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compression ratio 1966 289

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Old 02-10-2009, 10:33 AM   #1
kalli
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Default compression ratio 1966 289

Hiya all,

i was wondering. I have a 289 from 1966 and from what I see the CR seems to be 9.81:1 (according to a few sites). as well they mention to have 54cc heads stock. I can't for the life of me find info about piston cc and underdeck clearance. But if I let's say drop in 61cc heads wouldn't that dramatically drop compression to ~9.0:1?
in what way would that affect me? anyone any ideas?
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302ci, Edelbrock RPM heads, xe268h, 650 speed demon, Hooker Long Tube headers and Flowmaster 40s
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Old 02-10-2009, 11:03 AM   #2
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Decreasing CR will lower horsepower some. It is not much, but it is less.

Not sure if you have a 2v or 4v motor, but according to my trusty book, the 289 2v in 1966 had:
200hp@4400
282ft*lbs@2400
9.3:1 CR
52.5-55.6cc Combustion Chamber Volume
.016 Piston to Deck Clearance
1.6 Compression Height Pistons
5.155 Connecting Rods

If you need 4v 289 specs, just holler.

FYI, my trusty book is Ford Performance by Pat Ganahl Published by SA Design. SA Design make a bunch of excellent books. I have a big library of them that are great for reference stuff like this.
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Old 02-10-2009, 12:32 PM   #3
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thanks a million for that. exactly what I neded to know (original 2v)
with that and and 54cc and my current head gasket i calculate 9.55:1
with 61cc heads that will go down to 8.75:1
according to desktop dyno that will be only measly 5%-10% max. since i was asking because of (still maybe) new heads (225hp->300hp at flywheel with my current setup) i needed that for my calculations. cheers for that. very much appreciated. i'd prefer 58cc but could get a deal on 61cc.
I guess that means as well less problems with 92 octane and engine not running as 'loud' in idle. that right?
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1964 1/2
302ci, Edelbrock RPM heads, xe268h, 650 speed demon, Hooker Long Tube headers and Flowmaster 40s
Quick Performance Racing 9" rear, Moser axles, 3.5:1 trac-loc from FRPP and T5 transmission.
CSRP disc brakes front and FRPP discs back.
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Old 02-10-2009, 12:46 PM   #4
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looks like i'm missing a lot of low end torque though
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1964 1/2
302ci, Edelbrock RPM heads, xe268h, 650 speed demon, Hooker Long Tube headers and Flowmaster 40s
Quick Performance Racing 9" rear, Moser axles, 3.5:1 trac-loc from FRPP and T5 transmission.
CSRP disc brakes front and FRPP discs back.
http://www.gascc.ie

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Old 02-10-2009, 12:48 PM   #5
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2V's are better for bottom end torque than 4v's

4v's are better for top end performance than 2v's
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Old 02-10-2009, 12:57 PM   #6
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Lower CR such as 8.8:1 should allow you to run 87 octane with the proper timing. That is close to what every stock 351W EFI was.

What do you mean by missing a lot of low end torque? Compared to what?

Remember that the 289 is not a high stroke motor. 2.87 stroke is pretty small which you look at the 302, 351, or strokers. It will make power at rpm, not down low. If you get some heads that flow well and are not crazy low compression (which high 8s to low 9s is not), the power band is dependent on what cam you choose.
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Old 02-10-2009, 01:22 PM   #7
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i quickly checked my 289 with 570cfm carb, stock heads, stock cam and small tube headers with mufflers. I compared the exact same engine (no cam mod) with AFR165 (reduced down to 8.75 CR because of 61cc). AFR results in brackets

rpm HP TQ
2000 106(103) 278(271)
2500 132(131) 278(275)
3000 159(160) 278(279)
3500 190(197) 284(295)
4000 215(235) 282(308)
4500 225(270) 262(315)
5000 216(296) 227(311)
5500 204(315) 195(300)

from this I'll loose tq and HP under 3000 and only then they start screaming

if I'd get the 58cc AFRs I'd be at virtually the same values at 2000 and then increasing from then on.
I don't dare spinning the engine to 5500 maybe that changeswhen it actually makes power up there),. it seems currently above 4500 is a waste of time.

I do understand that I should match all that with a camshaft (XE262 would bring me to 350HP/340TQ@5500)but I'm probably to scared to **** up something else ;-)

again: this is all a maybe situation, so don't waste time on that
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1964 1/2
302ci, Edelbrock RPM heads, xe268h, 650 speed demon, Hooker Long Tube headers and Flowmaster 40s
Quick Performance Racing 9" rear, Moser axles, 3.5:1 trac-loc from FRPP and T5 transmission.
CSRP disc brakes front and FRPP discs back.
http://www.gascc.ie


Last edited by kalli; 02-10-2009 at 01:27 PM.
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Old 02-10-2009, 01:47 PM   #8
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you can always get those heads milled down a little to help bring your compression back to where it should be.

just food for thought.
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Old 02-10-2009, 02:02 PM   #9
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the idea is correct and very valid but I rather live with less compression than bringing the head to paddy the farmer to have it milled down ...
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1964 1/2
302ci, Edelbrock RPM heads, xe268h, 650 speed demon, Hooker Long Tube headers and Flowmaster 40s
Quick Performance Racing 9" rear, Moser axles, 3.5:1 trac-loc from FRPP and T5 transmission.
CSRP disc brakes front and FRPP discs back.
http://www.gascc.ie

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Old 02-10-2009, 02:43 PM   #10
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I doubt that this much CR loss would result in more than a 5% power loss, but if it did 5% is significant.

