Home  |  Forums  |  914 Info  |  Blogs
 
914World.com - The fastest growing online 914 community!
 
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG. This site is not affiliated with Porsche in any way.
Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners.
 

Welcome Guest ( Log In | Register )

 
Reply to this topicStart new topic
> stub pipe and header flange, can a leak make my car run like crap?
machina
post Apr 29 2007, 04:22 PM
Post #1


Advanced Member
****

Group: Benefactors
Posts: 2,030
Joined: 21-June 03
From: Miami Beach, FL
Member No.: 848



i think one of my stub pipes is leaking where the flange meets with the header. Can a leak there make the car run really bad? Right now it idles OK since i cleaned the carbs but part throttle and mid speed is awful, bucks and kicks...
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
r_towle
post Apr 29 2007, 10:55 PM
Post #2


Custom Member
***************

Group: Members
Posts: 24,705
Joined: 9-January 03
From: Taxachusetts
Member No.: 124
Region Association: North East States



it should not make that much of a difference, certainly not enough to make it buck. loud yes, buck ,,,I doubt it unless you have a really high strung motor that runs at 6-9k and has a tuned exhaust...

did you sync your carbs?
If you are unsure of if the carbs are synced, try this
Un hook the throttle linkage and snyc the carbs by the book, adjusting each port to match...by this I mean that the two ports on any given carb must flow the same...not carb to carb, but on the same carb.

the two carbs can be different from each other,,while that is not optimal, it can be tuned out with the linkage.

In an ideal world, with a perfect motor, no leaks in the cylinders/valves, you want all four cylinders to pump the same amount of air.
This can be done by adjusting each individual port using the air adjustment screw on each port.

If you can make all of them flow the same at idle, you are almost there.

Then, put the linkage back on and adjust it so both carbs flow the same, all ports, both carbs, so now you know the linkage is correct.

Now, bring it up to 2k, 3k, 4k, 5k and check all four ports at each step.

This is where the carb tuning gets wierd.
Your motor is not perfect, and there are leaks, get over it.

Try to tune the carb so you are flowing the same when you drive it...so between 2-4k...WOT takes care of itself.
Idle may suffer a bit, but you drive the car between 2-4k and you should tune your carbs there as well.

Also, before you go hog wild, tighten all the intake bolts, manifold to head, manifold to carb...check all of them..you might have a leak that is causing the bucking..

Rich
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
machina
post Apr 30 2007, 07:07 AM
Post #3


Advanced Member
****

Group: Benefactors
Posts: 2,030
Joined: 21-June 03
From: Miami Beach, FL
Member No.: 848



QUOTE(r_towle @ Apr 29 2007, 11:55 PM) *

it should not make that much of a difference, certainly not enough to make it buck. loud yes, buck ,,,I doubt it unless you have a really high strung motor that runs at 6-9k and has a tuned exhaust...

did you sync your carbs?
If you are unsure of if the carbs are synced, try this
Un hook the throttle linkage and snyc the carbs by the book, adjusting each port to match...by this I mean that the two ports on any given carb must flow the same...not carb to carb, but on the same carb.

the two carbs can be different from each other,,while that is not optimal, it can be tuned out with the linkage.

In an ideal world, with a perfect motor, no leaks in the cylinders/valves, you want all four cylinders to pump the same amount of air.
This can be done by adjusting each individual port using the air adjustment screw on each port.

If you can make all of them flow the same at idle, you are almost there.

Then, put the linkage back on and adjust it so both carbs flow the same, all ports, both carbs, so now you know the linkage is correct.

Now, bring it up to 2k, 3k, 4k, 5k and check all four ports at each step.

This is where the carb tuning gets wierd.
Your motor is not perfect, and there are leaks, get over it.

Try to tune the carb so you are flowing the same when you drive it...so between 2-4k...WOT takes care of itself.
Idle may suffer a bit, but you drive the car between 2-4k and you should tune your carbs there as well.

Also, before you go hog wild, tighten all the intake bolts, manifold to head, manifold to carb...check all of them..you might have a leak that is causing the bucking..

Rich


thanks rich, don't know if my motor is really high strung compared to full on race motors, it is a rat 2270, runs race gas, spins to 7500 but i shift much earlier most of the time. I guess i was wondering if an exhuast stub pipe leak is as bad as an intake leak. i have synched the carbs with the linkage disconnected but she still runs bad. Was thinking of checking the ouput of each accel jet (do you know how to do that?)

anyway its really hard to test the motor on the street the way it gets driven on the track. i can really only get a couple seconds blast at WOT before things get going real fast. I R&R the carbs yesterday and will re-synch and check it out.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
rhodyguy
post Apr 30 2007, 11:27 AM
Post #4


Chimp Sanctuary NW. Check it out.
***************

Group: Members
Posts: 22,248
Joined: 2-March 03
From: Orion's Bell. The BELL!
Member No.: 378
Region Association: Galt's Gulch



any snapping back thru the carbs when you give it throttle or back fires out the exhuast on decel? just eliminating some indications.

k
User is offlineProfile CardPM
Go to the top of the page
+Quote Post

Reply to this topicStart new topic
1 User(s) are reading this topic (1 Guests and 0 Anonymous Users)
0 Members:

 



- Lo-Fi Version Time is now: 2nd July 2025 - 04:15 PM