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Flathead deck height Does anyone have a factory reference of Fords Deck Heights for the Flathead engine and are there any variation of the deck height for 32-36, 37-39, 40-48 and the last version of 49-53?
As far as the math goes, 1.875 (half the stroke) + 7.00 Rod length) + 1.627 (piston compression height to start of the dome) = 10.502. The dome is .154 but, I can't find a reference to the deck clearance. Also, I know that the valve angle was changed, did that have a effect on deck height? Frank |
Re: Flathead deck height The connecting rod length stayed the same for most of the v8 production. Only the pistons changed for the two different strokes. If a person registers off of the crankshaft centerline, the deck height can be checked since there are likely plenty of old engines that never had the decks cut down. I would imagine variations would not be very much if any since the deck surface is rather thin. They can only be planed off so much. Most machinists that do plane them only take enough to true them back up. The valve angle change would not have been enough to warrant any change that I'm aware of.
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Re: Flathead deck height The valve angle change doesn't have anything to do with the deck height - as deck height is strictly based off of crankshaft centerline.
Since all of these engines came with the same length rod and the compression height was the same for all 3 3/4 stroke engines, the deck height "should be" the same for all years. With that said, I typically see a variance between one bank and the other - so I usually figure out which side is lowest, then use it to determine how much more to take off the high side -- to get them both even. |
Re: Flathead deck height Does the crank off-set come into play on that?
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What measurements have you gotten, when you measure the deck clearance? Frank |
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The crankshaft offset (about 0.265") does influence the valve angles as well as exactly how the pistons are located in relation to the crank pin at certain rotation angles (rod angles - relative to the centerline of the rod are different at TDC). Attached is a cross-section drawing I made that shows a bit of what I'm talking about - hopefully you read it (this is 59x through 8BA - is different for 32 - 42): Enjoy! Attachment 402795 |
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Re: Flathead deck height The deck clearance, is the distance from the top of the piston (on domed pistons, it's measured from the start of the dome) to the top of the block.
In more modern, OHV engines, it's usually between .025 in the case of the sbc and .016 on SBF. It's a needed dimension when setting up a engine to calculate compression ratio. That's why I'm asking about the block's deck height. You would take the dimensions that I listed in my first post, and subtract the 10.502, from the deck height and that will give you the deck clearance. The other thing that it effects is the distance from the piston to the underside of the head. For OHV engines, you need at least .040, to insure that the piston, doesn't hit the head at higher RPM. In the case of the FH, you have to add the dome height to the deck clearance and compressed head gasket thickness, to insure you have that clearance. Of course you don't have the dome on the early flat top pistons and so, you don't use it on those engines. Frank |
Re: Flathead deck height It is much easier (and I would think more accurate) to measure it directly. The top of the pistons are often not a perfect dome, same applies to the area of the head over the piston dome. That is why it needs to be checked in several locations on each cylinder. There is also variation cylinder to cylinder. I'm not sure trying to figure it mathematically is the best approach. Takes some work to get the heads matched up to the pistons, the target value is normally in the .040 to .050 range.
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I don't know what Ford would have used for tolerance on the FH but, more modern tolerances is .005. Ford would have had to list that info (deck height and tolerance) somewhere or the engine could not have been built. The block is the basic "Building block" to the whole engine and everything is built to it. Frank |
Re: Flathead deck height I'm sure there are original blueprints if you are that interested. You can contact the Ford facility that keeps the original copies.
"The block is the basic "Building block" to the whole engine and everything is built to it." That is true, but if you have the block in front of you, you have that information. Short of a NOS block, almost all blocks have several rebuilds on them which my or may not have included decking the blocks. Flathead blocks are very thin in the deck area to begin with, so any decking needs to be kept to the bare minimum. What are your objectives with the engine? If it is all out competition there are some world recorded holders here on the barn that may or may not be willing to share some of their secrets. :) A lot of us have considerable high performance/race experience in the non-world record category. A little more information on what you are after might help. |
Re: Flathead deck height Since I'm a machine shop owner, I can measure any component to a engine. For most w/o that ability, what JSeery suggests, is the best that that can be done but, if you can measure each component, you can place them (or replace) to match OA lengths as evenly as possible, before assembling them together.
