Hello all you six banger Stangers!

Since this is a hot topic among classic Mustang owners, we have put together a thread that should have most, if not all of the handy information that should enlighten, and hopefully dispel any misinformation that may be circulating out there. I'll start with this...

There are only 2 reasons that make a conversion worth while:

1. Sentimental reasons like the car has been in the family for decades, you can't get rid of it, but it needs more get up and go.

2. You are doing a ground up restoration, and all the 6cyl-specific parts need to be replaced anyway, and you value the experience of building it yourself.

The reason for this is that the suspension and brakes need to be changed along with the engine, transmission (with some exceptions), and rear end. Heck, add paint and body, interior and wiring, and you might as well do the whole car. It is always easier, and more financially sound to buy a car that is either an original V8, or one that has already been properly (and thoroughly) converted.

 

Changing a ‘65-’66 Mustang from an I6 to a V8.

The following is a list of parts required to convert an I6 '65-'66 Mustang to a V8. Unless otherwise noted, the parts listed are for V8 Mustang application. If you decide to cut corners, do not use the small 6 cylinder brakes. The V8 drums were barely adequate and the front discs only delayed the fade problem. Upgrade to the V8 spindles and rear axle assembly as neither 6 cylinder counterparts are going to last long when you get hooked on V8 power.

FRONT SUSPENSION:

1. Drag (center) link. The I6/V8 drag links are different. The power ram and pump are the same.

2. Inner tie rods (LH and RH are the same for manual steering but LH different for p/s).

3. Tie rod adjusters LH, RH (LH and RH are the same for manual steering but LH different for p/s) Note: For 6 cylinders with p/s, if you plan to retain p/s with your V8, these adjusters are the same, just don't interchange LH with RH.

4. Outer tie rods LH, RH (LH and RH are the same for manual steering but LH different for p/s).

5. Idler arm

6. Pitman Arm - Note: Steering boxes are the same whether I6 or V8 however, p/s equipped cars from the factory had higher ratio (lower numerically) steering boxes. The P/S boxes are typically designated with HCC-AW while manual boxes are HCC-AT. If you have HCC-AX it would be an oddity, since the handling suspension steering box was only available on V8 Mustangs.

7. Spindle LH, RH

8. Two front Hub and brake assemblies including hoses (Stainless Steel Brake Corp offers original Kelsey-Hayes 4-piston front disc brake set up using the same spindles the V8 drum brakes use).


9. Pair of front coil springs

REAR SUSPENSION:

10. Pair of leaf springs.

11. Rear differential assembly 8" or 9".

12. Rear brake lines and hose that are attached to the rear differential assembly.

13. Emergency brake cable. Note '65s and '66s are different. The '66s use a single cable to both rear brakes while the '65s have two separate cables. Choose wisely.

14. Pair of 10"x 1-3/4" rear drum brake assembly.

DRIVE TRAIN:

15. Engine (duh!) Don’t forget the ground wire that goes from the passenger side cylinder head to the firewall.

16. Radiator. If your V8 has a driver side output water pump you can bolt on a passenger side exit pump (late '65 - '66). Note: '64.5 and early '65s used a slightly different style that won't work on late '65 on up timing covers. Then you will have to hassle with getting all the accessory pulleys to line up. An alternative is get a radiator shop to mod your radiator to accept the driver side outlet water pump. Don't forget, if you have an automatic transmission, make sure the radiator has the ports for the trans fluid lines.

17. Upper and lower radiator hose.

18. Motor mounts LH, RH.

19. Motor mount to frame bracket LH, RH.

20. You can reuse the alternator but you will need to get the correct alternator brackets to mount it (depending on other engine accessories). Most folks seem to get the engine fully dressed so already have the alternator, water pump, pulleys, and fan parts. Depending on whether you're installing a/c or p/s you will have to find appropriate pulleys that line up. Note that 289s and 302's made '69 and before had a three bolt crank pulley while 302s after '69 had 4 bolts.

21. '65 or '66 Fan and fan spacer if your engine didn't come with them. Beware, later fans and fan spacers or clutch fans vary in length and diameter.

