All Small Six Wrong Head?

[fritschn]

Hello,

I have a few questions. I have a ’66 Mustang with a 200 cui engine. Someone installed a ’78 block and a ’66 head. Now, I was lucky enough to get a ’69 M head. Currently, the compression should be way too high, right?

Apologies if this is a dumb question, but if I want to install the 250 cui head, do I need to have anything machined off? Originally, the ones from ’77 onwards also had 62 cc, is that correct?

Regards
Chris

 

[powerband]

NOT dumb questions..
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... current compression ratio will depend on whether the '66 head was milled. Typically also milled with a 'valve job' to ensure flat head sealing surface integrity.
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Also can be milled to compensate for 'modern' thicker composite head gaskets to maintain original compression ratio. Additionally can be milled to raise compression ratio above stock levels.
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Not sure what a '69 M Head compression chambers are supposed to measure OEM, but again depends on if milled already.
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ONLY way to be sure of chamber volume when calculating your target compression ratio with composite gaskets is to measure the chambers first, then calculate milling ... .
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'70's D3xx 250 head with @ 62cc chambers and '71 170 DODE head with @ 54 cc 'Closed Chamber' head.
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have fun
.

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[drag-200stang]

Look at the pic's that pb put up and tell us which one looks like your 69 head.

 

[fritschn]

Thank you for your responses.

I think it should be like the one on the left.

I have attached a photo, even though it is not particularly good.

The head needs an overhaul anyway, and I would also like to convert it to run on unleaded fuel. Additionally, I am considering installing larger exhaust valves and, while I’m at it, having the intake ported—basically, a complete overhaul of the head.

What I was wondering is this: You often read about a ’66 block receiving a ’77 head, with, for example, 0.05” being machined off. But what about the other way around—a newer block with an older head? Is it generally sufficient to just have it resurfaced?

Chris

 

[drag-200stang]

The head in your pic is a 200/250 head which should be about 62cc, and does not look like it has been milled much or at all, but you will have to measure to make sure.
Putting a 66 small log about 54 cc chambers on a 77 short block is like having a 66 engine with the same 9. something comp. ratio. It will run just like a 66.
Most people cut the 77 200/250 .050'' to bring up the compression some because you can only get gaskets that are about .025 thicker than what it came with.

 

[fritschn]

Thanks! Now I understand better, and I’ll take some measurements soon.

You’re right—I completely forgot that the gaskets are thicker now.

Once I get to that point, I’ll be happy to get back to you.

Best regards,
Chris

 

[B RON CO]

Hi, if you have the adjustable rocker arms many guys would keep them. Check any rocker assembly for wear. The kidney shaped oil port on the rear head bolt should be clearanced after milling to improve oil flow to the rocker arms. The machine shop should clean the head and check for cracks before any other work is done. Our heads sometimes crack underneath the center 3 and 4 exhaust area. Intake and exhaust bowl cleanup will help performance. ARP head bolts are really nice. Good luck

 

[fritschn]

Hi,
Unfortunately, I don’t have adjustable rocker arms. I’ve already considered RAU or YellaTerra, but I’m not at that stage yet.

Thanks for the tips! I’ve found a great company that specializes in refurbishing and restoring old cylinder heads. They have an excellent reputation here in Germany, so I think I’ll go with them.
As soon as there’s any news, I’ll let you know.

Thanks again, and best regards,
Chris

 

[awasson]

I have a concern that if you don’t have adjustable rockers, you may need to measure the pushrod length and possibly do something to compensate for the difference in height of the 250 head and the 200 head, especially when shaving the head. It’s not a deal breaker but definitely something to track.

 

[fritschn]

Hi awasson,

Thanks for the hint—I’ll definitely keep an eye on it. Unfortunately, adjustable rocker arms are hard to find here, so I’ll have to see how I can solve that once I get to that point. Either I get lucky and find some, or I’ll go with the ones offered by RU or YellaTerra. Since I’m not in a hurry and want to do things properly, I’d rather take my time. I don’t want to rebuild everything just to start over again.

