425 rebuild advice

[1977 Cutly]

I've rebuilt several engines, but I want to know specifically from people with 425 experience.

What would you do differently? What would you do over the same way? I'm looking for a long lived street engine very close to factory specs.

Is there a parts house I should definitely buy from, or stay away from?

[Graniteman]

My advise is to get on realoldspower.com, from there get in touch with M&J or one of the other OLDS specialist guys that you'll see as board members there. There are 3 or 4 guys you'll find there that are real good and good to deal with, these guys really know their sh*t!
Also I highly recommend getting a copy of Bill Trovato's book on building OLDS' , you'll find him there also!
JMO but I would stay away from the guy in New York (Andy not Bill), Dick Miller, and Mondello (Joe Mondello is dead now and hadn't had anything to do with the operation of Mondello Olds in California for several years anyway)

Start by getting and reading Trovato's book, you'll be glad you did!

Mike
TOA #70

[xgecko]

I have to say that while I have heard many a horror story about Mondello under Lynn, they have been fantastic to deal with as far as I am concerned. A bit pricey, yes, but they have taken care of me very well and I am no longer concerned about doing business with them - I was a bit wary at first but they had parts I needed so I took a chance and have no regrets.

I have used their products in all of my Oldsmobile rebuilds and have yet to have an issue. Their Hydraulic Roller Cams have the proper cam gear hardening such that I did not need to worry about the gear being eaten by the distributor gear and the 94-95 profile sounds nasty and produces very strong power.

I suspect they got burned by their attitude in the past and have taken steps to change how they operate. I would not hesitate to do business with them and in fact will no doubt be buying products from them in the future.

I cannot make any guarantee that your experience would resemble mine, nor that they will give perfect advice, but so far I have had nothing but a good experience with them. I think people need to consider that they may have learned from past experience and give them a chance again.

Just my 2 cents worth...

[69W34]

What if any problems are you experiencing in the way of problems? Are you in contemplating a rebuild for the long haul or in the mood to tear the motor apart to see what's what?

[1977 Cutly]

What if any problems are you experiencing in the way of problems? Are you in contemplating a rebuild for the long haul or in the mood to tear the motor apart to see what's what?

The mileage on my Toronado says 151K. I am the third owner, and the last owner swears its original not rebuilt. Its tired and burns a quart of oil every 300 miles. It Still starts and runs like an Olds.

I pulled the 425 out of my 66 parts car, it had green coolant in it, the oil looked good, and it turns over nicely. I want to rebuild the 425 thats on my engine stand right now, while leaving the car running until I have a new powerplant for it.

I'm not interested in a 'perfect' restoration or building a 800 hp street freak. I want to rebuild it with the best modern parts, but stay close to 400hp or whatever was stock. I want to cruise this car, not race it. and I want to cruise it for a long long time. I want to wear this out again.

I bought this car to drive it. Everyday. Everywhere. As long as the road is salt free. I love driving this car. My 455 Cutlass Supreme mostly sits since I bought the Toronado. I feel like I was born to drive THIS car. (There are many like it, but this one is MINE!)

[xgecko]

You might consider one of the smaller of the Mondello cams. I used a JM18-20 back in the early 1980s and it was a great compromise between a bit of extra performance with a fairly smooth idle and good low end power.

I built a motor two years ago with the next step up - the JM 20-22 - and it was just aggressive enough to sound very good and to lose a bit of vacuum. I should have had good vacuum but for some reason did not and never found the cause if any - it could have been the combination of piston, cam, and lack of headers but I am not sure as I threw a bearing in that motor.

My current cam is the RH 94-95 Hydraulic Roller and I would not recommend that unless you want a very lumpy idle and are willing to deal with the issues arising from lack of vacuum. I personally love this cam; it is right at the bottom edge of a truly nasty idle which is where I want it yet it pulls from about 1,500 on up. This cam definitely needs a higher stall torque converter so it is probably not for you.

Of these three, based on your description below, I would suggest the JM 18-20 or, if you want a bit more cam and are willing to deal with some potential issues with vacuum (I upgraded to a hydroboost braking system which eliminated any issues while giving me much better braking performance).

If you have the cash I would recommend the equivalent grind to the JM 18-20 in a roller cam as roller cams eliminate the need to use a high-zinc oil. If you use a flat tappet be sure to either use the Castrol 5W-50 oil designed for classic cars, the equivalent in another brand, or add ZDDP (the needed zinc compound) to whatever brand of oil you want. Drive for the first 3,000 miles on non-synthetic then switch to synthetic.

