Hey guys rebuilding a 1971 Oldsmobile 350 rocket with 88,000 miles , using edelbrock 2711 performer 350 olds intake manifold , I have a Ol4B but needs work . I was wondering what cam and carburetor would be best. I’m thinking of picking up a Holly 4175 model 650 cfm classic carburetor spreadbore Quadra jet style. The olds has a 3.55 rearend, 2 1/2 inch dual exhaust with headers and also functional OAI system I’m concern about hood clearance . Any suggestions would help .

 

What pistons / compression ratio? You need that info in order to select the camshaft.

 

Here's a partial outline of how I rebuilt my '72 350 using the 2711 manifold and original 7A heads - it's set up at approx 9.5:1 CR, stock hood, 2.25 exhaust w/stock manifolds and 3.08 posi.

Fairly stout power increase over stock specs, though still with smooth idle and 18 lbs vacuum - no issues with my a/c or power brakes.

bored .030 over, heads/block decked approx. .010 combined; new Speed Pro L2320F flat-top pistons, rods reconditioned and balanced; factory nodular crank turned .010 and polished; new Howards CL510011-12 cam/lifters kit, new Howards cam-matched valve springs and locks/retainers, new Comp Cams rockers (stock), new Edelbrock 2711 intake, rebuilt Q-jet electric choke 800 cfm carb p/n 17056253 ('76 cutlass), new Cloyes 2x roller timing chain, MSD p/n 8529 electronic distributor, with MSD blaster 2 coil and 8.5mm plug wires; heads fully rebuilt with all new valves, valve stem seals and guides.

Also running a 2300-2600 stall converter, which also aids in off-idle performance.

 

Have a Quadrajet rebuilt for your engine and calibrated for your cam specs. 1971 Olds 350 Quadrajet is #7041250

 

Unfortunately you are dealing with a 8 to 1 350, if stock. Changing pistons is the only proper way to improve it. Either one of the Speedpro or even better the Mahle or DSS forged will work. The 10cc Mahle or 12cc DSS have better ring packs, are lighter and require nearly half of the Speedpro piston to wall clearance. You can also run better quench and keep compression in the low to mid 9's with factory heads. A properly built Qjet is a good way to start. Also the factory converter stalls around 1600 rpm, it sucks for launch. Something like the Jegs 2000 to 2300 stall will give a noticeable off the line improvement. Get or make a dual snorkel air cleaner set up and run hoses if you like. I made one that looks surprisingly factory, ran dryer hose and stainless heating elbows cut in the plastic fenders, the hoses probably do nothing for power. The dual snorkel with one big and small opening like factory probably adds a couple of hp over a small single snorkel air cleaner.

 

Thanks for the info guys , we pulled the motor out Tuesday and will start to tear her apart and provide information, I already have the set up OAI ram air 350 set up no need to make a air cleaner set up ,I have a functional W 25 hood, also I’m not going to use the original qjet I have or rebuilding it I just don’t like them
I rather use a holly , we grew up on holly and the performance way better than a stock qjet..

 

I don't see how that 650 cfm Holley spreadbore will perform better than the original 750 cfm QJet.

 

Go to a 750 Holley instead of the 650 spreadbore

 

I like to say Happy Thanksgiving and thankful for all your opinion and options and the Oldsmobile site is the best place to get information, I grew up on holly carburetor and love them I’m not saying i’m right or wrong just giving my opinion with having them , I gave my son my 1970 W-30 442 years ago all original and this project is my fathers car which was sitting for 5 years , parts laying around and so forth .. So many decisions to make not going to drag it just cruise with it and have some fun ..tear up the street when I want too..again I want to say thank you guys

 

Just some information. In the 80s I acquired a Holley 0-1850 600 cfm vac secondaries carb for free. After lots of tuning parts purchases and time tuning, I was finally able to get the engine to launch and run as well as it did with the QJet. Then I took a road trip and got less hwy MPG than city mileage. So the Holley was donated to a friend and the QJet was reinstalled on my engine.

Not saying a person can’t get decent MPG with a Holley. Maybe it’s just that I am much better with QJets than Holleys. Maybe it was just the difference in carb designs.

 

I’ve had a half dozen Qjets on my Dyno and a host of Holley style carbs, and I can tell you the Holley style carbs are much easier to get a flat fuel curve out of than a Qjet. Plus various Qjet metering rods and hangers are getting pretty slim these days.