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Question on "B" head change.

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PAUL161

PAUL161

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Because of the switch from leaded to nonleaded gas way back when, does a 72 head have soft valve seats? Does a 79 head have hard valve seats? Are the heads interchangeable? Is there any other differance? If so, what is it? I know that, without lead in the gas, this is a problem in some antique cars if thier driven a lot as most of them have soft valve seats. PJ /ubbthreads/images/graemlins/confused.gif
 
'79 has hard seats...don't remember exactly which was the change point...but, with some minor modifications, you can put nay 1800 head on any 1800 engine....easier putting a late head on an early engine.
 
The lead in gas cooled the valves and prevented premature valve seat wear. You have three options:

1. Install a later cylinder head.
2. Have hardened valve seats installed in your cyl. head.
3. Keep driving, and add a lead substitute to your gas. Given the low miles our cars accumulate, this should hold you over for a few years or more.
 
Thanks Tony, I have a 79 head that needs new valves. No 1 exhaust is burnt. I think I'll totally rebuild the head and put it on the 72. Where is the best place to buy new valves without having to give up your shirt? PJ
 
I've been putting unleaded gas in my early cars since I got them & have never had any problems - & I don't add anything to the gas.....an occassional tank of 93-octane to the cars that are occassional drivers....only 93-octane to the daily drivers.
 
Well 200MPH, Tony says that a 79 head has hard valve seats. Untill I get the 79 head I have rebuilt, I think I'll take your suggestion and put in some lead additive. Thanks PJ
 
Paul! You hurt me when you ask where is "the best place to buy new valves without having to give up your shirt"....send me your list & get ready for a shock when I send you my prices!
 
What Tony said. The shock is his low low prices compaired to the leading parts house.
 
Well, Tony, since rebuilding this car, I've already had a few shocks! So I guess a few more won't hurt. And, I guess that throws me in the same boat as everyone else, so how can I complain? How hard is it to put new guides in? PJ
 
They just have to be pressed in & then bored to fit the valves...I always leave that part to the machine shop.
 
Tony, I just checked in Moss and found out that there are three intake valve sizes. The valve in the Moss book is 1.75 in dia. Is that for a standard 79 head? Acording to Moss, a 73 & 74 take 1.625 and 72 on back take 1.563. To me, that would indicate The 72 engine would perform better with the 79 head. It should breath better. Right?? Or, would you have to port and relieve it also? PJ
 
If you're getting into flow & performance, there are certain MG heads that are better than others...however, I don't think you'll see a whole lot of difference if all you d is change heads - but, then, I'm not an expert on building a racing engine...Hap's the guy there.

...but, you can put any valve in any head so long as you cut out & replace the seat & the guides, IMHO

I know I always 'modify' the 'tip' out of early head combustion chambers to get more volume regardless of anything else I do to a head - again, I'm not the expert in this area, just do what those guys suggest.
 
The only thing I see is the older heads had dual valve springs. The response seemed better with the older head. I don't know if you can put the older dual springs on the newer head. I like Tony use my 73 as a daily driver and have not had any problem with the gas/valve situation. If you start in porting, etc. remember you have to do all the same or you lose anything you gain. I have polished and ported small block heads for drag racing and it is time consuming. If you want to match the ports to your intake make sure you only go and inch into the head and taper and smooth and smooth. There are ways to determine how much to take off keeping in mind the location of water jackets, etc,.
CC is opening the combustion chambers up to the largest size (after measuring) and then reducing compression by milling the head. If you are getting the idea this is not just a simple procedure then you have got the drift.

/ubbthreads/images/graemlins/nonod.gif
 
I've driven pre-79 cars the whole time and all I've ever done is be sure to put the highest "octane" (93) available in 'em. No premature failures, no problems. The "lead substitute" is a poor surrogate for tetra-ethyl lead, which was bound chemically with the benzine ring: "substitute" is just adding $$ to the tank. Throw some Marvel Mystery Oil in there, an ounce for 12 gallons, once in a while instead. Won't do anything better'n the additive, but it costs less, won't hurt and you can feel as if you've done *something*. /ubbthreads/images/graemlins/grin.gif

Bruce! Our cars only have FOUR holes... It ~is~ simpler to match ports, and CC the chambers than a V8!! /ubbthreads/images/graemlins/jester.gif
 
Well Doc, (Not knowing you I hope that is the proper verbage), strange as it may seem, I've been using Marvel Mystery Oil for years. I've used it in racing outboards with tremendous success and also in race cars as a top lube only. I wanted to test it once in an aircraft engine, but couldnt get permission from the proper authority. Oh well, the FAA is pretty tough. I'll try it in the car as a top lube. I usually have two or three gallons of it in the shop. Just never thought of it. PJ /ubbthreads/images/graemlins/smirk.gif
 
Call me whatever ya want, I answer to 'bout anything /ubbthreads/images/graemlins/wink.gif

MMO is great stuff. Smells good too! /ubbthreads/images/graemlins/jester.gif
 
And I thought the brakes were draging! No wonder I'm kicking up more dust than normal! /ubbthreads/images/graemlins/iagree.gif /ubbthreads/images/graemlins/lol.gif
 
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