22. Starter - match to transmission type

23. Exhaust manifolds (or headers), exhaust pipe, muffler(s) and tail pipe(s)+ hangers.

TRANSMISSION

24. If autotrans, you can use the 6 cylinder's C4 (unless your V8 is modified for more power) but you must change the block plate and bell housing for one that will bolt to a V8. Note: Very early '65 260-289s used 5 bolt bell housings and the '65 and later engines were 6 bolt. You will also need the V8 flexplate and torque converter. Warning: After '81 all 302s used 50 oz imbalance on their flexplate/flywheel and the harmonic balancer is different from the pre ’81 harmonic balancer. Also, '70 and later C4s had larger input shafts so match the torque converter to the trans. Don't forget the trans cooling lines, kick down linkage if '65 or kick down cable if '66. One last thing, if you're changing to an C4, make sure it's one from a car that had a floor shift selector and not one on the column. The shift lever on the trans (and I think the internal rod) are different. Don’t forget the Auto trans torque converter access plate.

If manual get a V8 3 speed or better yet a 4 spd toploader. You will need the engine block plate, clutch bell housing, flywheel, clutch disk, pressure plate, throw out bearing, pilot bearing, dust boot, clutch fork to fulcrum retainer, and clutch fork. Mechanical clutch linkage includes clutch pedal to equalizer bar (Z-bar) push rod, Z-bar, clutch pivot - engine side, clutch pivot - frame side, 2 felt washers, two clutch pivot *****, clutch return spring, clutch rod from Z-bar to clutch fork. Or you could chose clutch cable conversion. See Vintage-Mustang.com (www.Vintage-Mustang.com) and search their forum regarding clutch cable conversion. See above auto trans info regarding 5 bolt vs 6 bolt engine blocks and correct flywheel imbalance.

25. Drive Shaft: If your I6 originally had the C4 auto trans Lucky You! You can reuse your existing drive shaft, trans yoke, and U-joints. If you had a three speed or the Dagenjam transmission, bummer. You get to either hunt for a '65/'66 V8 drive shaft or have one made. If you are converting from manual to auto, you can use any auto trans driveshaft. If you had a manual trans, try to get the drive which matches the transmission of your choice. Granted, I managed to use a V8 auto trans driveshaft with a '73 4spd toploader in a previous '65 FB but I'm not sure if the length was exactly right. Be aware that some very early '65 4spd toploaders had 25 spline output shafts so the trans Yoke must match. I suggest locating a drive shaft with the more common 26 spline trans yoke, it would be easier to find a transmission to match. Pay attention to the U-Joint type. If the rear U-joint is an external type, don't try to match a trans yoke to it which uses an internal type U-joint. This is assuming you are using an 8" rear end. If you are swapping in a 9", you're on your own (you'll more than likely have to have one built - good excuse to go aluminum!).

26. Set of tires (if converting a '65) and a set of five lug rims (don't forget the spare - Doh!). Grab 4 extra lug nuts, too.

ANNOYING STUFF:

27. Engine wiring harness. This harness includes the oil and temp sending unit wiring plus the wires that go to the coil.

28. Alternator wiring harness

29. Starter cable from solenoid. The 6 cyl’s negative battery cable may be a bit long but may be useable on a V8 – critical part is the terminal lug that is bolted to the block. 6 cylinder’s may have a smaller bolt hole.

30. Accelerator pedal linkage assembly. Suggest using the ’66 style with the extra arm on it for the kick down cable if you have an auto trans. The '65 accelerator pedal assembly was the same irregardless of manual or automatic transmission. The '66 manual transmission cars had the same accelerator pedal assy as the '65's. Only the auto equipped '66's had the extra arm on the Accelerator pedal assy for the kick down cable. The V8 throttle rod (The link between carb throttle shaft and the accelerator pedal assy) is different than the I6 bell crank linkages.

31. That little arm on the autotrans that accepts the kickdown cable ('66 and up) or the kickdown linkage ('65 only)

32. Fuel line. Yup the entire hard line. You're going to get vapor lock if you use the 6 cylinder's.

33. If you have p/s, Hose, p/s pump to control valve and Hose, p/s pressure, control valve to pump . Match to type of p/s pump you have.

34. 14" wheel covers (if you have a '65 and using stock V8 rims)

35. Two (2) "289" badges for your fenders. Hey, if you went through all that trouble to drop in a V8 you might as well advertise it. If you dropped in a 302 or 351 you'll have to make your own badges.

