[6pack] Timing and compression

[Chuck Arnold]

.25 inch of standard late head leaves a head of about 3.30 inches height.
That is around 11.5:1 or so.  Hope you did not mill it that much or you need
race gas!

Do not know if the chart I attached below came through your email, but it
shows compression for various head thicknesses and piston diameters.
Standard is 3.55 thick and yields 7.6 ratio.



Head Thickness

[inches]

Combust chamber volume in cc

STD bore Comp ratio

Ratio .020" over

 Ratio .030" over

Ratio .040" over

3.550

58.5

7.62

7.71

7.76

7.80

3.539

57.7

7.75

7.84

7.88

7.93

3.518

55.5

8.00

8.09

8.14

8.18

3.498

53.4

8.25

8.35

8.4

8.45

3.479

51.5

8.50

8.60

8.65

8.70

3.462

49.7

8.75

8.85

8.91

8.96

3.445

48.0

9.00

9.11

9.17

9.22

3.430

46.5

9.25

9.35

9.41

9.47

3.416

45.0

9.50

9.61

9.67

9.72

3.402

43.6

9.75

9.86

9.92

9.98

3.388

42.2

10.00

10.13

10.19

10.25

3.377

41.0

10.25

10.37

10.44

10.50

3.366

39.8

10.50

10.63

10.69

10.76




On Sat, Jun 14, 2008 at 5:43 AM, michael lunsford <mblunsfordsr at yahoo.com>
wrote:

> Al,
>
> I found the Goodparts G-2 cam to be a little more radical than I expected.
> It works fine but it is lumpier than expected at idle. Most people who hear
> it at idle and know about these things ask if I "have a cam" in the car so
> it is noticeable.  I think I have between 9.5 and 10.0 to 1 compression
> ratio on my car and have to use premium. If I get a dose of bad gas I can
> tell it from the pinging under light load.  I took a lot, I'm not sure but I
> think it may have been as much as .025 (1/4 inch) off of the late model head
> I purchased for the experiment.  From the responses you got to your question
> I ported, and deburred the head, intake and exhaust and the car runs great,
> especially with Rick Patton's TBI setup.
>
> Mike Lunsford, 1970 TR6
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-- 
Chuck Arnold