300 Six Compression Ratio, Intakes, Heads, etc

[Gary Lewis]

Gary, maybe I am just catching up to your thinking... but having looked at the master parts catalogue I find it lacking data.

First of all, if you ignore all the oversize pistons there seems to be only ONE part number for all HD and Canadian models from ‘80-‘86 although they appear in two places in the catalogue. (Yellow)

The light duty ‘80 pistons were replaced by the light duty ‘81-‘82 part so I think it’s safe to assume all three years’ pistons were comparable. (Green)

The ‘83-‘84 light duty pistons (Blue) show as being replaced by the 1987 EFI piston type... but there is no mention of light duty ‘85-‘86 pistons anywhere.

I also looked through the parts list and I can’t find any compression related component that says it is specifically for the 1983 fuel saver model to explain the 8.7 CR.

Since ‘85-‘86 has new heads, one for LD and one for HD it is at least possible that any compression ratio differences could be there rather than the pistons...

What still does not add up is how ‘83-‘84 HD’s had a CR of 8.4 with the same head and pistons as the ‘80-‘82 HD’s that yielded 8.0 and how did they raise the compression to 8.7 on the ‘83 fuel saver?

I did notice that starting in 1984 the facts book added the word “nominal” after compression ratio to 1. I don’t know what that means, if anything.

Yes, the MPC is certainly lacking data. I don't see any way, given the information there, that the compression ratios shown could have been achieved. I'm not saying it wasn't, but that we just don't have enough info to know how it was done.

I wonder if a trip to the microfiche tower is needed?

[Gary Lewis]

Yes, the MPC is certainly lacking data. I don't see any way, given the information there, that the compression ratios shown could have been achieved. I'm not saying it wasn't, but that we just don't have enough info to know how it was done.

I wonder if a trip to the microfiche tower is needed?

Well, score one for the microfiche tower! (You had to have been at the GTG last year, meaning in 2017, when Chris/ctubutis and Bill/Numberdummy brought me not one, but two microfiche viewers and a 1990 version of the Master Parts Catalog. It resides on top of the powder coating/paint booth, and is reached via an 8' ladder - hence "the microfiche tower".)

The 1990 version of the MPC shows pistons and heads that the 1994 version, which the rest of the world is working with, doesn't show. (But, we knew they had to be there!) I don't know that we've found all of them yet, as I still can't explain how they got the compression bump for the Fuel Saver Package. Nor have I gotten my head around what I've found. But, it is on the page at Engines/300 Six on the Compression Thoughts tab.

So, please take a look at let me know what y'all think.

[85lebaront2]

Well, score one for the microfiche tower! (You had to have been at the GTG last year, meaning in 2017, when Chris/ctubutis and Bill/Numberdummy brought me not one, but two microfiche viewers and a 1990 version of the Master Parts Catalog. It resides on top of the powder coating/paint booth, and is reached via an 8' ladder - hence "the microfiche tower".)

The 1990 version of the MPC shows pistons and heads that the 1994 version, which the rest of the world is working with, doesn't show. (But, we knew they had to be there!) I don't know that we've found all of them yet, as I still can't explain how they got the compression bump for the Fuel Saver Package. Nor have I gotten my head around what I've found. But, it is on the page at Engines/300 Six on the Compression Thoughts tab.

So, please take a look at let me know what y'all think.

Gary, just like the 460, the pistons on the 460 were the same from 1968-1987 which have a 0.240" depression in the piston top, but two things happened, one was in 1971 the deck height on the block was raised from 10.300 to 10.310 and in 1972 to 10.320, this lowered the compression slightly. The second thing was the change in combustion chamber volume, the later heads have much bigger combustion chambers. In 1988-1991 Ford went to a smaller depression, but even bigger combustion chamber to keep the compression where they wanted it, in 1992 the piston design was changed again by a deeper dish, still not as deep as the early one, but the compression height of the piston was raised.

I would go look at a good aftermarket piston catalog, like Mahle and see what the pistons actually look like.

