Is this the Chev head for a O/H valve covnversion ???

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Model T Ford Forum: Forum 2008: Is this the Chev head for a O/H valve covnversion ???
Top of pagePrevious messageNext messageBottom of page Link to this message  By David Dare on Sunday, January 04, 2009 - 02:34 am:

Hello , l have been busy trying to find a good servicable Chev head for the O/H valve conversion and have located a willing donor, can anyone advise if this 1927-28 chev 4 cylinder is the correct one ?
It looks similar to the bright green one l have in my picture file, but l neglected to include the year with the pic !!



Thanks in advance for any thoughts.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Heyen on Sunday, January 04, 2009 - 02:53 am:

This link to Gen III shows a 1928 Chevrolet head.

http://gen3antiqueauto.com/model_t_parts.htm


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Dare on Sunday, January 04, 2009 - 03:34 am:

Thanks Rob, it kinda looks similar, geeeeez, 70-80 Hp up to 100 HP , Hmmmmmmm - personal damage could occur !
Now l'm sure that would propel a Tudor along at a decent pace.


Top of pagePrevious messageNext messageBottom of page Link to this message  By BRENT in 10-uh-C on Sunday, January 04, 2009 - 09:52 am:

Exactly where did the horsepower rating of 100 horsepower come from? Is this someone's guess or fact proven by some accepted method?

Why I ask is I have not one but two of the OHV Chevy set-ups. While I never used a Stipe cam in my T set-up, I did use a Model B cam (304") with my 'A' set-up. On the dyno, the most we were ever able to get out of a Chev. OHV head was about 60 horses --corrected! This was on an .080" over block, and I have several carb/manifold combinations including an old dual side-draft set-up. A Miller-Scofield head on the same block yielded about 15 more Hp which I attribute to better combustion chamber and flow, --both of which the Chev. OHV severely lacks in IMO. For the record, with a better cam and carburetion, my Serr-Miller, OHV Gemsa, and Lingo heads have done way better than the 100 horse uncorrected on a dyno.

Therefore, while I am not about to say that 100 horsepower from this 'T' combo is not possible, I do find it difficult to fathom as realistic when I know we were unable to obtain this number with the larger displacement Model 'A' combination.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Sunday, January 04, 2009 - 10:04 am:

Just curious, Brent, what rpm were you turning to get max hp?

rdr


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dexter Doucet on Sunday, January 04, 2009 - 10:27 am:

That's a 28 Chevy head no doubt.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth Harbuck on Sunday, January 04, 2009 - 11:01 am:

And Dex should know...

Hey Dex - Happy New Year!

Seth :-))


Top of pagePrevious messageNext messageBottom of page Link to this message  By Fred Houston on Sunday, January 04, 2009 - 11:06 am:

Sixty hp not only sounds reasonable, but would make a well performing Speedster or touring engine.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenneth W DeLong on Sunday, January 04, 2009 - 11:25 am:

David,The 28 Chevy had two exhaust ports so it is considered better than the large sq port of pre 28. I think in about 25?? The larger Chevy/only a few shared a 3 port head with the 4 cyl Olds engine of the time?? Rare but out there so finding one?? Not the first time Chevy and Olds shared engines either as the Northway V-8 some models of both shared in 17 18 and 1919.Bud.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tim ( www.ModelTengine.com ) on Sunday, January 04, 2009 - 11:29 am:

David,

That looks like the right head to me. If you need help, ship it over and I'd be happy to build an engine around that head for you. There are some issues you need to be aware of, trial and error method may have you tearing your hair out (like I did). If you plan on doing it yourself, feel free to write me with any questions I might be able to answer for you.

And to clear the air, 100hp was a number given to me by others that did this before me - a guess based on the math. I don't have a dyno yet, so a guess is all I have. This site http://www.speedwaybids.com/calcs/powerfromcfm.html comes up with 103HP based on 100cfm flow, which is about what I think will run through my little green engine. I would love to see some actual dyno results for this exact setup.

Now - facts: My heavy sedan goes like stink with this engine in it. So far I've gone as fast as 58 in it, got hit with a cross wind (pushed into the next lane) and backed down to a manageable 50mph. I decided that over 50 is probably too fast for this body style and finding the real top speed was not worth dying over. The problem is that this thing is so top heavy and rectangular. I have no idea what the top speed would be, I've never gone past 1/2 throttle. It does 50 easy with five of us in it. I can keep up with modern traffic with it on the roads I drive it on, smiling the whole way. I do plan on fine tuning some more after the snow melts, it's been set a little too rich to help get past the cold intake issue we struggled with all summer.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Sunday, January 04, 2009 - 11:41 am:

To get the most out of an engine, you need the right gearing. Stock T is geared for max speed at max hp - about 43 mph. Whether it's 60 hp or 100, you are stabbing in the dark without a torque curve.