Otherwise find a good shop you can trust and use good components. You might consider the Mondello oil restrictor kit which helps keep the oil in the bottom end where it is needed. I have done it both ways and it might have saved my last motor since I pumped all the oil up to the top due to a high pressure AND high volume oil pump. Stick with a stock oil pump unless you plan to use the oil reliefs on the faces of the rods which allows more oil into that area but may need a high volume pump.

I just got my fully blueprinted and balanced motor back and I am as happy as can be with it. These Oldsmobile Big Block are just wonderful motors and you should get many miles out of a good rebuild.

[69W34]

"I bought this car to drive it. Everyday. Everywhere. As long as the road is salt free. I love driving this car. My 455 Cutlass Supreme mostly sits since I bought the Toronado. I feel like I was born to drive THIS car. (There are many like it, but this one is MINE!)"

Well Matt, I would go back stock, it will most likely need to bored it out 20/30 thousands and would not be unusual give its miles oil consumption. There are of course the laundry list of things to buy and do but first word about 'blueprinting' a motor. There is a mystique that surrounds the term blueprinting and often followed by $$$$ signs.

In truth the blueprinting process is nothing more than taking the time to assemble the motor back to within factory specification, all of which are listed in the factory service manual under the engine section. This will give you the best case for long health motor life. It goes with out saying short cuts or blowing off an item because of expense it would be no more than pissing $$ down the drain.

Boring (the block) aside with the exception of the crank everything everything else can be correctly dialed in. As for the crank they can sometimes be polished and remain with tolerances if not then it will need to be ground, try to avoid going over .020 though preferably stay as .010 .
The reason: baring material is soft and the thicker it is, over time, (it can, not that it will) egg out and effect oil pressure.

As far as recommendations: I would consider balancing, and B/C heads from a 88/89 as the intake valves are smaller 2.00 / 2.077 intake the exhaust are the same size 1.629 /1.629 the larger intake beneficial at higher RPM and smaller valve provide better low end torque.

As for cams I would find something that provides good bottom end and mid-rang torque, unless you planning to drive this 90 mph all day high lift /rpm cams are not worth it. Crain, Comp Cams and yes Mondello. Follow the cam with Cloyes true roller timing chain or similar and god sakes stay as far away as you can from high volume oil pumps their a (PITA)

If you have the expertise to build the motor your looking at a cost of $1500 -$1800 give or take though you may need to borrow or buy a few tools, should you choose a reputable shop built it for you it goes up from there.

Hope this helps Matt

PS There will be an engine repair article in upcoming Drive.

[Graniteman]

Just a couple of quick notes; IMO I can't stress enough how good Trovato's book is, [u]he's noted for his race car work having the fastest Olds in the world but the book covers lots of practical info, I think everyone who wants to build an Olds that lasts should read it!
Also as many people know Engle Cams ground all the Mondello cams and unless things have changed Mark Engle is the man to talk with about Olds cams.
Joe Mondello help me very much and spent plenty of time with me on the phone 30+ years ago when I was racing Olds powered oval track cars. Just didn't want anyone thinking I had anything but respect for Joe RIP.[u][/u] [/u]Mike

TOA # 70

[xgecko]

Graniteman:

My comments about Lynn at Mondello's was more or less to offer my experience which so far has been quite the opposite of all the stories I see on the net. I do not doubt many of these stories are true, however, I get the feeling that Lynn figured out that it was hurting his business and implemented the changes needed to turn it around. This may or may not be the case, the only thing I know for sure is that so far I have been very happy with them. I cannot say that this will hold true for others, but at least you know I have had a good experience so fa.

Regarding the cams, I think you are correct about them being sourced from Engle. This may hold true only for the flat tappet cams as I do not see any roller cams for the Olds listed in their catalog:

http://www.englecams.com/downloads/2010_engle_catalog.pdf

Cutly:

As I mentioned, the 18-20 grind is a great balance between a performance cam and a stock cam. You may lose a small amount of off the line performance with the stock torque converter but it is likely to be unnoticeable. I recently ran the 20-22 grind with the stock torque converter and it worked quite well so the lesser cam should work fine (I used a high stall converter years ago when I had the 18-20 cam; this was to maximize performance by allowing the motor to rev up to a point where it develops significant power before it sees the load but it will work fine without the high stall converter). Feel free to PM me if you want more details.

