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Been a while since I've posted but I'm still working to get her on the road. Recently found out that the engine has bad main bearings and was recommended I do a full rebuild. The shop originally quoted me for around 9k. I unfortunately don't have that $$$ so I decided to take on the task of rebuilding myself with a mechanic homie who has more knowledge, experience and tools than me. BUT I wanted to get some input from the real experts on how I should tackle this rebuild. I think my goal is to get her as close to stock as possible. Maybe a different cam or aluminum intake. But nothing crazy for sure. I've been reading a lot of different threads on past 400G rebuilds and taking notes.
AGAIN open to all recs on what I should do? Will post updated pics soon.
I'll be honest. With a G block, unless you're going for a numbers restoration, I'd find a 455 and rebuild that. Costs will be similar, easier to source internal parts and not as prone to grenading itself.
If you stick with the 400, hopefully those bad bearings haven't damaged the crank too badly and you can get by with a polish or .010 cut.
I bought this car from a guy who said he had the engine rebuilt. There was a new timing chain and sprocket. BUT opening it up I found that EVERY SINGLE bearing was turned. There was even one bearing that was flattened and wider than the rest. I think on the 4th or 5th piston. And there was numbers etched on the prod cap and big end im guessing to coincide with the piston number but the way it was assembled was actually backwards from its numbering. The crankshaft was was not rotating easily. And it had a '010 010' etched on it already.
It's your car and you can go whichever route you want. If it were mine, I wouldn't even consider abandoning the 400G. Sounds like you're not going to be prioritizing horsepower numbers and want a close to original strong engine. If that's the case, you'll be more than happy with a properly built 400G. Too many guys take the easy road and drop in a 455. To me, that's little better than doing an LS swap. Everybody goes straight to the 455. Dare to be different.
OK, enough of my commentary. Rebuild components for the 400G are available. Aftermarket cranks, bearings, pistons, rods etc. are out there. I know because I built mine. Hell, a lot of the stuff is the same for the 455 anyway. Talk with somebody like cutlassefi to get quality advice on parts combinations.
Yes that is 100% my plan. I have a numbers matching engine and trans and I just want it as close to original as possible.
just realized i have the wrong carb for it tho. But not sure if this will work the same.
So I will be on the hunt for the original carb 7029251 RJ if anyone has one they would like to sell me. Preferably in working condition. I bought this one off of a member here and had it rebuilt and it didn't seem to run too nice. But it could be cause the whole engine was ****.
But yes thanks for the reply. I've seen @cutlassefi pop up on every single thread related to rebuilding engines. I am def going to reach out him for some help real soon. Just took everything to the machine shop. They said it was salvageable.
Sounds like, as is all too typical, someone who knew nothing about Oldsmobile engines got their hands on it. Even if their knowledge was Ford engines I'm having trouble wrapping my head around how this individual buggered up the rod and bearing installation. What is so hard about left bank 1-3-5-7 and passenger bank 2-4-6-8?
How bad is the crank? As you may know it's 68-9 400 only if you want to stay original. If it's already been cut 10/10 the next step is 20/20 if polishing won't clear up the damage. You may find a good machine shop that can build up the bearing surfaces by spray welding them, then machine them to original diameter.
455 Cranks are inexpensive just buy a new crank have it ground 10/10. Find one with the large N or small CN 68 to 73?
400 G is notorious for spinning rod bearings so make sure you get the clearances right and go with an aftermarket rod if its in the budget.
If your car is a 4 speed you will need a four speed crank or drill the new crank for a pilot bearing.
When selecting an aftermarket rod make sure it fits through the small bore.
Last edited by Bernhard; August 23rd, 2023 at 07:43 PM.
Nice, but last thing I heard you say was you wanted to keep it original ...?
"Everyone has a plan until they get punched in the mouth"-Mike Thyson
That was the plan going in until I learned the original cam was busted beyond repair. At that point i was convinced by the guy helping me to go for a roller cam bc of efficiency and blah blah blah. Made sense to me and I feel like I'm still keeping all the original parts for potential later original rebuild and I'm still keeping the factory heads, carb, and exhaust manifold. He also convinced to upgrade the water pump since we discovered it was not the original 400269 but rather the set up off a 65-67 442 384783. To me it seems like a slight upgrade from bone stock but still has the original engine essence if that makes sense haha..still plan to keep interior and body all original.
