Hesitation at 3000 RPM/Oil Leak?

[KDMatt]

Correct KDMatt, the 75-76 heads came with softer bronze valve seats for use with leaded gas. I wouldn't cross that off your "to do list" because it sure sounds to me that the Valve Seats are the cause of your problem. If it were a head gasket problem then she would be smoking like crazy all the time. even when warm. If your not comfortable doing this job and don't have the tools required to do it, then I guess the best thing for you would be to ask that "friend of a friend" and see if he would be willing to help you out.

As for the Valves and Valve Springs- I don't know who told you that they need to be changed every 25,000 miles but thats False. Like Lance said "in a normally driven car valve springs last forever" Just inspect there condition when it's taken apart.

Best of luck.

Thanks. :classic:

...If I changed the valve seats wouldn't I also have to look at how the valves fit to them? Isn't it possible that the current valves and seats have somehow 'contoured' to one another and that replacing both the valves and the seats at the same time could be a good idea?

I'm just curious about that, since I've heard hearsay of people resurfacing their seats so that the valves fit to them.

'Glad to know that the spring thing is just an oddball rumor I picked up though. Saved me an extra 100+ dollars there, heheh.

[DatsunZsRule]

Yes, the valves can get deformed. However like mentioned earlier, I doubt your valves are in that bad of shape unless whoever had the car before drove the hell out of it. You should be able to get by with just doing the seats only. Only way you will know for sure what all needs to be done is when you have it apart obviously to see.

[LanceM]

Correct KDMatt, the 75-76 heads came with softer bronze valve seats for use with leaded gas.

Thanks for clearing that up, I didn't realize they used soft seats!

Changing the seats isn't a backyard job, it will have to be done at a machine shop. The seats are pretty much blanks when installed and then are ground to the correct angles in the head. At this time the valves will also be ground to clean them up (remove any burnt spots/pits) and match them to the seats. There is a spec for minumum valve edge thickness, after grinding any that are below this spec will have to be replaced with new. It isn't unusual to reuse a full set of valves, by the same token it isn't unusual to replace one or two on a valve job.

For what you are thinking of doing I would recommend checking shops in your area and find out what a valve job with new seats and guides would cost and let the shop handle the part buying and the work. When you get the head back from them it will be all set up ready to install.

[KDMatt]

Changing the seats isn't a backyard job, it will have to be done at a machine shop. The seats are pretty much blanks when installed and then are ground to the correct angles in the head. At this time the valves will also be ground to clean them up (remove any burnt spots/pits) and match them to the seats. There is a spec for minumum valve edge thickness, after grinding any that are below this spec will have to be replaced with new. It isn't unusual to reuse a full set of valves, by the same token it isn't unusual to replace one or two on a valve job.

For what you are thinking of doing I would recommend checking shops in your area and find out what a valve job with new seats and guides would cost and let the shop handle the part buying and the work. When you get the head back from them it will be all set up ready to install.

Bah, that's what I was afraid of. Is it even worth it to pull off the head to just replace the seals (and guides)? (the thing that initiated this whole 'let's-pull-off-the-head project'), since it might take me a bit longer to amass the financial 'cushion' to finance a machine shop trip than to just acquire the parts and do my own (supervised) labor...

[LanceM]

Guides are another "machine shop" do only. You can replace the valve seals with the head on the engine.

Here is a link to replacing seals with the head on, it will give you an idea of what is involved.

http://www.geocities.com/inlinestroker/seals.html

[KDMatt]

Awesome link Lance!

Thanks man.