MORE POWER from a 170

[FBSixtyEight]

Hello all! I have a 1968 Bronco with the stock 170 straight six engine, new exhaust with a glasspack muffler. We just took it out the road to get inspected and this was the first time we could see how fast it could really go. Standing on the gas pedal it would only go 55, maybe 60-ish mph! Now I know this is a 101 hp lawnmower engine from the factory, and I know I will never hit the top speed of 85 mph in the manual, but I would think this little brute could hit 75. I was wondering what you guys have found to increase hp in the 170. I know about the website classicinlines.com and the others like it, but that is not what I am asking for. Whether it is going from points to electronic ignition, or putting in a new camshaft and lifters, I want to see what results my fellow six bangers are getting. Any help would be greatly appreciated, thanks in advance!

P.S. - Please don't just tell me to swap out to a V8, I know that would help! ;D

Ben Garland

 

[broncodriver99]

Do a search for a member here Explorer. He built an I6 for his bronco and got some very respectable numbers out of it. I think he ended up with an aftermarket head which made the most difference. If you are dead set on staying with the I6 a 200 it's slightly bigger incarnation in the later years(73+) may be a better starting point.

 

[broncodriver99]

You may also try checking the Falcon and Mustang forums. They were both available with the 170 or 200.

 

[thegreatjustino]

I too have a '68 with a stock 170. Stock engine rebuilt about 30,000 miles ago, stock 1bbl carb, stock intake and exhaust. 4.11 gears, stock size tires. I can get up to 70 on flat stretches of highway. Any kind of mountains and I'm between 50 and 60.

There are improved heads, intakes, and headers that you can install, but how much do you really want to sink into a six banger. Personally I'm curious about some of the intakes that allow you to bolt on a 2bbl carb. Simply bolting on a bigger carb doesn't seem like it would do much, but who knows.

 

[00gyrhed]

I had a friend dolled up a 300 I6 with 4bbl carb headers etc. Lots of torque but when all was said and done he spent a lot more money on parts (clifford research) than a good running 35W from a yard would have cost him.

i6's are great but they are not only limited by displacement, the aftermarket doesn't support them much either and anything to increase HP will cost more than a comparible SBF part.

I know this isnt what you want to hear, but if I had a good running i6 i would leave it alone and drive it and enjoy it until it petered out. Then go get a V8. You can drop a lot of money on a 170 and at the end of the day you will still have a 170 trying to push a top heavy brick down the road. I grew up when these things were new, and the 170 just isnt designed to cruise 65-70 MPH. New and well tuned maybe sometimes.

Besides you are going to fall in to the never ending cycle of lift, tires, more engine, heavier drive train, bigger tires, more engine anyway. You will need you money.

 

[FBSixtyEight]

Thanks for the replies, everyone! This is going to just be a daily driver bronco to and from school, so it does not need to go fast anyway. I just figured it would be nice to hit the higher numbers on the highway if I ever needed it, and to get out from a stoplight. I will probably cut my losses someday and replace the engine with a good 5.0, but until then I would like to keep the bronco as close to number matching as possible. There are not many of these gems out on the road anymore that don't have cut quarters and lifted and all the rest. Besides, it only has 46,000 miles on the odometer (no, it is not 146,000)! I guess I will live with what I have for now and enjoy every minute of it. I have heard about the two bbl intakes and I can't imagine that it would help much because it is still hindered by the log intake design robbing cylinders of fuel. I will be switching from points to electronic ignition with a new coil which should help quite a bit. I could also send the carb out to be redone by Pony carbs. They improve the engineering of the carb to fix some of the flaws with the original design. I will keep you posted with my progress, thanks again!

Ben Garland

 

[broncodriver99]

I could also send the carb out to be redone by Pony carbs. They improve the engineering of the carb to fix some of the flaws with the original design.
Ben Garland

I wouldn't advise that. Do a search here and on the Mustang forums and you will find they have a lot of issues if they are even still in business. A good cleaning and a rebuild along with a carb book and some jets will get you most of what they can accomplish. Get the timing tuned in right and set the carb up using a vacuum gauge and you will notice a pretty good difference.

