the Rochester

C3 Specific - Technical and Performance

Moderators: DOC, MR.WOLF, australi, smackC4

Wobbles
General Forum User
Posts: 26
Joined: Wed Mar 01, 2017 10:42 am
Location: Gladstone, Central Qld

the Rochester

Postby Wobbles » Thu May 04, 2017 10:02 am

Hi all
Have a small problem that I have hopefully narrowed down to the carby.
I upgraded my 305 Californian to a 350 Wobbles. Tongue in cheek meaning I (we) have built a 350 and planted it in the C3.
No problems with this except that you have to keep in mind that money is very tight and I don't really have time for an off chassis rebuild like others I have seen on this forum. Although if I ever win lotto I am sure that my beast will be stripped quicker than, well...anything. :-o
Anyhow, back to the story, with the "upgrade" I transferred the carby from the 305 to the 350 with no changes. I now have a "flat spot" on hard acceleration at low revs, not good, and also at higher to "mid" revs, embarrassing.
I have disposed of the filter in the front of the carby (replaced by an in line one) so I suspect there are no restrictions in flow.
Could it be starvation from jet size?? If that is the thought then what size replacements should I consider?

I have no wish for one of those other carbies at this stage.

HELP !!!!
hopefully ..with thanks
Wobbles

User avatar
68ragtop
*Gold Class Member #245
Posts: 824
Joined: Wed Dec 01, 2010 12:13 pm
Location: Brisbane, QLD
Contact:

Re: the Rochester

Postby 68ragtop » Thu May 04, 2017 12:21 pm

Wish I could help but I just have a fuel guzzling Holley. Do a Google search for rochchester tuning papers by Lars. He had a brilliant one for the holley.

Wobbles
General Forum User
Posts: 26
Joined: Wed Mar 01, 2017 10:42 am
Location: Gladstone, Central Qld

Re: the Rochester

Postby Wobbles » Thu May 04, 2017 6:07 pm

Thanks mate. I'll see if I can find the site asap. Appreciate the help.

RHD454
General Forum User
Posts: 93
Joined: Sat Mar 29, 2014 4:26 pm
Location: Redcliffe Qld

Re: the Rochester

Postby RHD454 » Thu May 04, 2017 8:45 pm

Hi Wobbles,
I have to agree with 68Ragtop. Lars papers are the best source of information on troubleshootiing Qjet problems.
I have finally got my Qjet running like a dream.
Is your "flat spot" felt immediately when you tramp it? If so,this could be the dreaded "Quadrajet Bog". Usually this is caused because your Secondary Airvalve opening rate is not set properly.
Here is a section I have copied from Lars' tuning paper.

The secondary spring windup is adjusted with a small, slotted-head screw on the passenger side of the carb, right at the top of the carb
on the secondary side. The screw head points right out to the side. 90 degrees from this, on the bottom, there is an allen-head lock
screw that keeps the slotted screw from turning. If you have trouble seeing it, place a mirror under the area until you spot it. With a
small slotted screwdriver holding the adjustment screw, loosen the allen screw about ¼ turn. This will allow you to turn the slotted
adjustment screw. Counting the turns, allow the slotted screw to slowly unwind until all spring tension is gone. You can use your
mirror to see the spring disengage contact from the pin lever underneath the air horn. If the spring tension was lost after only ½ turn,
the windup was too loose. Bring the spring into contact with the lever. Note when it just barely touches. From this point, wind the
spring up between ¾ turn and 7/8 turn. This is a good starting point, and will prevent any bogs or hesitations due to premature
secondary opening.


I hope this helps. I have other tuning info from Lars & Cliff Ruggles if you would like that too.

:D

Andy

Wobbles
General Forum User
Posts: 26
Joined: Wed Mar 01, 2017 10:42 am
Location: Gladstone, Central Qld

Re: the Rochester

Postby Wobbles » Fri May 05, 2017 10:43 am

Gidday Andy,
That helps heaps. It sounds as confusing as hell but I'm sure that with a mirror, some bright lights and a bit or perseverance I will get my fat little fingers in there and give it a go.
I'm about to see if I can find the site but if unable I may call on you to send more info.
Thanks again. I will put on here if I ever get the thing right.

