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MGB MGB Head being redone

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703MGB

703MGB

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Ok ..Today I have sent my spare MGB head to me modified by a tuner for american muscle cars.
The head is getting the usual treatment which includes:
-Stellite valves
-Bronze guides
-porting
-3 angle valve seat and so on..

But I hesitate on how much I should have the head skimmed in order to increase compression.

The car and engine are 73 18V with a big valve head (1.625)at this point I have decided on 20 thousands of an Inch but I feel this is not enough.

Any comments out there?

PS Before you ask this is the last piece going in for my performance set-up. I am already running a 270 camshaft, tuned HIF4, Peco Big Bore headers...you get the picture.

Thanks in advance
 
Are you running high compression pistons? If so, I wouldn't mess with it too much.
 
Last compression check had 150LB on all cylinders +/- 2LB. I am looking for a full compression Jump ratio of 1 in order to bump up compression to 175LB. With a ratio of 9.5:1.

The book that I have recommends to skim 80 thousands and thats alot.
 
Received the new head on Friday. Here are some important notes for fellow MG friends:

- The DPO had changed the cylinder head for an older one. Pre 67 without smog ports. Although a lot of folks think that head are interchangeable they are not. Pre 18V engines had a cylinder head with 43cc chambers while 18V head are 38cc chambers.

- Thus a pre 18V head will lower compression quite a lot. So my DPO probably realized that and had the head skimed but not enough for good ratio.

anyhow....

Took me 3 hours to remove and install the new head. First compression test (engine cold no oil flow) a nice 170 lbs.

Put the carbs on turn the key and starts immediately. Adjusted the timing.

She runs so smootly now it is simply unbelievable...and powerfull.

I am now able to have her idle at 500 rpm without missing a beat. Adjusted the idle to 700.

First road test...impressive.

Came back adjusted the valve clearance, engine hot.

I finally had the head skimmed .015

Final footnote: Even with my set of headers there is NO valve noise anymore...boy am I happy /ubbthreads/images/graemlins/cheers.gif
 
Well done! It's good to see that this project was a success for you /ubbthreads/images/graemlins/smile.gif

I have a question though, what did you set your valve clearance at cold, and then at hot?
 
Valve clearance is .013 when hot. I adjusted the valves to .013 cold. Took the car out for a test drive then re-ajusted to .013 but hot now.

Just did another compression test but engine hot. 175LB to 180..yes sir!
 
Machine shop cost was 250$ cdn or approx 200$ US. This included hot tank, guide replacement, head skimmed .015, 3 angle valve job, head checked for cracks.

My head did not required seat replacement and I supplied all the parts (guides, Valves and springs).

If you have the choice go with bronze guides.

Also do not forget if your car is a TR4, if not done already, you should have hardened seats installed.
 
It is amazing how smoothly an engine will idle after a fresh valve job. Enjoy your new found smoothness and power!
 
Sorry to be so happy.

It rain for the last couples of days with cold temperature.
Today the sun is out with a 8 degre C. Pulled the choke, turned the key and vroum perfect start with very little choke.
I pushed her hard this morning, revs past 5000, going to work and I still feel like I have a brand new car.

Sorry again to share my joy /ubbthreads/images/graemlins/cool.gif
 
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