Click Here -> Please Consider Making a PayPal Contribution to the FordSix Forum!
2019 Contributors:
NJwpod, 1strodeo, mightynorseman, maxtrux, 6d7coupe, broncr, Phase3, 68Flareside240, bmbm40, mustang6, WorldChampGramp, justintendo, BigBlue94, ags290, motorsickle1130, Rooster, ousooner919, ethanperry, rzcrisis, DoctorC, jamyers, Motorboy, fastpat, Silverback280, chad, drag-200stang, THE FRENCHTOWN FLYER, Jimmys61falcon, rjonah, Sooshi, Robert92867, Invectivus


PLEASE TEST ON http://dev.fordsix.com

<<<***PLEASE READ*** New Site Update >>>

Compression Ratio Woes

Moderator: Mod Squad

User avatar
StarDiero75
Registered User
Posts: 982
Joined: Tue Jun 13, 2017 9:39 pm
Location: Bremerton, WA

Compression Ratio Woes

Post #1 by StarDiero75 » Tue Oct 29, 2019 2:17 am

Howdy guys,

So my 2V 1980 head just finished at the shop. It's got the VI port flow stainless valves, 1973 302 exhaust valve springs, new hardened seats, new guides, new seals, larger exhaust valve to 1.5", and he gave a light pass on the exhaust port side as well as took off .010" on the chamber side. I didn't want him to cut the chamber side till I got it back so I could CC it but it't too late now.

After running my calculations, I'm assuming stock bore/stroke/piston/deck height b/c I have no idea until I take the head off the car, I'm running a 8.789 comp ratio with a 50cc head. That's terrible. I'm planning on running at least in the 9's as it will compliment my 256H Schneider cam nicely. Here are my calculations: (all in inches and inches^3)

bore=3.68;
stroke=3.126;
gasBore=3.81;
gasThick=.044; Victor
chamber=16.387^-1*50; conversion from cc to in^3
piston=16.387^-1*6.5; conversion from cc to in^3
deck=.030;

cylinder=pi/4*bore^2*stroke;
gasVol=pi/4*gasBore^2*gasThick;
heightVol=pi/4*bore^2*deck;

VTDC=gasVol+heightVol+piston+chamber;
VBDC=VTDC+cylinder;

CompRatio=VBDC/VTDC

=8.789

The only way to get it where I want it looks like I need a FOMOCO gasket with a crush and bore of .024" and 3.75", respectively. With that gasket it gets me to 9.246, but I still have to shave the head to 50cc. Which I can live with. With this setup and my Schneider 256H cam, I'll have a 8.39 DCR. I think this will be alright with 92 octane, but what do you all think? Is 8.39 too high for a DD on 92 octane without worrying about heating issues or anything? If I change the chamber to 52cc, it puts me in the 9:1 SCR and 8.17 DCR. What is my best choice here?

I guess my final question now is, does anyone know of where I can get or have an old 200 FOMOCO gasket?

Thanks,
Ryan
--1965 Ranchero w/1966 200, dual friction diaphram 9" Modern Driveline clutch and billet flywheel all balanced, 1985 SVO WC T5 with front shift, 1966 2.8 Ford 8", 2V converted built 1980 head, Autolite 2100 1.08, Dual out VI headers, Custom curved DUI, 256H Schneider cam 2.5 degrees advanced with dual roller chain, 2" exhaust with H pipe and Flowmaster 40s
--Creator of the only Weber 32/36 conversion video

User avatar
chad
Registered User
Posts: 5492
Joined: Sat Oct 24, 2009 9:51 am
Location: Lawrence Swamp, S. Amherst, MA

Compression Ratio calc & machining

Post #2 by chad » Tue Oct 29, 2019 9:35 am

"..get or have an old 200 FOMOCO gasket?"
by chance on flee-bay, they do come up.
OR
custom...
but let's wait till a lill further on the initial Qs U just posted...
"Big thing is only make one change at a time. Change 2 or more things at a time it becomes difficult to figure which change helped or hurt" turbo2256b » 1/16/2017
Chad - '70 LUEB on '77 frame (i.e. PS, D44, trapezoidal BB 9", 4.11), '69 250ci, NV 3550 & DSII, "T" D20/PTO, 2" SL, 1" BL, 4 discs, 33"X15", tool boxes, etc. Seeking: Hydraulic gear motor for Koenig pto. chrlsful@aol.com

User avatar
cr_bobcat
Registered User
Posts: 710
Joined: Sat Sep 21, 2013 8:13 am
Location: Cedar Rapids, IA

