Sticky: I6 to V8 conversion

Rusty67

15 Year Member
Dec 3, 2002
3,749
36
109
Seattle area, WA
I6 to V8 conversion

Ok, since we get asked this question about 9 times a day, I talked to the mod and got permission to start a sticky thread for this.

What will I need to convert my 1964 1/2 to 1970 Mustang to a V8 ?

Power Plant:
You are going to need a complete engine. This means:
All of the accessory brackets
Front sump oil pan
Flywheel or flexplate for the correct transmission
Motor mounts
Motor mount frame brackets for the type of V8 you are installing (big block or small block)

Cooling system:
You will need a new radiator, that I6 on is not going to cool your new V8 engine. Upgrade to a 4 core copper or a 2 core aluminum (aluminum cores are 2x the size of copper cores)
New radiator hoses
I recommend to run a seperate trans cooler if you have an auto transmission (as I live in a hot climate)

Transmission:
You don't technically NEED to change from your I6 trans, you could just change the bell housing on the transmission BUT believe me when I say that the your I6 trans will not survive long behind your new V8. The 250 and 300 straight sixes have the same mounting pattern as the small block V8 so if you have one of these motors in, you can bolt your existing trans right to the V8 (Info provided by Hack, also see tjnavyblue's comments a few posts down). I still highly recomend geting a V8 trans to use !

If you have an auto and want to upgrade to another auto there are a lot of options. Ask around and ask us and we can talk about what kind you want/need. Same goes for a car that will end up with a manual trans.

Rear End/Driveshaft:
You need to change your entire rear axle assembly. People have got away with not changing this out in the past but just like an I6 transmission, an I6 rear end is definately going to brake. It was not built to handle the torque of a V8 motor. You can easily upgrade to an 8" or a 9" rear end (9 inch will cost more and may not be worth it for you). An 8.8" rear in is also possible but it is a lot of trouble and for the same or little more money you can have a 9".

As for the drive shaft, you are going to want a brand new one. Most of the early drive shafts were 2 piece units and they are not reliable and should be replaced ASAP. Stuff like that always brakes at the most inconvienent times.

Front suspension:
You are going to need to change the front suspension for a couple reasons. Your rear end now has a 5 lug wheel pattern and your front has 4, matching is a good thing. Also, the old 4 lug stuff isn't strong enough to support that new V8. You will need to change your:
Front spindles
Coil springs
Shocks
Upper control arm (not sure)
Lower control arm (not sure)
Strut rods (not sure)

Rear suspension:
Leaf springs
Shocks

Brakes:
Hopefully the V8 spindles you get will get will have brakes with them. If not you are going to need to put some brakes on them. You can get drum brakes for the front but DON'T. There are a myriad of brake options for the front of these classic Mustangs so put on something that will stop the car well. This isn't the place to discuss brake upgrades. Maybe we will make another sticky for that later ! Just make sure you put on adaquite stoping power for you new motor !

As for the rear brakes, a lot of people feel that drums are fine. I'll be puting discs on my rear soon, I don't like the way drum brakes react and they are a pain in the butt to service.

Steering linkage:
More stuff to change ? Thats right.
Inner tie rod
Outer tie rod
Drag link
Idler arm

Exhaust (added at 65fastbackresto suggestion):
Your I6 exhaust system is not going to work with your V8. You are basically going to need an entirely new exhaust setup. It is more expensive, but PLEASE try your best to get a mandril bent exhaust instead of a crush bent exhaust. They look better and perform much better.

Misc.
On a 64-66, the gas pedal will need to be changed (added at 65fastbackresto suggestion). I'm not sure about other years.

Now, I don't claim that this list is 100% complete or 100% accurate. Little things vary by year and I might have forgot stuff. As people post more or PM me information I'll edit this post to make it more complete and accurate. Something we didn't cover in here ? Post it in the forum !
 
  • Sponsors(?)


Hack

15 Year Member
Mar 23, 2004
1,945
12
69
Minneapolis
Good post, but it's already stickied in the FAQ in classic talk.

edit: I see that the link in the FAQ currently isn't working. Hopefully it can be fixed.
 

65fastbackresto

Active Member
Apr 13, 2007
1,229
7
39
AR
2 piece drive shaft?