BTW,what C/R do most of the Chevy conversions run?

rdr


Top of pagePrevious messageNext messageBottom of page Link to this message  By Fred Houston on Sunday, January 04, 2009 - 11:56 am:

Bud, the 28 Chev is the only year that had the 1.5 to 1 rocker arms. Even on the Olds, the 28 Chevy or some other rockers should be used.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tim ( www.ModelTengine.com ) on Sunday, January 04, 2009 - 12:30 pm:

I ordered a 6:1 plate but you can get whatever ratio you want. My 6:1 setup produces 100 psi ( 6.8:1 at sea level? ) so the thickness calculations may be a little off. I would have gone 7:1 (which would really be 8:1 ? ), but I was worried about the babbitt and the crankshaft so I opted to keep it tame. I did get a little bolder last week and clocked the cam timing to my preferred position.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth Harbuck on Sunday, January 04, 2009 - 12:48 pm:

Tim,

Compression ratio is not the ratio of compression pressure to atmospheric pressure, it it the ratio of total cylinder volume at BDC (swept volume plus combustion chamber volume) to volume at TDC (combustion chamber volume).

Seth


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tim ( www.ModelTengine.com ) on Sunday, January 04, 2009 - 01:03 pm:

I'm not going to argue with you because trying to prove you right or wrong will give me a math headache. I will say this though. a 6:1 Z head on a stock T will net you 88psi (6*14.7). When I ordered a plate designed to give me the same 6:1 compression as that Z head, I expected to see 88psi. The plate I have is fine, seems to get the job done and the rest of the engine is not complaining.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth Harbuck on Sunday, January 04, 2009 - 01:10 pm:

Change to a cam with longer duration on the intake and watch the compression pressure go down. Set the valve clearances huge and watch the compression pressure go up.

No point in trying to prove me wrong since compression ratio is a ratio of volumes and it has always been that way.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenneth W DeLong on Sunday, January 04, 2009 - 07:03 pm:

Fred,So maby the reason was not the single exhaust port rather thr rocker arms?? Thanks Bud.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Brent in 10-uh-C on Sunday, January 04, 2009 - 07:37 pm:


quote:

Just curious, Brent, what rpm were you turning to get max hp?



Ralph, I don't remember exactly but likely somewhere under 3000. The better heads were only pulled to 3000 too since that is the rpm range in which we are running our engines on the track. I'm of the opinion the Chevy head does not breathe well being restricted on the exhaust side and a "non-existant" combustion chamber. While I'm sure it is better flowing than a L head 'T' engine, I would think that even an F-head would outflow it.

One other thing to ponder. The Model A Ford when new produced about 40 horsepower. Granted the engine was a little bigger but the 'A' Sedan also weighed more. One of the sales pitches from ole Hank himself was "The New Ford" in 1928 was guaranteed to be able to go 60 mph off the showroom floor. Therefore, I don't doubt Tim when he claims their Fordor will go 58 mph. Very possible it has a tad more in it however it has been proven that the same thing can happen with just 40 horses, --which is substantially less than 60, ...or 70, --or even 100 horses. If someone nearly doubles the horsepower over a stock set-up (40+/- vs 22+/-), I would think by comparison it should accelerate fast enough to make someone notice.



quote:

Compression ratio is not the ratio of compression pressure to atmospheric pressure, it it the ratio of total cylinder volume at BDC (swept volume plus combustion chamber volume) to volume at TDC (combustion chamber volume).



This is correct. I might add that I have found that compression guages vary greatly due to quality and design. I think most would agree their main use is for immediate comparison between cylinder readings, --and not for comparing pressure readings between different gauges on different engines.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tim ( www.ModelTengine.com ) on Sunday, January 04, 2009 - 11:45 pm:

The engine that came in my car was done in 1976 by a very competent gentleman in Maine. I couldn't get more than 35mph out of it downhill with a tail wind. I drove it for a year or so before two triple gears (that seized to the pins) cut deep grooves in the flywheel, and the drum cracked. Going on tours with other T's was interesting, I put everyone behind me down in low gear on the slightest hills, very embarrassing. Adding that head was a good thing.

