All Small Six Large Log Head Questions

[Mattsmall1972]

Hi all - I am new to this as I just purchased a 1966 Mustang with the 200. I’m doing a mild build. The plan is:

Holley Sniper 1100
HEI distributor
Headers/dual exhaust
Schneider 256-2H cam
Large log head

I have purchased a 1977 large log head from ebay. Assuming it’s stock head, I am looking for milling information.

1) Do I tell the shop the ccs that I need and have them figure it out? If do, what is that number for my build?

2) Are there any recommended machine shops in SC for this work?

3) Are the stock springs and valves sufficient? If not, what’s recommended?

Thank you!

 

[Jmustang_65]

1. Check out the tech archives on here. https://fordsix.com/ci/Tech.html
3. The springs/installed height is going to be based on the cam. In this case the Schneider 256-2H cam card with tell you the seat pressure.

I would get rid of the HEI and get the full Holley hyperspark for the for 200 inline 6 so that you can control timing. You need hyperspark distributor, coil, and cd box.

 

[Mattsmall1972]

1. Check out the tech archives on here. https://fordsix.com/ci/Tech.html
3. The springs/installed height is going to be based on the cam. In this case the Schneider 256-2H cam card with tell you the seat pressure.

I would get rid of the HEI and get the full Holley hyperspark for the for 200 inline 6 so that you can control timing. You need hyperspark distributor, coil, and cd box.

You pushed me over the edge with the timing... I returned my HEI and have ordered the hyperspark.
I'll check with Schnieder on springs and the tech forum for the deck. Thank you!

 

[TrickSix]

Before you can figure out what size to make your combustion chambers, you'll need to measure your deck height. If you're rebuilding the block you can adjust to suit. If you're just swapping heads, after you remove the old one you can check to see what you have. Then that variable goes into the formula with all the others to determine the combustion chamber size for your desired compression ratio. Also, if you didn't get much for history on the engine and any work done on it, check to see if the pistons have a stamp indicating an oversize from a prior rebuild. You'll need the cylinder bore for the compression ratio formula too.

 

[Mattsmall1972]

Before you can figure out what size to make your combustion chambers, you'll need to measure your deck height. If you're rebuilding the block you can adjust to suit. If you're just swapping heads, after you remove the old one you can check to see what you have. Then that variable goes into the formula with all the others to determine the combustion chamber size for your desired compression ratio. Also, if you didn't get much for history on the engine and any work done on it, check to see if the pistons have a stamp indicating an oversize from a prior rebuild. You'll need the cylinder bore for the compression ratio formula too.

Thank you for the information. The engine has been rebuilt in the past and I agree that all of the above needs to be figured out. That said, I have been playing with a compression ratio calculator to get the right numbers for a bone-stock engine with a ratio of 8.7 to use as a baseline of where I would start at stock:




The numbers I am unsure about are dome volume, crush thickness and head cc which seem to be variable for stock figures across forums on the internet. But that said, I will assume they are correct since they get me to the right number and I can control the cc and crush.

Per Jerry at Schneider, I need to get to 9.1+ ratio to meet the 200ish hp that I am looking for. Setting the thickness to a modern Mahle head gasket number of .45 means I have to set head ccs to 43 to get to 9.15:




Now that I have this figured out, I am wondering if I ought to go just one more cc to 42 which results in a 9.27 ratio - this is free hp, isn’t it?

I get the real numbers will be different, but this seems like a starting place to understand what I am looking at. What are your thoughts?

 

[Mattsmall1972]

Not 5 minutes after my previous post I found the dome volume:



This changes my calculations significantly for stock numbers:

I used .050 as the gasket because that seems more correct but still am not sure what the correct number is. Regardless, I am glad I got that figured out because the amount that needed to reduced seemed signifcant. Now my ccs should be 48 to get to 9.2:


I hope it seems right this time.

 

[PSIG]

I returned my HEI and have ordered the hyperspark.

If it's done, that's fine. But just FYI, the Holley box will run controlled timing on VR/magnetic distributors, such as the HEI distributor you had. Or the Ford DuraSpark distributor (new about $40), which BTW are the guts the MSD distributors use. You can run any coil, such as the powerful Ford TFI coil. You'll find the info on options in your Holley manual.

 

[Mattsmall1972]

If it's done, that's fine. But just FYI, the Holley box will run controlled timing on VR/magnetic distributors, such as the HEI distributor you had. Or the Ford DuraSpark distributor (new about $40), which BTW are the guts the MSD distributors use. You can run any coil, such as the powerful Ford TFI coil. You'll find the info on options in your Holley manual.

Thank you for the feedback. I knew that, but the lure of electronically controlled timing was just too much.

 

[DON]

When I selected springs, I got the recommended closed pressure, and open pressure for my particular cam from the manufacturer. There are many charts of springs with pressures online. I ended up using a spring from PAC Racing. They have a neat tool for their springs that you can change the installed height for the given spring and it will give you adjusted pressures. IMO valve job needs to be done first. Also get retainers and locks from the same manufacturer. Different retainers will produce different installed heights. Fifty thousandths makes a difference in pressures. I had to reorder locks with plus 50 to get the pressures right

 

[drag-200stang]

Before you do a lot of planning, a lot of things could have been changed with your engine. It may not be a 66 and the rebuild could have flat top pistons, maybe pull spark plug and look with an adjustable beam flashlight. We had one guy with a 66 Mustang, and it turned out to me a 250.