But while we’re on the topic, which option would you recommend, RAU or YellaTerra? The car won’t be turbocharged or EFI-powered. I was thinking of using either an Autolite 2100 with a 1.08 venturi or a Weber 38/38—both of which I already have. I’m also considering a different camshaft. I already have an eBay header at home, so I’d still need to upgrade to a 2” exhaust system. As I said, I don’t want to build a monster—just something with a bit more power while keeping it reliable.

Best regards,
Chris

 

[awasson]

Hi Chris,
I just noted that you are in Bavaria so yes, I suspect that parts are more difficult to obtain for our engines where you are. If at all possible, I would try to find a set of rockers and push rods from a 1965 or older Ford 200 or 170. They are the adjustable type and they use a rod with a cup at the rocker end and a ball at the lifter end. It may be that someone in the for sale/classified section has something like that.

I don’t know enough about the Yella Terra and RAU rocker arms to make a suggestion. I’m more than certain they do have great rocker arm solutions though and if I do any more performance upgrades on mine, I will probably move to an adjustable rocker of some kind. RAU appear to have the original adjustable rockers from what I can see on their website. You may need to phone them. I have emailed them in the past and never got a response.

I suppose if you can’t find adjustable rockers, you can get an adjustable push rod and find the appropriate length to order the correct sized rods. Maybe someone here with experience will be able to advise on the subject.

I think you have a very good recipe for a dependable and more responsive engine with the header, carb, large log head and camshaft. You will also want to consider what distributor and ignition to use. We have a lot of options. I went with an aftermarket HEI type ignition but many use the Duraspark II and I have read that Bosch makes a very good electronic ignition for our engines (mage in Germany or Spain).

I have the Weber 38/38 on mine with the original 66 small log head and the adapter that reduces the 2v plenum to the small log intake opening. It works remarkably well on mine. If I were using the large log head, I would look into machining the log for the larger opening and fitting the aluminum mounting plate for the carb right on the log. There are some YouTube videos that cover that kind of thing and I know that it has been done successfully by members on this site.

In terms of camshafts, I only have experience with Clay Smith camshafts and lifters and am quite happy with my choice. I chose the H-6474-0-B which appears to be a popular choice for our engines. It has a nice lumpy idle and plenty of response when you accelerate. I would recommend getting adjustable timing gears when you do the camshaft because there is a lot of variance in our engines and you will want to dial in the camshaft as close as possible to the cam card that comes with the cam.

Hopefully that helps a bit.

Cheers,
Andrew

 

[fritschn]

Hey Andrew,

Thanks for your message! Yes, that’s right—I’m from Bavaria. We have a lot of great things here: pretzels, beer, and roast pork. But when it comes to parts for an L6, the supply is pretty scarce. Occasionally, you’ll find a complete engine because most people here believe that the only real option is a V8. Sometimes you get lucky—time is the only thing you really need.

I was just about to check on a 144 cui engine that was recently listed for well 1,000 euros. However, I did come across a 144 cui cylinder head with adjustable rocker arms at an attractive price. If I’m not mistaken, I could also use the intake valves from the 144 head as exhaust valves in the 250 head—at least if they’re in good condition.

Regarding the ignition, I also got myself an HEI small cap. I even have a Bosch ignition coil lying around—I might swap it out. It’s used, but that shouldn’t be an issue.

Thanks for the tip about the Clay Smith camshaft—I’ve added it to my wishlist right away. The timing set with the adjustable gears seems to be out of stock at the moment, so once again, patience is key.

As soon as it’s time to install the camshaft, I’ll get back to you. I watched a video on it, but I didn’t fully understand everything. I guess once I’m actually working on it, it will make more sense… or maybe not.

I also just wanted to say that I really appreciate this community and how helpful everyone is—thank you!

Best regards,
Chris

 

[TrickSix]

Will you get some pushrods with the 144 head? I'm not sure if the adjustable rocker pushrods are still available new. There's only one set on eBay now for almost $200. I don't see used sets for sale very often either. The adjustable rocker assembly does you no good if you can't find the pushrods too.

 

[fritschn]

Hey TrickSix,

Thanks for the heads-up! I immediately messaged the seller to ask about it—let’s see what he says.

200 dollars is pretty steep—that’s more than what the seller is asking for the entire head.

Cheers,
Chris

 

[fritschn]

Hey,

One problem solved, another one found. The seller unfortunately doesn’t have any more push rods.

