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Author Topic:   289 rocker question
MidLifCrisis
Gearhead

Posts: 253
From: USA
Registered: Oct 2001

posted 02-18-2002 09:34 PM     Click Here to See the Profile for MidLifCrisis   Click Here to Email MidLifCrisis     Edit/Delete Message   Reply w/Quote
Well, I got the intake and valve covers off to replace leaking gaskets and to add a 4 barrel carb and stock cast intake. I would love to cam the motor, but I don't want to tear it down any farther just yet. Considering that the stock rockers are 6:1, would it be cost effective putting 7:1 rockers on an otherwise stock 289? Would I feel the difference and would the pistons need to be fly-cut or can I just bolt the rockers on without worry? Charlie

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clevelandstyle
Gearhead

Posts: 583
From: Connersville, IN
Registered: Jul 2001

posted 02-18-2002 10:51 PM     Click Here to See the Profile for clevelandstyle     Edit/Delete Message   Reply w/Quote
You should hold out for the new cam. You'll see more improvement for the money.

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Ben
Grabber Green '70 Mach I 351C 4V
Robbin Egg Blue '79 Fairmont 351C 4V

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Moneymaker
Administrator

Posts: 19611
From: Lyons, IL, USA
Registered: May 99

posted 02-19-2002 02:11 AM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
Ditto!

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Alex Denysenko
Co-Administrator and Moderator
NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
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SteveLaRiviere
Administrator

Posts: 32655
From: Saco, Maine
Registered: May 99

posted 02-19-2002 08:33 AM     Click Here to See the Profile for SteveLaRiviere   Click Here to Email SteveLaRiviere     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by MidLifCrisis:
Well, I got the intake and valve covers off to replace leaking gaskets and to add a 4 barrel carb and stock cast intake. I would love to cam the motor, but I don't want to tear it down any farther just yet. Considering that the stock rockers are 6:1, would it be cost effective putting 7:1 rockers on an otherwise stock 289? Would I feel the difference and would the pistons need to be fly-cut or can I just bolt the rockers on without worry? Charlie

You mean 1.6:1 and 1.7:1

BIG difference.

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'70 Mustang Mach 1 M code 351C 4V/FMX/3.25 open
'72 Mustang Sprint Coupe 351C 4V/FMX/4.30 Trac Lok
'94 F-150 XL 5.8L/E4OD/3.55 Limited Slip
'97 Probe GTS 2.5L DOHC

MCA Member # 47773

Recycle --- Restore a Classic Mustang!

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MidLifCrisis
Gearhead

Posts: 253
From: USA
Registered: Oct 2001

posted 02-21-2002 07:21 PM     Click Here to See the Profile for MidLifCrisis   Click Here to Email MidLifCrisis     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by SteveLaRiviere:
You mean 1.6:1 and 1.7:1

BIG difference.


Steve, is that sarcasim or is there enough increase in lift to make a difference? Tenths of an inch make a difference in cam grind, as do a couple of degrees duration.
A mechanic near work said that the stock springs would bind and bottom out before the valve could open all the way. What do you think? Charlie

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SteveLaRiviere
Administrator

Posts: 32655
From: Saco, Maine
Registered: May 99

posted 02-21-2002 07:54 PM     Click Here to See the Profile for SteveLaRiviere   Click Here to Email SteveLaRiviere     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by MidLifCrisis:
Steve, is that sarcasim or is there enough increase in lift to make a difference? Tenths of an inch make a difference in cam grind, as do a couple of degrees duration.
A mechanic near work said that the stock springs would bind and bottom out before the valve could open all the way. What do you think? Charlie


No, sorry I should have been more clear. You said the rocker arm ratios were 6:1 {six to one} and 7:1 {seven to one}.

They are actually 1.6:1 {one point six to one} and 1.7:1 {one point seven to one}

That's what I meant by the big difference.

The difference you'll get by swapping the 1.6:1 rockers with 1.7:1 would be {lets use, for the sake of example, a lift of .440" at the valve} would be as follows:

.440" / 1.6 = .275" lobe lift

So, .275" lobe lift x 1.7 = .4675" at the valve.

You would pick up only .0275" lobe lift, also a minute increase of duration because of the increased time the valve will be lifted off the seat. Which isn't much of a difference, just like Ben and Alex said.


------------------

'70 Mustang Mach 1 M code 351C 4V/FMX/3.25 open
'72 Mustang Sprint Coupe 351C 4V/FMX/4.30 Trac Lok
'94 F-150 XL 5.8L/E4OD/3.55 Limited Slip
'97 Probe GTS 2.5L DOHC

MCA Member # 47773

Recycle --- Restore a Classic Mustang!

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V8 Thumper
Gearhead

Posts: 3267
From: Orange, Ca. United States of America
Registered: Dec 2001

posted 02-22-2002 11:21 AM     Click Here to See the Profile for V8 Thumper   Click Here to Email V8 Thumper     Edit/Delete Message   Reply w/Quote
I haven't read the entire thread, I just think your user name is unique!

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MidLifCrisis
Gearhead

Posts: 253
From: USA
Registered: Oct 2001

posted 02-22-2002 06:10 PM     Click Here to See the Profile for MidLifCrisis   Click Here to Email MidLifCrisis     Edit/Delete Message   Reply w/Quote
Thanks for the clarification Steve. I appreciate the math. It isn't much at all.

V8Thumper: When I turned forty my wife was more hyper than me about attaining this age, so anytime something happened to me I attributed it to midlife crisis. It really came into play when I got a motorcycle to replace my '68 fastback owned for twenty years. I had to give up the bike, too much time away from the family, so now a '67 convert is my vehicle of choice. Just impracticle enough due to it's age and fast enough to keep me out of the mainstream. Thanks for the compliment! Charlie

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Moneymaker
Administrator

Posts: 19611
From: Lyons, IL, USA
Registered: May 99

posted 02-22-2002 09:07 PM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
WIFE ?

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Alex Denysenko
Co-Administrator and Moderator/ non 65-66 Mustang owner sensitivity co-ordinator

NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Part time secret agent license #0089
US Class Nationals link

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mvierow
Gearhead

Posts: 155
From: Bay Area, Ca
Registered: Apr 2001

posted 02-22-2002 09:58 PM     Click Here to See the Profile for mvierow   Click Here to Email mvierow     Edit/Delete Message   Reply w/Quote
Motorcycle to replace '68 fastback?

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