(Above information shamelessly lifted from This Webpage)

 

How does this change if you are working on a 67, since I have been considering doing this.

 

It all applies to the '67 model as well.

 

Thank you, I am just a kid looking for some more power out of my Mustang, thank you.

 

Much of the above only applies to 65-66 cars.

In 67 and later, the differences between I6 and V8 cars were significantly fewer.

For what it's worth, I think it can be worth getting an I6 car and converting it to v8.

My '67 coupe, which had a straight body, decent paint, new interior and semi-blown I6, was $1900.

A '90 GT with a rebuilt 5.0 and stripped body/interior was $900.

This gave me the engine, transmission, EFI system, fuel lines, wiring harness, etc. Even the rear end is usable with some welded on spring perches, but I'm running the v6 rear end for now.

I have it running, but still need to put on a cool side-exit exhaust and a radiator (I have the I6 radiator jury rigged so I can drive around the block :-), v8 springs, etc.

I bought headers rather than used exhaust manifolds, a new rather than used front-sump oil pan, engine mounts, fuel pump, $140 transmission crossmember made for the conversion, etc.

I also converted the c4 to a 5 speed, so I had to shell out about $300 for a clutch pedal and cable conversion kit.

Even if I spend $1500 on conversion parts (which it doesn't look like I will) I'd have a 5.0, 5 speed, EFI '67 for $4300 minus what I've been selling left over parts for.

On e-bay, the I6 power steering bracket went for $70, the 90 transmission crossmember went for $40, etc.

It's not a good first project though :-)

 

Really, if you're going to build a driver you're going to replace most of those components anyways, right?

 

If you're going to "build a driver" yes, but a lot of people take a running 6cyl car, and just want to do an engne/tranny swap.

 

We are in the middle (completely disassembled) '65 I6 auto conversion to 351 with 4 sp.
Any additional info Ideas to watch out for?

 

Yea, when going from single to dual exhaust the rear brake hose from the chassis to the rear axle housing needs to be repositioned on the underbody so as not to be in close proximity to the pipes and cause brake failure. This applies to all single to dual exhaust conversions for 65/66 I believe.

http://members.boardhost.com/Mustang...sg/151514.html

 

I have a '65 that was converted from an I6 to a V8 long ago but the suspension and steering was never addressed. I finally got some "new" spindles but they are from a '69. They are much beefier than the '65 spindles and have larger holes for the ball joints and tie rods. Will I need to get '65 V8 outer tie rods and ball joints or '69s?

 

Since lower ball joints are commonly replaced by replacing the entire lower A-arm- you'll need to becareful not to use a '69 lower a-arm-- it's a different length than a 65-6. I'm not sure whether the ball joints (which you used to be able to replace separately) are different or not-- your parts man should be able to tell if different #s are pulled up. You'll need the '69 part to mate to your spindle. Pull both ball joints to check the mounting bolt pattern. As a last resort, you would have to buy '69 lower A-arms drill out the rivets, and bolt them to a '65-6 lower a-arm.

With the tie rod ends, I have to apologize again, I don't have access to my parts catalogs at this time, but use the '69 tie-rod ends-- they're most likely the same as the '65 V8s. Note the earlier post about the centerlink, idler arm and pitman... I believe the centerlink for your '65 I6 is a smaller thread & diameter, so these would be needed as well.

 

I did some calling around and was told that the tie rod end tapers are the same for all V8 Mustangs from 1965 thru 1969 so '65 V8 outer tie rods will work. NOT TRUE! The '69 and later tie rod end tapers are larger. The lower ball joint part numbers come up different for the different model years but I found a source for lower ball joints without having to buy '69 lower control arms. The upper ball joint part numbers are the same.
As for the idler and center link the '65 I6 has a smaller diameter and has to be replaced with the V8 version. The inner tie rods on the V8 connect to the center link while they connect to the pitman arm and the idler arm on the I6. In short, it all has to be replaced!
I wound up with used '69 spindles, new '65 inner tie rods, new '69 outers, a new V8 pitman arm, a new V8 idler arm and idler arm bracket, a new '65 V8 center link, new '65 lower control arms, new '65 upper ball joints on my original upper control arms, new sway bar end links, new strut rod bushings and new tie rod adjuster sleeves. It's all in and it all works!