98TM heads on a '93 Ranger 4.0L

[Carguy3J]

Pic of the two cc

Thanks for the side-by-side. The pics are at two different angles. The 90/93TM is "straight on", where as the lower 98tm pic is at an angle, so direct comparison is slightly difficult, but it close enough to see that it really wouldn't be hard to get the 98tm chamber shaped/sized similar to the "older" style. The area on the bottom-right (in the pics) and right to the right of the plug boss, looks close enough to use as a starting point. I could make a paper tracing of the "old" chamber, and lay it over the 98tm, and mark it with machinist dye, as a guide. I know I wouldn't get the same quality as a CNC port job, but with a lot of patience, and grinding stones (and polishing bits for the dremel), I can get fairly close. Certainly close enough, to make an improvement.

I would actually keep some things about the 98tm chamber, including the more "sloped" chamber floor/wall, in that right hand area. Actually, I think I would do VERY little,if any removal (other then a light polishing) to the whole "plug side" of the chamber. The "bottom" of the chamber (bottom in the pics), actually already looks pretty good. Neither of the valves are shrouded much, if at all, in this area. The "top side" (in the pics), especially the intake valve, is where some work is needed, and where I would take out material. That intake valve is heavily shrouded, and needs whatever help it can get, especially if a "bigger" cam is also part of the plan. I think huge gains can be made here.

Without a way to measure the cc of each cylinder or the flow of each port you can hurt the performance VERY easily. Its not a ""wing it"" type of deal trust me, I have spent THOUSANDS of dollars of the ohv doing research and finding what makes power and doesn't.current motor has close to 20k into it.......

Colored alcohol, a little grease, a flat rigid plexiglass plate, and a graduated cylinder (a pipette) are all that is needed to accurately measure combustion chamber volume. although time consuming, and somewhat tedious, It's not "hard" to make them all equal; provided one isn't too aggressive or ham-fisted with the grinder.

Yes, you are right, I will most likely never be able to match the performance of a professional CNC port job, but I also know there is a ton of room for moderate improvement with some fairly conservative home-based port/polish. I have done my home work as well. Not specifically on this motor, but I've read several VERY good books on engine performance, airflow, and porting. At the time, I was mainly interested in it for my Chevy truck, and stock car I had at the time ; both of which used a small block Chevy. Nonetheless, much of the "basics" of engine fundamentals are universal. An engine is an engine, in the sense that they are all just air pumps. Sure, each design has its own "quirks" that must be kept in mind when going for "maximum" power. However, there are a number of "tricks" that are pretty much universal. Un-shrouding the valves being one. Polishing the chamber, and everywhere else you can get to being another. I also have a good idea of where to work on, and where not to.
You're right that you can very easily ruin a good head. Most of the time, when a "Backyard Bubba" screws up a port job, its due to the "bigger is always better" mentality. I know that is wrong, and I know why. The goal is to maximize air flow VOLUME as much as possible, WITHOUT hurting flow VELOCITY. This means not enlarging ports/runners any more then required, and only in areas where it is most helpful to flow. For instance, it is usually a bad idea to do much, if any work on the floor of a port or runner, as there is very little air flowing down there. All that will do is increase the size of the runner/port, and kill velocity. Air tends to "stick" to the port/runner "roof", and the "long side" of a bend/turn, so that is where to concentrate any port work. Just polishing out casting flash can make an improvement, as well as carefully reshaping "transitions",so as to be more gradual. Air does not like sharp turns. It creates turbulence and hurts flow.
A good mild port job is not about making things bigger, but rather it is about making things "cleaner"

the early heads 90-93tm have 60cc and 95-98tm have 48cc..all head gaskets are the same design, there is a slight differences in thickness from different companies but not enough to bring you down a point.

Oh well. In the small block Chevy world, different gasket thicknesses are a useful tool in controlling CR. I wonder if a steel shim spacer plate could be machined instead? It would require two sets of gaskets, or the plate and block deck would need to be machined for o-rings, but I imagine it would be possible; but perhaps not really cost effective due to the custom nature of it?

If it was me I would just clean them up and not remove much of anything. Then hone the cylinder walls and replace the pistons.pistons are cheap and sure better than spending DAYSSSSSS porting a head and ending up just hurting the motor.

Yes, but "just" changing the pistons a.) does nothing to unshroud the intake valve, or polish anything (which itself helps to reduce detonation, by eliminating "hot spots" that can cause "pre-ignition" b.) is much more then "just" changing pistons. It requires an expensive custom balancing of the crank, as the later pistons are much lighter. In turn, at that point, I would be hard to resist the urge to polish and shot peen the rods, as well as clean up and lighten the crank. Things would really start to snow ball at that point. In any case, even if I did use the later pistons, for control of CR, I would still want to do work on the heads, for flow,etc...

410-422 do not require a tune but always helps.422 requires dual springs and seat work.both require longer pushrods.both could benefit from premium gas also..

Thanks for the confirmation on that.

Just a fyi going to 10:1 and running 90+ gas makes the motor MUCH more efficient and increases power and mpg.in my case it was worth the added cost of gas to get better mpg, ended up using less gas than the cost of 90+......10:1&422 cam goes very nice together also

Really? I know that higher compression is more efficient, generally speaking, but still, I'm surprised at the net savings you're reporting. In the past, I would have been more inclined to believe that, but over the last several years, the "spread" in the cost of regular vs premium has gotten wide enough that I just don't see it working out. I think you would need to see an increase in mpg of at least 20% for the math to work out. For me, assuming a current average of about 19mpg, I would need to see a nearly 4mpg increase to come out ahead. Do you really think this would result in 23mpg+?

