Rebuilding a 225.

Alright, I have a 69 Commando, with the 225. Now a rebuild kit for the 225 is just a touch over $450.00 I've looked and priced it around, and thats the average. Now a 231 Rebuild kit is $284.00. Both are master kits and include the same things. My question is this; I read that the cams and bearings are different, but ifi bore it .05 over or to 3.8 can I use a 231 kit? Can it be bored that far? Will I be able to use the cam? Likelyhood of being able to reuse the Cam bearings? It sat for 5 years before I bought it for $500. Paid $250 for a 72 for body parts and spares. Pretty nice. Right now her name is ol maude, but once complete I might just rename her Sassy.

 

There's some excellent information in the Technical Library at the top of the page. Not much interchanges. Best to spend the extra on the 225, just my humble opinion. Whether you choose a 225, a 231 Odd fire or a 231 Even fire, soon as you say Buick, open your pocket book.

 

So Talked to Tyson at www.performance-auto-parts.com and he told me, after talking about a commando that he is looking to buy for 5-10 minutes, that the parts are all the same, except the cam. He said that the two kits even use the same cam bearings. He told me that he would be more than happy to sell me a 231 kit with a 225 cam for the same price. Part number is MK-Bu231o. Nice people so far, the last question that needs answered now, is the question about boreing .05 over. Anyone done it? I read about the guy that was going to add the super charger to his and he said that he did. I know that it depends on the condition of my block, but as a general rule, can I go .05 over?

 

Before ordering you should check with the tech department at TA Performance. Buick is their only thing and they would know for certain. Seems to me that I remember boring 0.040 over to use stock 231 pistons and rings. This was 10 years ago so I could be mistaken.

 

I plan to have the machine shop check to see if it could be bored out before I order the kit, I am going to have Tyson check the diameter that the cylinders need to be and confirm that way. I believe it has to b 3.8 where as the 225 is 2.75. That is the information that I have found here and on other sites.

 

Come on noone has done this?

 

I have heard of it (in one of Dick Datson's books)... haven't done it. I understand that the 231 pistons are equivalent to a 50-over standard bore on a 225. I think the main thing you would be giving up is lifetime of the 225 block. At 50 over, you may not be able to bore the block again. Most conventional blocks are thick enough so that they can be bored twice, once at 30 and again at 60, before the wall thickness becomes questionable. Even at 60 over, some engines can go further if sonic tested for core shift.

What are your plans for this engine? Have you measured the bores? If the bores aren't terribly tapered, you may be able to reuse your pistons. The pistons are the most expensive part of a rebuild, and if the engine is for a hobby car, you can get away with more bore taper than you might tolerate in an engine that you want to put a lot of miles on. Excess bore taper will make the rings fatigue faster than they would if the bores were straight. However, this may not matter if you aren't going to drive the car a hundred miles a day for the next decade.

Another thing - have you measured the compression and oil pressure of this engine? Why do you think this engine needs to be rebuilt?

 

I'm not too keen on ever boring this engine again, the best way to never have to tear an engine down again is good maint, and not letting it sit. I got the engine freeed from the transmission, and getting ready to pull it and tear it down.

the main reason that i ask about this is that Buick just bored the engines out for part compatability and cost effectiveness with buick 350. Did they just bore it out and forget it? or did they modify the tooling to allow for more metal.

I know they didn't for the 327 and 350 they just bored out more metal.

I don't think I'll be able to reuse much of this engine, it sat for a LOOOOOOONG time outside, under a tree, with no care. It's not going to be a daily driver, but should have the option for being once my son gets older.

 

As I understand it, the casting is different between the 225 and 231. A big auto company would not simply bore out another 50-thou from the block and use the same old casting. Instead, they would adjust the casting design so that the rough bore is 50-thou larger, and the bore wall thickness is the same. They do this by changing the mold and by changing the "core" - the sand inside the block that forms the water passages. Check the tech pages to see if the casting numbers are the same - I'm sure they are not.

I understand the claim that Buick wanted to rationalize the line by sharing more parts between the 231 and 350, and I think that's likely true.

However, it would be uneconomical to spend the machining time on the extra boring, in addition to throwing away that much material and extra tool life. The block wall thickness is designed to minimize the material required, provide sufficient wall thickness for strength and thermal stability (no hot spots!) and to accommodate any core shift during casting. Optimizing engine design is a big deal to these manufacturers... it's what they bet the company on. This is not somewhere that they would skimp.

Also, I doubt very much that the 327 and 350 use the same block casting if they have different bore diameters. As above, it's just not economical to throw away time and materials on unnecessary machining. Sounds apocryphal to me.

 

Another quick suggestion, which you may not like...

If possible, I'd for darn sure start and run the engine before I started to tear it down. You can tell a lot about the condition of the engine from how it runs, much more than when it's sitting on the shop floor. You may be able to avoid a tear-down entirely.

 

Well the carb was rusted through and the jets were completely gone, the air cleaner wasn't on the carb, and I'm pretty sure from the lopsided crank turn that its a touch warped.

