[AReg]

Hello,
I'm in the process of rebuilding a 105 series 1750 GTV engine which has been stripped and stored since about 1985. I think its only done about 50k miles.
Please could someone advise on a couple of queries?
1) The inlet valve seats all have a small lip around their edges. See photo. They are consistent all the way round and they look pretty much the same on all 4 inlet seats. The exhausts do not have them.
Are they anything to worry about? I'm guessing they have been there since new. So I was thinking of just lapping the valves in again and ignoring the lip as I imagine they could be difficult to grind off. Unless there was a bit of performance to be gained.
2) What is the shallow recess for that runs into the spark plug hole? Is it worth taking the sharp edges off around that before I clean up and polish the chamber?
Many thanks in advance AReg.

 

[Alfar7]

The ridge is caused by the valve`s seating forces on the seat. The seats in the head should be machined by a competent shop. Along with the valve`s seating area. These are 30 degree seat angles .

The factory seat only has a single 30 degree cut for the seat. Commonly the seats should be opened with at least another cut of 60 degrees to enable better flow.

The exhaust seat should be cut with a 60 degree cutter leaving a seat width of 2 mm(.080")

These heads are basically 1600 heads and the valve/seats restrict flow.

If I were doung the work on the head both the intake and exhaust seats would be opened (wider) with a 75 degree cutter (BowlHog) to improve flow.and reduce the widths of the seat contact area to 2mm on the exhaust and 1.5mm (.060") on the intake.

These are cast iron seats so springs shouldn`t be stiffer than stock (when new)

 

[AReg]

Hello Richard and thanks very much for the reply,

I am aware there may be some performance gains to be had here, but I am not rebuilding it for that reason. I just want a nice reliable engine. Plus I would like to avoid the expense of re-machining at a machine shop.

I am surprised you think the valves have deformed the seats causing the lips, because the valves themselves look undamaged.

Anyway, I assume re-machining the seats to the specification you suggest would remove the lips, so I will have a go at grinding them off myself.

I will try to get the seat widths nearer to the 1.5 mm and 2.0 mm figures you mention by blending the inside corners of the seats and careful lapping.

Whilst I am at it, is it worth doing anything with the recess near the spark plug hole? What is it for?

Its interesting to hear this is really a 1600 head as I have another 1600 engine. If all goes well with the 1750 I may be a bit more radical with the 1600 next time!

Thank you again for your trouble.
Best regards,
A Reg

 

[Alfar7]

I`m afraid you will damage the seats trying to remove the "lips'. As I`ve said seats are cast iron far softer than the valves.

If you have the equipment to cut the seats more power to you.

 

[goats]

I`m afraid you will damage the seats trying to remove the "lips'. As I`ve said seats are cast iron far softer than the valves.

If you have the equipment to cut the seats more power to you.

Richard, what are your thoughts on using the Neway seat cutter system to freshen up seats? I was gifted a nice set of reamers, pilot rods, and Neway cutters with 30 , 45, and 75 degree cutters. I used them a few times and have been happy with the results, but wanted to get your thoughts on these. Thanks!

 

[Alfar7]

They work great.
His issue is really needing a initial cleanup using a 20 degree cutter to unshroud and get the seat level with the combustion chamber on both intake and exh., Then to re-cut the 30 degree seat correctly. Lapping wont do it.

 

[AReg]

Hello Guys,
I'm not familiar with the Neway system, so will have a look later.

Richard, yes, you are correct, the valve seats are far from flush with the chamber walls. However, I was not thinking of taking these back flush, although I can see that you might want to on a performance engine.

I was thinking more along the lines of a tidy up and re-lapping to ensure a good seal. Haviing said that, getting a bit more flow by blending of the insides of the seats and reducing the seating widths as you describe does not seem too big a job so may give that a go.

Thanks again, AReg

 

[Alfar7]

You are wasting your time. Lapping won`t remove metal to seat the valves.
Do it your way then have it done correctly.
You are wasting BB time.

 

[4sfed]

I am surprised you think the valves have deformed the seats causing the lips, because the valves themselves look undamaged.

The seats are worn because they were designed for leaded fuel ... which provided lubrication. Unleaded fuel increases the wear rate, and as you discovered, the seats wear faster than the valves. At some point the seats will wear far enough that you can no longer find thin enough valve shims and the seats will need to be replaced. That can also be a problem if your machine shop takes too much off the seats.

Did you measure tappet clearance before disassembly? I would expect them to be under spec.

 

[AReg]

Hello Jim,
Thanks, that is something I had not even considered.
However, in this case its a UK engine that I believe was taken out of service in the mid 1970's so it will never have been run on unleaded fuel.
Plus, its very low mileage and the lips are only around the inlet valves.
Unfortunately I did not check the clearances before dismantling it.
You do raise an interesting point though about unleaded fuel. From the limited research I have done online, I came to the conclusion that these engines were fine to run unleaded anyway. It sounds like your experience tells you otherwise?
I will look into this further here in the UK to see if I find a definitive answer.
Thanks again for your trouble.
AReg.

 

[4sfed]

It's fine to run on unleaded fuel. The wear will just be something to watch. Unless this will be your daily driver, you're unlikely to put enough miles on it to have any problems.

 

[AReg]

Jim, thanks for the confirmation and no, it will not be a daily drive.
I assume by watching for wear you mean by regular checking of the tappet/cam clearance?

 

[4sfed]

I assume by watching for wear you mean by regular checking of the tappet/cam clearance?

Yes, every couple of oil changes.

If I can recommend a method that will improve your chances of getting the desired clearance with the first adjustment. When you measure clearance, turn the cam until the adjacent valve is slightly open ... Maybe 2 mm. The reason is to lift the cam up against the cap and eliminate the clearance between the cam and cap. If the bearing clearance is above the cam, inserting the feeler gage may or may not lift the cam, resulting in an inconsistent reading.

 

[becko]

Hey Jim, is this for wear at the camshaft bearings, so the cam lobe pushes cam up to top of bearing

 

[PSk]

Maybe get the seats replaced with modern seats that can handle modern fuel?
Pete

 

[4sfed]

Hey Jim, is this for wear at the camshaft bearings, so the cam lobe pushes cam up to top of bearing

Yes ... even when new there is some clearance.

 

[AReg]

Yes, every couple of oil changes.

If I can recommend a method that will improve your chances of getting the desired clearance with the first adjustment. When you measure clearance, turn the cam until the adjacent valve is slightly open ... Maybe 2 mm. The reason is to lift the cam up against the cap and eliminate the clearance between the cam and cap. If the bearing clearance is above the cam, inserting the feeler gage may or may not lift the cam, resulting in an inconsistent reading.

Hi Jim,
Thanks, this makes perfect sense and sounds like a great tip.
Best regards,
AReg,