I have a 302-cubic-inch small block Ford engine that I’ve inherited from a friend. It’s an older carbureted engine that I think is stock – it still has a 2-barrel carburetor. What kinds of parts should I buy like a four-barrel carburetor and maybe a big cam or something to make more power? I’m relatively new at this, but a couple of friends will help me remove the worn out inline six out of my ’69 Mustang and replace it with this V8.
Jeff Smith: Sounds like a great little project. First, we will assume that your engine is in good shape. If the engine has sat around for a long time, the first thing to do would be to change the oil and filter and remove the spark plugs. Next, I’d recommend pressure lubing the engine to get oil to all the bearings, lifters, and rocker arms. Pressure lubing an engine is not difficult, but it will require you to remove the distributor and then drive the oil pump with a suitable hex drive. You can buy this drive from ARP (PN 150-8801) but you can make one out of an old Ford distributor shaft that will drive the hex so you don’t have to spend the money for something you might only use once.
The key is to get oil to all the critical components. Next you might want to squirt some oil in each cylinder. This will help the rings seal. Then you can do a simple little compression test to make sure all the cylinders are actually working. The actual cranking pressure isn’t as important at this point as is making sure all the cylinders are balanced with near equal pressure.
Assuming you have good cylinder pressure, we now have an engine that’s probably in decent shape. If you have a dead cylinder, no amount of tuning or parts will help if the engine has problems.
Before we get too deeply into this, let’s talk about horsepower potential. With stock heads and cam and a decent intake manifold, carburetor, and headers, you’re looking at making between 250 and perhaps 275 horsepower. In order to make 300 horsepower you’re going to have to have better cylinder heads and a mild camshaft. We only mention these numbers because inevitably one of your friends will spout off about making 400 horsepower.
That’s certainly achievable, but the reality is it will take a good set of aftermarket aluminum cylinder heads, between 9.5 and 10:1 compression, a fairly stout camshaft, headers, a good dual plane intake, and probably a 650 or 750 cfm carburetor to produce that much horsepower. It sounds like you might just be happy with a few mild bolt-on upgrades that don’t require you to tear into the short block – like changing the cam. So we’ll stick to simple bolt-ons.
You didn’t mention what year small-block this is but we’ll assume it is an engine from the late ‘70s – for grins let’s say it’s from a 1976 Granada. That engine with a 2-barrel carb made a stunningly weak 134 horsepower with 8.0:1 compression. Not exactly a barn-burner for power but then you get what you pay for, right? Assuming the engine’s in good shape, there are several weak points in these ‘70s engines centering on the soft compression and poor exhaust port flow.
So let’s start with the simple stuff first. The best way to wake up any stock small block Ford is to improve the exhaust flow. Early, stock small block Ford Windsor heads are notorious for weak exhaust ports and restrictive exhaust manifolds.
This makes a set of headers nearly mandatory to improve breathing. This may sound counter-intuitive but everyone tends to focus more on the induction system than the exhaust. But our experience consistently reveals that even a stock 2-barrel engine will respond to a higher-flowing exhaust system. By reducing the backpressure in the exhaust system, this pulls more spent gases out of the cylinders, allowing the engine to make more power.
Headers come in a variety of configurations. The most popular are the long-tube four-into-one style headers. These style headers improve low-speed response because the longer primary tubes increase torque. The down side to long-tube headers is that by placing the header collector underneath the floor pan, ground clearance can be an issue. Intermediate length headers are shorter and use a smaller collector that bunches the tube together before the primary tube turn under the floor pan. These headers are still an improvement over stock manifolds, but they do sacrifice a bit of low-speed torque. They are much easier to install, so keep that in mind as well.
Another advantage to intermediate headers is their low cost. We found a set of Patriot Clipster headers that would fit your Mustang (PN H88433-B). These come with a three-bolt exhaust flange that can be welded to a 2 ½-inch dual exhaust system that would really complement the headers. Coated headers look nice for a long time but will probably cost more money.
Next on the list would be to upgrade the intake and carburetor. The stock 2-barrel Autolite carburetor is a descendant of the Holley but the flow numbers are nothing to get excited about. We’ll assume this carburetor will deliver roughly 300 cfm, but it might be much smaller depending upon the size of the venturis. The best move is to upgrade in a good streetable four-barrel dual plane intake manifold and a small four-barrel carburetor.
Here you have quite a breadth of selection opportunities. The trick for this engine is to not get caught up in all the horsepower hype. Two excellent choices would be the Edelbrock Performer intake or the Weiand Street Warrior. Dual plane intakes are the ideal choice for a mild street engine where this style intake really improves low and mid-range torque while still delivering decent top-end power. Ignore all those guys who lobby for a single plane intake to make any power. Single plane intakes offer shorter intake runner lengths that sacrifice low-speed torque to make top-end power. We’ve seen these intakes on a mild street small-block lose 30 to 40 lb-ft of torque against a good dual plane.
As for a fuel mixer, this small engine would respond very well to a 600 cfm carburetor. There are plenty of really good carbs to choose from. We’ve had good luck with all three of the ones we’ll suggest. In no particular order are the Edelbrock Performer 600 cfm carb, the Street Demon 625 cfm carb and the Holley 600 cfm vacuum secondary carb.
The Edelbrock with the electric choke is Edelbrock’s mileage version of this carburetor line. The Edelbrock carb offers one small advantage that it shares with the 600 cfm Street Demon that we really like. Both carburetors offer a small cover that allows quick access to the part throttle primary metering rod. Loosening one small screw allows access to either the metering rod or the primary power valve spring. By changing metering rods or the springs, you can tune your carburetor for both part-throttle and wide-open throttle (WOT) metering. With the Holley, you must remove the float bowl. This isn’t a big deal, but it usually requires changing the bowl gasket as it might tear when removed for the first time.
The third carburetor is the Holley 600 cfm which is the electric choke version of the standard 600 cfm Holley. This carb also incorporates the Ford automatic transmission kick-down linkage which the other two carbs do not. I would hazard a guess that all three of these carburetors would deliver similar power numbers.
There’s far more to go into if we want to get into making more power, but it would be challenging with your engine’s stock 8:1 compression ratio. One of the best ways to make more power and better fuel economy is with compression up around 9:1 to 9.5:1. There’s a reason that all the late model engines now are running between 10 and 11:1 compression ratios. It really helps.