My simple job to replace a thermostat on my 1965 Mustang turned into this:
(Ford 200 I6 engine block with new gasket before cylinder head install)
I broke a bolt off in the original cylinder head housing and had to drill it out. My amateurish attempts to rethread the hole with an old tap and die set proved fruitless, leaving me stuck somewhere between my propensity to optimistically dive headlong into a project, and the limits of my skills. So it seemed like a good idea to double down on optimism and take the opportunity to do some engine upgrades.
The biggest shortcoming of the early six-cylinder Mustangs is the design of the intake manifold, which is cast as part of the cylinder head. Ford decided they could save real money that way, but it results in an engine that breathes like a hamster with emphysema. In 1968 Ford enlarged and improved the intake manifold and added larger valves in 1977. The intake manifold looks a bit like a log, so pre-1968 heads are known as "small logs" and the 1968 and newer ones are "large logs". Production of the engine spanned from 1960 to 1983 and it was used in just about all of Fords smaller/economy vehicles.
The Ford 144/170/200 inline 6 will never be in the same league as the Toyota 2JZ or BMW N54 for performance tuning. In various guises it makes between 90-120 gross horsepower. But it's a stout engine, and it's possible to increase power output by 30-50% fairly easily and cheaply.
In my case, it was cheaper to buy a large log cylinder head than have my old one rebuilt. From there, I decided to also upgrade the carburetor and distributor with the goal of making 20-30 more horsepower. Here are the details for my build:
- Remanufactured 69-79 Ford 3.3L 200ci L6 w/ 1 3/4" Carb Throat C9/D3/D5/D7 Cylinder Head from Allied Motor Parts. This head came from a 1973 Ford Maverick, but has the larger intake valves. All Allied does is cylinder heads and they ship nationwide.
- New Carter YFA 1 barrel carburetor from Mike's Carburetor Parts. Mike's specializes in carburetors and has a lot of great technical and troubleshooting articles. They do quality work and are made in the USA. There are lots of options for carburetor upgrades on the Ford inline sixes, including two barrels using an adapter or modified cylinder head. This article on Classic Inlines provides a wealth of options and information. I chose the Carter YFA for the following reasons:
- I wanted something that would work with a "stock" engine, provide good low end torque and drivability on the street, and be reliable and easy to maintain.
- I am not ready to modify the intake for a two barrel, or do a performance build on my engine. I also didn't think a two barrel adaptor would provide better performance than the Carter 1 barrel, and I'd lose some of the drivability.
- The Carter YFA was the standard carburetor for 1969 and 1970 inline 6 engines and a good match for the larger log head. It was also standard on Ford's 240 and 300 cubic inch truck engines until Ford switched to fuel injection in the 1980s.
- New Performance HEI Distributor - Besides the large log head, the biggest performance upgrade is to replace the Load-o-Matic distributor with a Duraspark or DUI distributor. This HEI distributor got good reviews and was 1/2 to 1/3 the cost of either the Duraspark or DUI. NOTE: You will need to replace the Load-o-Matic distributor if you swap out the Autolite 1100 carburetor because the LoM does not have a mechanical advance. This article on Load-o-Matics from Classic Inlines will tell you everything you ever wanted to know. .
- New ARP Cylinder Head Studs from Vintage Inlines - these are overkill, and are 10 times stronger than the stock head bolts. But after breaking bolts on several other parts of the engine, I felt the cost was good insurance, especially if I decide to tear down the engine again someday.
Over the next few weeks, I plan to write about installing the cylinder head, setting up the carburetor and distributor, and any other tasks needed to get my Mustang back on the road.