 

[Kritas]

I bought a cheap endoscope that attaches to my phone. I was able to look at my pistons and into areas of rust, etc. It's a handy thing to have.

https://www.amazon.com/gp/product/B0BR845FSP/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

[pmuller9]

just FYI, the Holley box will run controlled timing on VR/magnetic distributors, such as the HEI distributor you had.

This is for a Holley Sniper.
The problem we see on the inline six is the VR signal has to be routed either over the top of the valve cover or around it to get to the Sniper which is a long run in proximity of the plug wires.
The VR signal is relatively small at low rpm and picks up RFI which corrupts the signal causing the Sniper to malfunction.
The Hall Effect signal is much more reliable.

 

[PSIG]

Thank you for the feedback. I knew that, but the lure of electronically controlled timing was just too much.

If I wasn't clear, the Sniper will electronically control the timing with those other distributors (locked-out advance), as well as the HyperSpark. Signal interference with any sensor type can be an issue if the system components are incorrect or not maintained, and you must use resistor spark plugs, and high-grade suppression plug wires such as quality spiral-core in order to avoid signal interference. Ford has been using spiral from the factory for decades. Grounds are also a common source of voltage offsets or ground loops. It's a yawn if you are diligent, and complaints if you're not. EMI/EMR is a gremlin to avoid in every installation.

 

[Frank]

Hi all - I am new to this as I just purchased a 1966 Mustang with the 200. I’m doing a mild build.
2) Are there any recommended machine shops in SC for this work?

Welcome Mattsmall1972! . If you're looking for a trustworthy machine shop in S.C., I recommend B&T Auto Machine. It's in Beaufort, south east corner of the state. Call (843) 521-1092, ask for Gary. He has close to 50 years experience, and is a nice guy, won't make you feel intimidated. Tell him honestly what you have in mind and he'll make good recommendations, and will be honest whether or not he can do what you need. Tell him Frank with the 240 gave you his #. He likes sixes, and just did the work on my 240 engine- he's pro.

 

[Mattsmall1972]

Reviving this thread…
I sent my large log head to a good shop for a recondition - valve job and mill to 48 ccs. In the meantime I pulled the head and found that my piston is .040 over. I am waiting for my deck gauge to arrive to check the piston to deck clearance. It’s definitely not zeroed out and I can’t find a stamp on the block.

The cylinders appear to be in very good condition with honing marks visible on all walls.

I ordered a NOS head gasket from ebay. Given the .040 over and assuming the deck is still .019, the compression ends up at 9.9. Does that seem high for a NOS gasket or should I consider a new Felpro?

This is contingent on the deck still being .019.

 

[rocklord]

The compression height (CH) of original pistons is 1.511"; aftermarket/replacement pistons CH are 1.50".
The difference was to compensate for milling of the block. If your block hasn't been milled, the deck clearance would be 0.030".
You definitely need to measure the deck clearance.

As for the NOS head gasket, the original was made of steel with a compressed thickness of 0.025".
There are two different NOS steel head gaskets; one to fit the 3.50" bore of the 144/170 and the other to fit the 3.68"bore of the 200/250. If you have a NOS steel head gasket measure the bore diameter to make sure it isn't one for a 144/170.

 

[Mattsmall1972]

I bought a cam degree ing kit and used the dial gauge to measure deck-to-piston clearance. If I did it right, I measured .045 which is very surprising to me. Would replacement pistons be able to explain it? They look exactly like stock pistons that I've seen on the internet.

 

[Frank]

I bought a cam degree ing kit and used the dial gauge to measure deck-to-piston clearance. If I did it right, I measured .045 which is very surprising to me. Would replacement pistons be able to explain it? They look exactly like stock pistons that I've seen on the internet.

As rocklord posted above, replacements have a shorter deck height by .011"- quite a bit. It's difficult to get an accurate read with the dial indictor IME. Knowing true TDC is important. Another alternative is to bolt a flat steel bar to the deck and measure clearance with a feeler gauge.
I got a bigger than true reading using a dial indicator on my recent build. Using the flat angle iron bar bolted to the deck gave me a smaller clearance reading with the feeler gauge, which agreed with the calculations used on the build.

 

[Mattsmall1972]

This is actually great because it made me think that I was very off in my measurement. Assuming that the standard dtp clearance is .030 (as stated above) and knowing that I have replacement pistons which likely lower the piston, I might expect such a number.

When I use .045 in the compression calculator with the rest of my numbers, I end up with 9.32 which is exactly where I want to be. If I am off a little bit - say I am at 0.30 - then I am at 9.67. This range works fine for my build. I think I can run with my NOS valve gasket and have a happy little six about 200ish hp.

 

[rocklord]

When checking clearance, set the gauge at the centerline of the crank. If you measure at the right or left side of the piston, you can get erroneous numbers because the piston can rock in the cylinder.