How to add a bit more realiability/endurance to a stock 1275 engine rebuild?

[twas_brillig]

Looks like we're going to have to have a 1275 rebuilt this summer and I'd appreciate suggestions for improvements.

Cylinder head was worn out and we had it done previously (including valve seats for unleaded gas) but the free advice I'd received years ago that the block was fine was apparently worth what I paid for as the shop it's in advised that it smokes quite a bit.

We'll stay pretty much stock and will be using existing carbs/header, but I was thinking to:
- spend a bit of time and match the ports/gasket/intake (just because)
- ensure it's got the double row timing chain
- get the crankshaft main caps machined and add straps
- have components balanced
- higher capacity oil pump?
- better piston rings? (decades ago, I had a BMW 2002 engine rebuilt and the shop recommended non-BMW rings)
- if it doesn't have a rear crankshaft oil seal conversion (we have a Datsun 5 speed behind it so may have already done that upgrade; age is going up and memory is going the other way)
- talk to the machine shop about 'lapping' the oil pressure relief 'bullet' into the block (anyone else have thoughts on this?)
- pertronix ignition
- retain the spin-on oil filter
- head gasket upgrade? I'm thinking that the stock one will be just fine, but advice appreciated
- upgraded bolts/studs/etc? Again, I'm thinking that stock will be find, but advice appreciated
- keep stock starter (replace with gear reduction when it fails)
- any recommendations for 'better' valve cover and oil sump gaskets?

Comments on the above? What else would be worthwhile?

Thanks, Doug

 

[twas_brillig]

Okay, I can spell 'reliability'; I apparently can't type it. Doug

 

[Gerard]

Doug,

-Payen black head gasket
-ARP studs - It'd use them at a minimum on the head, but you should alo use them for rods and mains. They make flywheel bolts too. Expensive, but I don't find most aftermarket replacements to be all that strong/reliable.
-Adding a center strap is expensive and will require a complete teardown for machne work. It really won't be of much benefit if you aren't racing.
-Check ring land tolerance on pistons before ordering rings. Often, these pistons have too much wear to replace rings instead of entire piston.
-I've personally had a lot of reliability issues with Pertronix. I prefer Crane or some others that are avaialble. If you decide on Pertronix, I recomend you carry a spare dizzy with points at all times.
-if you don't have one of my rear seals, don't bother - anything else doesn't work as they are not designed correctly and usually fail withinn the first 100 miles.
-don't think there's a need to lap PRV. If yours has issues, new ones are available cheap.
-A-series engines even in mediocre conditons have more than adequate oil pressure - no need for a high capacity pump.
-double row chain is standard issue - just make sure you get a good quality one. AE or German made chains are the better ones.
-balancing is always good, but can be expensive to do right
-1275s with stock SUs have alignment rings on the intake mainifold. If you are not porting the head, anything more will make liittle difference

 

[Trevor Jessie]

I agree mostly with Gerard, but I'd go ahead and install new pistons with an overbore, that way you can dial in the CR you want. I wouldn't spend money on lightening the crank or rods, but I would have them balanced. Of course when you switch over to ARP rod bolts and main bolts the big ends and mains will need to be machined.

You don't mention a camshaft, but obviously you need to check it carefully for wear and replace if needed. If you do need a new cam be sure and get some high quality (hardness) lifters.

 

[Gerard]

Out of the dozen or two engines I've rebuilt, I've never reused old pistons. Between cylinder wear, bore taper and rings lands being out of tolerance, I've never found it to be a viable solution. I think I've had maybe only one engine that had reusable pistons. I know some people will do that and just replace rings, but it's not a path I personally pursue.

I agree mostly with Gerard, but I'd go ahead and install new pistons with an overbore, that way you can dial in the CR you want.

 

[SaxMan]

If you have the head off -- replace the blanking plug between cylinders 2 & 3. Hap Waldrop posted about this in a bit more detail -- basically you replace the blanking plug with a threaded brass bolt and then have the machine shop grind it until it is flush with the head. This will prevent head gasket failure due to the recession of the blanking plug, which sometimes happens in an overheating type situation. If you search the forum for blanking plug -- you'll get the specific details.

 

[twas_brillig]

Thanks all. My expectation is that it'll be a complete disassembly and rebore/new pistons. My recollection is that I could not feel a wear pattern in the top of the bore with a finger so I believed the opinion that the engine was good (until I learned the head was toast). The intention at the moment is to basically keep it stock (compression ratio and cam) but make it durable. Still thinking about the bearing caps, and now planning on ARP fasteners (the older Brit who's puttering away building a 1275 for the Silver Sprite is using all ARP bits as well). Wasn't aware of the brass bolt; looks like I'd better do a search for all of Mr. Waldrop's postings. Creative Spridgets/Joel Young is developing a supercharger system so I can always dream about that! Thanks again, Doug

 

[drooartz]

My old website is offline now, but I did a long writeup on the build that Hap did for me back in 2008. Has it been 10 years... boy I'm feeling old today.

I've gathered that writeup into a Google doc for reference:
https://drive.google.com/open?id=1-LySs7QGptHjaQCde2PNaA-QUP2vGrSquP63De_CXiw

That was a good build, hopefully still running strong with the Tunebug's current owner. I'm getting ready (okay, maybe next year) to do a build for Penny so this is a good thread to get me thinking again.

 

[JimLaney]

Thanks Drew for the documentation of your build. I know it takes some time to create such a document. Again thanks, it will be a help to me.

 

[Boink]

If you have the head off -- replace the blanking plug between cylinders 2 & 3. Hap Waldrop posted about this in a bit more detail -- basically you replace the blanking plug with a threaded brass bolt and then have the machine shop grind it until it is flush with the head. This will prevent head gasket failure due to the recession of the blanking plug, which sometimes happens in an overheating type situation. If you search the forum for blanking plug -- you'll get the specific details.

Did this when I re-built my head. Had to as it had recessed... and made for a terribly difficult problem to diagnose (and pulled the head as a last resort). The machine shop fixed the blanking plug (as well as other routine head matters).