If you order pistons, you need to know the stroke length, rod length and the deck height, to get a accurate fit, for you application. That will inlude a acurate compression ratio, that is so important in a FH. Frank |
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Re: Flathead deck height Unless you are ordering special pistons, deck height is not listed for flathead pistons. I find that most of the pistons bought these days end up with the edge of the piston below the deck. Not ideal, but that is what you get these days.
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Re: Flathead deck height I know that in at least one case the block was shaved INSTEAD of the heads because if you were a winner they would tear down the engine right after the race to check the bore & stroke etc. before you got paid!!!
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Well just to muck the waters up a bit. Piston manufacturers usually don't talk about deck height at all - it is really not their problem. Also, they may or may not talk about crankshaft stroke and rod length. What they almost ALWAYS talk about is CH - or compression height. This is the distance from the center of the wrist pin to the top edge (in the bore) of the piston. This is NOT to the top of any crown or raised area (almost as if you were measuring a flattop piston).
From a piston manufacturer's perspective, all they care about is where is the piston pin centerline going to be . . . in relation to the top of the piston. It is up to the builder to determine HOW to get the piston pin centerline to that location. In modern OHV stroker applications there are all sorts of rod lengths, deck heights, etc.. When you order custom pistons, they will always require the CH number. When I build a custom engine (high end), I have my decks trued/aligned first and I have my crankshaft and mains work done (in case I'm align boring the thing) and then I install the crankshaft, one rod and a piston pin (in the rod end). Then I bring the rod up to TDC (measured with a dial indicator), then I measure/calculate the actual compression height that is required to put the piston edge/dome exactly where I want it. On a flathead, the CH will be calculated so I'll be about .010 above the deck (edge of the piston). I do this because standard head gaskets compress to about .050 to .052 - and I want a .040 quench distance between the dome and the head chamber. I then order my custom pistons with exactly the right CH number. Rarely is the number the same as a "stocking piston". This is the only way I can get exactly what I want . . . and it increases the cost of a set of pistons and rings. Sometimes I move the ring package around a bit as well - depending on the type of rings and whether a NA engine or blown and also the depth of a relief (if I'm using one). Here is an example of a Ross flathead piston specification on Summit's website - shows a compression height of 1.374 . . . which is supposed to be for a 4.125 stroke crank. In my world, the off-the-shelf pistons rarely seem to do the trick . . . but I'm a bit picky! LOL Attachment 402845 |
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I 'zero and square deck' almost everything I build - because I want my quench to be exactly what it needs to be. I usually run about a .040 quench on SBC type engines as well - and with a stocking piston, that usually means the block has to be decked. In the higher quality forged pistons, they will specify the exact Compression Height - end the builder must figure out if they want to use that piston, deck the block or find another piston (if it is down in the hole a bit). |
Re: Flathead deck height Look guy's, I didn't join this forum, looking for a argument. I specify joined, to ask this question. I asked on the face book site, Flat Spot and couldn't get a answer there so, I thought that I might find it here.
I come from the manufacturing world and may think differently than others. My motive in this is the '35 truck pictured in my avator, it has a 68 engine that I want to rebuild to my spec's, to get the highest compress possible, with some aluminum, 21 stud heads and intake, that I recently bought, possibly modifying them to use domed pistons. Frank |
Re: Flathead deck height Don't think you are getting arguments, your getting information from folks who know and build flatheads and have for years. If I knew the deck height number I would give it to you, I don't. Don't need it and don't use it. You are on a site with some of the top flathead builders in the world. If people post on your thread it keeps it near the top of the listing, if they don't it tends to get buried. If there are any builders that have that information and use it they will see the thread and most likely comment. Just a hint, there is no reason to come across as superior in the way you do or go about an engine build. Again the top flathead experts in the world are on this site! I have years of experience in building late model drag and circle track engines and understand exactly what you are referring to. That is something I am concerned with on OHV builds, flatheads are different. One of the biggest differences is how the heads are manufactured, there is a lot of variation from cylinder to cylinder. If you are wanting top performance you are going to have to modify each combustion chamber to match the piston. You might be able to machine the head for consistency or start with a billet head, but off the shelf they are going to need work. And as stated, custom pistons would help.