[Gary Lewis]

Gary, just like the 460, the pistons on the 460 were the same from 1968-1987 which have a 0.240" depression in the piston top, but two things happened, one was in 1971 the deck height on the block was raised from 10.300 to 10.310 and in 1972 to 10.320, this lowered the compression slightly. The second thing was the change in combustion chamber volume, the later heads have much bigger combustion chambers. In 1988-1991 Ford went to a smaller depression, but even bigger combustion chamber to keep the compression where they wanted it, in 1992 the piston design was changed again by a deeper dish, still not as deep as the early one, but the compression height of the piston was raised.

I would go look at a good aftermarket piston catalog, like Mahle and see what the pistons actually look like.

Bill - You raise a good point. Perhaps the block changed along there somewhere. So, I took a look, and lo and behold there was and, at first blush, there were four. But, the 1980/83 one has a prefix of E7, so it is a replacement. And, that E7 is actually shown in three places.

But, using the breakdown on the left it looks like there were four: 1980 - 83; 1984 - 85; 1985 - 86 ex EFI; and 1987 on inc EFI. Right?

If so, we need to figure out what, if any, difference there was in deck height. Anyone know where to get that info?

[85lebaront2]

Bill - You raise a good point. Perhaps the block changed along there somewhere. So, I took a look, and lo and behold there was and, at first blush, there were four. But, the 1980/83 one has a prefix of E7, so it is a replacement. And, that E7 is actually shown in three places.

But, using the breakdown on the left it looks like there were four: 1980 - 83; 1984 - 85; 1985 - 86 ex EFI; and 1987 on inc EFI. Right?

If so, we need to figure out what, if any, difference there was in deck height. Anyone know where to get that info?

Maybe from a machine shop. In the past I would have said Jack Clifford, he was to the 6 cyl world what Tim Meyer is to the 335 world. He built speed parts for everything from Hudson Hornets to modern in-lines.

[Ford F834]

Well, score one for the microfiche tower! (You had to have been at the GTG last year, meaning in 2017, when Chris/ctubutis and Bill/Numberdummy brought me not one, but two microfiche viewers and a 1990 version of the Master Parts Catalog. It resides on top of the powder coating/paint booth, and is reached via an 8' ladder - hence "the microfiche tower".)

The 1990 version of the MPC shows pistons and heads that the 1994 version, which the rest of the world is working with, doesn't show. (But, we knew they had to be there!) I don't know that we've found all of them yet, as I still can't explain how they got the compression bump for the Fuel Saver Package. Nor have I gotten my head around what I've found. But, it is on the page at Engines/300 Six on the Compression Thoughts tab.

So, please take a look at let me know what y'all think.

That’s great Gary... at least we got our answer about the 85/86 light duty truck pistons. It does support that the change in CR for the last two years was in the heads, but then again late 84 may have deviated from what the facts book says... I’m assuming the book was prepared based on what was happening at the beginning of the new model year.

I noticed the same thing about the blocks. It does seem to be a replacement which does not help us identify if earlier blocks contributed to the facts book numbers. Maybe I should write a thread over at the Ford Six forum and see if the Frenchtown Flyer chips in... he was a Ford engineer(?) if I remember right.

[1986F150Six]

Maybe I should write a thread over at the Ford Six forum and see if the Frenchtown Flyer chips in... he was a Ford engineer(?) if I remember right.

He was a Ford engine development engineer. He worked extensively on the 302 engines [Mustang GT], but loves and races with the 300 engine. He has one of the few Ford experimental [prototype] cross flow heads.

[1986F150Six]

Maybe I should write a thread over at the Ford Six forum and see if the Frenchtown Flyer chips in... he was a Ford engineer(?) if I remember right.

He was a Ford engine development engineer. He worked extensively on the 302 engines [Mustang GT], but loves and races with the 300 engine. He has one of the few Ford experimental [prototype] cross flow heads.

The Frenchtown Flyer was contacted and responded to my inquiry as follows:

I am a member of another forum: *Bullnose Enthusiasts Forum*; part of *Gary's Garagemahal*. This forum primarily helps those with 1980 - 1986 Ford trucks, vans and Broncos.

http://www.garysgaragemahal.com/

There (http://www.garysgaragemahal.com/There) is a current thread titled *300 six compression ratio, Intakes, Heads, etc*. Research has been done using Ford Dealer Facts Books and Ford microfisch [striving for accuracy].