I`m doing a I-6 to V-8 conversion, but I got a one piece drive shaft, but....I have found other evidence that a V-8 has prob been in this car in the past.

I guess if it was 2 pieces it would be pretty obvious? LOL

OH, dont forget the exhaust, I`m looking at almost $1000 for quality headers, x-pipe, and exhaust pipes, this was one expense I underextimated big time. I could do it cheaper.....but I`d be cheating my motor outta what its capable of.
 

geostang351

Member
Mar 30, 2005
946
0
17
49
Danb., CT
OH, dont forget the exhaust, I`m looking at almost $1000 for quality headers, x-pipe, and exhaust pipes, this was one expense I underextimated big time. I could do it cheaper.....but I`d be cheating my motor outta what its capable of.
:eek: :eek:

You may want to price this around if this is the cost you're looking at.
 

65fastbackresto

Active Member
Apr 13, 2007
1,229
7
39
AR
headers and stuff

Headers are $526, x-pipe is $100, rest is pipe work. After spending 4k on the motor SO FAR, and it aint done, want all it`ll make, quality headers are the biggest expense, but good ones should outlast the motor I hope.
 

Hack

15 Year Member
Mar 23, 2004
1,945
12
69
Minneapolis
Since this is being stickied..

You don't always need to change the bellhousing for a 6 to 8 swap. The 250 and 300 straight sixes have the same mounting pattern as the small block V8.

As you have said though, the motor brackets and mounts are different.
 

Rusty67

15 Year Member
Dec 3, 2002
3,749
36
109
Seattle area, WA
Good to know, I'll edit the first post.

Would the 250/300 trans hold up to the abuse of a V8 or are they as week as the 200 motor's trannys ?
 

tjnavyblue

Member
Feb 21, 2007
64
0
7
While a 300 will bolt up to a v8 bellhousing this is not a big help for Mustang owners. 300's never came in mustangs and are in fact harder to install than V8's due to overall height and length. Over at Fordsix.com they have a few, but they are labors of love and not something the average joe would want to install. Some 250 bellhousings will work after some point in the 1970's. Again, www.fordsix.com is a great place for mustang six information. Their FAQ page has all of this information.
 

65fastbackresto

Active Member
Apr 13, 2007
1,229
7
39
AR
Heres another item you can add to the list

Throttle assembly is different, all the way from the gas peddle to the carb needs replaced.

Found one though, YEA.
 

57fairlane

New Member
Apr 2, 2005
560
0
0
Oakwood, GA
my cent and half to add is that the inline six throttle linkage is shorter and operates on the passenger side of the motor where as the v8 setup is taller and on the driver side. You can weld something up but is much easier to use a v8 throttle linkage.

I also had to add an extension plate for my transmission linkage when using the column shift and longtube headers.
 

65fastbackresto

Active Member
Apr 13, 2007
1,229
7
39
AR
Transmision linkage

if you have a floor shift, save the old shift linkage from your 6 cyl tranny, have it put into your v-8 tranny, there are a bunch of different kinds of these apparently. My tranny guy pretty much insisted I bring him the old tranny so he could change this part out.
 

65fastbackresto

Active Member
Apr 13, 2007
1,229
7
39
AR
You can add pitman arm

to the steering section. yea, I just crossed this bridge.

Soaring 1, as to your comment on "this sounds expensive". I did pretty much everything on this list at it was pushing 14K with all new parts (cept for motor from salvage year).. I could have saved a little money here and there, but I couldve spent alot more here and there to. If your gonna do a 6 cyl to v-8 conversion and do it right you better have a fat wallet.
 

65-Fstbk

Active Member
May 20, 2007
280
13
29
Vancouver, B.C. Canada
Not That Bad

I really don't think the I6 - V8 conversion is that big a deal. The key is your time frame and whether or not you can do the mechanical stuff yourself. So far for me its been a pleasant experience.

If your restomodding one of these cars keep in mind there are a few constants whether or not your doing the I6-V8 conversion.

You will be building a new engine anyway. I picked up a complete 289 with original bore from a 67 mustang for dirt cheap.

I picked up Granada spindles complete with outer tie rods and proportioning valve for $75.00.

Stock 8" Mustang 5 lug rear $100.00. (You would probably re rebuilding the third member anyway on you V8 car)

Restomod exhaust will need to be redone whether it's a I6 conversion or a stock V8 car.