And David, if it was not said already, you have a 28 there, with 1.5:1 rocker arms - this takes a stock lift cam from .250 up to .375" lift at the valve, or .420 with a 280 cam.

It makes a big difference, and the conversion is well worth the effort if you ask me so GO FOR IT!

But - make sure everything else can take the boost, balance and alignment is key. Check this out if you have not already: http://clubs.hemmings.com/frameset.cfm?club=mtfctulsa look under technical, then transmission alignment


Top of pagePrevious messageNext messageBottom of page Link to this message  By HEYWOOD U JUSTDROPIT on Monday, January 05, 2009 - 01:13 am:

Tim you need to realize no matter what you say you will always have mr know it all brent model A man and seth have a hissy fit and leave the club harback pouncing on everything you say.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank Harris on Monday, January 05, 2009 - 01:27 am:

The Oldsmobile heads were four port making it unnecessary for a two up two down crank shaft. You can still find them so don't put a Chevy head on a Ford, go with the old Olds if you want to get it on. .


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Tomaso on Monday, January 05, 2009 - 11:20 am:

Why not just step up to the plate and purchase a bolt-on overhead like a Fronty or Rajo ? Obviousily not cheap but not near as hokey-pokey as the Olds or Chev. head. I recently did a conversion to a Chev. overhead for a fellow and it was the last one I'd do. I have a couple Rajo's and I'm sticking with them.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Fred Houston on Monday, January 05, 2009 - 11:52 am:

Steve, Rajo's and Fronty's are hard to find these days and getting very expensive. The Chevy or Olds makes a good alternative Speedster engine, especily with a Model A crank.

Frank, My Olds has only 3 exhaust ports?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim in Indiana on Monday, January 05, 2009 - 02:39 pm:

Computer illiterate me is going to attempt to upload an attachment.This should be the remains of a '28 Chevy in junkyard near me.Engine has no manifolds.The whole car,such as it is is available.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim in Indiana on Monday, January 05, 2009 - 03:01 pm:

Well,that did not work.I attempted to resize the picture but for reasons beyond my understanding,it will not post.I have a bunch of pictures from a friends junkyard here in north central Indiana.The oldest car is a '28 Chevy 2dr in extremely rough shape.No body parts forward of the cowl.All body parts aft of the cowl detatched and on ground,naturally.Disc wheels,rims probably no good.If anyone wants all or part of this,email me or post,I'll give you Freds' phone number.There is at the very least 500 cars there.He does not crush.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim in Indiana on Monday, January 05, 2009 - 03:19 pm:

I should mention that if someone does want info on the above old Chevy,I will be away at least until tomorrow evening.Now,if I can just get this woman and her 75lb. overnight bag out of here....


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Todd on Monday, January 05, 2009 - 04:44 pm:

Mr. "HEYWOOD U JUSTDROPIT", whoever you may be, you're entitled to your opinionn. But, IF YOU CAN'T SAY ANYTHING NICE, DON'T SAY ANYTHING AT ALL.
This forum doesn't need jerks like you agitating and stirring up hate and discontent.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Stan Howe on Monday, January 05, 2009 - 05:27 pm:

John Steele in Manhattan, Montana just bought three 28 Chevy engines. He would probably sell them. I had a beautiful one stored at a friend's place and after he dies his sons gave away a whole bunch of my stuff. It was just junk to them. Anyway, Chevy and Olds heads are available.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Brent in 10-uh-C on Tuesday, January 06, 2009 - 11:48 am:


quote:

Tim you need to realize no matter what you say you will always have mr know it all brent model A man and seth have a hissy fit and leave the club harback pouncing on everything you say.




How funny!!

If Tim can make 100 horsepower out of his engine, ...that's great. I just know that I couldn't even get close with a Model A engine using that same head and a bigger cam. I guess that means I sure don't know it all huh!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Tuesday, January 06, 2009 - 02:07 pm:

Fred said, "Rajo's and Fronty's are hard to find these days and getting very expensive. The Chevy or Olds makes a good alternative Speedster engine, especially with a Model A crank."

