big... knockers? (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif) M |
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| rhodyguy |
Aug 7 2005, 10:02 PM
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#18
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Chimp Sanctuary NW. Check it out. Group: Members Posts: 22,084 Joined: 2-March 03 From: Orion's Bell. The BELL! Member No.: 378 Region Association: Galt's Gulch |
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| Type 4 Unleashed |
Aug 7 2005, 10:59 PM
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#19
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CREATIVE TYPE lV ENGINEERING Group: Retired Members Posts: 787 Joined: 20-June 04 From: Aliso Viejo, ca Member No.: 2,231 Region Association: None |
You, have plug wires, mixed up. (IMG:http://www.914world.com/bbs2/html/emoticons/happy11.gif) |
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