Sticky: I6 to V8 conversion

Rusty67

15 Year Member
Dec 3, 2002
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I may or may not be a better choice. An I6 conversion to a V8 may be desirable because the chassis hasn't seem power from a V8 ever. If you find a rust free I6 it may be a much better investment time wise to convert it to a V8 then it would be to sink money into body work on a V8.

There is no clear cut and dry answer. Not to mention that someone have have owned the I6 for a long time and become attached to it.

Definitely a good question but its one that each person should ask themselves and answer themselves as well.
 
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65coupe408w

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Mar 26, 2010
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If anyone is looking for V8 conversion parts, I have an 8 inch housing and big V8 rear drums....$100 plus shipping takes it all. PM me if you are interested.

Thanks
 

HDTony

Member
Oct 15, 2010
134
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Plainfield IL
As far as cost goes, i am tracking all my expenses in an excel spreadsheet. So far in gathering materials i have about 6 grand into the project not including the price of the car.

Although i still need
Headers
Exhaust
Radiator
Wheels and tires

I was able to find a 9" rear end feeshly rebuilt with an eaton trac loc for $900, T5 for $400 and the 289 that i am rebuilding came with the car on the side. Previous owner probably read this thread and decided to sell the car lol
 

Rusty67

15 Year Member
Dec 3, 2002
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Seattle area, WA
You could provably junkyard a set of oreo rims for super cheap. The radiator you could have a custom shop build for fairly cheap. There are some prebuilt exhaust kits for sale for a reasonable price that go from manifold to tail pipe. Headers aren't always the way to go out of the gate. Do some research on them before you buy.

You can get all those thing you listed for under 800 bucks if you shop carefully. Its all about how extreme you want to go.
 

chockostang

New Member
Jun 16, 2009
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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 !
Excellent idea to "get specific information" to do a 6 cylinder to V8 Conversion.

There are a bazillion combinations that will need to be listed.

Engine, Early 65-69, late 70 up 289/302---BIG difference in brackets, Pump, pulleys, Yes, no a one of early will fit late.

Then comes the Brakes, GEE Whiz, The market is full of the "Will Fit" if you do this,get that, fit, grind that, combinations..

Granada, Brakes from a T-Bird, brakes from a S 10, or Dodge Truck, it goes far beyond writing here.

The installer/Restorer will need to amply relate all the supplies, parts he/she will be implememting into the build, to get a answer to the fit.

The two items mentioned above (Engine/Brakes) are the Big items.

Rear ends, Linkages, Clearance issues can not be explained in detail due to various parts Available.

Dan @ Chockostang
 

Rusty67

15 Year Member
Dec 3, 2002
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Seattle area, WA
The point of the thread was so that new people didn't post the same question time and time again. Like you said, there are many specifics not covered but this gives people the gist of it and allows them to ask the questions that are more specific to their individual swap rather then asking the base question and us experienced people having to drop the same knowledge time and time again.
 

D Durden

DEEP FAT FRY
Founding Member
Mar 9, 2000
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This may be a good subject for another sticky, but I'll dare ask the question:

Considering how much work is involved and how much modification that is required, why convert to a V8 CONSIDERING all the V8 cars available . . . and considering how easy it could be to get similar performance out of the I6 package?
 

Rusty67

15 Year Member
Dec 3, 2002
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Seattle area, WA
Consider this, if you upgrade the inline six that is in there to the point that it is making as much or more power then a stock V8 was making then shouldn't you upgrade the steering, suspension and differential to match the amout of power you are making anyways ?
 

NickR23

Member
Mar 16, 2011
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Willow, Alaska
This may be a good subject for another sticky, but I'll dare ask the question:

Considering how much work is involved and how much modification that is required, why convert to a V8 CONSIDERING all the V8 cars available . . . and considering how easy it could be to get similar performance out of the I6 package?
There are many reasons to start out with an Inline 6 car and convert to a V8. I started out with an Inline 6 because that was what was available...60's Mustangs are rare in my area compared to most other places. I also have a V8 engine and rear axle sitting around, and all my chassis parts are worn out and need replacing anyway, so I figure why not upgrade? I could spend the same amount of time and money fixing up the Inline 6 parts as a V8, I'd rather end up with the V8 and beefier parts.

Some people like starting with an Inline 6 because it is more of a 'virgin' chassis compared to the V8, as not many of them were hot rodded and were just daily drivers/grocery getters, and thus usually tend to have lower mileage and be in better condition.

That and cost factor. There are many instances where you could pick up a clean inline 6 car for fairly cheap just because of what it is, and upgrade it to a V8, vs buying a rougher shape V8 car with a higher price just because it is a V8, and spending much more money bringing it back to good condition.

And you can spend money putting a head, cam, intake, exhaust on an Inline 6 and have it put out V8 power, but wouldn't it just be easier to start out with that much power, and THEN add heads, cam, intake, and exhaust and be that much more ahead?
 

workingonit

New Member
Mar 30, 2011
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I`d like to start out by saying this is a really nice forum,and that If my question has been asked I haven't found it asked previously so sorry if it has.