What will not show on paper is that a higher compression engine, all else being equal will feel snappy. It's nothing you can measure, but it just does.

8.75:1 may not get into the mushy area that I'm talking about, but it might. In the seventies, they built Beaucoup engines with 8:1 CR. Granted there were MANY other issues that made those engines low performers, but when compression gets that low, the engine gets a mushy feeling, even if everything else is up to snuff.

My $0.02,
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Old 02-10-2009, 03:23 PM   #11
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The difference in HP and Torque could be attributed to flow as well as compression ratio. What flow numbers are you using for each type of head in the desktop dyno program? Also, what size valves do you have programmed in for each head type? I am implying that the number may not be accurate in comparison depending on how accurate your flow numbers are.

Another explanation may be that the increased flow of the new heads is just able to compensate for the loss of CR in the lower rpm range, but at higher rpms, it runs away with it.
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Old 02-10-2009, 03:42 PM   #12
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head flow data i used was for afr: 1.9/1.6 valves with the flow data published on their website (measured with 1.9/1.67) and compression ratio of 8.75
for the stock i used CR of 9.5 with 1.78/1.45 valves and the flow data i have for the C5AE measured with 1.78/1.45 (0.200 96/64 03.00 124/88 0.400 155/98 0.500 160/100)

so what you're saying makes kinda sense.

Thanks mdbiag. i was suspecting something like this but i couldn't put my words around it
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1964 1/2
302ci, Edelbrock RPM heads, xe268h, 650 speed demon, Hooker Long Tube headers and Flowmaster 40s
Quick Performance Racing 9" rear, Moser axles, 3.5:1 trac-loc from FRPP and T5 transmission.
CSRP disc brakes front and FRPP discs back.
http://www.gascc.ie

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Old 02-10-2009, 03:43 PM   #13
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Quote:
Originally Posted by MIL1ION View Post
2V's are better for bottom end torque than 4v's

4v's are better for top end performance than 2v's
While generally true for cleves, that has no bearing at all on 289/302 motors. There are no differences between 4V and 2V 289 heads. The only significant difference between engines are the pistons (flat top vs dished) and the intake/carb.
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Old 02-10-2009, 04:23 PM   #14
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Ran the numbers too using the new DynoSim5 and got similar, but slightly different numbers. Based on a mythical stock type cam and the stock head flow numbers you gave, it looks like your two options (higher compression vs better flowing heads) is a wash under 2500rpm. Above that the AFRs start to shine. Take that for what it is worth.
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Old 02-10-2009, 04:30 PM   #15
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"paddy the farmer"? LOL

don't you have any decent machine shops over there?
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Old 02-10-2009, 04:35 PM   #16
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Quote:
Originally Posted by my77stang View Post
"paddy the farmer"? LOL

don't you have any decent machine shops over there?
Hahahaa, do they machine using a potato peeler!
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Old 02-11-2009, 05:41 AM   #17
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there is actually a decent engine shop in Cork. but I'd say they've probably never seen AFR heads. i know a miller is a miller but bringing brand new heads to a shop who don't hve experience with those types of cars ... i don't know

cowboy: thanks for testing as well. I get the same result. under 3000 nothing happens and then the thing goes insane.
tonight I'll try what mystang77 suggested on my last postings. 1.7 ratio rockers. see what difference that makes ...

Kalli
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CSRP disc brakes front and FRPP discs back.
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Old 02-11-2009, 05:57 AM   #18
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anyways my intake just arrived. this time a edl 2121. wish me luck!
if that solves my problems then i won't need heads ;-)
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1964 1/2
302ci, Edelbrock RPM heads, xe268h, 650 speed demon, Hooker Long Tube headers and Flowmaster 40s
Quick Performance Racing 9" rear, Moser axles, 3.5:1 trac-loc from FRPP and T5 transmission.
CSRP disc brakes front and FRPP discs back.
http://www.gascc.ie

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Old 02-11-2009, 08:17 AM   #19
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i dunno why you had all these intake problems, the 8124 is supposed to be a great intake
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Old 02-11-2009, 10:24 AM   #20
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only if you're not too stupid to put it in.
I torqued them with hand (my best torque spanner). And never re-checked on them
Bolts got loose, engine overheated. since then I changed gasket twice. So know i'm hoping I have 'bent' the intake as alum goes quicker than cast iron. that's the reason i'm trying replacing. i thought i get a different one just for the sake of it. my first choice would have been the 8124 alright.
the reason why i still have hope it's the intake leaking water and not the heads is that I have true dual exhausts and both are steaming. i changed both head gaskets and can't believe i fried both heads ... so i'm still on the please please please let it be the intake route. it's going in tonight, so i'll see from there
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1964 1/2
302ci, Edelbrock RPM heads, xe268h, 650 speed demon, Hooker Long Tube headers and Flowmaster 40s
Quick Performance Racing 9" rear, Moser axles, 3.5:1 trac-loc from FRPP and T5 transmission.
CSRP disc brakes front and FRPP discs back.
http://www.gascc.ie


Last edited by kalli; 02-11-2009 at 10:43 AM.
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Old 02-11-2009, 10:24 AM
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