New Oldsmobile Enthusiast
August 7th, 2018, 10:24 PM
#1
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Join Date: Aug 2018
Location: Tyler Texas
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New Oldsmobile Enthusiast
Hi, I'm new to the forum. I have recently purchased my first Olds muscle car. A 1970 Cutlass S with a 350 auto trans. Unfortunately the engine froze and cracked at some point in the past. I have decided to replace the original engine with a 455. I own and operate a small engine performance shop where I have access to a complete engine machine shop including flow bench and chassis dyno. In the past I have built a few Oldsmobile performance engines but I have never built one for myself. I am very interested in learning as much as I can and applying it to my own custom 455 build. I look forward to build and testing some of the ideas and tricks that I have applied to other makes of engine in the past. I intend to share as much of that information with everyone and learning as much from you guys in the process. Thanks
August 8th, 2018, 04:37 AM
#2
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Join Date: Jun 2014
Location: Ft. Wayne, IN
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Welcome! Pics of you new Olds would be spectacular! You've come to the right place, numerous folks here are way happy to help you with your questions, I know they've helped me alot.
Since you are planning on upgrading your car to a 455, you might also consider upgrading the trans to a TH400.
BTW, assuming your username reflects one of your rides, what year Z06?
Since you are planning on upgrading your car to a 455, you might also consider upgrading the trans to a TH400.
BTW, assuming your username reflects one of your rides, what year Z06?
August 8th, 2018, 05:40 PM
#8
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To address the trans. I already rebuilt the TH350 with a performance kit before I found the crack in the 350 block. If i locate a TH400 before the engine is complete I will replace the TH350. If not I will use the TH350 until it fails.
August 9th, 2018, 11:25 AM
#9
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Join Date: Aug 2017
Location: Bay Area, CA
Posts: 79
Sounds like a fun project. The th350 should hold up fine and if it does break down then consider the swap would be my 2 cents. I am also a casual hobbyist so take my 2 cents for it's TRUE value, 0. 
August 18th, 2018, 11:02 AM
#14
Just an Olds Guy
Join Date: Jul 2008
Location: Edmonton, AB. And "I am Can 'eh' jun - eh"
Posts: 24,525
Nice 70.
Unless you really build that TH350 it's not going to handle anything a built 455 is going to throw at it. I'm sure you have all the knowledge and experience to build a really nice 455 that will be suited to your driving needs. If you do change to a TH400 you already know the differences for crossmember, throttle linkages, and driveshaft? Are you planning an upgrade to the gears too? Have you considered a 200 4R or an L460? They bolt in exactly the same as a TH400, only need the TV cable. It would give a great final drive ratio and rpm on highway if you decide to go grand touring.
BTW, those sport mirrors are a one year only production and worth their weight in gold.
I see Jim hasn't been back to address your question
It happened while he was driving it IIRC. Started as an electrical fire under the dash and went from there. Not enough fire extinguishers to put out the fire. Lots of interior damage and burnt paint on the outside. He sold the burnt out hulk and he says the guy who bought it restored it and sold it on BJ.
Unless you really build that TH350 it's not going to handle anything a built 455 is going to throw at it. I'm sure you have all the knowledge and experience to build a really nice 455 that will be suited to your driving needs. If you do change to a TH400 you already know the differences for crossmember, throttle linkages, and driveshaft? Are you planning an upgrade to the gears too? Have you considered a 200 4R or an L460? They bolt in exactly the same as a TH400, only need the TV cable. It would give a great final drive ratio and rpm on highway if you decide to go grand touring.
BTW, those sport mirrors are a one year only production and worth their weight in gold.
I see Jim hasn't been back to address your question
69 H/O burnt to a crisp 9/4/2010
August 27th, 2018, 03:29 PM
#16
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Well I have purchased a standard 455 block, crank, rods, and bare C castings. I have already turned the crankshaft 10/10 on the split. I have filled the heat cross over int the heads. I am working on baseline flow numbers on the C heads vs a set of Ga castings that I have. I have a posted in the parts wanted section looking for an intake manifold. I am going to start on the block soon. I will be investigating the oiling problem that I have heard about. I will try to post pics as we go along.
August 28th, 2018, 02:26 AM
#17
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Location: So. Ca.
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I picked up Bill Trovato's book on Olds engines and was surprised to read that the so called oiling problems were a myth. With good machine work and blueprinting the engines showed no difference modded or not. Nice car, good luck.
September 4th, 2018, 03:08 PM
#18
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So far what I have found is the rear main cap issue seem to be the most likely cause of Oldsmobile oiling issues. Also I scored an Edelbrock O4B intake manifold. I can not wait to get on the bench with this timeless jewel.
September 8th, 2018, 03:03 PM
#20
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Location: St. Clair, MI
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Is youre O4B a spreadbore version or squarebore? A well built Quadrajet will supply all your fuel needs, plus allows you to use factory throttle and trans downshift/throttle valve cables.
Remember your O4B is designed for off idle torque, so pick your cam accordingly
September 13th, 2018, 03:11 PM
#21
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The rear main cap on the Oldsmobile engines has an oil drain back passage for the rear main seal. This passage sometimes interferes with the oil pump to main cap seal allowing oil pressure to return to the oil pan causing low oil pressure. It is my understand that Melling has redesigned the oil pump mounting flange to correct this, but it should still be checked. Because of the nature of performance engine building , once an engine is labeled with " poor oiling system" it is very hard to change that opinion. So it is my opinion that in the past the rear main cap issue caused oiling issues in the Oldsmobile engines forever branding them with having "bad oiling systems" leading to many necessary oiling modifications. From what I have found the oil drain back in the engine needs attention. Other than that, just the normal engine building techniques. Just my thought.
November 7th, 2018, 06:48 PM
#23
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A few weeks ago I scored an unmolested 1974 Olds 455 at my local pick and pull. Here are some pictures of the "oil pressure Issue" that may have cause the 455 to be branded as an engine with a poor oiling system.
November 7th, 2018, 07:16 PM
#26
Out of Line, Everytime😉
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Location: Melville, Saskatchewan
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That probably doesn't help. Most of the failures I have seen on here and knowing guys who owned the 455, much less with the smaller main 350's, is improper machine work or too tight of clearance on the huge main bearings. Also factory soft rods, so so bottom end that can flex with the heavy parts flying around all lead to disaster. Olds didn't design the 455 to be a high RPM motor but guys have made it work with the right parts and machine work. Cutlassefi tested the OB4, he thought it was a terrible design and the Dyno numbers showed it. Nice car, enjoy.
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