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Frank |
Re: Flathead deck height I'm not trying to act superior, I'm just trying to get some basic info. I have deck heights for most all major American OHV engines from the '52 Lincoln (10.94), on but, not the FH.
I know some general info on FH's as I have always loved the look of them and my very first car (1959) was a '48 Merc, with a 3/16 over bore. If you'll read my bio, you'll see my dad worked for a authorized Ford rebuilder from '46 - '51. I started out as a mechanic, at 18 with his tools. I've built many FE's and 289-302 (even had a Edsel, 410 MEL) but, this is only my second FH. My back ground for the last 45 years, has been as a machinist (not auto motive) and I look at all things from that perspective. Frank |
Re: Flathead deck height The number you all may be wondering about is 10.438".
If we do mill the decks (most builds do get milled) we remove the bare minimum, even though these blocks weigh over 200# they are still "flimsy". It's also the very reason every block gets plate-honed. Thanks, Gary in N.Y. P.S. Haven't found too many to be "dead-on" but they are relatively close considering the machining was done a long time back! |
Re: Flathead deck height Hey Frank - not trying to argue with you - we actually agree on most things. :) You and I both know that we can measure something many different ways - as long as we're working from the same starting point, we can get to the same answer. If you want to know what the deck height should be, then all you had to do was read the drawing I posted - it is all right there.
From the Drawing: a) Crankshaft stroke = 4.125 b) Rod Length = 7.000 c) Compression Height = 1.3745 So - the deck height = (4.125 / 2) = 2.0625 + 7.000 + 1.3745 = 10.437 Knowing that Henry tended to use standard increments, the spec was probably 10.4375 or 10 7/16. Now - what I can't say is what tolerance the various flathead production locations actually held. And you asked the question up above: How can you calculate the CH, if you don't know the deck height? Do you assemble a rotating assembly, then measure the deck clearance and adjust you CH from that measurement? In the paragraph above that - I explained that this is exactly what I do. I don't have the luxury of having a block/crankshaft jig all setup for a flathead - to measure from the crankshaft saddle, so I do it the hard way and then I give the machine shop the instructions as to what I want done on both sides and I give the piston manufacturer the corresponding CH. Good luck! B&S |
Re: Flathead deck height OK, I have a basic question: How do you determine the main bearing bore centerline, in order to get an accurate deck height measurement?
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Re: Flathead deck height You lay the deck on a flat surface, a surface plate in my case, with a main bearing cap installed, you measure to the center of the main bearing bore. You get the center by measuring to the bottom of the main bearing bore and adding 1/2 the main bearing diameter. I use a height gauge for that type measurement.