 

[Carguy3J]

IIRC, as he was walking up to the car, he dropped his doughnut, it hit his foot, and rolled under the car. When he went searching for it, he found that there were no cats, and wrote a summons.

It was a long time ago... I may not recall all the details exactly as the occurred.

LOL!

 

[jd4242]

Thanks for the side-by-side. The pics are at two different angles. The 90/93TM is "straight on", where as the lower 98tm pic is at an angle, so direct comparison is slightly difficult, but it close enough to see that it really wouldn't be hard to get the 98tm chamber shaped/sized similar to the "older" style. The area on the bottom-right (in the pics) and right to the right of the plug boss, looks close enough to use as a starting point. I could make a paper tracing of the "old" chamber, and lay it over the 98tm, and mark it with machinist dye, as a guide. I know I wouldn't get the same quality as a CNC port job, but with a lot of patience, and grinding stones (and polishing bits for the dremel), I can get fairly close. Certainly close enough, to make an improvement.

I would actually keep some things about the 98tm chamber, including the more "sloped" chamber floor/wall, in that right hand area. Actually, I think I would do VERY little,if any removal (other then a light polishing) to the whole "plug side" of the chamber. The "bottom" of the chamber (bottom in the pics), actually already looks pretty good. Neither of the valves are shrouded much, if at all, in this area. The "top side" (in the pics), especially the intake valve, is where some work is needed, and where I would take out material. That intake valve is heavily shrouded, and needs whatever help it can get, especially if a "bigger" cam is also part of the plan. I think huge gains can be made here.



Colored alcohol, a little grease, a flat rigid plexiglass plate, and a graduated cylinder (a pipette) are all that is needed to accurately measure combustion chamber volume. although time consuming, and somewhat tedious, It's not "hard" to make them all equal; provided one isn't too aggressive or ham-fisted with the grinder.

Yes, you are right, I will most likely never be able to match the performance of a professional CNC port job, but I also know there is a ton of room for moderate improvement with some fairly conservative home-based port/polish. I have done my home work as well. Not specifically on this motor, but I've read several VERY good books on engine performance, airflow, and porting. At the time, I was mainly interested in it for my Chevy truck, and stock car I had at the time ; both of which used a small block Chevy. Nonetheless, much of the "basics" of engine fundamentals are universal. An engine is an engine, in the sense that they are all just air pumps. Sure, each design has its own "quirks" that must be kept in mind when going for "maximum" power. However, there are a number of "tricks" that are pretty much universal. Un-shrouding the valves being one. Polishing the chamber, and everywhere else you can get to being another. I also have a good idea of where to work on, and where not to.
You're right that you can very easily ruin a good head. Most of the time, when a "Backyard Bubba" screws up a port job, its due to the "bigger is always better" mentality. I know that is wrong, and I know why. The goal is to maximize air flow VOLUME as much as possible, WITHOUT hurting flow VELOCITY. This means not enlarging ports/runners any more then required, and only in areas where it is most helpful to flow. For instance, it is usually a bad idea to do much, if any work on the floor of a port or runner, as there is very little air flowing down there. All that will do is increase the size of the runner/port, and kill velocity. Air tends to "stick" to the port/runner "roof", and the "long side" of a bend/turn, so that is where to concentrate any port work. Just polishing out casting flash can make an improvement, as well as carefully reshaping "transitions",so as to be more gradual. Air does not like sharp turns. It creates turbulence and hurts flow.
A good mild port job is not about making things bigger, but rather it is about making things "cleaner"



Oh well. In the small block Chevy world, different gasket thicknesses are a useful tool in controlling CR. I wonder if a steel shim spacer plate could be machined instead? It would require two sets of gaskets, or the plate and block deck would need to be machined for o-rings, but I imagine it would be possible; but perhaps not really cost effective due to the custom nature of it?



Yes, but "just" changing the pistons a.) does nothing to unshroud the intake valve, or polish anything (which itself helps to reduce detonation, by eliminating "hot spots" that can cause "pre-ignition" b.) is much more then "just" changing pistons. It requires an expensive custom balancing of the crank, as the later pistons are much lighter. In turn, at that point, I would be hard to resist the urge to polish and shot peen the rods, as well as clean up and lighten the crank. Things would really start to snow ball at that point. In any case, even if I did use the later pistons, for control of CR, I would still want to do work on the heads, for flow,etc...



Thanks for the confirmation on that.



Really? I know that higher compression is more efficient, generally speaking, but still, I'm surprised at the net savings you're reporting. In the past, I would have been more inclined to believe that, but over the last several years, the "spread" in the cost of regular vs premium has gotten wide enough that I just don't see it working out. I think you would need to see an increase in mpg of at least 20% for the math to work out. For me, assuming a current average of about 19mpg, I would need to see a nearly 4mpg increase to come out ahead. Do you really think this would result in 23mpg+?

You can just change the pistons.they all use the same crank.the later models had a different""key"" for the balancer..sounds like you pretty set on porting the heads so post some pics as you go.
Around here its about a $.11 difference in gas price, that is from 89 to 93.I wouldnt run anything under 89 even in my lawnmower. .I get 23mpg in my ex with 4.88s and BIG 36x14.50 the ohv is seriously under powered and ford tends to use the wrong gears...