You might want to consider headers as they don't detract in my opinion and are a very day two type modification.
I def have been considering headers at some point. But I'm also getting very impatient and want to drive her asap. Also, it's my first muscle car and I really want to feel the upgrades after this..
I def have been considering headers at some point. But I'm also getting very impatient and want to drive her asap. Also, it's my first muscle car and I really want to feel the upgrades after this..
Is there any headers you recommend??
Bernhard wrote:
We ran KB and hooker headers in the past both fit well and sealed well. I don't have any current experience with other brands that are on the market today. I do like the look of the ARH headers, they are not cheap. You should do a search as this question has been asked many times.
If you are looking to chip away I'm a fan of classic daytwo modifications.
1. Taller rear gear
2. Ignition MSD 6AL box or other brand.
3. Fuel pump that can keep up to performance modifications
Bernhard wrote:
We ran KB and hooker headers in the past both fit well and sealed well. I don't have any current experience with other brands that are on the market today. I do like the look of the ARH headers, they are not cheap. You should do a search as this question has been asked many times.
If you are looking to chip away I'm a fan of classic daytwo modifications.
1. Taller rear gear
2. Ignition MSD 6AL box or other brand.
3. Fuel pump that can keep up to performance modifications
Gear is a must. I'm realizing that with my 400G build-I kept the 3.23s and im regretting not bumping up to at least 3.55. Also, with headers.. isn't there a concern with the factory routing for power brake setup/lines/valve?
Gear is a must. I'm realizing that with my 400G build-I kept the 3.23s and im regretting not bumping up to at least 3.55. Also, with headers.. isn't there a concern with the factory routing for power brake setup/lines/valve?
Bernhard wrote:
I never had problems with the KB or Hooker headers. Most aftermarket bolt performance upgrades are not OEM bolt on, but require some minor modification. I personally enjoy this part of the hobby as I'm aiming to make as clean a install as possible. I always appreciate seeing others clean install of aftermarket parts. Some go to great lengths to hide or make their performance up grades appear stock, this shows how creative the installer is.
Last edited by Bernhard; March 24th, 2024 at 04:28 PM.
QUESTION: I installed the edelbrock aluminum intake manifold. But now I need to install a electric choke for the carb. Does anyone have a good recommendation for the electric divorced choke kit?
Yes that is 100% my plan. I have a numbers matching engine and trans and I just want it as close to original as possible.
just realized i have the wrong carb for it tho. But not sure if this will work the same.
So I will be on the hunt for the original carb 7029251 RJ if anyone has one they would like to sell me. Preferably in working condition. I bought this one off of a member here and had it rebuilt and it didn't seem to run too nice. But it could be cause the whole engine was ****.
But yes thanks for the reply. I've seen @cutlassefi pop up on every single thread related to rebuilding engines. I am def going to reach out him for some help real soon. Just took everything to the machine shop. They said it was salvageable.
Will post more updates as I go.
depending on your body build date a 29251 with a build date of the 79th day of 69 is the correct carb for an automatic 442. It's well documented that the "70" was left off on some carburetors.
Gear is a must. I'm realizing that with my 400G build-I kept the 3.23s and im regretting not bumping up to at least 3.55.
I would tend to disagree ... these engines are (in)famous for being low-end torquers that don't like to rev. 3.23 is probably optimum for keeping a G-block in its sweet spot. 3.55 might start to run into the law of diminishing returns unless you're going to address limited breathing and reliability over 5000 RPM, and at that point you might as well swap in an LS and be done with it.
I would tend to disagree ... these engines are (in)famous for being low-end torquers that don't like to rev. 3.23 is probably optimum for keeping a G-block in its sweet spot. 3.55 might start to run into the law of diminishing returns unless you're going to address limited breathing and reliability over 5000 RPM, and at that point you might as well swap in an LS and be done with it.
That last part was a joke. Don't do that.
Lol. To be fair, I've since realized part of my issue was transmission related. Haha. I do agree though, the higher (numerical) gear will drive the need for better flow the be more and more.
August 12th, 2023, 11:38 AM