[Schurkey]

You might consider the Mondello oil restrictor kit which helps keep the oil in the bottom end where it is needed.

1. The restrictor kit cuts oil to the cam bearings. It's pointless. There isn't that much excess oil going to the cam bearings.
a. The cam bearing clearance is it's own restriction.
b. If you aren't satisfied with the cam-to-bearing clearance as a restriction, you can simply re-drill the oil supply hole in the bearing an inch over from the original location, and install the bearing with the new, smaller hole aligned with the oil passage. Costs absolutely nothing beyond your labor to drill a few holes.
c. The excess oil on the top-end comes through the lifters, not the cam bearings. It's not practical to mess with this as long as hydraulic lifters are involved. Better to drill the tiny oil return passages in the heads oversize than to restrict oil supply to hydraulic lifters. With the return passages oversized, the oil can return to the pan better.

There is NO need to buy a "restrictor kit", and then pound the restrictors into the oil passages.

Stick with a stock oil pump unless you plan to use the oil reliefs on the faces of the rods which allows more oil into that area but may need a high volume pump.

Olds and many other manufacturers quit the "spurt holes" on the rods as they felt they didn't do any actual good, but may contribute to excess oil on the cylinder walls.

These Oldsmobile Big Block are just wonderful motors and you should get many miles out of a good rebuild.

Rebuilt properly, it'll be BETTER than new by a considerable margin.

As for the crank they can sometimes be polished and remain with tolerances if not then it will need to be ground, try to avoid going over .020 though preferably stay as .010 .
The reason: baring material is soft and the thicker it is, over time, (it can, not that it will) egg out and effect oil pressure.

If you can buy bearings for the reground crank, you'll be fine. If they make .060-undersize bearings, the crank will have no problems with a .060 cut.

The soft bearing material isn't any thicker on an undersize bearing, the steel shell is thicker.

As far as the myth about "weakening the crank" with a regrind, be aware that until the Communists and the Communist Collaborators flooded the market with cheap crankshafts, it was a common Chevrolet practice to cut 400 cid SBC crankshaft main journals .200 to fit into 350 cid SBC blocks. Makes a .030--.040 cut look like childs-play.

As far as recommendations: I would consider balancing

ABSOLUTELY.

, and B/C heads from a 88/89 as the intake valves are smaller 2.00 / 2.077 intake the exhaust are the same size 1.629 /1.629 the larger intake beneficial at higher RPM and smaller valve provide better low end torque.

I'm thinking you mean heads from 68/69, not 88/89.
Putting the 2.07 intake valves into castings originally machined for 2.00 valves gets you onto fresh iron, and with no valve recession. The 2.07 valve is still very small for a 400+ CID engine. There's no downside other than cost.

There is perpetual debate about installing hardened seats for the exhaust valves. Some folks still bring up the "Olds heads are high-nickel, and don't need hardened seats" argument. GM didn't debate, though--they went to hardened exhaust seats across the board in the early '70's. If your machinist can't install seat inserts into an Olds head...you need a different machinist.

and god sakes stay as far away as you can from high volume oil pumps their a (PITA)

But the bolt-on pickup on the Mellings high-volume pump is a nice touch. Better than a press-in pickup.

PS There will be an engine repair article in upcoming Drive.

I would JUST LOVE to review that before it's committed to ink and paper.

What hasn't been mentioned--or at least I didn't see it--is that when the machinist has the block for boring and honing, insist that the machinist install a torque-plate before honing the cylinders. The cylinder walls move quite a bit when the heads are torqued on, the torque plate simulates that stress during honing, so the cylinder walls are round AFTER torquing the heads on.

I do not want the machinist to install any oil gallery plugs. I put a soapy brush though all oil passages, so I just have to remove any plugs he's put in. If I had a cam-bearing installation tool, I'd tell him to leave out the cam bearings for the same reason--I do not trust the machinist to clean the block, and until the block is cleaned to my satisfaction, nothing else should be installed into it.

Since there isn't a proper supply of steel-shim head gaskets any more, and since "rebuilder" pistons are designed to be EVEN FARTHER down-in-the-hole, you may want to assure the block is "zero-decked" to match the piston/rod combination selected. If you don't deck the block so the pistons are level with the block, you'll destroy quench/squish, and increase the potential detonation problems. Stock Olds head casting have almost no quench area, though. There is some debate as to whether it's important to maximize the tiny quench area; or if that quench area is so small that it just doesn't matter.