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Old 07-25-2015, 05:36 PM
Brushwolf Brushwolf is offline
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Default 1968 4v 390 10.5 CR? Pump Gas?

Tearing down a 68 Mercury 4v 390 to replace the one in my 62TBird. I believe these are 10.5:1 motors. Can I use same Flattop piston or have to use a dished one to lower CR? Some of you running 10.5 CR still?

Have heard that a larger cam drops CR some anyway and wondering if RV cam will work with the 10.5 CR?

Here are some desktop dyno results posted on FE board using several different cams, but with 9.5 CR instead of 10.5. You have any cam recommendations for torque increase over stock?

I will probably change to Performer or Performer Plus intake primarily for weight reduction (painted Ford intake color). Not sure what to do about exhaust yet...

WerbyFord On cams:

Assuming you have the c1ae-a heads for about 9.5cr, here is what the Gonkulator says - assuming the best 2" glasspacks you can get on the back or equivalent see-thru muffs. With 2" pipe it will not be loud anyway:
Stock 186-186
Torq 382 at 2800
Powr 289 at 4500
2.49 60ft
10.44 at 68.7 1/8 mile
16.14 at 85.5 1/4 mile
8.34 0-60m

Performer 194-204
Torq 386 at 3000
Powr 301 at 4700
2.51
10.42 at 69.3
16.06 at 86.8
8.22 0-60m

Melling 204-214
Torq 391 at 3200
Powr 318 at 4800
2.53 (note the 60ft is slowing down...)
10.41 at 69.9 (1/8 mi is tapering off, cant go much more)
15.98 at 87.9
8.12 0-60m

390gt/428cj
Torq 387 at 3300
Powr 318 at 4800
2.55
10.48 at 69.6 (slowest of all)
16.07 at 87.7
8.23 0-60m

The Melling 204-214 looks like the best choice?
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