You would then measure the other end, to determine if the main bearing bore is in alignment to the deck. If it isn't, it's a good reason to deck the block. Frank |
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Many thanks, both of you. I've also been looking for that number for years. Would a 221 block be the same? That's a great drawing, Bored and Stroked, thanks much for sharing it! Is there a chance you did the same for an early engine? |
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S&B,
I saw that in the PDF but, if you look at my addition of the crank throw, rod and CH, it adds up to 10.503. That would put the piston .065 out of the block. The CH I use, is the replacement piston, that TRW made in 1978, L912F. So, something isn't right. Frank |
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The fixture is used to not only square-deck the block, but for all decking operations - as everything is based off of the mains . . . which are indexed/mounted into the fixture. Some fixtures allow you to rotate the block (one deck to the other) - such that you can easily deck one side, rotate it and do the other side the exactly the same way. |
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Note: Their dimension for 'Comp Dist' is wrong - here are the basic numbers for the different strokes - which are easy to calculate - just add/subtract from the numbers in my drawing (based on 1/2 the stroke change/difference): 3.750 = 1.561 4.000 = 1.436 4.125 = 1.374 (what my drawing shows - as that is the crank I'm using) 4.250 = 1.311 PS: The drawing is correct - the math works out and matches the 'stocking' pistons that Ross and others supply. What is your math? |
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I don't have the detailed early drawings from Ford (32 - 42 production) - have never seen them. BUT - from the drawings that I have seen, these are the numbers. I did use these dimensions to validate my 42 Merc block - as best as I could manually measure the valve angles, they were extremely close (which was what I was after). Note - this CAD model also shows a 4.125 stroke crank - as I wanted to compare things to the later engines and my particular setup (42 Merc). So - obviously there is some simple math to do to calculate CH - given any stroke. Attachment 402868 |
Re: Flathead deck height The drawing I have here at my desk does not have the crank CL to deck dimension. It is listed in a different view and that drawing is out in the shop. However, the dimension from camshaft CL to deck is 7.0654 to 7.0704
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Re: Flathead deck height B&S,
What is the origin of your drawing? Frank |
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I don't think anyone is arguing just adding info. |
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Thank you Dale! You are generous! Most folks won't appreciate what you just gave away in terms of hours spent to create and validate that. |
Re: Flathead deck height Important! Okay guys - was pondering this last night when I went to sleep (you know how it goes) and decided to think back at the purpose of my drawing (which was to look at valve angles and show the CH and crankshaft offset).
For the purposes that I used it for (easy calculation of compression height - given crankshaft stroke and experimenting with rod lengths), it is fine. It doesn't show the block in relation to the crank - which is offset about 3/16. So, the math I previously showed (and the drawing) is fine for determining CH, but not deck height . . . as until I actually add "the block" into the picture, you won't know the number. Hope I'm making sense here - and I owe an apology to Frank! It was not correct to extrapolate deck height . . . when there is no deck to be found in that drawing. :) |
Re: Flathead deck height If your a machinist, I'd suggest measuring your deck height on both sides and ask others if they get similar dimensions. Ford had big machines that planed multiple engine blocks at the same time. The 68 series or LB blocks were the last of the pump in head blocks but as I mentioned earlier the deck is thin on all of them so Ford machinists likely set them all up for the same deck height so as not to make them too thin. Not too many folks out there are concerned with the dimension other than they want the deck square, intact, and as crack free as is possible.
If a person has a mandrel to fit the diameter on the main bores in the block, it can be measured from the deck down to the mandrel to get a dimension that can be calculated. The LB was the larger bearing than the previous engines and the first to have removable bearing shells. |
Re: Flathead deck height FWIW, as a quick and dirty check I measured a 37 block this morning. I used a pair of dial calipers from the main bearing saddle to the deck, then added half the bearing bore. The bearing bore looks like 2.590", the saddle to deck looks like 9.150" This is not a great way to measure, and I could only reach at one spot, the front of the driver's side of the block because of the length of the jaws on the dial calipers. So 2.590 /2 = 1.295. 1.295 + 9.150 = 10.445. I'm confident that this is accurate on this block to ±.005. I bought this block disassembled and cleaned and don't know it's history, but it doesn't appear to have been machined at all.
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Re: Flathead deck height Heres my simple thoughts which is similar to what others have written. The actual deck height standard dimension is of no concern to most of us. What is a concern pertains to the decks being exact heights side to side from the crank center line. On every block I have built this dimension side to side has always been different. Seeing your interest is in the rebuild of your engine relatively stock at that to help you get what your looking for you simply need to contact the Ford archives. The Flathead block prints are located there and for a small fee you can get the print which of course will show the dimension your looking for if the print still exists. I have a couple of NOS flathead blocks and they to are not accurate side to side the variations reflect the machining process at the time and the huge amount being produced daily.
Ronnieroadster |
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