I need some advise from the guys that have been doing the Y-block thing for a while. I have owned fords since 1986 and until I bought my 1955 F100 4 years ago I had never heard of a Y-block. I am now the very proud owner/daily driver of a 239, 3 speed, 3.92 rear truck that I completely love. Yes, I have toyed with the idea of swapping in a newer 302 and AOD and have even bought 2 combinations, crossmembers, engine and tranny mounts but cannot bring myself to go through with it because of everything being original. My 239 runs really well and I am commited to sticking with it. I want to lower my rpms on the highway to reduce wear on the motor and want to do so in the most economical and least altering way. Charlie has suggested going with an overdrive unit, and some of the guys on the y-blocks forum have also given good advise on rearend gearing. so, if you have time I welcome suggestions as the wife has asked me to know what I am doing before breaking out the debit card buying parts. What would be a good gear ratio to swap with? I do not tow a lot but do use it as a truck. also, would dual exhaust be of any benifit over the crosspipe? Would an alternator be better than the 12V generator I put on? Should I stick with the same distributor? Thanks for your input. Steve

 

My opinion is that a 239 needs to have a low rear end ratio to be able to haul much of anything, including itself. No put down intended at all. But 130 hp (likely less) has its limitations. Before you spend any money on an OD, find someone with a 239 that has one in place first. If they love it, I stand corrected.

 

An upgrade to the later 60s distributor and a set of headers or ramshorns on a dual exhaust should help with power and milage without alot of risk this assumes that you already have a 12V setup though.

Lower gears are neccisary to a point and your usage should be the determination for the gear. A cruiser could use a 2.73 rear but if you plan on towing a boat or hauling stuff the 3.92 is probobly needed. A 3.3 or 3.5 is an in between medium that gives some of both but does nothing great. Though unloaded driveability would probobly be phenomanal.

Some more info on what you use it for and what 239 casting # you have will put us in a better position to advise. There were to different 239 Y's.

 

Dennis on Y-blocksforever uses an overdrive behind his 239. I think he has a T85 with an R11 overdriive. He loves it.

You've made the better choice by sticking with the Y. So far, all of the 302s swapped to our trucks I've heard mileage figures for are actually worse. Compared to the 239, a 302 will get you more power, but you can more easily swap to a 292 or 312 and be ahead of the 302 once more. A similar displacement swap just isn't worth the time.

 

He told me about his set up and it sounds like a good route to take. He mentioned finding one at a swap meet, so I will start doing my homework looking around. Is that set up able to go on my column or will I have to go through the floor? My truck has no holes that it did not leave the factory with and I hate to be the one to put the first one in it. I have read a lot of posts about building the 292's and 312's and will probably go that route if/when the 239 retires.

 

It can go on your column. It's a normal 3 speed transmission with an overdrive unit that mounts between the tailhousing and transmission case. You'll need to shorten the driveshaft and add some wiring. That's about it.

 

I could have had two 3 spd ODs for a $100 last winter. One for the FEs, one for the Ys. After posing a general question about the tranys it came back as they were slightly problomatic and difficult to get parts for. Since I was planning on purchasing for resale I determined not to buy them for fear of tarnishing my name.

I think in the hands of a nice, polite driver they would be fine. Lighting the tires and hard usage will trash them fairly swiftly.
The cost of doing this will probobly exceed a gear swap so make sure that this is what you need/want. Though I think either option would be a good choice to getting what you want.

 

Thanks guys, I think I will try the rear gear first since it seams to be the easiest to reverse if it doesn't do what I want. I should probably hook a tach up first to do a before/after comparison. Any suggestions on a good type for a Y or are they all created equal.

 

The T85 and R11 is a very strong unit. I'm not certain which transmission and overdrive Dennis has but he drag races with it and does some towing and hasn't had any trouble. Behind a 239 it will be bullet proof.
If that is the route you want to take, and you think you might upgrade to a 292 or 312 at a later date, look for the T85/R11. Otherwise, you may be able to find an overdrive that will bolt directly to your transmission.
Parts for the overdrive units can be hard to find but the transmission stuff should be pretty common.

RE the tach, install a tach first. Note your RPM for the desired road speed. Take that RPM and multiply it by the new ratio divided by the old ratio, so RPM x (new ratio / old ratio) and that will give you your new rpm. You'll notice that it will take a significant change in the axle ratio to achieve the results you want. To reduce your RPMs by 1000 will require around a 2.8 gear set. Since you are going to use it as a truck, I suggest installing an overdrive transmission. That way you can still use it as a truck and get the lower cruising rpm.

 

Thanks Charlie, that does make sense. I am not too familiar yet with the overdrive units and how they operate so I guess that will be my next task. I will search through some old threads on the subject before asking a bunch of questions as I am sure this has had to have come up before.