All Small Six 68 small log head porting
- Thread starter clochard68
- Start date
This relates to all small sixes
Hello 78,
I finished porting the head and opnening up the intake, I will post pictures soon.
Right now I just wanted to check how much milling would be OK since the head will be in the machine shop by tomorrow.
If only the octane level is the limiting factor, I will shoot for a compression between 9.5:1 and 10:1. Thank you all for your help!
I finished porting the head and opnening up the intake, I will post pictures soon.
Right now I just wanted to check how much milling would be OK since the head will be in the machine shop by tomorrow.
If only the octane level is the limiting factor, I will shoot for a compression between 9.5:1 and 10:1. Thank you all for your help!
My stupid mistake. I didn't read the whole thread from the start. I won't do that again.
Your engine should run great with the head work and a Weber carb
You should see a big power increase over a 68 engine with a stock carb size.
I once found that with the same Autolite 1100 size carb the small log head (65) had more power than a large log with the same 1100 type carb adapted to it. (I put the 1100 carb on the large log head because of the throttle linkage fit.)
The engine was a 65 200 with flat top pistons.
The 65 200 with the 78 large log head that I put on it ran smoother though and didn't ping.
Once I switched the large log head to a larger (about 200 CFM) Carter YFA carb. the power increased greatly over the Autolite 1100 size carb on either head.
I now have a 78 200 with dished pistons. The 78 head milled is milled .060.
I don't have any ping problems with the cheapest gas.
Your engine should run great with the head work and a Weber carb
You should see a big power increase over a 68 engine with a stock carb size.
I once found that with the same Autolite 1100 size carb the small log head (65) had more power than a large log with the same 1100 type carb adapted to it. (I put the 1100 carb on the large log head because of the throttle linkage fit.)
The engine was a 65 200 with flat top pistons.
The 65 200 with the 78 large log head that I put on it ran smoother though and didn't ping.
Once I switched the large log head to a larger (about 200 CFM) Carter YFA carb. the power increased greatly over the Autolite 1100 size carb on either head.
I now have a 78 200 with dished pistons. The 78 head milled is milled .060.
I don't have any ping problems with the cheapest gas.
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Head gaskets will not be a problem normally aspirated; it is when you boost it and and detonate it that problems happen.
Never use a gasket for any porting...Should have been apparent that there was a divot behind that bump..who ever started the gasket port matching should have his porting license taken away.
So I made a little comparison here, just to summarize the infos a bit. I assumed the deck height with 0.019” (standard, like my block) and the compressed head gasket thickness conservatively with 0.045” (like a Mahle gasket, I will use one). The following calculations are vaguely accurate, they are just to have something to compare and talk about:
cr-bobcat once wrote in a post that his m code C9 (=1969) head went with a shave of 0.070” from 60cc/61cc to 48cc (with a little more proud valves a minus of 12cc).
The calculated static compression ratio with dished pistons (7cc) is 9.23:1 .
78_200_C4 milled his 78 large log head (~62cc) and shaved it 0.060”. Assuming that the milling landed the combustion chamber in the range of 52cc (minus 10cc, linear approach like in the example above).
The calculated static compression ratio with FLAT TOP pistons is 9.63:1 . No ping and runs with cheapest gas.
I plan to get my head to at least 44cc chamber volume (minus 9cc, shave 0.053”), that would result in a compression ratio of 9.75:1. A chamber volume of 42 (minus 11cc, shave 0.064”) would result in 10.06:1.
One thing I also read is that wsa111 wrote on a thread on cranking compression that for a higher compression a cam with a later closing point is needed to bleed off some of the compression à I have a stock cam with a short duration on both intake and exhaust, would that be a problem?
cr-bobcat once wrote in a post that his m code C9 (=1969) head went with a shave of 0.070” from 60cc/61cc to 48cc (with a little more proud valves a minus of 12cc).
The calculated static compression ratio with dished pistons (7cc) is 9.23:1 .
78_200_C4 milled his 78 large log head (~62cc) and shaved it 0.060”. Assuming that the milling landed the combustion chamber in the range of 52cc (minus 10cc, linear approach like in the example above).
The calculated static compression ratio with FLAT TOP pistons is 9.63:1 . No ping and runs with cheapest gas.
I plan to get my head to at least 44cc chamber volume (minus 9cc, shave 0.053”), that would result in a compression ratio of 9.75:1. A chamber volume of 42 (minus 11cc, shave 0.064”) would result in 10.06:1.