307(I believe) 327 and 350. Same Core. Chevrolet.

 

Looked it up. I'd believe the 327 and the 350 have the same casting, because they have the same bore and different strokes (4.00"x3.25" and 4.00"x3.48" resp). The 307 looks like a 327 crank in a 283 block, at 3.875"x3.25". So, no contradiction, but not comparable to the 225 vs. 231 question.

 

See now that is why I am asking these questions, I knew they were the same core, because derby cars use the 307 because of its thick walls, not 350s they cool easier. That is why I thought that about this block. I knew the crank was different in 307, and 327.

That is why I prodded so much. See I found an answer, that I was wanting to get!

Fantastic. I now know why they had the same core and different displacements, not for the reasons I had thought.

Thanks, I think.

 

I guess i'll get in on this.went out to the garage and retraived the 1969 MOTORS manual
chev 327 bore 4.00" x stroke 3.25"
302 4.00" x 3.00"
350 4.00" x 3.48


buick 225 3.750" x 3.40"
300 3.750" x 3.40"
340 3.750 " x 3.850"
350 3.800" x 3.850"
231 3.800" x 3.40 "

just having a little fun with these numbers.remember that all these pistons had different compression ratios ( flat top,dished.domed,etc) and different compression height (center of wrist pin too top of piston.also had to go back and get thenewer book cuz i forgot 231 wasn't out till 1975 when buick bought it back from jeep.

 

IIRC the main reason to use the dauntless piston is compression ratio.225 had 9:1 compression and the 231 had 8:1. thats quit a bit to give up for a few cubic inches. i used .020" over pistons from TA Performance.the 231 pistons are a lot less moneybut i would have the cylinders sonic mapped before boring .050" .

mike s.

 

Okay late on the thread but heres my 2 cents.

The engine can be bored we elcted to only do 40 Over bore so if there was a problem we could always take to to 50. 50 over makes the 225 a 231 and to what I understand is the max bore you can do on the 225 block.

It's been a year or so since I ordered my rebuild kit, but I think it came from the same people but I had a nightmare getting it delivered. Firstthey said UPS lost the order and had to reship, then they left out parts.

and on and on.

I did a 40 over bore, Instead of going with the stock cam though I went with http://www.compperformancegroupstor...roduct_Code=CL63-235-4&Category_Code=BuickCam

We also did a mini port and polish

Also if you are ordering new rods watch out. The 225 Rods are not self oiling and a lot of folks will try to sell you a self oiling rod supposedly for the 225, but if you double check the measuremment the Self oiling rods are too short. I went through 3 sets of rods before I actually had Napa find me a set that fit perfect. I had a simalar problem on new Valves. The rods from COMP cams do not fit the 225 they are self oiling and too short for sure. I think they cross ref all the 225 parts with the 231 and although several parts are interchangable not everything is so.

I was VERY picky on the rebuild as was my builder. Mostly since he builds professinal race engines he doesnt play around unless everything fits perfect.

I did do an Offey Intake with a Holley 390 CFM carb, Had some over heating and tuning issues at first, but this was due to out of sequence firing order, bad radiator (or one that couldnt handle the new engine) and carb problems which Holley fixed for me.

Here is my engine now less the rad and the new Braided Rad hose:



I could go one more, like my Rocker pedestals not measuirng to spec, looks like someone in the past might have milled the stock ones down or the foot on the heads had been milled down. To get proper Rocker Geometry and I mean 100% Dead on we ended up having to shim all the Rocker pedestals.

For the record, after your build DOUBLE check your cooling, Even though my rad had been recored to a 3 core rad, it needed to be rodded and flushed, I had some BAD overheating problems early on boiling the fuel in the carb etc I have my carb on a 1" spacer block as well.

Now for the bad news for me

I dropped a valve seat on the number 5 piston last week. No idea why besides maybe early tuning problems casued it? (over heating and extremely over rich runiing) Valve looks okay but not sure, piston is most def "Injured" but not sure how bad We need to pull it and check it out worried about rod and bearing as well.

 

Okay if your still watching this thread I got a BIG heads up for you.

DO NOT USE SEALED POWER PISTONS

Got my new single piston in from Sealed Power/Fed Mogul. They changed manufactuers. The new 225 Pistons are pieces of garbage. Heads are cast not even milled, core thickness is random in places, they are 40 grams heavier than the old Sealed Powers.

Unfortunatly, Sealed Power is one of the few makers of the piston for the 225 besides Egge?(spelling?)

If you are still building this engine and you want to do a 40 over bore, Sealed Power is sending me an entire new set of Pistons, because of this. I might be selling these to get back some of my $$ for the engine work since I am not using the new pistons, we repaired the orginal piston by welding and remilling the weld since the seat gash wasnt that bad.

Had to bad mouth the pistons but then offer to sell you a set but I personally would not use these pistons If I was trying to build more performance into the engine, based on the head cast its a lower comp[ression than the old pistons for sure. Probably closer to the 231 Compression.