 

[needabronco]

Pour a little ATF in the crankcase and the let the carb suck some in through a vacuum port, it'll smoke like hell but I promise you if there's any built up carbon in the engine it will run better. Change your oil after 50 miles or so... Then give it a good tune up, adjust your valves and rebuild your carburetor and you should feel a difference.

 

[rguest3]

I built a 200 that was pretty nice for an Inline six. Classic Inlines Aluminum Head and Intake combo with a Comp Cam and Holley 390cfm carb. Night and day from stock.

Was very nice for an Inline 6, but it's still a six cylinder. A 302/351 swap would have been fairly straight forward as well and may have cost less with A LOT more power potential.

 

[spap]

I believe just a 2 barrel carb, header and cam, would make a big difference in that motor. Won't be anything crazy but at least letting you hop on a Fwy once in awhile. A Motor is a big air pump and your not getting air in or out very effectively.

 

[eaglenest66]

What is the drive train gear ratio? If you are maxing at 50-50 mph, guessing you have 4:56 gears? Mine with 4:11s will hit 65 easy in stock formation. Not racing material but will do better than you say.

 

[Explorer]

Many things can be done, but I really would not invest any money in a 170ci. With a 200ci you would gain 15hp and 32ft.lbs. torque (pre-"72" numbers) right off the bat. I would advise purchasing the Ford Falcon Performance Handbook available at Classic Inlines and explore your options. Another factor is your gear ratio. If yours has the 4:56 gears instead of the more common 4:11"s, top speed will be more difficult to increase. Prepare to spend money or enjoy your Bronco as is.

 

[bmbm]

Good advice from Explorer. The easiest and lowest cost increase will come from a 1978 and up 200 six with DSII. You can still find them used but it takes some time.
You may have 4:56 gears. My original, tired 170 with 4:11 gears would easily cruise at 60 on flat roads for as long as you could listen to it. Going to a 31" tire will help a little if they will fit.
Or get a 250 and od transmission.

 

[blubuckaroo]

I love the sound of those! They have their own cool snarl. Get rid of the glass pack though.
Your idea for pointless ignition is a good idea. Just do a good tune-up, factory tires, and keep it light.
101 HP isn't bad considering my 302 came with only 127 HP.
I've often thought how cool it would be to have a 6 cylinder LUBR. If it has 4.56 gears, that's what I'd do!

 

[FBSixtyEight]

What is the drive train gear ratio? If you are maxing at 50-50 mph, guessing you have 4:56 gears? Mine with 4:11s will hit 65 easy in stock formation. Not racing material but will do better than you say.

That is a great point, I never really thought about what gear was in the back. I will check it once it gets back from the shop for inspection. If it is a 4:56 gear, and I wanted to switch to a 4:11 gear, would I need to change the front differential at all? I would imagine they would need to be in-sync for the 4WD to work.

 

[eaglenest66]

That is a great point, I never really thought about what gear was in the back. I will check it once it gets back from the shop for inspection. If it is a 4:56 gear, and I wanted to switch to a 4:11 gear, would I need to change the front differential at all? I would imagine they would need to be in-sync for the 4WD to work.

Yes they both need to match for 4WD. Otherwise, never lock the front end in and rear wheel power only!

 

[buck68]

I would drive/enjoy that bronco just like it is! Not too many untouched Broncos out there . I'd love to have that gear ratio in my son's truck.

 

[00gyrhed]

you need to sit down and think about what you want long term and where this project is going or you will spend a lot of money. if you have 456s and you change them to 411s you have spent money just to keep the 170 that might be better spent on an OD transmission, or taller tires. new gears and paying someone to set them up could set you back a lot of money.

Its a never ending cycle. Enjoy what you have and come to grips with your long term goal before you spend money to go 10 MPH faster with the 170.