Re: Compression Ratio Woes

Post #3 by cr_bobcat » Tue Oct 29, 2019 10:57 am

Good luck getting the old steel shim gaskets. They are not easily found and are a limited commodity. I have a 0.035" FoMoCo gasket. I've bought a few more of the valve grind gaskets I bought to get this one, but they've all ended up being thicker (0.045"-0.050" range). They can be found, but it's going to start getting harder and harder to acquire.
Block: Stock C8 Block/pistons, C9-M head, 1.75/1.5 valves, dual spring, 1.65 RAU Rockers, port divider, direct mount Holley 4412-500, HEI w/20* advance, manifold vac, dual-out Arvinode exhaust, Clay Smith 264/274 110* installed w/ 4* advance, adjustable dual chain timing, C4 w/ shift kit, 3.20 (TBC) rear ratio, 9.44 SCR / 7.97 DCR

Build that Six with parts from http://www.vintageinlines.com

User avatar
powerband
FSP Moderator
Posts: 2082
Joined: Fri Nov 08, 2002 6:45 pm
Location: Mid Hudson Valley - \H/

Re: Compression Ratio Woes

Post #4 by powerband » Tue Oct 29, 2019 3:58 pm

Steel shim gaskets for 3.50" 144/170 bore are fairly available and often sold as suitable for 200/250. The 3.68 200/250 bore steel shim gaskets (AFAIK) are unobtainable except for rare appearances on Interweb' sales sites.

Original STEEL shim gaskets with 3.50 bore : FELPRO 7915

Image

Image

I run a steel shim gasket with a D7 head cut to 48cc's BUT on a 170 (71 Maverick C9xx block) with the 3.50 bore. With 48cc chambers and steel gasket the 170 is close to 9.5:1 CR. Runs great for @ 10 years on HiTest ...

have fun
" Everything in my garage has a story ..."

User avatar
cr_bobcat
Registered User
Posts: 710
Joined: Sat Sep 21, 2013 8:13 am
Location: Cedar Rapids, IA

Re: Compression Ratio Woes

Post #5 by cr_bobcat » Tue Oct 29, 2019 8:23 pm

Yeah. The smaller bore ones are regularly available. 90% of the time that I think I've found one for the 200, I find out it's the small bore :cry:
Block: Stock C8 Block/pistons, C9-M head, 1.75/1.5 valves, dual spring, 1.65 RAU Rockers, port divider, direct mount Holley 4412-500, HEI w/20* advance, manifold vac, dual-out Arvinode exhaust, Clay Smith 264/274 110* installed w/ 4* advance, adjustable dual chain timing, C4 w/ shift kit, 3.20 (TBC) rear ratio, 9.44 SCR / 7.97 DCR

Build that Six with parts from http://www.vintageinlines.com

User avatar
StarDiero75
Registered User
Posts: 982
Joined: Tue Jun 13, 2017 9:39 pm
Location: Bremerton, WA

Re: Compression Ratio Woes

Post #6 by StarDiero75 » Wed Oct 30, 2019 1:12 am

Howdy again guys,

So i got decent news. I was able to find one of the 1969 FOMOCO gaskets C9. It has a 3.81" bore and it should have a .035" crush. This works if I shave the head to 49cc. This leaves me with a 9.1:1 static and 8.25 dynamic. I think this is a good settlement. THANK YOU EBAY!

Ryan
--1965 Ranchero w/1966 200, dual friction diaphram 9" Modern Driveline clutch and billet flywheel all balanced, 1985 SVO WC T5 with front shift, 1966 2.8 Ford 8", 2V converted built 1980 head, Autolite 2100 1.08, Dual out VI headers, Custom curved DUI, 256H Schneider cam 2.5 degrees advanced with dual roller chain, 2" exhaust with H pipe and Flowmaster 40s
--Creator of the only Weber 32/36 conversion video

User avatar
chad
Registered User
Posts: 5492
Joined: Sat Oct 24, 2009 9:51 am
Location: Lawrence Swamp, S. Amherst, MA

Re: Compression Ratio Woes

Post #7 by chad » Wed Oct 30, 2019 9:08 am

Good Find !
check it close. Unknown entities @ flee-bay.
(arms length purchases)
I'd attempt one if it fit the 250 (got 2 of'em)...
"Big thing is only make one change at a time. Change 2 or more things at a time it becomes difficult to figure which change helped or hurt" turbo2256b » 1/16/2017
Chad - '70 LUEB on '77 frame (i.e. PS, D44, trapezoidal BB 9", 4.11), '69 250ci, NV 3550 & DSII, "T" D20/PTO, 2" SL, 1" BL, 4 discs, 33"X15", tool boxes, etc. Seeking: Hydraulic gear motor for Koenig pto. chrlsful@aol.com

drag-200stang
Registered User
Posts: 1191
Joined: Sun Oct 19, 2003 6:10 pm
Location: Michigan

