Everything You Ever Wanted To Know About Swapping a 351w into a 1965/1966 Mustang- by 65Fastbackman
First off, I am not a certified mechanic nor am I saying that what I did will work for you in your situation, this is just the setup that I used when I did a 351w swap into my 65 fastback. I am a mustang enthusiast and owned a 68 fastback and currently own a 65 shelby gt 350 replica, I have been working on mustangs for over 10 years and did this swap by myself, other than needing help taking the engine in and out of the vehicle.
Second, make sure you know what youíre getting into before doing this swap, it is not incredibly difficult but I didnít do much research before and it ended up taking me much longer than I had anticipated. Another reason it took so long is that, as good as the internet is, everyone seems to have an opinion on everything and very few times are the opinions factual. Because of this I often times got information that I believed to be accurate from one individual and inaccurate from another, so this is for all of the guy out there doing this swap who have a bunch of questions that other guys claim to know the answers to but most likely have never actually done the swap before.
-So, the parts that will switch over in the swap are: air cleaner, carb, intake Ė Iíve heard mixed things but I bought a new intake, water pump, fuel pump, oil filter, alternator, pulleyís, brackets, starter, bellhousing, clutch linkage, clutch, pressure plate, flywheel.
-Parts that will not switch over: distributor, oil pan, oil pump, valve covers, motor mounts and the biggest one are the headers Ė a specific swap header is needed for the application.
- My setup:
-Block: 1994 351w roller motor, roller rockers/cam/timing
-Carb: Holley 670 street avenger
-Intake: Edelbrock air gap #7581
-Dist: Pertronix flamethrower #pnx-d7131701, coil #pnx45011
-Water pump: Flowkooler #1681 water pump, passenger site outlet
-Alternator: Same one from my 302
-Starter: Powermaster #9604 for a T5 trans
-Radiator: Champion cooling 3 core #251 with electric fan
-Flywheel: Centerforce 164 tooth flywheel #ctf700240
-Clutch: Hays 11Ē clutch and long style pressure plate #85-210
-Bellhousing: McLeod #8660 scattershield
-Fuel pump: Holley #12-833
-Dipstick: Spectre #57235
-Return Spring bracket: Spectre #4708
-Clutch Linkage bracket: made my own off the purchased style
-Motor Mounts/Brackets: 1966 mounts and motor mount brackets
-Headers: JBA Shorty style ceramic coated #1653SJS
-What I was thinking:
-Block: I went with a 1994 roller motor that was built by a local company that turned it into a 396 stroker motor with approximately 400+ hp and 375 ft./lbs of torque. The motor has roller rockers/cam, it came with an edelbrock air gap intake, oil pan/oil pump, valve covers, and I told them I wanted a 164 tooth flywheel which it came with as well.
-Carb: Iíve had nothing but good luck with the Holleyís, I talked to their tech advisors and they recommended a 670, plus it has a lifetime warranty and above all I wanted a new carb for a new motor especially since the old carb was a 4160 which isnít as desirable.
-Intake: Iíve only ever used Edelbrock intakes; the air gap keepís it cool, gives good hp and it still fits under my hood with a Shelby scoop on it and has room to spare. Not sure if it will work with a stock hood but it would be very close.
-Dist: Iíve heard nothing but good things about Pertronix and their distributors/coils
-Water pump: heard good reviews plus a lifetime warranty, decent price.
-Alternator: Had it on my old one and was just rebuilt so Iím going to use that since it is pretty much brand new
-Starter: 180ft/lb gear reduction starter, rotates 360 degrees so it can be away from headers or heat sources, good price and works amazing, well worth the money.
-Radiator: More cubes/hp, need a bigger radiator and I like the electric cooling fan, doesnít take the hp away from the motor etc, great deal on ebay.
-Flywheel: Big debate here - The reason for the 164 tooth as opposed to the 157 is that you can use a 10.5 or 11Ē clutch with the 164 where you can only use a 10.5Ē with the 157. So down the road if you want to get more hp you have the opportunity to go really big if you have a 164 tooth flywheel as opposed to only being able to use a 10.5Ē clutch with the 157. Plus more surface area, better at getting the torque to the rear wheels without slipping and/or breaking something.
-Clutch: Bigger is always betterÖmost of the time. Name brand, decent price
- Motor Mounts: Aftermarket polyurethane 1966 style motor and frame mounts, they really do move the engine up higher and make it easier to install headers. Most of the conversion headers require this style; I had to swap mine as my car was an early 1965 with the older style mounts. Plus the 1966 style is much more structurally sound and the polyurethane limits the flex of the engine on acceleration so you donít dent or scratch your new headers.
-Bellhousing: Got a screaming deal, most name brand scattershields are $450 and up, I got this one for $299 with free shipping, and safety first. If you want to race, I think under 12 seconds you have to have a blowproof bellhousing anyway, and Iíve heard stories about guys getting a blown flywheel or clutch and having it fly through the floor board when they were only running 400 or so hp.
-Headers: This is the biggest issue of the entire swap and the most important. I tried Hedman shorty swap headers and they didnít fit at all so I returned them, I was told that JBAís are the best fitting and I completely agree. They are a shorty header with 1 5/8Ē primaries and 2.5Ē collectors, you must use 1966 style frame and motor mounts because they really do, contrary to what everyone else says, raise the motor up nearly an inch higher so you can have better clearance for headers. You must use the 66 style brackets/mounts, have a minimum distance of 33 ĺĒ on center between the two shock towers and the engine has to be properly centered. Get a nice one-piece monte carlo bar and install it before putting the motor in as you may have to use a port-a-power to spread out the shock towers/inner fenders. My engine dips down on the passenger side, but then I hear all do that because of anticipating body weight and only having a driver most of the time so the dealers didnít center the engine completely, so Iím planning on shimming it to make it level. The headers are a perfect fit, no modifications whatsoever, very close to the shock towers and steering box but no rubbing, and I was recommended to get polyurethane motor mounts because there is only about 1/4Ē clearance on each side. These mounts are supposed to severely limit engine twist/flex on accelerating/decelerating, which they do and for $80 I canít complain.
Iím not a salesman for JBA but I would definitely recommend these to anyone, perfect fit, no modifications of any kind, install very easily with one person, I canít say enough good things about them. I figured they werenít going to fit worth a darn like the Hedmanís but I was shocked when they did. And for those of you complaining about the price, yes they are on the expensive side but are you really into the muscle car hobby to save money? I didnít think so. And one of the best pieces of advice that Iíve ever gotten is ďyou get what you pay for.Ē This is in every way true here, I got my ceramic coated ones for $600 shipped to my door, shop around and get the best deal, Iíd much rather pay $600 for a set that work perfectly than pay $400 for a set that you have to beat the **** out of just to install them. These are hands down the easiest headers Iíve installed and I have installed probably 5 sets on my two mustangs that Iíve owned. Yes they are definitely more money but they are money well spent and will save you the headache, increase in blood pressure and so much more when you do install them and realize you donít have to notch the fenders or dimple the header tubes at all. If I had to do it all over again I would still buy JBAís and will recommend them to anyone, I originally bought the Hedmanís, because like everyone I wanted to try and save some money, but they were a terrible design and in no way would fit with my setup, the number 1 tube on the passenger header goes directly into the shock tower and would in no way work. Spend some more money and save your fenders/header tubes from the blade of a saws-all.
Thank you and if you have any questions feel free to email me at