Wobbles (Warren)

RHD454
General Forum User
Posts: 93
Joined: Sat Mar 29, 2014 4:26 pm
Location: Redcliffe Qld

Re: the Rochester

Postby RHD454 » Fri May 05, 2017 12:45 pm

Hi Wobbles.
There is no website
You have to email Lars & ask him for all his Qjet tuning papers. He will gladly help anyone. He seems to be the best when it comes to the Rochester Carby.
His email is
V8FastCars@msn.com

:D

Andy

Bazzas77
*Gold Class Member #269
Posts: 2300
Joined: Wed Apr 11, 2007 12:01 am
Location: Cooloongup Western Australia

Re: the Rochester

Postby Bazzas77 » Fri May 05, 2017 5:51 pm

ask him about his tuning for beers tour(s). he seems like a real nice guy and will help you

Wobbles
General Forum User
Posts: 26
Joined: Wed Mar 01, 2017 10:42 am
Location: Gladstone, Central Qld

Re: the Rochester

Postby Wobbles » Sat May 06, 2017 9:54 am

Thanks guys..
So much info on the puta that it may take me the next 5 years to get through it all.
The Lars stuff is full of goodies so as per your advice I will probably follow up with him more than all the others.
Thanks again and keep up the good info.
Wobbles (Warren)

User avatar
sirfixalot
Posts: 429
Joined: Fri Jun 04, 2010 11:55 am
Location: Gods Country Sutherland Shire NSW

Re: the Rochester

Postby sirfixalot » Sat May 06, 2017 5:38 pm

I have a no of a guy in Victoria rebuilds them $375 from memory fixes 45 faults with carby does one a day my mate says it is the best carby he has had on his 350 monaro & he has tried them all. He apparently test drives every one on a HQ before sending it out

Wobbles
General Forum User
Posts: 26
Joined: Wed Mar 01, 2017 10:42 am
Location: Gladstone, Central Qld

Re: the Rochester

Postby Wobbles » Mon May 29, 2017 12:17 pm

Just a very late postscript for you all.
After much reading and finally getting to the correct writings, I have discovered that the ex-305 carby is electronic and therefore incompatable with the new 350 (unless I get the computer, that has been totally bypassed, working again.) Gotta then bore a hole in the exhaust for an O2 sensor and on and on it goes. (And I thought I was making my life easier by getting rid of all that stuff.)
Have now decided ???? to replace a perfectly good carby with another, when located.
Well I guess the ongoing saga will continue for a while....I will probably give it a rest for a while and see if I can get the speedo working next.
Thanks for your help up to date an I'll keep you all up to date as it happens so you can all get a bit of a laugh out of me.
Cheers
Wobbles :D :-o :horse:

User avatar
DOC
*Gold Class Member #777
Posts: 3696
Joined: Sat Jun 21, 2008 12:41 pm
Location: Rocky QLD Australia

Re: the Rochester

Postby DOC » Mon May 29, 2017 5:53 pm

Best of Luck Wobbles. Had to get my Speedo working a fair few years back. Start at the plastic gear in the trans and work forward would be my advice.

Wobbles
General Forum User
Posts: 26
Joined: Wed Mar 01, 2017 10:42 am
Location: Gladstone, Central Qld

Re: the Rochester

Postby Wobbles » Tue May 30, 2017 10:04 am

Thanks for that Doc. I have found the problem...all is good except that the tiny weeny little shaft that turns the speedo needle has been broken off on the end. I would suggest a heavy handed extraction would have caused this.
I somehow think that finding a replacement shaft will be impossible so I guess I shall start looking for a complete mechanism.....maybe an old holden one will do...it looks about the same.

User avatar
DOC
*Gold Class Member #777
Posts: 3696
Joined: Sat Jun 21, 2008 12:41 pm
Location: Rocky QLD Australia

Re: the Rochester

Postby DOC » Tue May 30, 2017 7:42 pm

Maybe, There all G.M., I have found a fair few items from Corvette wreckers in the states.
Might be worth a goggle search.

Wobbles
General Forum User
Posts: 26
Joined: Wed Mar 01, 2017 10:42 am
Location: Gladstone, Central Qld

Re: the Rochester

Postby Wobbles » Wed May 31, 2017 5:49 pm

Thanks mate..if all else fails I will give I a go.

User avatar
billet
General Forum User
Posts: 88
Joined: Fri Dec 02, 2011 9:09 am
Location: Sydney

Re: the Rochester

Postby billet » Thu Oct 12, 2017 7:24 pm

Wobbles wrote:Thanks for that Doc. I have found the problem...all is good except that the tiny weeny little shaft that turns the speedo needle has been broken off on the end. I would suggest a heavy handed extraction would have caused this.
I somehow think that finding a replacement shaft will be impossible so I guess I shall start looking for a complete mechanism.....maybe an old holden one will do...it looks about the same.


Your broken speedo cable is the result of your cruise control transducer locking up, had the same issue


Return to “Third Generation C3 (1968-1982) Technical and Performance”

Who is online

Users browsing this forum: No registered users and 2 guests