Depending on the year as well as tonnage [1/2, 3/4, 1 and LD or HD], compression ratios are listed as 7.9, 8.0, 8.4, 8.5 & 8.9 to 1. There were different heads, pistons, valves and blocks [i think].

One rather interesting fact is that in 1983, the compression ratio was @ 8.4:1, except with the *"fuel saver"* package @ 8.7:1.

Would you please consider visiting [or joining?] the Bullnose Enthusiasts Forum [link above], or share your thoughts here and with your permission, I will quote you.

What we are seeking is the answer to what accounted for the varying compression ratios?

Thank you in advance, David

---End Quote---

Hi David,

I won't be joining any additional sites, but I'll give you the answer to your question as I see it.

All the carbed 300 heads chambers are the same with 76 cc chambers +/- 2. All the blocks are the same deck height wise. The pistons vary - industrial engines were a bit lower CR. Also, some HD engines had upgraded valves and it is possible that the dish size in the valves made a difference in the CR too.

 

Hope this helps.

Merry Christmas

Greg

 

[Gary Lewis]

The Frenchtown Flyer was contacted and responded to my inquiry as follows:

I am a member of another forum: *Bullnose Enthusiasts Forum*; part of *Gary's Garagemahal*. This forum primarily helps those with 1980 - 1986 Ford trucks, vans and Broncos.

http://www.garysgaragemahal.com/

There (http://www.garysgaragemahal.com/There) is a current thread titled *300 six compression ratio, Intakes, Heads, etc*. Research has been done using Ford Dealer Facts Books and Ford microfisch [striving for accuracy].

Depending on the year as well as tonnage [1/2, 3/4, 1 and LD or HD], compression ratios are listed as 7.9, 8.0, 8.4, 8.5 & 8.9 to 1. There were different heads, pistons, valves and blocks [i think].

One rather interesting fact is that in 1983, the compression ratio was @ 8.4:1, except with the *"fuel saver"* package @ 8.7:1.

Would you please consider visiting [or joining?] the Bullnose Enthusiasts Forum [link above], or share your thoughts here and with your permission, I will quote you.

What we are seeking is the answer to what accounted for the varying compression ratios?

Thank you in advance, David

---End Quote---

Hi David,

I won't be joining any additional sites, but I'll give you the answer to your question as I see it.

All the carbed 300 heads chambers are the same with 76 cc chambers +/- 2. All the blocks are the same deck height wise. The pistons vary - industrial engines were a bit lower CR. Also, some HD engines had upgraded valves and it is possible that the dish size in the valves made a difference in the CR too.

 

Hope this helps.

Merry Christmas

Greg

That's a big help. Now we know that the CR change was all due to pistons, not blocks nor heads.

However, that begs several questions. For instance, where are the pistons used in the fuel saver package?

Looks like I'd better fire up the Microfiche Tower and check out the Feb 1982 version of the MPC I have............................................................

[Gary Lewis]

That's a big help. Now we know that the CR change was all due to pistons, not blocks nor heads.

However, that begs several questions. For instance, where are the pistons used in the fuel saver package?

Looks like I'd better fire up the Microfiche Tower and check out the Feb 1982 version of the MPC I have............................................................

Well, right about here the plot thickens. We now know that the blocks and heads didn't really change, so the difference in CR is in the piston. Heretofore I've looked at the 1994 version of the MPC and then corrected it with info from the 1990 version which I have on microfiche. Now I've looked at the Feb '82 version on microfiche and have found completely different #'s than before.

In fact, the information is so different that I'm not quite sure how to process it. So I'll post it here and then puzzle with how to incorporate the info into the spreadsheet:

• 1980 on: D3TZ 6108-A for HD US trucks (E-F 250/350 over 8500) and all E-F100/350 Canada w/leaded fuel

• 1980/81 before 12/8/80: D7TZ 6108-A for LD trucks (E-F100/250 & U150 under 8500 w/unleaded fuel)

• 1981 from 12/8/80: E1TZ 6108-A for LD trucks (E-F100/250 & U150 under 8500 w/unleaded fuel)