Re: Compression Ratio Woes

Post #8 by drag-200stang » Wed Oct 30, 2019 9:09 am

Can I ask you how much did it cost? If so how much?
A ford shim should be about .025 or so when compressed...There is a thinner one and a little thicker one, but both are about ..025 or thinner.
66 Mustang Coupe
200 turbo w/lenco 4-spd
stock adj. rockers, stock timing set, ARP studs
best 1/4 mile ET 9.85/best mph 139 on 8 lbs progressing to 15 lbs boost
Went 9's when 10's was fast.

User avatar
StarDiero75
Registered User
Posts: 982
Joined: Tue Jun 13, 2017 9:39 pm
Location: Bremerton, WA

Re: Compression Ratio Woes

Post #9 by StarDiero75 » Wed Oct 30, 2019 3:11 pm

drag-200stang wrote:Can I ask you how much did it cost? If so how much?
A ford shim should be about .025 or so when compressed...There is a thinner one and a little thicker one, but both are about ..025 or thinner.

Yeah it was $30. According to the handbook, Ford had a steel shim which compressed to .025 and they had a composite that compressed to .035. The steel shim is part number D2xxx, the composite is C9xxx. I got the C9. If this compresses to .025 that's great, but I don't believe it is supposed to.

Here's a picture of it. Our site ain't letting me post pictures here anymore so here's a google drive.

https://drive.google.com/file/d/1VDS6ND ... sp=sharing
--1965 Ranchero w/1966 200, dual friction diaphram 9" Modern Driveline clutch and billet flywheel all balanced, 1985 SVO WC T5 with front shift, 1966 2.8 Ford 8", 2V converted built 1980 head, Autolite 2100 1.08, Dual out VI headers, Custom curved DUI, 256H Schneider cam 2.5 degrees advanced with dual roller chain, 2" exhaust with H pipe and Flowmaster 40s
--Creator of the only Weber 32/36 conversion video

drag-200stang
Registered User
Posts: 1191
Joined: Sun Oct 19, 2003 6:10 pm
Location: Michigan

Re: Compression Ratio Woes

Post #10 by drag-200stang » Thu Oct 31, 2019 9:28 am

I thought that you were buying a shim and not a replacement composite gasket, my mistake.
That gasket should be about .035.
66 Mustang Coupe
200 turbo w/lenco 4-spd
stock adj. rockers, stock timing set, ARP studs
best 1/4 mile ET 9.85/best mph 139 on 8 lbs progressing to 15 lbs boost
Went 9's when 10's was fast.

User avatar
StarDiero75
Registered User
Posts: 982
Joined: Tue Jun 13, 2017 9:39 pm
Location: Bremerton, WA

Re: Compression Ratio Woes

Post #11 by StarDiero75 » Thu Oct 31, 2019 6:38 pm

drag-200stang wrote:I thought that you were buying a shim and not a replacement composite gasket, my mistake.
That gasket should be about .035.

I wanted a shim gasket but apparently they are rarer than I thought. I saw this one and figured it was as close as I'm gonna get to what I need. I just gave a call to a special NOS parts place that has helped me out before. I'll let you all know if they have any
--1965 Ranchero w/1966 200, dual friction diaphram 9" Modern Driveline clutch and billet flywheel all balanced, 1985 SVO WC T5 with front shift, 1966 2.8 Ford 8", 2V converted built 1980 head, Autolite 2100 1.08, Dual out VI headers, Custom curved DUI, 256H Schneider cam 2.5 degrees advanced with dual roller chain, 2" exhaust with H pipe and Flowmaster 40s
--Creator of the only Weber 32/36 conversion video

User avatar
cr_bobcat
Registered User
Posts: 710
Joined: Sat Sep 21, 2013 8:13 am
Location: Cedar Rapids, IA

Re: Compression Ratio Woes

Post #12 by cr_bobcat » Wed Nov 13, 2019 11:19 am

Did you happen to measure the thickness of that gasket to confirm that it is an 0.035"?
Block: Stock C8 Block/pistons, C9-M head, 1.75/1.5 valves, dual spring, 1.65 RAU Rockers, port divider, direct mount Holley 4412-500, HEI w/20* advance, manifold vac, dual-out Arvinode exhaust, Clay Smith 264/274 110* installed w/ 4* advance, adjustable dual chain timing, C4 w/ shift kit, 3.20 (TBC) rear ratio, 9.44 SCR / 7.97 DCR

Build that Six with parts from http://www.vintageinlines.com

User avatar
StarDiero75
Registered User
Posts: 982
Joined: Tue Jun 13, 2017 9:39 pm
Location: Bremerton, WA

Re: Compression Ratio Woes

Post #13 by StarDiero75 » Wed Nov 13, 2019 8:30 pm

cr_bobcat wrote:Did you happen to measure the thickness of that gasket to confirm that it is an 0.035"?