One thing I also read is that wsa111 wrote on a thread on cranking compression that for a higher compression a cam with a later closing point is needed to bleed off some of the compression à I have a stock cam with a short duration on both intake and exhaust, would that be a problem?
The botched head exhaust port was found in the photo collection of the guy that made the 2V conversion with a cutoff wheel.
I didn't port my large log head except the intake bore because I figured I could easily screw it up.
I also found a photo where it looks like he may have botched a 2V conversion with a large cutoff wheel.
Maybe he just wasn't finished?
I didn't port my large log head except the intake bore because I figured I could easily screw it up.
I also found a photo where it looks like he may have botched a 2V conversion with a large cutoff wheel.
Maybe he just wasn't finished?
Edit:
A Slivolite catalog claims a 2.220” dia. head recess .085” deep. If this is correct:
Using an online calculator and if I didn't make a mistake the following would be the dish volume on my 78 pistons.
.32901428622148 cubic inches
5.3915781652 CC's
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Ok, that changes things a little
With a dish in the piston of 5.39cc and a chamber of 52cc the static compression ratio would be 8.95:1 , that would go well with pump gas as you said I guess.
@wsa111 could you help me out with my question about your statement on cranking compression that "for higher compression a cam with a later closing point is needed to bleed off some of the compression"
I have a stock cam with a short duration on both intake and exhaust (advertised 240/240), would that be a problem? Is a longer duration needed for a compression ratio above 9.5:1 ?
Hi clochard68, in answer to your above question a tighter Quench Distance helps in preventing Detention and will therefore let you run a slightly higher C. R. Generally this ideal Quench Distance is in the .035 to .050 range, in this case less is better with some even going with a Q. D. as tight as .030, as an example a stock 200 six with a Std. Bore has a Piston with a 1.511 Compression Height this sets piston top .019 below the block deck and with a stock steel shim head gasket of .022 we have a pretty good Quench Distance of .041. With today’s thicker comp. head gasket the Q. D. Is much more.
I don't have a ping problem on cheapest gas.
I have read that dished pistons lower the compression .9.
The 5cc I gave you could be wrong or the .9 could be wrong.
Look up dynamic compression ratio or effective compression ratio
Dynamic Compression Ratio Calculator
fordsix.com
I have read that dished pistons lower the compression .9.
The 5cc I gave you could be wrong or the .9 could be wrong.
Look up dynamic compression ratio or effective compression ratio
Dynamic Compression Ratio Calculator
Effective Compression Calculations
Effective Compression Calculations: Installment One
Here is a little info which will perhaps help you if you are into reading camshafts rather than tea leaves or hops. It covers what happens to the pressure in the cylinder when you wind up the camshaft duration. These are some tables which I have compiled which are based on the calculations used...
fordsix.com
I didn't mean to imply you have ping, I meant if you have dished pistons and therefore your static compression ratio is below 9:1 (if I calculate either with 5cc or your suggested 0.9 ratio, you are below 9:1) it is logical you don't have ping. I am asking for static compression ratios above 9.5:1, where knock/ping is a possibility.
Thank you for the link, that thread from xctasy is basically everything I was looking for (some numbers for orientation! Thanks again!!
Thank you for the link, that thread from xctasy is basically everything I was looking for (some numbers for orientation! Thanks again!!
I didn't think you implied anything but wasn't sure what I meant.
Long cam duration can lower the dynamic compression which would reduce pinging.
It's the actual compression with the valves closed.
I have read that some old short duration mileage cams increased the dynamic compression + resulted in pinging.
Long duration cams would have the opposite effect.
Maybe someone here has run 9.5 compression with a earlier shorter duration cam. I think they were 246 degrees.
My cam is a stock Enginetech 256 cam that came installed in large log head sixes.
If you do a "Xctasy" search at the Fordsix archive you can read a lot of interesting stuff. I have saved some of in text files.
FordSix Performance Forum - Index page
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Read this thread about quench/squish.
All octane ratings in it are US
fordsix.com
If you are measuring and going for high comp ratios you need about 35 to 40 thou squish. Only way with a 45/50 thou thick head gasket is to have the pistons pop out of the deck where they are matching the squish/quench pads on the head.(rather than a thin squish ring around the edge of a dished piston(like a ford 250 piston)..)
