Cylinder Head Clearance

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Model T Ford Forum: Forum 2016: Cylinder Head Clearance
Top of pagePrevious messageNext messageBottom of page Link to this message  By Joseph A. Stearns on Thursday, March 24, 2016 - 01:39 pm:

I am installing a Reeder high compression aluminum head on my freshly rebuilt engine. Flat top aluminum pistons, new 250 cam, valves set at .015. I checked the top of piston to head clearance in each cylinder using modeling clay, also did this on each valve. There was NO cly gasket installed on these checks.

Piston to Head clearance: (1) .390. (2) .375 (3) .390 (4) .404

Valve clearance: (1) .376 (2) .374 (3) .392 (4) .378 (5) .365 (6) .345 (7) .352 (8) .345

I also checked depth of each combustion clamber using a straight edge and caliper with results as follows: (1) .685 (2) .676 (3) .693 (4) .713

I was expecting results like I have seen with Z -HEADS with Pistons actually hitting the head to .060 clearance. As I have no history with the Reeder head, looking for advise. Maybe mill some off the head???

Thanks, Joe


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Thursday, March 24, 2016 - 02:42 pm:

Well, the Reeder head wasn't designed with a squish surface over the pistons according to Ricardo's principles. It would have developed even more power if it had.
The limiting factors on how much you can mill it would be the thickness and thus the strength of the deck plane.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tony Bowker, Ramona, CA on Thursday, March 24, 2016 - 04:16 pm:

I had problems with my Reeder head after it was milled. It seems that it warped in the center where the is a hole in the head and not in the block. Eventually I tossed it and bought a Prus.....


Top of pagePrevious messageNext messageBottom of page Link to this message  By Allan Bennett - Australia on Thursday, March 24, 2016 - 07:49 pm:

I know of more than a few Reeder heads which have warped around the centre water passage. Any reduction of the thickness here would be even more likely to cause problems. One fix was to weld up the large hole and redrill just the stem hole, as is in the block.

Hope this helps.
Allan from down under.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Joseph A. Stearns on Friday, March 25, 2016 - 07:56 am:

Thank you all for the input, I will not mill the head--not looking for more issues to deal with.

Question, does the Reeder head perform well as the increased performance one sees with a "Z " head? I would appreciate input on this. Thanks again. Joe


Top of pagePrevious messageNext messageBottom of page Link to this message  By Allan Bennett - Australia on Friday, March 25, 2016 - 08:58 am:

Joe, I have no dyno figures or any other objective measurement of the difference in power between a Z head and my Reeder. The Reader with which I had the warping issues, was on my speedster. It went like stink with just a straight bore Holley NH, a Chaffins tour cam, an alloy intake and a set of home built headers, apart from meticulous balancing of the motor and transmission. But that car is light.

My 1912 chocolate van has a low alloy head too. I think it is a Reeder. It has performed flawlessly for 21 years now. It has plenty of low end pull to get a much heavier body underway.

Both these are brass veterans. My 1924 tourer with the Z head is more staid, as befits a period correct car. Dyno figures for it showed a 7 hp increase over standard, which gives it quite adequate performance.

Hope this helps.
Allan from down under.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Friday, March 25, 2016 - 11:30 am:

Any increased compression over the std 3.8:1 with a high head helps power, it's just that the squish style combustion chambers helps even more.

You can figure out some by reading the Tulsa Model T club's articles on heads, though they didn't have any Reeder head to measure, so it's hard to say how much compression it really has?

http://mtfctulsa.com/Tech/head_design.htm

If you put in a spark plug, level the head on a table and fill a combustion chamber with a measuring glass, we could find out the actual ratio?

The theoretical max power with 6:1 compared to 3.8:1 should be 26 hp.

Both Z heads and Prus heads has about 5:1 but the Z still gives about 26 hp and the Prus about 28 hp, so the equal or higher power with a lower compression can be explained by the better shape of their combustion chambers.

So if the Reeder turns out to be about 5:1 as so many others, then maybe the output would be slightly lower than the Z, like 24-25 hp on a fresh engine?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Friday, March 25, 2016 - 12:28 pm:

Standard replacement T pistons are not flat tops - where did you get those?



I have a Reeder low head on my '15. I don't know how much it increased compression, but the cold cranking pressure increased from 55 PSI to 70 PSI. It yielded a nice increase in power. It has been on the car since 2003, and has gone tens of thousands of miles.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Joseph A. Stearns on Friday, March 25, 2016 - 04:44 pm:

Ya Royce I guess you are right, they are not flat across the entire top surface diameter. A better way to describe them is to say they are not the high compression dome type but are the standard aluminum Pistons from Snyders.

Thanks for your input. Joe


Top of pagePrevious messageNext messageBottom of page Link to this message  By R. S. Cruickshank on Friday, March 25, 2016 - 05:12 pm:

Am I wrong in thinking that the high compression can cause problems eventually with the standard crank? Dick C.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan Treace, North FL on Friday, March 25, 2016 - 05:20 pm:

The only busted crankshafts I have personal knowledge of were with other's stock engines, iron head, standard compression.

Have run high compression heads since 2000 and no issues, engines are all rebuilt, new Babbitt, that no doubt helps longevity.

So far, am still in the no-break crank club after 50 years of T'ing. :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Friday, March 25, 2016 - 06:35 pm:

I think it also has to do with how much of the new strength that is actually used..
If you reduce the throttle and only drive as fast as you did before you put the new head on, then the crankshaft shouldn't be exposed to any more strain than before.

In my humble opinion the worst strains on a Model T crank comes from twistings that are amplified at certain resonance rpms, so it's also important to avoid all rpm ranges where the engine sounds strained and unbalanced - "thum speed".


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Tomaso - Longbranch,WA on Friday, March 25, 2016 - 08:44 pm:

Careful there, Dan - don't bring no "bad joo-joo" on yourself !!!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan Treace, North FL on Friday, March 25, 2016 - 09:54 pm:

Steve

You're correct. Carefully driving the T's

Just try to keep the speed down so that crankshaft won't whip itself over, leaving a journal behind for an odd reason. :-)


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