I reached out to Vintage Inlines and also came across the Melling MPR81. Has anyone here used them? Would they fit?

Cheers,
Chris

 

[awasson]

Hey Chris,
Excellent job on jumping on the 144 head and rocker assembly. I hope you can get those push rods as well.

Regarding the ignition, I've got the small cap HEI with remote coil on mine and I am quite happy with it.

It might be worth calling Clay Smith to ask if they know when they’ll have a set of the adjustable gear timing sets in. I called them when I was dialing in my camshaft to make sure I was close enough to the cam card and they were very responsive and helpful. I don’t know if there are any other retailers who carry the adjustable gear and chain set. The manufacturer is Normandy Automotive and they are in Australia: https://norndaautomotive.com.au/

The surprising thing about swapping in a performance camshaft for me was the amount of extra initial ignition timing my engine requires. For anyone familiar with the engines, it’s not a surprise but for me, it was a little bit of a shock. The stock engine with manual transmission species +6 degrees of initial timing. The engine as it is built now seems to be happiest with around +18 degrees initial. The vacuum advance kicks in when the 38/38 Weber comes onto the main circuit and that is another +10 degrees from my distributor. The centrifugal on this distributor is curved up to +14 degrees which by that point the vacuum advance is nil so all in, it is probably around 32 degrees advance WOT. It seems pretty happy set up like that and it sounds good and makes decent power.

 

[awasson]

Hey,

One problem solved, another one found. The seller unfortunately doesn’t have any more push rods.

I reached out to Vintage Inlines and also came across the Melling MPR81. Has anyone here used them? Would they fit?

Cheers,
Chris

Yes. MPR81 are the correct push rods. They’re pretty hard to find and expensive compared to the non adjustable push rods.

 

[TrickSix]

They are just a hair shorter than the stock ones. But it can be made up for easily with the adjustments. The stock ones do come in two slightly different diameters, so watch out for that in a used batch if you want a balanced set.

 

[bmbm40]

Hey Chris,
Excellent job on jumping on the 144 head and rocker assembly. I hope you can get those push rods as well.

Regarding the ignition, I've got the small cap HEI with remote coil on mine and I am quite happy with it.

It might be worth calling Clay Smith to ask if they know when they’ll have a set of the adjustable gear timing sets in. I called them when I was dialing in my camshaft to make sure I was close enough to the cam card and they were very responsive and helpful. I don’t know if there are any other retailers who carry the adjustable gear and chain set. The manufacturer is Normandy Automotive and they are in Australia: https://norndaautomotive.com.au/

The surprising thing about swapping in a performance camshaft for me was the amount of extra initial ignition timing my engine requires. For anyone familiar with the engines, it’s not a surprise but for me, it was a little bit of a shock. The stock engine with manual transmission species +6 degrees of initial timing. The engine as it is built now seems to be happiest with around +18 degrees initial. The vacuum advance kicks in when the 38/38 Weber comes onto the main circuit and that is another +10 degrees from my distributor. The centrifugal on this distributor is curved up to +14 degrees which by that point the vacuum advance is nil so all in, it is probably around 32 degrees advance WOT. It seems pretty happy set up like that and it sounds good and makes decent power.

Is this the adjustable gear timing sets:

Product ID: JPP-200-DRC Dual Roller Timing Chain Set (170/200ci)

Clay Smith Cams Engineering, home of the famous Mr. Horsepower, the cigar-chomping woodpecker, bringing you world class camshafts, custom cams and lifters.

claysmithcams.com

 

[bmbm40]

Is this the adjustable gear timing sets:

Product ID: JPP-200-DRC Dual Roller Timing Chain Set (170/200ci)

Clay Smith Cams Engineering, home of the famous Mr. Horsepower, the cigar-chomping woodpecker, bringing you world class camshafts, custom cams and lifters.

claysmithcams.com

Available at VI for less:

Dual Roller Timing Chain Set (170/200ci) | Vintage Inlines

These dual roller chain sets feature billet gears with hardened teeth. The crank gear has nine key ways for adjusting cam timing in 2, 4, and 6 degree increments (advance or retard). They offer greater strength and reduced chain stretch over stock chains to maintain accurate cam timing, and...

www.vintageinlines.com