No not yet. I need to get a micrometer. It is the same part number as the one that was mentioned in the book. I might borrow one from school.
--1965 Ranchero w/1966 200, dual friction diaphram 9" Modern Driveline clutch and billet flywheel all balanced, 1985 SVO WC T5 with front shift, 1966 2.8 Ford 8", 2V converted built 1980 head, Autolite 2100 1.08, Dual out VI headers, Custom curved DUI, 256H Schneider cam 2.5 degrees advanced with dual roller chain, 2" exhaust with H pipe and Flowmaster 40s
--Creator of the only Weber 32/36 conversion video

User avatar
chad
Registered User
Posts: 5492
Joined: Sat Oct 24, 2009 9:51 am
Location: Lawrence Swamp, S. Amherst, MA

V.Caliper / micromiter

Post #14 by chad » Wed Nov 13, 2019 11:14 pm

geta cheep venier caliper style, save the bx it came in, throw them in ur tool bx @ home.
Use one myself several timesa wk. Lost my micromiter I use it so lill. VC can measure inside, out side,
and depth. Now have'em w/a 100th (or is it 1000?) ona lill dial (not mine), or 1 that is i.finger-operated & all electronic
"Big thing is only make one change at a time. Change 2 or more things at a time it becomes difficult to figure which change helped or hurt" turbo2256b » 1/16/2017
Chad - '70 LUEB on '77 frame (i.e. PS, D44, trapezoidal BB 9", 4.11), '69 250ci, NV 3550 & DSII, "T" D20/PTO, 2" SL, 1" BL, 4 discs, 33"X15", tool boxes, etc. Seeking: Hydraulic gear motor for Koenig pto. chrlsful@aol.com

User avatar
Econoline
Registered User
Posts: 1454
Joined: Tue Nov 12, 2013 8:37 pm
Location: Anacortes, WA

Re: Compression Ratio Woes

Post #15 by Econoline » Thu Nov 14, 2019 12:12 am

Have you pulled the head yet? Measured the deck height and seen what gasket is in there now? Don't put the cart before the horse.
It ain't gonna fix itself

User avatar
StarDiero75
Registered User
Posts: 982
Joined: Tue Jun 13, 2017 9:39 pm
Location: Bremerton, WA

Re: Compression Ratio Woes

Post #16 by StarDiero75 » Thu Nov 14, 2019 2:26 pm

Econoline wrote:Have you pulled the head yet? Measured the deck height and seen what gasket is in there now? Don't put the cart before the horse.

No i haven't yanked my head b/c its my daily. I need to have everything ready to swap it in before I do anything.
Yes after measuring everything when I yank my head and putting all the measurements into my program, I'll know exactly what kind of compression ratio to expect. Currently I'm assuming everythjng is stock measurements to get a rough idea, but I will be measuring everything when the head does come off.

That will likely go on about April time during spring break
--1965 Ranchero w/1966 200, dual friction diaphram 9" Modern Driveline clutch and billet flywheel all balanced, 1985 SVO WC T5 with front shift, 1966 2.8 Ford 8", 2V converted built 1980 head, Autolite 2100 1.08, Dual out VI headers, Custom curved DUI, 256H Schneider cam 2.5 degrees advanced with dual roller chain, 2" exhaust with H pipe and Flowmaster 40s
--Creator of the only Weber 32/36 conversion video

User avatar
chad
Registered User
Posts: 5492
Joined: Sat Oct 24, 2009 9:51 am
Location: Lawrence Swamp, S. Amherst, MA

Compression Ratio Woes

Post #17 by chad » Thu Nov 14, 2019 8:16 pm

Better get the Stud going, then
"Big thing is only make one change at a time. Change 2 or more things at a time it becomes difficult to figure which change helped or hurt" turbo2256b » 1/16/2017
Chad - '70 LUEB on '77 frame (i.e. PS, D44, trapezoidal BB 9", 4.11), '69 250ci, NV 3550 & DSII, "T" D20/PTO, 2" SL, 1" BL, 4 discs, 33"X15", tool boxes, etc. Seeking: Hydraulic gear motor for Koenig pto. chrlsful@aol.com

Who is online

Users browsing this forum: No registered users and 25 guests