MG MGB and MGB GT Tech Talk
Now that I have a rebuilt block running in the B I want to modify my old cylinder head to use unleaded gas. I notice VB and Brit-Tek sell kits, the latter being significantly cheaper. Does anybody have any experience with these and, if so, what kind of machine shop costs can I expect?
When the machine shop does the head for you, they will probably put in the hardened seats. All parts are available thru your local machine shop anyway, so just call around and get a couple of prices! GOOD LUCK!!!!
It's all in the "hardened" valve seals. That's really all thats out there these days, so its easy to get confused thinking you need a kit. Full blown head re-do will be a couple hundred + because you want it done the best. When I took the "kit" to my machinist, it was $90. However, I'd probably just ship the head off to someone like Tom B. and be done with it.
Eric,
Have your exhaust valves burned up? If not, then there's no need to do a no-lead conversion (unless you planned on rebuilding the head anyway). I've always ran mine with no-lead and haven't had any problems.
Reason is that the guides and seats are bad so it needs a rebuild anyway - so I thought "what the heck" I might as well buy the kit and be done with it. Fortunately I do use a GREAT machine shop (Mike's Machine Shop, Wixom, MI if anybody is interested) - they did a superb job on my block - bored/decked/new cam bearings and a neat job putting helicoils in my old exhaust manifold so I think they will do a good job installing the seats and guides - I was just wondering what experiences others had - good or bad?
All I would get is the bronze guides. Let the machine shop get the seats. You don't need them on the intakes. That's a waste of money. Be sure they fit the exhaust guides slightly looser than the normal cast iron guides. If they don't they will seize up. Also don't put any valve stem seals on the exhause. For sure have them check for cracks before they do anything. Between #2&3 is usually where it happens. They need to check real good both in the combustion chambers and between the spark plugs.
I bought my parts from Brit-tek and had no problems at all. Talk to Bob Ford. He is very knowledgeable and doesn't mind spending the time to talk with you.
Thanks guys - I am leaning toward the Brit-Tek kit as I have to supply all the parts to my machine shop.
I am confused by the "no seal on the exhaust" comment as well. I have put seals on all the A and B series engines I have built and had no problems.
You don't need them. What little oil slides down the valve stem helps lub the guide, and disapate heat. On the intake because of the vacuum created on intake it is drawn into the combustion camber. On the exhause that isn't a factor.
I have never put seals on the exhause of any MG motor. Matter of fact Triumph motors don't have seals on exhause, or intake. They came from across the pond that way.
I agree with Tom. You probably need to order the guides, but the machine shop's going to put hardened seats in there unless you specifically tell them NOT to. So don't bother ordering them. Probably cheaper if the machine shop just pulls them off the shelf anyway.
For seals, there's some felpro seals that were used on various US cars that are supposed to be the bees knees, but I couldn't get them to work with dual valve springs, so now I can't remember the part number.
Author: John D. Weimer (---.cape-tcc1.clas.net)
Date: 06-05-03 20:57
Because intakes suck. The exhaust valves blow. Kinda like gay liberation without the mess.
The machine shop won't put any seats in at all if the old ones will regrind without much cuting or unless they're loose or cracked. A lot of guys working those shops don't even remember anything about leaded gas heads or valve seats that were softer than what they work with every day. Valve seats are another of those more or less generic items that can be chosen by size or by catalog application..
Tom isn't saying to not put seals on the exhaust valves. He's saying he doesn't and never has, and it's his method of doing things. It's not a question of him being right or wrong, either way is right or wrong depending on your way of doing it. Most areas of engine work have no middle ground, but this is one that is all middle ground.
Well, yea I am saying not to put seals on the exhaust. I have had problems with bronze guides seizing on exhaust valves on either # 2 or 3. They get hotter than 1&2 because of the siamies port. That's why I have my machine shop size the exhaust slightly looser on bronze in the exhaust. That is also why I leave the seal off on exhaust. That small amount of oil helps prevent seizing. I also ask my customers with new engines to add 8oz of marvel mistery oil to every tank full on the first 1000 miles of break in period.
Once again, thanks for all the input - all good, and usefull, stuff. I'll call the machine shop and see if they stock seats. If not, I'll get a kit. I like the Marvel Mystery Oil idea! Not sure I'm ready to comit to no seal on the exhaust - but the reasoning makes sense!
Eric, I probably have somewhere between 20-30 MGB rebuilt engines out there without seals on exhaust, and have never had a problem with it. I decided to try it on one of my cars years ago and descovered it wasn't needed.
The guy that did my headsaid no seals in the exhaust also!! He says he never uses them!!
O.K. Guys - you convinced me - no exhaust seals on the no-lead head!
Just curious if anyone is running a Mike Brown head here. I think he charges about $600 for the valve job including parts, port & polish the head and intake manifold. Not only hardened seats, but about 15 extra HP to boot.
I haven't had any head work done for quite a few years so I don't have the current cost. I see the Brittek head update kit is about $225 with no labor.