Bought this 66 stang with a 200cid like 12 years ago and left it set till the other day. I bought a 302 and c4 rebuilt tranny to put in it the same time i bought the stang. Went to a salvage yard and found a 66 stang that had the 289 motor mounts a few years ago and bought them and the drive shaft/rear end.

3 days ago installed the motor mounts,today went to drop the motor in and the oil pan is hitting the steering arm that crosses from the steering box over to the idler arm,it also looks like the starter would hit it if the oil pan was not in the way.

The motor is out out of a 78 Lincoln, I searched oil pans and they all look the same.

Also the engine was fitted with serpentine pulleys,but is missing the water pump pulley.As far as I can tell the water pump does spin in reverse,the outlet low passengers side

Question, Is there a special oil pan needed? risers for the motor mounts? change the steering arms? input is much appreciated....thanks:)
 

Rusty67

15 Year Member
Dec 3, 2002
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109
Seattle area, WA
First off, this should be in its own thread. Second, I would check to see if the oil pan for the 78 Lincoln is the same as the oil pan for an early model Ford. If it is a double sump pan then it definately wont and you will need a new pan and oil pump pickup.
 

workingonit

New Member
Mar 30, 2011
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Sorry about posting in wrong thread,started another one . Could you delete the post in this thread? Thanks.
 

HDTony

Member
Oct 15, 2010
134
2
19
Plainfield IL
I picked up a super clean 65 I6 for 5 grand from arizona. interior is mint, body is a good 10 footer. price is so low because of the 6, if it was a v8 car in this condition, it would have been a boatload more money. Now granted I'm speeding a ton on it, but it will be done how I want it in the end. if I started with the more expensive v8 car, I would have spent just as much, upgrading suspension, motor and trans etc beyond original v8 car specs anyway.
 

Ronnieo2011

New Member
Nov 9, 2011
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Not to hijack this thread...but i'm actually considering doing this myself. I have a 67 with an I6 and I called my local Mustang resto shop looking for parts to upgrade my I6 for more power etc..and was told that with all the money i'd spend I'd get maybe 20 more HP. I'm scratching my head on that...but they are evidently the "pro's" so he's recommending that I pull the engine and tranny from a fox body and drop it in. I'm ok with that..but just not sure how accurate his suggestion is. She is going to be a daily driver from time to time so I'm not looking for drag racing numbers..but i would like it to be more powerful than my girls camry..:) Thoughts?
 

D Durden

DEEP FAT FRY
Founding Member
Mar 9, 2000
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Not to hijack this thread...but i'm actually considering doing this myself. I have a 67 with an I6 . . . Thoughts?
Honestly, if this is REALLY a daily driver, I'd ease out into left field and see if you can find a wrecked 300HP V6 Mustang, and swap all of THAT out.

Think about it . . . you're dropping that setup into a car that's 800-1000 pounds lighter, and it already gets 30 MPG with the first scheduled maintenance predicted somewhere in the book of Revelations.

You could have A/C, power everything, V8 performance, V6 economy, and 2011 reliability in a classic that's ready to do 100k miles on a few oil changes.

And, unlike every other "IT'S GOT A BAWWWZZZZ 302 MAAAHN" Mustang, you'll have something both utterly trick and wicked efficient.

Meh, it's a thought . . .
 

Rusty67

15 Year Member
Dec 3, 2002
3,749
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Seattle area, WA
A v6 ? Really ? Do you know how much work you have to do to put that new V6 in and hook up all the fuel injection and what not. Forget it. If you are going to go through that much trouble you should put the new 5.0 in for not a lot of extra trouble and all kinds of extra performance and support.

A 90s EFI 5.0 can easily be converted to a carb and is a mostly straight forward swap into a classic. There is no compairing the difficulty level of puting in a newer Ecoboost motor or a modular v8 into a classic. They aren't even in the same ball park.
 

Rande

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Aug 1, 1999
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Winona Minnesota
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"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?"

Yes, and it makes NO SENSE to do the swap. The cost of all the parts combined with the time and effort just to locate them, then go get them, or have them shipped, exceeds the added cost of a V8 car. THEN you have all the time and work doing the actual conversion.

Look over the lusts here. Think about all that work.

Check parts prices, check shipping costs, how many weekends will you waste doing all this? Pull out your checkbook, add $2k to the purchase of your Mustang and drive your V8 car home. Don't hack an I6 Mustang. The gods will frown. You don't want gods frowning at you. Trust me.

Oh yeah, earlier in this thread the weak 6 cylinder tranny is mentioned. Starting with 1967, Ford began putting the 3.03 V8 3spd tranny behind the 200. So, if you have a'67 and up 6 cylinder car with the 3 spd, its good for a V8 car (if you want to use a 3spd). The '66 and earlier 2.77 3spd tranny is well suited for use in a riding lawnmower.
 
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