1275 Head Question

[bugedd]

I have a 1275 from an emissions car, and I was going to search out a head to rebuild as the one on the car suffered extreme corrosion in the thermostat area. What heads are interchangeable, and what heads, if any, are sought after. And lastly if anyone has one to spare.....

 

[ghostgrunt]

There's nothing wrong with the emissions head--in fact some people prefer them. I have a good emissions head stored away,but shipping from NC would probably be pretty expensive. Since you're in Chico,I'd seriously consider getting a later 12G940 Metro head from Dave Anton at APT. In my mind,it's a heck of a bargain--you get the better-flowing Metro casting,plus Dave installs unleaded exhaust seats and "sweeps" the chambers(his terminology)--which is the primary cut to unshroud the valves. The heads are cleaned,magnafluxed,primed,etc. I bought one a while back from him and the price was $175. You won't beat that anywhere,and you'll know it was done right. Just a thought.

Jim

 

[bugedd]

I'll look into them, thanks!

 

[Boink]

I've been perfectly happy with my, very common, later 12G1316 (emissions from late 60s) head. All holes plugged up. Had it machined though.
Whatever you do, with a replacement head, be sure to inspect for any recession of a brass blanking plug. This is the problem I had with mine. One of those blanking plugs crosses the gasket fire rings.
In addition to APT, Hap Waldrop does a nice job with heads too.

 

[Spridget64SC]

With regards to "sought-afterness" for 1275 heads:

1st: 12G940, from the 67-ish Spridgets is probably the most desirable. Seems to consistently have bigger ports than the smog version. Intakes and exhausts are usually up to 0.060" taller in the ports. A bit more flow in stock condition than the rest.

2nd: 12G1316, from 68 to mid-71, These still have the better exhaust port without the port pocket casting encircling the exhaust valve guide. A good thing for the restricted SCCA racers in HP.

3rd: 12G1316, after 71, These have cast iron around the exhaust valve guide which inhibits exhaust flow on the long radius of the port. Not a concern for full preparation racers. It gets removed as part of the porting process.

Haven't had my hands on too many 12G940 Metro heads. A number of the internet pictures show the exhaust ports similar to the post-71 Spridget heads with the big exhaust valve guide boss. For stock or mild-performance use, this should really be no consequence to the engine. As far as flow goes, I would initially put them in the same category as the later 12G1316 head.

All the above heads assume 1.312" intake with 1.156" exhaust. If using the 1.4" intake, then an increased potential for cracks in between the valve seats in a cylinder occurs. Happens with stock valve sizes too, but seems to happen a bit more frequently with the bigger intake.

The 948/1098 heads will fit the 1275, but not a desirable swap. The 1098 head with casting 12G295 has a nice intake port that matches up well with the 12G940/12G1316 head, but the exhaust is just too small with the 1.00" valve size. It can be made to use the 1275 exhaust, but it wouldn't be worth the effort unless that is all one had available.

HTH, Mike

 

[ghostgrunt]

I did forget to mention a few things about the early-mid '80s A+ Metro head castings:

1. They do not have the fitting for the bypass hose to the water pump. My engine will be a full rebuild,so I just bought a water pump w/o bypass. Your situation may be different,so I thought you should be aware of the bypass issue.
2. These engines came with larger,1.4" intake valves from the factory,along with nicely cut throats into the port,below the valve. Exhaust valves were 1.15".
3. Supposedly the factory improved the ports a bit over earlier heads,since the Metro was in the market with other,more modern hatchbacks,and the factory was looking for more power. So,improved porting,larger intake valves,and the Metro cam(very similar to the 266 Kent) was the factory recipe. Comparing the Metro and Midget 12g1316 heads side by side,the difference in factory finishing of the ports is immediately obvious.
4. These are also 12G940 castings,but there are a few different heads out there with 12G940 casting numbers. This info is readily available online,and I'm trying to keep this short,so I'm not going to list them here. A couple minutes of research will spell it all out for you.
5. One quick way to spot the later heads is to look at the thermostat gasket area--the early heads are dead flat all the way across the rocker cover and thermostat gasket surfaces. The later heads have more of a gasket sealing "rail",running around the rocker area and thermostat. Bad description--if it doesn't make sense,let me know and I'll send a photo to you.
6. It does have the large valve guide bosses in the ports--especially on the exhaust side--intakes are a little better. Spend some time with a carbide burr to cut those bosses down,if you think you need to. All depends on what spec you're building your engine,and how you plan to use the car.
That's about it,and those are the reasons I went with this head for a reliable,every day driven Midget with a warm street engine. Buying the head through APT meant I got the casting I was looking for,unleaded seats,some combustion chamber work done,etc. I'm cleaning up the ports,blending in a few abrupt edges here and there,slimming down the guide bosses,etc,on my head,just to finish it off. New guides,valves,springs,and seats cut on a Serdi 100 machine and I should have a nice(unleaded) mild performance street head that will last. Fingers crossed,that is!

Finally,this head is a good fit for what I want out of my Midget;it may or may not be what you're looking for.I don't have or pretend to have the knowledge base of some of the guys on this forum. We're ****ed lucky to have Hap,Mike and some of the others on here as go-to guys when we have questions. They won't steer you wrong.

Jim

 

[Gerard]

I'd seriously consider getting a later 12G940 Metro head from Dave Anton at APT. In my mind,it's a heck of a bargain--you get the better-flowing Metro casting,plus Dave installs unleaded exhaust seats and "sweeps" the chambers(his terminology)--which is the primary cut to unshroud the valves. The heads are cleaned,magnafluxed,primed,etc. I bought one a while back from him and the price was $175. You won't beat that anywhere,and you'll know it was done right. Just a thought.

Jim

Jim,

I've purchased several ported heads from Dave Anton... no disagreement, but I think you are missing a 4th digit on the price though...

 

[ghostgrunt]

Gerard,

Yes sir,his fully-ported,fully assembled heads are a bit more than $175. I bought one 10-12 years ago and I think it was around $1400 then. Sorry if I was unclear before;the head I'm talking about is something David Anton offers on his site,and it's not a finished,complete head. No valves or springs are included--it's a bare head.However,it is a great,affordable way to get a head casting that has been cleaned,magnafluxed,has unleaded exhaust seats fitted,and has a valve unshrouding cut applied to the chambers. How far you take the head from there is up to you. Check the APT site;I just went there to confirm,and it's listed right there on the home page. Heck of a deal,don't you think?

Jim

 

[Hap Waldrop]

I have had my hands on at least 4 of the later 12G940 Metro heads, three of them had cracks between the seats, this is the last head on earth I would seek out for a 1275 engine. Of course porting can fix any of the other heads.