Fordmods Logo

low vac??? 

 

Page 1 of 1 [ 9 posts ] 

 
 Post subject: low vac???
Posted: Mon Jan 01, 2007 10:47 am 
Getting Side Ways
Offline

Age: 31

Posts: 771

Joined: 20th Nov 2005

Ride: AU XR8 220 Manual

I have a vaccum problem. I have a mild 250 that i just put together and although im very pleaed with its performance it has low vac and slight rough idle when in gear at a stand still. if put into neutral or when driving at any speed above idle the problem goes away and vac appears ok (i have a vac guage connected to confirm all of this).

the needle dosnt jump around violently so im assuming that a cyl isnt missing. The car has EFI induction with a straight gas system (impco L convertor and 225 ring).

The cam is standard EFI but comp is up and i had to put spacers under the rockers (all set with pre load between 1/4 and 3/4 turns). The old engine used to have much better vac.... im stumped...

any ideas would be appreciated no matter how silly you may think thy are

Cheers
Top
 Profile  
 
 
Posted: Mon Jan 01, 2007 11:06 am 
Stock as a Rock
Offline
User avatar

Age: 40

Posts: 196

Joined: 30th Jun 2005

Gallery: 8 images

Ride: EBII XR6 /ED XR6 /EF XR6

Power: 154 rwkw

Location: gold coast
QLD, Australia

my efi xf has the same problem, it's problem is the cam is worn, but if yours is a fresh engine i spose that is not your problem, re-grind cams have the same effect on these engines too.
Top
 Profile  
 
 
 Post subject: vacuum
Posted: Mon Jan 01, 2007 1:52 pm 
Oompa Loompa
Offline

Age: 33

Posts: 29

Joined: 27th Mar 2005

Gallery: 6 images

Ride: 02 Ford Falcon XR6 Turbo

Location: Mudgee
NSW, Australia

you gota have a pretty wild donk with a pretty wild cam to run virtually no manifold vacuum, I'd say a more likliy reason for it to be running rough from what you've said is that u have a vacuum leak somewhere e.g split vacuum hose, leaking inlet manifold, brake booster has a hole in it ect, but it isnt big enough to register much on a gauge, you might be able to find where it is by spraying aero start or carby clean around the inlet manifold and vacuum lines, if the engine idle smooths out or the revs increase you've found the vacuum leak. Also listen for any hissing sound.
This is all assuming it is a vacuum problem of some sort. Hope it helps, Good luck with her mate.
Tom
Top
 Profile  
 
 
Posted: Mon Jan 01, 2007 2:06 pm 
Getting Side Ways
Offline
User avatar

Age: 79

Posts: 1233

Joined: 7th Apr 2005

Gallery: 7 images

Ride: GTHO PH 1 EF ex chaser

Location: Willow vale, GOLD COAST
QLD, Australia

Are you SURE that the cam timing is correct as this can contribute to a poor vacuum at idle :shock:

 

_________________

Rotten Old Revhead!!! XW GTHO + EF ex cop car (exractors 2.5 cat back zorst !6" Simmons K&N +airbox mods Lowered with Bilstein shocks+Whiteline Bars NEXT THING Swap HO for GTP or Ferrari!

Top
 Profile  
 
 
Posted: Sat Jan 27, 2007 1:57 pm 
Smokin em up
Offline
User avatar

Age: 31

Posts: 264

Joined: 5th Jan 2007

Ride: E-Hybrid Falcon

Location: nowra, nsw
NSW, Australia

spraying aero-start round your engine bay sounds good for a giggle, providing it's not your car...

 

_________________

crow cam,cai,exaust,bbm,190 reg & el injectors,xr6 interior,guages,white cluster,pioneer/mtx stereo,big boot install w.i.p, 17"rims,koni/pedders shocks&springs with nolathane re-bush,ssv kit,stainless inserts,clear lights,t5 & short shifter,chardonay/pearl paint

Top
 Profile  
 
 
Posted: Sat Jan 27, 2007 2:21 pm 
Oompa Loompa
Offline

Age: 44

Posts: 43

Joined: 15th Jan 2007

Gallery: 3 images

Ride: 99 xr6

Location: Brisbane
QLD, Australia

use crc around it its not as harsh and has the same effect also put your foot on brake pedal without wearing shoes with car at idle if you feel air on your feet its the booster i agree with the others its a simple vacumm leak

 

_________________

ONCE YOU GO BLACK YOU WILL NEVER GO BACK,what a shame im white ..........

Top
 Profile  
 
 
Posted: Sat Jan 27, 2007 4:55 pm 
Smokin em up
Offline
User avatar

Age: 31

Posts: 264

Joined: 5th Jan 2007

Ride: E-Hybrid Falcon

Location: nowra, nsw
NSW, Australia

if it's not a simple vacume leak it's a ford.
if i had a dollar for every ford out there that didn't idle properly i'd be a fcukin millionaire. 3 times over. their not formula 1 cars, nore touring cars, nore race cars.
they idle where they want to & nothing you can do will stop them.
if you've built it properly from ground up then theres something you've fcuked up. simple.
go throuigh absolutely everything you've done & fix it from there. nice n easy like every other engine builder had to do time n time over.

 

_________________

crow cam,cai,exaust,bbm,190 reg & el injectors,xr6 interior,guages,white cluster,pioneer/mtx stereo,big boot install w.i.p, 17"rims,koni/pedders shocks&springs with nolathane re-bush,ssv kit,stainless inserts,clear lights,t5 & short shifter,chardonay/pearl paint

Top
 Profile  
 
 
 Post subject: aero start
Posted: Mon Jan 29, 2007 11:51 pm 
Oompa Loompa
Offline

Age: 33

Posts: 29

Joined: 27th Mar 2005

Gallery: 6 images

Ride: 02 Ford Falcon XR6 Turbo

Location: Mudgee
NSW, Australia

if ya donk cant handle a bit of aero start or carby clean to find a vucuum leak, then it aint worth the metal its made of. The dust its already sucked from the vacuum leak would be worse for it than the aero start.
Top
 Profile  
 
 
Posted: Tue Jan 30, 2007 10:24 am 
Getting Side Ways
Offline
User avatar

Age: 36

Posts: 8655

Joined: 5th Nov 2004

Gallery: 37 images

Ride: V8 EF Futura

Location: Adelaide CBD
SA, Australia

vibr8n wrote:
spraying aero-start round your engine bay sounds good for a giggle, providing it's not your car...


It's the oldest trick in the book to find a vac leak... i dont get your point?

TUF... what's the actual vac reading you're getting?? It's only at idle where the low vac condition is occuring??

 

_________________

I promise..... I will never die.

Fordmods Administration Group MINOR PUNKED

Top
 Profile  
 
Display posts from previous:
Sort by  
 Page 1 of 1  [ 9 posts ] 

Who is online

Users browsing this forum: Google [Bot] and 38 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

 

 

It is currently Tue Dec 12, 2017 10:03 pm All times are UTC + 11 hours

 

 

(c)2014 Total Web Solutions Australia - Australian Web Hosting and Domain Names