Why not just go with the Chevy block, crank and rods under that fancy head, Fred, and be done with it much sooner and at much less cost? Tall pistons will give plenty high CR for power.

rdr


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tim ( www.ModelTengine.com ) on Tuesday, January 06, 2009 - 02:11 pm:

Brent If you have a dyno, extra money, and the ambition, feel free to duplicate what I have here. I'll help you make it match mine exactly, right down to carburetor innards for an apple to apple comparison. I would love to see the real numbers. It would make a great story for the speed guys. I'll even write the article for you and get it published if you want.


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Dare on Tuesday, January 06, 2009 - 05:20 pm:

WOW !!!! thanks for the confirmation on the head and the addittional details, why does the 1.5 ratio on the rockers make the difference, does it allow the valve to move lower into the head with the right cam, not sure why can you explain.
Cheers David Dare


Top of pagePrevious messageNext messageBottom of page Link to this message  By Brent in 10-uh-C on Tuesday, January 06, 2009 - 08:36 pm:


quote:

Brent If you have a dyno, extra money, and the ambition, feel free to duplicate what I have here. I'll help you make it match mine exactly, right down to carburetor innards for an apple to apple comparison. I would love to see the real numbers. It would make a great story for the speed guys. I'll even write the article for you and get it published if you want.




Hey Tim, while I appreciate your offer, I believe I will pass as you are correct, I don't have the ambition. Since you stated you would like to see the real numbers, might I make the suggestion that you do like we do on many of our customer's vehicles and put your Sedan on a chassis dyno. The fee to do this is quite reasonable in my mind.

We do this as a way during the winter-time when the roads are not condusive to taking a freshly restored vehicle out to test drive it. We can tune the carburetor, set the float level, adjust/tweak timing, etc. while listening for any foreign noises in the transmission or rear end. When we are done, we know when the car is shipped back to the customer and it is unloaded off of the transporter, it will perform as it should.

I would think this same set-up would be a great selling point for your engines. To be able to advertise a proven horsepower of what your engines make would be great when some tout numbers that are just guesses. Then when your customer receives his rebuilt engine from you, he knows it should match the numbers of what yours did if he ordered it correctly, --and if he has any doubts he can take it to a local chassis dynoshop and they can prove it to him. If you see the advantage like we do, I would imagine there is one in a reasonable driving distance from your shop. Good luck.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth Harbuck on Tuesday, January 06, 2009 - 10:34 pm:

A 178 cubic inch four cylinder four-stroke engine making 20 hp at 1,600 rpm has a brake mean effective pressure (BMEP) of 55.6 psi. This is a stock T engine.

For that same engine to make 100 horsepower at 3000 rpm, its BMEP would have to rise to 148.2 psi (2.67 times as much).

In my educated opinion there is no dang way that replacing the head with one from a 1928 Chevrolet is going to make that happen without it inhaling a whole lot of nitrous oxide or air that is more like 40% instead of 20.8% oxygen.

A modern Mopar 5.7 liter Hemi V-8 makes 345 horsepower at some 5,200 rpm - that's 150 psi. There's no way some "tractor" head from the 20's is going to achieve that kind of BMEP.

My guess (again, educated) is that BMEP might rise to 80 psi and it will produce 54 horsepower at that 3000 rpm.

I have no dynomometers like Brent does but I agree with everything he is saying.

No headache here, Tim!

Seth


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tim ( www.ModelTengine.com ) on Wednesday, January 07, 2009 - 09:31 am:

I don't have access to a dyno. I thought about it before putting the engine in the car, but I could not find one available locally. I almost bought one last year and the deal fell through. The chassis dyno is a good idea, but there are two problems. First, who can say what the driveline loss in MY car is, or what it is in your car. So it would still be only a guess what the engine is actually putting out. And then there is the other problem:

And the salt that goes with it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Wednesday, January 07, 2009 - 10:08 am:

That's an excuse, Tim. . Think about it: the first part of the Real World Dyno setup is to record the driftdown/slowdown rate of your own car, which takes in account the driveline loss. That takes your car out of the equation. The customer could do his own driftdown measurements.

I could make a spreadsheet template, where you just plug in your own numbers, and it draws the graphs, but so far, nobody has offered to pay me. Besides that, by the time I'd sold a few, somebody would be giving them away to their buddies, or selling them cheap on Tbay.

Well, really, I would just as soon make the template and give them away myself, but I do have other things to do.

rdr


Top of pagePrevious messageNext messageBottom of page Link to this message  By George on Wednesday, January 07, 2009 - 11:47 am:

If the debate on horsepower is to continue....would one of the more informed tend to advise the rest of us as to apples to apples comparison on HP rating?

