ive just acquired at 425 olds motor. Dont know anything about them and was wondering if anyone could tell me bout them. ratings? reliability? is it worth building?
They are good engines. Depending on what you want to do with it, sure, it's worth building. They can make a lot of torque, as they were originally designed to haul around big Olds lux-o-barges of the '60s. Stock heads should be either A, B, C, or Ca, which are all decent enough as Olds heads go. For more serious use, you may want to step up to Edelbrock heads, if you plan to have the stock heads ported; it's more cost-efficient. One thing to note before doing anything with it- depending on the year and application, it could have either one of two different lifter diameters, and also either one of two lifter bank angles. Cams and lifters are not interchangeable between the setups, so confirm what you have before buying.
Great motors , I spin mine to 7k on occasion, been in car 15 yrs since I built it . A lot of prep work to do that though , Nothing to exotic about it . Tell us what you want it to do and we can give specifics on how to get it .
425s all have forged cranks. Stock HP ranged between 345 and 375 HP. Most had 10.25:1 compressions. Need to be careful of lifter bank angle. Many had a 45 deg angle - later Olds motors had a 39 deg angle. If you are changing the cam, be sure you get the one that matches the lifter bank angle. The 1964-67 Olds motors used a different crank flange bolt pattern than the 1968-1990 motors, so you need the flywheel to match as well. Otherwise, these are externally identical to any other big block Olds motor and all aftermarket parts fit the same.
Had one in my chopped 49 Studey pu. Loved the power, no problems in 5 years of use, except the one motor mount kept seperating, torque. Was daily transportation and raced alot. Miss that truck.
thanks guys! its going in my 58 apache as a daily driver after the rebuild of course. not going to crazy with it, ill probably do some gasket matching and maybe a mild cam but other than that stock. its a 67 model also if that helps
One other note of importance. The crankshafts are different for automatic and standard shift transmissions. The hole for the pilot bearing is not in the motors that ran auto transmissions. Couple of the well know Olds builders sell a special pilot bearing that fits the auto crank, and you shorten up the input shaft in the tranny for clearance(about 3/16"). If your going through your motor( and plan on running a manual trans), the machine shop can drill the crank for a standard pilot bearing. I have a 425 going into my 49 Olds 88 coupe, so I have learned quite a few things about Olds motors in the last 6 months. Good luck with your build.
had a 65 88 425 ultra high comp and the car was an torque monster would with most anything within reason, hard to get gas for to be fair.
Maybe post a pic of the cast # and letter beside it. 425's with a 45 degree bank angle are a little more pricey and less desired. IMO There is a lot of turmoil when it comes to a '67 425 the best way to tell is with a straight edge... "With the manifold off, put a straightedge on the intake surface of the head. Measure the distances (above and below the head) between it, and the pushrod. If they are the same, you have 45° bores, if the bottom is closer, than the top, it's 39°. I don't remember the number, but it's more than obvious." from another source. I hope this helps you out. If you can post the casting # on the block we can tell you (normally) from that. As far as worth building, it depends on what you want to do with it and budget. Last rebuild kit I priced was close to $1,300.00
They aren't worth the powder it takes to blow one to hell. I have to go to Tulas to visit family in the next week or so. Give me directions and I'll haul that turd off for ya. Good engines, lots of power adders available if you are into that. Dependable as a hammer.
The Jalopy Journal
