I want to raise the compression on a 72 maverick 250 - without going too deep into the engine. I have possible access to an early 60's 170 head with adjustable rockers. Does anyone know what the compression change would be? PaulS
pauls, i have been running a 170 head on my 250 but i don't know what the c.r. is. i used the stock pushrods and rocker shaft. the only prob. i see is getting the right p-rods for the adj. rockers. the info. i got when i went with the adj. rockers was the adjs. have a ball on the and i was going to have to order a set of p-rods with a cup on one end. i was told that a stock set of 260 v8 p-rods were the right size, wrong for my motor. i ported the head and had it milled.the block was decked and i am running a perpormance cam. when i was through the p-rods were too short . everyone that looked at it said after all that they should be too long. i had the rocker shaft stands milled .022. and that took care of that. my c.r .is too high for my 77' dist. so i am putting a 69.5 170 points dist. in today. i will be running the pertronic mod. in it also. the 77' had a dura spark dist. and the t.a.t.was way too high and too fast. the answer to the ?, i don't know but it will up the compression "much"...frank...
The best flowing heads are on the 78 - 83 200s and 250s they have bigger valves a bigger "log" they are a better head. You`ll want to mill it ~ .060 to get you`r comp. up , if you were to just bolt on a 170 head you would lose flow so unless you spent a "little" money on it for bigger valves and porting then all you would have is a head with a lot of money in it that don`t flow any better than you`r stock 250 head because of the small log and just a tad more comp. because the thicker replacement gasket is 2 xs as thick as the ford one . If you`r wanting to upgrade then get a head of a 78 - 83 200 or 250 it will be a ton better than a 170 head IMHO.
Elliot, I guess I should explain that I am not building the engine for racing or even street performance. The added compression is for economy. A side benifit is that it will also produce more horsepower. The engine will never turn faster than 5000 RPM and the small passages will increase the velocity of the mixture. Manifold vacuum will remain higher and that increases the fuel distribution and vaporization within the mixture. This is a recipe for better fuel efficiency. If I have to use the 250 push rods and rockers that is OK as long as the geometry is kept within tollerable limits. I know where I could have push rods made if I knew the length but for an economy sleeper, it may not be worth the cost. PaulS
I think you nailed that. Economy will be a benefit of the higher compression and the small valves/log. You may even improve the emmissions as higher compression will improve the burn. I could imagine mid 20 mpg with a manual trans and skinny tires pumped up to max pessure.
I am thinking more along the line of 30 MPG but anything over 25 is fine. The added HP will be welcome too but my wife (this is her car) already has enough to keep her happy. If she starts going through tires I will have to take the engine out and put in pedals. PaulS
pauls, i just ran 800 miles this weekend to n.c. and back. the 170 carb. worked very well. we ran 75-80 mph down I 20 east and back. my son was in his 302 and we got nothing but thumbs up all the way there and back. i have thought about putting a 250 carb on but don't know what a diff. that would make. anyone know the diff. between the 170 and 250 carbs.??? ...frank....:bananaman :bananaman
The 144 carb is 150 CFM and the 200 used a 223 CFM carb and I believe the 250 carb is about 300 CFM but it is not a Holley or Autolite carb and has a different flange and bolt spacing(???) than the other sixes. PaulS
Compression helps but.... That intake is the most restrictive intake you could put on and may put you C.R. past pump gas levels. The later log is your best bet and mill it .060 since the head gaskets are too thick. This restores compression then mill the block .060 and there you go.I heard milling the intake and block increases flow. I'm not sure why. Go to FordSix.com. Do a search and you'll find out more than you'll ever need to know about those engines. With an AOD or five speed you should be able to get 28 mpg on the highway. A 3.25 gear out back will help out alot around town. Currie has a good selection for the 8 inch rear. I want 3.55's myself with a 5 speed T-5.
