Good morning gentlemen, hope everybody is doing OK and staying safe.
My 1971 has its factory intake manifold and original two barrel carb on it. I am just doing some research before ordering parts, but I believe I’m going to be going with an Edelbrock 2750 intake in a new four barrel carb. I’m more concerned about around town drivability then out right performance, and it appears that a 500 CFM carburetor would better fit that priority then a 600+ CFM option. That said, I am far from confident that I have that trade off right and was hoping to get some coaching and real world experience from those that may have done this update.
From my experience 500 CFM is about right for a 289. Normally for a good running 289 or 302 I would use a 600 CFM Holley. Edelbrock carburetors are overrated by CFM, so in fact a 600 CFM edelbrock is about equivalent to a 500 CFM Holley on the dyno measuring airflow.
For a mild 351 Cleveland I would not use any less than a 600 CFM Edelbrock. It would probably run best with a 750 CFM Edelbrock or Holley if you are planning on any improvements like a aftermarket aluminum intake, better camshaft, or headers.
Thanks Royce - I asked the CFM question while out walking the dog and missed a fairly important consideration. The car has a 351c 2v with, as far as I know, stock internals and a factory exhaust set up.
This car is going to be a cruiser / roadtrip car so I am not planning on trying to warm it up too much.
All that said - maybe a 600 CFM Edelbrock would be a better choice?
I feel that the 500 cfm Edelbrock is a bit small for a 351 CI engine of any make. In your case with stock exhaust and internals I would go with the 600 Holley or Edelbrock. As Royce said if you have any plans for future performance upgrades you may want to go a bit bigger now. The Holley 670 Street Avenger is a great choice. I find Holley cars much easier to “dial in” and tune. Not too big now and will support some mild upgrades such as a larger cam and headers.
Yes, for sure better than the 500 CFM version. If the 750 is the same price I would get that. The 750 Edelbrock flows about the same as a 650 Holley. I actually do not recommend any of the Holley carburetors with the polished zinc finish. I had one that within a couple weeks after buying it new shed its zinc plating inside the carburetor, making the carburetor useless. Summit replaced it with one of the gold anodized versions which worked fine.
I used a 500 Holley on a mild 351W, 4v, it had excellent throttle response, still revved out, and a ton of torques.
351,s often had a 465cfm from factory, so be honest with your self about what you are going use it for, if its 100% street car,
then opt for the smaller carb, of you like big revs, then step up a bit.
Just be aware that a “feature” of the Edelbrock Performer carbs is that if you don’t run the car every couple days, you need to crank the car considerably to refill the bowls before it starts. I had a 1405 in a 72 Mustang with 4V 351C and it was annoying, to say the least.
They are great running carbs, require little maintenance, but that issue will keep me from buying another Edelbrock carb. The issue is well documented. I can’t speak as to whether the AVS or Thunder series carbs have the same issue. Just an fyi.
Pretty sure there was a version of the 2100 that was rated at 425-ish cfm. That would be the best bet, would work w/the stock intake/linkage, and give you easy tune-ability & the best drive-ability.
That car was a stock engine and intake, but the original quadrajet ran like crap, so I put the Edelbrock on it.
If you’re going to put a 4V intake on it, the performer intake is good for a mild engine.
You can even use an OEM ford 4V intake. Shipping would be pricey because of the weight, but can be found priced reasonably.
My first new Mustang was a 72 fastback with a 351 C 2V. After 2 years I installed a Holley 4412C 500 cfm carb and I went to a dual exhaust system from single. The car ran great- significantly more punch and better gas mileage cruising. I’ve since done the same upgrade on 2 other 351’s I’ve owned including my current 70 vert 351 W. Same results. 30 minute simple and inexpensive bolt off / bolt on upgrade with very noticeable performance improvement.
The poor 4300 Ford Quadrajet and the GM Rochester Quadrajet have such bad reputations. Rebuilt correctly and tuned properly they work very well. Especially for gas mileage. The 4300 does suffer as a carb for performance as it was designed for emission control. I just rebuilt two 4300’s for a 302 engines, wet tested them, and shipped them the Midwest. They run fine, but are not performance carbs. They have some rather unique idiosyncrasy’s and normal rebuilders do not do well with them.
That said I prefer the Holley over the Edelbrock for one reason. The Edelbrock can create some throttle linkage issues due to its width. The Holley is normally a bolt on. Keep that in mind and I hope some of the Edelbrock users can post a pic of the throttle linkage setup for the Edelbrock carb. I feel that the 750 Holley is too large for this application and your type of driving. It would perform fine especially at top end, but it will use a bunch of gas. The Edelbrock 600 will perform great at low end and in my experience provide the best gas mileage.
I have not experienced any problems of float bowl emptying from an Edelbrock. All seldom used cars will experience gas evaporation after a while. If you do not have an electric fuel pump I always “prime” an engine that has not ran in a month or so. I hate to grind starters to get gas up to the carb. A simple shot of gas down the throat will allow the engine to light off. You may need to do it a couple times.
Either 500, 600 or 750. You won’t notice a difference. For Edelbrock carbs, get one that has lean jetting from the factory. As I remember the ones that come with electric choke have a leaner setting. It will still be on the rich side for your application, just not as rich as the manual choke versions.
Emotionally, you want a 4 barrel because it could mean more power, it’s more impressive to look at and it is perceived as an upgrade above basic.
Logically, it is a waste if money as you wouldn’t notice a 10 hp gain in an rpm range you don’t use. Simply bolting it on is not the end. To do the job thoroughly there is X-amount of time to tune the carb for your vehicle to not have worse performance and ruined efficiency.
Best bang for the buck would be rebuild the 2v and recurve the distributor.
On the other hand, do what makes you feel good. Just determine whether it’s tinkering or cruising that makes you feel good.