Thread: 302 cyl head print (needed!)

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Originally Posted by Louey

Is this what you want ?

from the center of a bolt hole on the right side of the port hole to the center of the bolt hole on the left side of the port hole is 2.0000'' center to center the you subtract the width of the port hole which is 1.3200'' they are round to the nearest 4th decimal place so the precision = .01 or ten thousants so 2.0000'' -1.3200'' = 0.68" divided by 2 because there are 2 spaces one on each side of the port hole from the edge or the port hole to the center of the bolt hole both sides so 0.68"/2=0.34" so from the edge of the port hole to the center of the bolt hole is 0.34" both sides

Originally Posted by Dano61

from the center of a bolt hole on the right side of the port hole to the center of the bolt hole on the left side of the port hole is 2.0000'' center to center the you subtract the width of the port hole which is 1.3200'' they are round to the nearest 4th decimal place so the precision = .01 or ten thousants so 2.0000'' -1.3200'' = 0.68" divided by 2 because there are 2 spaces one on each side of the port hole from the edge or the port hole to the center of the bolt hole both sides so 0.68"/2=0.34" so from the edge of the port hole to the center of the bolt hole is 0.34" both sides

C'mon, the horizontal spacing is obviously centered and thus easily calculated. His question is the vertical spacing of the holes relative to the center of the port. That dimension is obviously not centered, and there is no way to calculate the amount of offset from the information given. You can scale it, but he's asking for factory dimensions, as I understand his question.

It's all really moot - as has been pointed out there are already a ton of bare flanges on the market by people buying materials in bulk, and doing one that reinvents the accuracy is not going to be the multi-million dollar marketing idea never done before, but may be a dandy highschool tech center project.

OK----put 2 bplts--3/8 with sesctoion of untreaded shank into the two bolt holes---take a starret ruler ( 1/2 wide) put across the two bolt shanks, measure to top of port----measure to bottom of port---play with the constant values in this game ----3/8, .375, 1/2, .500, .1875, .6875, .875----a little addition, a little subtration, a little of this, that, etc----if you can't fiqure out the diminsions--------

Originally Posted by jerry clayton

OK----put 2 bplts--3/8 with sesctoion of untreaded shank into the two bolt holes---take a starret ruler ( 1/2 wide) put across the two bolt shanks, measure to top of port----measure to bottom of port---play with the constant values in this game ----3/8, .375, 1/2, .500, .1875, .6875, .875----a little addition, a little subtration, a little of this, that, etc----if you can't fiqure out the diminsions--------

Yep, you can scale it either graphically or by Jerry's method, but the point is the kid is asking for a Ford drawing that shows that dimension, thinking that if the dimension shown on some design drawing is used the world is in balance. Not saying it cannot be figured out, just that it cannot be calculated. Look back at post #23 of this thread and you and I are on the same page, Jerry. He did not like it then, either

And the whole thing of making your own header flanges is to end up with a hole size that will exactly take a tube size--ie--the distance around the port hole in the flange equals the od circumferce of the tube for the header----like 2 x Pi ==6.28----adjust the location of the port so as to reduct reversion, etc

Sorry fellas, i'v been busy with other car stuff, (blown head gaskets in a 3.8l (88) thunderbird + getting parts for trans) and havnt had time to do much header work.

But here is the wood milled flange i made for a prototype. Its not the best picture because its just off my phone, and i was at a weird angle so the ports LOOK like they dont line up evenly, but i asure you that there is an even amount of port on all sides inside the flange.

i also changed the orginal design alittle. I got rid of the chamfer around the edges, and then i also changed the bottom out side corners to not interfere with the cyl head bolt, as it is in the picture. I'l hopfuly get a final product here soon and post pictures

you may have to make room for the lower row of head bolts / studs .that is why i made alot of my flanges

you need to raise the plate so the overlap is at the top instead of bottom to stop reversion

(and for bolt /plug clearance?

Ya i know, i changed the design for the head bolts in the way.
plugs fit in fine. i gota get a better picture up here soon.

what overlap are you talking about?
The school is closed for thanksgiving break so i'l have to start the metal work next monday.

the portion of the port at the bottom of the hole---works better if that overlap is at the top so it stops reversion factor of exhaust pulse back feeding into head/cylinder especially on valve over lap where you would contaminate the intake charge with exhaust

i dont understand what your saying. overlap? you mean cover up the bottom of the port? why would i wanna do that?

The most flow is out the top part of the port----reversion effect takes place letting the exhaust flow backwards into the port and then cylinder-----The header should be bigger than the port size----like the distance around the hole should equal the circumferance of the header tube. offset the flange upwards so that there is a dam to stop the reversion flow at the TOP where the flow would be more---reversion on valve overlap will dilute the mixture in the cylinder and even contaminate the mixture in the intake, possibly even to the point of igniting it occasionally(backfire)