Gino1X1 wrote:Nice work man. I've seen on stock 7MGE heads that it's always been cyl no. 3 or 5 that fails somehow to deliver based on how the pistons look after disassembly.
Hmmmm, no piston views to offer, but here is a view of the chambers before work began.... 1 far right, 6 far left - obviously because of gasket failure chamber cleaning
oldeskewltoy wrote:I'll get this back on the bench once I've finished the intake port and chamber... but I believe all these ports are now capable of 15% greater flow...
more to come....
.10 - 63.12, .15 - 94.87, .20 - 117.22, .25 - 130.27, .30 - 137.2
#1 exhaust port is now flowing substantially better, and well within an acceptable margin of #5 exhaust port
oldeskewltoy wrote:I'll get this out to the shop early next week to get the surface machined... but before I do I'll take a few chamber measurements to try and calculate how much the head needs to be surfaced to get the chamber volume back to 39cc...
The "new" chambers had grown to almost 40.2cc, I had the head machined .010" and the chamber volume is again @ 39cc
did you see the "new" hole? It was decided to add an addition coolant passage down outside of #6
I checked the valve springs against specs... they all are short... but barely. The spec is 41.64mm, they all are between 41.61 and 41.5. All of the spring have some tilt, ranging from 1mm to 1.6mm, spec is 1.5mm. I await my clients decision OEM springs for the 7MG are realtively inexpensive @ $5.30 each, 4AG springs are more than double that.
Oh... and I also mentioned the new intake ports...
A bit more to come...
Clean job!!! One question, in this case with all this maching going on what are the changes relating to piston-valve, valve timing etc.(I know about the tensioner but in the 4AG)? Drastic or only mild re-adjustment?
Gino1X1 wrote:Clean job!!! One question, in this case with all this maching going on what are the changes relating to piston-valve, valve timing etc.(I know about the tensioner but in the 4AG)? Drastic or only mild re-adjustment?
.010" is still .010". I've recommended that the owner acquire adjustable timing pulleys to correct cam timing. Concerning piston to valve clearance There is a fair bit of room here, for if I'm not mistaken this is an none interference engine. Machining the heads surface .010" can only possibly cause a problem if the timing belt breaks... and most likely not even then. Remember the 7MG cams only lift to about .300" rather short lift
from another forum wrote:what is your thinking with the valve lash being so tight?
you know, growing up and working on street cars in shops "a loose valve is a happy valve" was the standard (within spec of course). is this for better high-rev predictability?
The specification: Intake .15mm - .25mm(.006" - .010"), Exhaust .20mm - .30mm(.008" - .012")
My feeler gauges are in SAE... (the FSM does have SAE specs too) What is important to note... there is a little bit of fudge room... since .006" doesn't equal .15mm, it equals .1524mm
Since the specification allows me a range, why not try for the tight side of the range... still in range. Fitting everything tight (within spec) allows me more lift, and more duration from the cam to actually function the valve. Fitting the valves so they have the same, or nearly the same clearances allows for uniform draw on each valve since each valve is open as long, and as high as its twin.
Finally... we only have .300" lift total, why give any of it away if we do not have too.
Check the 5th valve down on the intake side
More numbers... all intake valves are set between .006" and .007", all exhaust valves (except one) are set between .008" and .009". The one except is one exhaust valve is set @ .010, for I didn't have .1083"(2.75mm), so I had to use a .1063(2.70mm) shim instead
using the valve tools to compress valve to allow room to swap shims.
This head is now done....
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