The FORD 20/22.5 rating is an old archaeic standard that is almost meaningless today. There are a zillion ways to define HP today, and yep, a flywheel dyno is the only tried and true unless you do something as Ralph suggests. I get the feeling what shows above is all of the modern ways to determine HP...but using the modern analytical ways...what WAS the starting HP with a stock stock unit? The 22.5HP was based on a a formula that called for a 'square' stroke x bore and was actually meaningless in all other areas.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Wednesday, January 07, 2009 - 12:33 pm:

Here's what I wrote some on this Forum back in '00, and I don't believe it was refuted - even by the Brits:
-----
Automobile engine horsepower quoted before maybe 1930 was not brake horsepower (bhp) as measured on a dynamometer, but a calculated number. . Following is from my "Brookes Automobile Handbook", @1919:

"The actual horsepower of an engine can only be determined by making a test with suitable brakes or dynamometers. This method would give the actual brake horsepower. In order to allow ready calculation, the Society of Automobile Engineers' formula is used and is generally recognized. The bore or diameter of the cylinder is first squared; that is, the size in inches is multiplied by itself. This number is then multiplied by the number of cylinders and the result divided by 2 1/2. Thus, for an engine with 5-inch bore: 5x5=25. If of 4 cylinders, 25x4=100, and 100 divided by 2 1/2 gives the result as 40 horsepower. In order to secure approximately correct results, the engine is supposed to be operating at 1,000 feet per minute piston speed."

The table accompanying this paragraph shows for a (Model T) bore of 3 3/4" and 4 cyl, a horsepower of 22.5. Wasn't that the
original spec for the early T? 1000 feet per min. piston speed for a 4" stroke, if you assume speed at mid-stroke is 955 rpm.

In other words, piston stroke, compression ratio, etc., were not considered in horsepower calculations. . This is probably another quaint
calculation we inherited from the Brits, and I believe it became known as Taxable Horspower. . That's the explanation for the small bore and long stroke of engines in English cars in past years.
rdr


Top of pagePrevious messageNext messageBottom of page Link to this message  By George on Wednesday, January 07, 2009 - 01:01 pm:

Thanks Ralph.

Yeah, the original computations were a simple plug n play that had no real meaning to actual developed HP. We originally inherited the Brit way since they were the first to write it down :-)

The Brit formula was arrived at for taxation purposes and there was a quaint fluke in it...the assumption that engine designs were all 'square'. The Brits never did catch on or apparently care, but as engines evolved, it was simply the bore that went into the claculation for taxation rated HP and the stroke was there for the taking :-)

I do also have another question. Somewhere a long time ago, I believe I read that those ancient other formulas for calculating automotive HP were all based on exactly 1000 RPM in order to have 'fairness' in developed HP claims. They didn't yet comprehend the torque/HP overlap curves that we know today. Just can't put my fingers on it now...ergo part of the original question.

As long as the math before and after is done on the same basis, it really doesn't matter much what the actual resultant number is...there is then some sort of level playing field.

I still get a kick out of the present day newbie motorheads who go to the store and buy an air cleaner claimed to give 5HP more, other little goodies, etc...and then find that the car may look good, but doesn't behave all that different!

What most fail to realize is that it takes a heck of a lotta horses to make any difference at all. Like my own brother who has a later Northstar than me and is absolutely convinced the meager HP rating difference makes a bigger difference when the rubber meets the road...I don't challenge it, he weighs a bunch more than me anyway so it wouldn't be fair :-)

Your 'windage and friction' approach is a true test of where the rubber meets the road :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth Harbuck on Wednesday, January 07, 2009 - 02:08 pm:

Dyno tests by the Model T Club of Tulsa indicate that the stock T engine did indeed produce 20 horsepower at 1600 rpm. Check out their website for more information.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ricks - Surf City on Wednesday, January 07, 2009 - 03:14 pm:

The SAE hp calculated for the T is 22.5, as above.

The SAE hp calculated for the Chevy is 21.7, due to slightly smaller bore. . It just happens to be the same stroke.


Top of pagePrevious messageNext messageBottom of page Link to this message  By George on Wednesday, January 07, 2009 - 06:20 pm:

OK, thanks all for that refresher...

Ralph, the original british taxable HP formula is

((bore squared) times number of cylinders)divided by 2.5 ) Amazingly, it equals the same as SAE HP...probably just by happenstance.


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