I will be putting in a WC T5 trans (rebuilt with upgrades $750.00)

Complete steering parts from Pittman arm through tie rods...$380.00 new.

Not that bad if spread out. My advice, take your time and have fun with it.
 

2+2GT

Well-Known Member
Apr 25, 2009
3,333
9
59
Southeastern Pennsylvania
Cooling system:
You will need a new radiator, that I6 on is not going to cool your new V8 engine. Upgrade to a 4 core copper or a 2 core aluminum (aluminum cores are 2x the size of
I recommend to run a seperate trans cooler if you have an auto transmission (as I live in a hot climate)
A 3-row brass radiator is about 90% as effective as a 4-row. Use a fan shroud and thermal clutch fan to improve this. Radiators have built in trans cooler, which doubles in winter as a trans heater. Figure where and when you drive, and decide.

Rear End/Driveshaft:
You need to change your entire rear axle assembly. People have got away with not changing this out in the past but just like an I6 transmission, an I6 rear end is definately going to brake. It was not built to handle the torque of a V8 motor. You can easily upgrade to an 8" or a 9" rear end (9 inch will cost more and may not be worth it for you). An 8.8" rear in is also possible but it is a lot of trouble and for the same or little more money you can have a 9".
If you worry about the 8", don't. It was an 8" version of the 9", even used the same 28-spline axles. If you get a four-pinion Traction-Lok™, or similar aftermarket diff, it'll be as strong as a 9", except the 31-spline version.

As for the drive shaft…
The 64-66 V8 was never 2 piece, and would be fine. The 2-piece was often used on big engine Mustangs and Shelbys, I've never even heard of one failing. A new one-piece is the way to go if you don't have a nice used one handy.

Front suspension:
You are going to need to change the front suspension for a couple reasons. Your rear end now has a 5 lug wheel pattern and your front has 4, matching is a good thing. Also, the old 4 lug stuff isn't strong enough to support that new V8. You will need to change your:
Front spindles
Coil springs
Shocks
Upper control arm (not sure)
Lower control arm (not sure)
Strut rods (not sure)
No! The spindles need only be changed on 64-66 cars. Struts, upper and lower control arms were the same on 200 cid through 428 cid.

As for the rear brakes, a lot of people feel that drums are fine. I'll be puting discs on my rear soon, I don't like the way drum brakes react and they are a pain in the butt to service.
Shelby dominated SCCA B production with 2.5" rear drum brakes. How bad could they be?

Steering linkage:
More stuff to change ? Thats right.
Inner tie rod
Outer tie rod
Drag link
Idler arm
Only on 64-66. 67-up these were the same.

On a 64-66, the gas pedal will need to be changed (added at 65fastbackresto suggestion). I'm not sure about other years.
67-68 also. Beware, if you are using a 390/428 and automatic, this throttle lever was different than the 289/302 item.
 
  • Like
Reactions: CRAM

68Blue302Coupe

New Member
Jul 30, 2005
74
0
0
Fairfax, VA
Regarding the suspension and steering, I thought the upper and lower control arms, tie rods, and spindles for 1967-68s were the same regardless of I6 or V8. I know they ARE different for the 19641/2-1966s. However, you'll probably want to replace most of that anyways if its original since it will most likely be pretty worn out.

I believe the fuel line will also need replacing?
 

BA Mustang

New Member
Jan 10, 2009
1
0
0
Huntsville, AL
Regarding the suspension and steering, I thought the upper and lower control arms, tie rods, and spindles for 1967-68s were the same regardless of I6 or V8. I know they ARE different for the 19641/2-1966s. However, you'll probably want to replace most of that anyways if its original since it will most likely be pretty worn out.

I believe the fuel line will also need replacing?
They are the same.
 

D Durden

DEEP FAT FRY
Founding Member
Mar 9, 2000
5,518
193
143
Has anyone done a cost justification to compare the cost of putting a V8 in an I6 Pony versus selling the I6 pony and buying a V8 car? Just curious to see which one would be the better choice.
 
