1970 Rocket 350 - Which carb ???

[Aceshigh]

Guys,

Got my 1970 Olds Rocket 350 with a Holley 1850 (600cfm) sitting on top of it.
BTW - the Vacuum secondary I circled I already found out what that was. LOL
I'm not a carb guy......I'm not very savvy with these.


Now I'm at a point where I am going to add an electric choke to it, to
resolves some of the cold starting issues I have with it. BUT.......

I have an option to get a Holley 3310 carb (750cfm) for $100 in new condition.

Now here's my question......
According the mathematical equations for carb selection , RPM, and volumetric efficiency I really only need a 600cfm.

But some people are telling me I should get the 750 because it's a better carb.
Thoughts ???

[svnt442]

If the car is running good don't mess with it!!!!
There is no need to swap carbs just because someone says this one's better than that one. Personally I think you should find a good quadrajet and put it back on there, but that just my opinion and you know how that goes.

[78cutlass]

find a #7040250 Q-jet core, and send it out to Greg/Bill, of Sparky's Carb Svc, and they'll have that SBO 350 burning rubber! Check out Sparky's website...

[70 cutlass s]

A 600cfm is big enough for a 350 its good up to 300hp plus some. The 750cfm would be nice for a stock 455. I would stay with the Holley I like them better than Q-jet but that's just me. If its running fine leave it on. Just add the choke.

[Aceshigh]

Well that's the problem.....the carb runs fine once the car is warmed up.

But getting it started is a real pain in the ass.
I have to pump the pedal 1-5 times while cranking several times if the
car has been sitting over a day. If it's been a few hours, it's okay.
After finally getting it started from a cold start, I have to hold the pedal to roughly 2,000 rpms
or it will instantly die. I have no choke at the moment. I read below in that hot rod article that
the idle circuit in the 1850 is kinda weak too......even adjusting it, I got nowhere.

So I've been looking at electric chokes for this 1850 which is the 45-223 from Holley.
THey sold that 750cfm yesterday apparently......kinda sucks, but the idle circuit in this 600cfm is weak.
They said if I'm having trouble with the idle circuit not being enough.....go 3310.

That's per this Hot Rod article anyways.
http://www.hotrod.com/techarticles/6...ons/index.html

[junior supercar]

I'll go x3 on the 7040250 qjet

[Aceshigh]

Originally Posted by 78cutlass

find a #7040250 Q-jet core, and send it out to Greg/Bill, of Sparky's Carb Svc, and he'll have that SBO 350 burning rubber! Check out Sparky's website...

Cost to gain considerations here.....
I found that this Rochestor Qjet is the stock carb on this motor, but what is the REAL benefit ??

What am I looking at in terms of investment VS gains in improvements??
My carb actually does run good once it's started. REAL good actually.

If I'm investing $250 or more to do this, it's not worth it to me.

[78cutlass]

There's nothing like a fine tuned Q-jet. In my case, I tasked Sparky's with rebuilding a '70 Olds 350 Q-jet core (#7040250). Sparky's shoehorned a late model Q-jet's 2004R linkage to it, since I have a 4-speed OD transmission. Like that, the TV cable will have the correct geometry.

The carb was custom tailored to my engine too. It started out as a crusty core purchased on Ebay for $58.00. I got a stunning carb back from Sparky's that performs like a fine tuned VIOLIN :-D. Sparky's does topknotch work! Here's pics of the carb:

[70 cutlass s]

When a Q-jet runs good there hard to beat. When they start having problems when a rebuild won't fix because all the parts are worn out than you just want to beat them with a hammer. Know a complete rebuild would be worth it, but you already have the Holley it might be easier to fix the Holley so the choice is yours. I ran a 600 Holley on a 350 had no problems pump it 2 times than hit the key start right up. The 750 would have to be pumped when you first start it too.

[joe_padavano]

Originally Posted by Aceshigh

Well that's the problem.....the carb runs fine once the car is warmed up.

But getting it started is a real pain in the ass.
I have to pump the pedal 1-5 times while cranking several times if the
car has been sitting over a day. If it's been a few hours, it's okay.
After finally getting it started from a cold start, I have to hold the pedal to roughly 2,000 rpms
or it will instantly die. I have no choke at the moment. I read below in that hot rod article that
the idle circuit in the 1850 is kinda weak too......even adjusting it, I got nowhere.

So I've been looking at electric chokes for this 1850 which is the 45-223 from Holley.
THey sold that 750cfm yesterday apparently......kinda sucks, but the idle circuit in this 600cfm is weak.
They said if I'm having trouble with the idle circuit not being enough.....go 3310.

Your starting problem is your non-functional choke, pure and simple. The electric choke kit, once adjusted properly, will solve that problem.

[Aceshigh]

Thanks Joe, that's basically what I was trying to find out in the end.
I wasn't sure if the Holley 1850 was too weak or not in the idle circuit or if an electric choke would resolve my issue.

I closed the choke completely by hand and tried starting it.....but it didn't fare so well.

Originally Posted by 78cutlass

There's nothing like a fine tuned Q-jet. In my case, I tasked Sparky's with rebuilding a '70 Olds 350 Q-jet core (#7040250). Sparky's shoehorned a late model Q-jet's 2004R linkage to it, since I have a 4-speed OD transmission. Like that, the TV cable will have the correct geometry.

The carb was custom tailored to my engine too. It started out as a crusty core purchased on Ebay for $58.00. I got a stunning carb back from Sparky's that performs like a fine tuned VIOLIN :-D. Sparky's does topknotch work! Here's pics of the carb:

Looks absolutely stunning....but what did it cost $$$ ??

That's my main concern. Cost.....and MPG.
I'm assuming I'm not going to see much of a difference in MPG.
You all might scoff at the MPG bit.....but I HATE paying the arabs for fuel.
So I'll invest thousands to get better fuel efficiency as I did in my 2nd gen Camaro with the LS1 / 4L60e.
I'm not a purist......so Fuel Injection is a consideration for me if the Q-jet from Sparky's costs a chunk.

Holding back the cost , makes me think this was a good chunk to invest in.
I can't deny it's absolutely stunning to look at for a show car engine bay.

Now I see you have a 200-4R and a Qjet......so what kind of city / highway MPG #'s do you throw down realistically ??
I know a guy with a 78 Camaro with a Q-jet and T-56 six speed and he gets pretty damn good #'s on the hwy, IIRC 14 city/25hwy.

[joe_padavano]

Originally Posted by Aceshigh

I wasn't sure if the Holley 1850 was too weak or not in the idle circuit or if an electric choke would resolve my issue.

I closed the choke completely by hand and tried starting it.....but it didn't fare so well.

Yeah, depending on the air and coolant temp, it usually wants to be partly, but not fully, open. The automatic (electric or hot air) will adjust accordingly.