7MGE Engine rebuild

oregonjoe · 08-23-2009, 05:04 PM

I’ve taken the head and block to the shop to have them cleaned up and inspected. The head and valves looked good for 20 years of use.

The good news on the block is no cracks after the magnetic test – so its just a hone on the cylinders and good to go. The bad news is the shop wants $500 to do a valve job on the head – even without replacing any valves. Claim the 24 valves takes a lot of labor and that OHC need to be ground to adjust!

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So – I took the head back to do a little porting and polish. The head had some casting marks and ridges from 20 years ago. Since I bought the car I have learned a thing or two about engines. One of which is that they are massed produced from casting molds. These molds are not all created equal and there can many flaws that are left as is in production. Some flaws include sharp ridges from casting seams and defects in the individual molds. Other are sharp angles from the machining process after the castings are poured. In production - they are all ignored.

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The cylinder chambers in the head have some sharp edges that can collect heat and cause preignition so I ground them off to smooth the transitions out the valve ports. Careful to not touch the valve seats.

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I focused on the exhaust ports and smoothed out the walls and take out any burrs and casting ridges. Just a little touch up on the intake side to remove any large defects as I understand its better to leave the “sandpaper” effect on the walls.

08-23-2009, 05:04 PM	#6
oregonjoe 3" Exhaust Join Date: Aug 2009 Location: Southern Oregon Coast Posts: 83	7MGE Rebuild - Head Port I’ve taken the head and block to the shop to have them cleaned up and inspected. The head and valves looked good for 20 years of use. The good news on the block is no cracks after the magnetic test – so its just a hone on the cylinders and good to go. The bad news is the shop wants $500 to do a valve job on the head – even without replacing any valves. Claim the 24 valves takes a lot of labor and that OHC need to be ground to adjust! So – I took the head back to do a little porting and polish. The head had some casting marks and ridges from 20 years ago. Since I bought the car I have learned a thing or two about engines. One of which is that they are massed produced from casting molds. These molds are not all created equal and there can many flaws that are left as is in production. Some flaws include sharp ridges from casting seams and defects in the individual molds. Other are sharp angles from the machining process after the castings are poured. In production - they are all ignored. The cylinder chambers in the head have some sharp edges that can collect heat and cause preignition so I ground them off to smooth the transitions out the valve ports. Careful to not touch the valve seats. I focused on the exhaust ports and smoothed out the walls and take out any burrs and casting ridges. Just a little touch up on the intake side to remove any large defects as I understand its better to leave the “sandpaper” effect on the walls.