Some pistons(not ford 6) have a D shaped bowl /dish. So the 'straight' part of the D is matching the squish/quench pads on the head for max squish/quench effect.
All octane ratings in it are US
New 200 build is running!
Hi all- Just did an intro over on the other page,and thought I'd let you know what I've been up to. I have a '60 Falcon 2 dr HT with 144/3 spd manual. Too slow for me,so I built a 200. I work in an engine shop,so all machine work was done by me. I used 6cc cast pistons (.040"),decked the...
fordsix.com
If you are measuring and going for high comp ratios you need about 35 to 40 thou squish. Only way with a 45/50 thou thick head gasket is to have the pistons pop out of the deck where they are matching the squish/quench pads on the head.(rather than a thin squish ring around the edge of a dished piston(like a ford 250 piston)..)
Some pistons(not ford 6) have a D shaped bowl /dish. So the 'straight' part of the D is matching the squish/quench pads on the head for max squish/quench effect.
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My opinion with a cast iron head is 10:1 is too much. 9.5 max with good fuel
would be ok for normal driver to leave a bit in reserve.
Disclaimer: i'm no ford 6 tuner....but we are talking 50/60 year old chamber shapes /designs, cast iron heads, carb controlled fuel ratios and distributor ignition.
Generally an alloy head over a cast iron is safe for 0.5 extra comp ratio
would be ok for normal driver to leave a bit in reserve.
Disclaimer: i'm no ford 6 tuner....but we are talking 50/60 year old chamber shapes /designs, cast iron heads, carb controlled fuel ratios and distributor ignition.
Generally an alloy head over a cast iron is safe for 0.5 extra comp ratio
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Hello gb500,
That build thread you posted is also very interesting.
I gave the high compression thing more thought and decided against it for my engine at the moment. I honestly believe that high compression can be made to work, but I have not enough experience and knowledge about what needs to be done to make it work... man gotta know his limitations haha.
I am planning on upgrading the camshaft next year, so maybe then I will try a little more compression ratio, have to do more research
For now I decided to only shave it 0.035". That should get my chamber from 53.5cc to a final 47.5cc and a static compression ratio of 9.29:1 .
I will definitely use high octane fuel (I only drive my mustang for fun on the weekends) to be safe with pinging.
I will post pictures as soon as I get the head back.
and regarding this link - i was referring to on ANY build to set up your quench/squish correctly at 35- 40thou.- ok dont need to be extreme squish and Comp as Falcon 60 was - and his machining was free and knew what he was doing -.machining and tuning -but he details how it helps his engine run well at high comp ratios he was using
if i read your post number 65, above ,you will have 65 thou squish . (19thou piston in the deck plus 45 thou gasket) but you are concentrating on the overall comp ratio
fordsix.com
if i read your post number 65, above ,you will have 65 thou squish . (19thou piston in the deck plus 45 thou gasket) but you are concentrating on the overall comp ratio
New 200 build is running!
Hi all- Just did an intro over on the other page,and thought I'd let you know what I've been up to. I have a '60 Falcon 2 dr HT with 144/3 spd manual. Too slow for me,so I built a 200. I work in an engine shop,so all machine work was done by me. I used 6cc cast pistons (.040"),decked the...
fordsix.com
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Yes this is correct, my squish height should be 0.065".and regarding this link - i was referring to on ANY build to set up your quench/squish correctly at 35- 40thou.- ok dont need to be extreme squish and Comp as Falcon 60 was - and his machining was free and knew what he was doing -.machining and tuning -but he details how it helps his engine run well at high comp ratios he was using
if i read your post number 65, above ,you will have 65 thou squish . (19thou piston in the deck plus 45 thou gasket) but you are concentrating on the overall comp ratio
New 200 build is running!
Hi all- Just did an intro over on the other page,and thought I'd let you know what I've been up to. I have a '60 Falcon 2 dr HT with 144/3 spd manual. Too slow for me,so I built a 200. I work in an engine shop,so all machine work was done by me. I used 6cc cast pistons (.040"),decked the...
At the moment I have no possibility to deck the block, so I have to work with that deck height. But thank you for the clarification.
Regards, Martin
see if you can track down a 25?thou steel head gasket . they are out there but rare!
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I was already looking for one of those but with no luck. I will try the “wanted” forum…
Or does somebody know a manufacturer that could reproduce one?
Or does somebody know a manufacturer that could reproduce one?
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