Thread starter Similar threads Forum Replies Date
T Rag Top has a sticky residue 2015+ Specific Tech 0
Tubbster66 Sticky moldings 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 5
Tubbster66 Build Thread Sticky 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 8
J Manufacturing Flaw Stickies In The Engine Bay 2015+ (S550) Mustang -General/Talk 0
billison Foxbody Nuts/bolts/screw List - Temp Sticky 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 15
A Electrical 2007 V6 Throttle Sticky 2005 - 2009 Specific Tech 0
DonSoares Weird Cooling Issue... Sticky Thermostat? Fox 5.0 Mustang Tech 7
DonSoares 89gt Vert Quarter Window Track Sticky Fox 5.0 Mustang Tech 9
90lxwhite Powers That Be, I Think I Have A Decent Sticky Idea 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 16
E 92 Fox Notch Build: Stock, Light And Sticky..what Next.. 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 57
revhead347 I think we need a new sticky thread. 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 12
RED2000GTRPH Oil in 4.6 Throttle Body and Intake, sticky throttle SN95 4.6L Mustang Tech 4
T Sticky Gauge Needles SN95 4.6L Mustang Tech 3
SRT Handz Got Some Nitto NT05's + Legit Alignment *Sticky Rubber Content* 1996 - 2004 SN95 Mustang -General/Talk- 32
W Let's Make this a Sticky Fox 5.0 Mustang Tech 5
C sticky accelerator pedal Fox 5.0 Mustang Tech 2
NIKwoaC Fox Talk's Popular Threads (miss An Old Stickied Thread? Find It Here.) 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 13
NIKwoaC Read me: An idea for a good sticky. 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 15
BigDanTheMan Sticky stuff in connecter Fox 5.0 Mustang Tech 17
70vert Sticky suggestion: Header Thread w/pics, model #s, and mods Classic Mustang Specific Tech 14
R throttle sticky Classic Mustang Specific Tech 8
3 'Sticky' clutch pedal... 1994 - 1995 Specific Tech 5
Ericf45040 Sticky Parking Break 2005 - 2009 Specific Tech 7
M Need a sticky! 1994 - 1995 Specific Tech 5
hungrymonkey The FAQ/write up/sticky compilation thread. Classic Mustang Specific Tech 4
gallags Ultimate S197 Sticky Issue 2005 - 2009 Specific Tech 4
94pony Sticky Cooling Problem Fox 5.0 Mustang Tech 17
T Exhaust help/opinion. I've seen the sticky 2005 - 2009 Specific Tech 11
BlownStangGT Sticky-THR.... 1996 - 2004 SN95 Mustang -General/Talk- 0
pirotec354 Anyone know of some good sticky tires? 1994 - 1995 Specific Tech 14
G Where did all the stickys come from? 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 33
M I need a tach install sticky/diy 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 6
bchampion Sticky Cable Clutch Mod. Driveline Classic Mustang Specific Tech 10
7 Unstick Sticky Stuff Classic Mustang Specific Tech 6
B Sticky injectors Fox 5.0 Mustang Tech 4
gcomfx.com Pic Tutorial: How to get your Nittos sticky.... in an AODE. 1994 - 1995 Specific Tech 15
notchnut tire/wheel fittiment ?, I know there is a sticky 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 3
mustang6tee8 Sticky throttle 1994 - 1995 Specific Tech 8
5 Help!! Sticky valve springs retainers Fox 5.0 Mustang Tech 4
DarkFireGT The Ultimate S197 Sticky: Wheels & Tires, Exhaust, How-To, Etc... All Covered Here! 2005 - 2009 Specific Tech 1
Foxfan88 sticky tire reccomendations.. Fox 5.0 Mustang Tech 11
B Sticky tires besides DR's.. 1996 - 2004 SN95 Mustang -General/Talk- 8
nonglossjason sticky pedal? Fox 5.0 Mustang Tech 9
R sticky shift lever 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 8
S sticky brakes Fox 5.0 Mustang Tech 2
T-Sho Good Idea For A Sticky? 1996 - 2004 SN95 Mustang -General/Talk- 7
ratio411 THIS SHOULD BE A STICKY! TAILLIGHTSTEVE IS BACK! 1965 - 1973 Classic Mustangs -General/Talk- 1
S Sticky Seat Tracsk Classic Mustang Specific Tech 1
W Sticky Tire Thread 1996 - 2004 SN95 Mustang -General/Talk- 11
H Sticky float on 850 DP? Classic Mustang Specific Tech 18
Similar threads