Technical Anyone with Rochester 4BBL 7011600 knowledge please? Help needed in the UK :-)

FURTHER ISSUES - PLEASE READ MY LAST COMMENT IN THIS THREAD, I APPRECIATE IT.

Hi, UK here with a 58 Buick Limited Coupe that has been laid up for 2 years. On restarting I cleaned out the fuel tank, replaced sender & replaced all fuel lines. I set the choke up as per the manual & the car starts well & goes thru the warm up period, albeit coming off the fast idle cam steps slower than I recalled. Idle, once off the fast idle cams, is at 485rpm as per the manual, throttle stop screw at 1 complete turn as per the manual & mixture screws are at about 3/4 to one turn out... but does seem a little lumpy, which initially I put down to a blow on the manifold that needs addressing.

However, the car runs fine down the road but as soon as you stop it, it won't restart... unless I close the choke valve fully?! So a hot engine is needing a cold start set up to restart? Am I right in concluding that I am possibly running the carb at too lean a mixture, hence the restart problem ( choke valve closed for less air / more fuel ). I do seem to recall I used to run them at a bout 1 1/4 turns out...

Or could this be my issue - Before all this started the accelerator pump cup was split, so I opened up the carb to replace it & noticed the air horn gasket was also split. I replaced it with a spare, however the spare did not have the areas marked with white arrows, cut out. I THINK these provide warm up for the mixture screws in cold weather but could be wrong but if I'm correct surely, in what is unusually hot weather for the UK, such a thing wouldn't cause a problem at present?

Any help appreciated.

 

I'm not familiar with that type of Rochester but your float level may be too low or the idle circuit is partly blocked.

 

Make sure that when you pump the accelerator looking down the front barrels of the carb, that you
see the jets squirting gas. If not, this will tell you what direction to go in...

 

You could fatten up the idle a bit (1-1/2 turns out) and see if it helps but I would look for a sticky float, possible vapor lock issues with new lines or possibley some debris that came loose. Check the float level. Check the fuel filter again for debris. Drive early in the morning when it is cool out and see if it repeats.

What's a "blow" in the manifold? Vacuum leak? Exhaust leak?

 

also remember the new eviormental gas is a bit different than old pre-eoc gas, you may need to jet up a bit, and good chance you will high octane for the motor. also on my 1960 Buick. i idle about 650, the oem spec of 450 is just to low, I suspect the eco-gas

 

That is a Rochester 4 jet Carb, it appears to be the correct carb for your Buick. You should contact Matt or Russ Martin at Centerville Auto Repair in Grass Valley California. 530-272-1564 They are Buick Nailhead experts.

 

THANK YOU all for your input, I really appreciate it - I took the carb apart & there was one slither of rubber in the primary float bowl, from the accelerator pump cup. I went through the whole lot & cleaned it all out, re checked float levels & cut out the holes in the gasket that weren't present & put it all back together again with a new pump cup. Started fine, came off the choke quite well until the last cam where I had to help it ( will sort that later ) & after some playing around it seems happiest at 1 1/2 turns out on the mixture ( smells a little rich but it was running for half hour in a tight garage ) & at around 580RPM ... AND I turned it on & off several times & it restarted !

Is it what I've done, or is it that I did have vapor lock & the lower temperature has helped OR both. Guess I'll never fully know. I'll go through the starting process again tomorrow ( from cold ) & see what I have then.

Thanks again all of you.

 

As mentioned, old carbs weren't meant for today's pump gas. It's likely the evaporation, venting and float levels are in conflict. Hard start when hot can often be cured by adding a small electric fuel pump back by the fuel tank.

jack vines

 

Yes, I'm thinking of doing just that ... I have one fitted on the Lincoln & starting is so much better in all conditions.

 

So I thought I had this licked - took the car out & she ran smooth & pulled like a train & now happily starts when cold or hot ... BUT even though idle is smooth & steady, when I pull away from a standstill the engine chuffs & splutters like crazy until about (guessing) 800rpm & then she smooths out & again pulls like a train ?!? In reverse gear it is worse & the car vibrates! I'm confident the carb is now clear of any issues other than - if the idle is set to the desired level the right mixture screw will not cut out the engine when wound in, whereas the left one will almost immediately (?).

I have tried all manner of settings mixture wise to sort out the above but none have worked & they're currently at 1.5 out & the idle is even & like I said, she goes down the road like a scolded cat but pulling away from a standstill is terrible initially with that same rough, spluttering pull away yet smooths out as soon as you give more right foot.

Fuel pump delivery is good, I replaced the accelerator pump & it fires out two good jets of fuel when you ask it too, yet I can't help wondering if the issue is somewhere there because on initial pull away that is surely when you're asking most of the accelerator pump?

I'm running on E5 here in the UK (98 RON) & my timing is set at 7 (original setting was 6-8 for this 364 nailhead) & whilst it runs SO smooth & pulls so fast when out on the road that I can't help wondering if advancing the timing might help me from a standstill?

I appreciate any input guys, I belong to several 58 Buick & 58 Lincoln forums & have come to the conclusion, from the lack of replies there, that this barber is the only guy in those groups that gets his hands dirty & wrenches on his own cars!

 

You've identified your problem; the right idle circuit or air bleed is plugged somewhere. Both the Rochester 4Jet and the Carter WCFB are wonderful carburetors, but have many small passages to get plugged.

Quick-and-dirty fix, turn off your electric fuel pump and run the bowls dry. Then, remove the right idle air screw and blow compressed air back through the circuit. Fixed more than one this way.

While the screw is out on the bench, examine it carefully and compare it to the seemingly good left screw; are they identical in taper and length?

jack vines

 

Thats a nice pair of land yachts you have there.

 

I don't know if the 98 in the UK is the same as in Australia but both my avatar HAMBster with a 1954 engine in it and my old Holden with 6 cylinder red motor of 1965 vintage both run better on straight 91 because 98 is for computer controlled, slow burn systems (told to me by a retired Shell oil company chemist). My HAMBster dropped 10H.P. on the chassis dyno when switching from 91 to 98.

 

Thank you ... hoping to give it a go tomorrow.

 

No 91 over here unfortunately.

 

I'm at a loss - took it apart ( again! ), cleaned it all out thoroughly with carb cleaner & air lined it right thru & it started up & ran fine. Took it out, runs fine, as before but when restarting it again later I'm back to rough idle until you get past 800rpm or so AND neither mixture screw make any difference now :-/ I'm starting to wonder if I have a sticking valve or something.