400 running like a dog on petrol - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars
LinkBack Thread Tools Display Modes
post #1 of 1 (permalink) Old 11-21-10, 09:25 PM Thread Starter
Registered User
Join Date: Jul 2008
Posts: 3
400 running like a dog on petrol

I have recently rebuilt a 400 for my 72 galaxie LTD. it has a 780 holley, holley streetmaster lowrise single plane manifold, a 268DEH cam, TMI 9.5 to 1 pistons and 302 closed chamber heads with boss valve springs and 4v valves.
I initially did the aggressive break in on petrol, but after a trip to Newcastle and back where it gobbled up 20 litres of petrol (gave the missus a fright as it ran out 10 meters from the home town servo!!) I decided to refit the LPG mixer/tophat so I could afford to run it. it is a 425 impco and mixer. I now come to my problem. I managed to start it on LPG straight away with no adjustment to the timing and proceded to take it out for a fang. It still starts really wel.l
To my delight it went just as well on gas as it did on petrol. But now when I switch it back to petrol it runs like a hairy goat. you can nurse it up to revs,but give it a hit on the loud pedal and it misses and farts until the load goes off it. I have even tried disconnecting the fuel shut off and rehosing it straight in case there was a restriction there,but to no avail. There seems to be enough airflow as it goes well on the gas, but I don't understand how when it is switched over to petrol it is now so poor.
could it be the top hat mixer assembly after all and how do i fix it? i could just disconnect the LPG again and refit the aircleaner assembly and try it to prove a point, but again I don't get how it can have such adequate air flow on LPG and be poor on petrol. Again I have not adjusted the timing in any way. Help.
crsmith is offline  
Sponsored Links

  Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars > The Garage - Tech Forums > LPG Tech
Gear in this thread - Powered by O'Reilly Auto Parts

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome