1968-1976 455 "block" differences.
March 20th, 2018, 09:09 PM
#1
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1968-1976 455 "block" differences.
Hello everyone, I'm new to this forum. Have been a member for a total of 2 minutes now. I have a 1972 F85 that I bought that has been cosmetically converted to a W30. Before anyone ask, yes I bought it knowing that and it is running and driving with a 2 barrel 350... the car is pretty cherry but I don't feel right with that 350 rocket on the hood. You guys probably understand.
Now to my question. I have been given the opportunity to purchase a 455 olds + th400 for a pretty sweet deal! It came out of a 1975 car, don't know what car tho. I've been researching and read articles and tech manuals to find an anwser but can't find anything... I know that in that year they started cramming all the emissions stuff and reducing the compression and killed power. But is the block and internals the same as the previous years? I'm planing on going with aftermarket top half.
Now to my question. I have been given the opportunity to purchase a 455 olds + th400 for a pretty sweet deal! It came out of a 1975 car, don't know what car tho. I've been researching and read articles and tech manuals to find an anwser but can't find anything... I know that in that year they started cramming all the emissions stuff and reducing the compression and killed power. But is the block and internals the same as the previous years? I'm planing on going with aftermarket top half.
March 21st, 2018, 02:49 AM
#2
Old(s) Fart
Join Date: Mar 2007
Location: Northern VA
Posts: 47,311
Welcome. The only difference in the blocks is the presence or absence of the provision for the clutch Z-bar pivot on the newer blocks. If you are running an automatic, there are no other meaningful differences. Note that Olds varied compression ratio with the piston dish, not the chamber size in the heads.
March 21st, 2018, 05:30 AM
#3
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Join Date: Nov 2008
Location: Central Fl
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There are some other differences, both good and bad.
First the good. The drain backs at the ends of the decks are scalloped away vs just having a 5/16-3/8” hole there.
Secondly I’ve found the cyl walls to be every bit as thick in the later blocks as the early ones.
Now the bad. That short block most likely has a true cast crank in it, not a Nodular one, and large dished pistons. If you’re planning on putting an aftermarket top end kit on it you’ll need to mill the crap out of the heads to get any decent compression with the stock pistons. And with the improved power level you’re playing with fire regarding that crank.
Pull it apart, put the right piston in it, a Nodular or aftermarket crank, THEN put your top end kit on it. You’ll be glad you did it that way I promise.
First the good. The drain backs at the ends of the decks are scalloped away vs just having a 5/16-3/8” hole there.
Secondly I’ve found the cyl walls to be every bit as thick in the later blocks as the early ones.
Now the bad. That short block most likely has a true cast crank in it, not a Nodular one, and large dished pistons. If you’re planning on putting an aftermarket top end kit on it you’ll need to mill the crap out of the heads to get any decent compression with the stock pistons. And with the improved power level you’re playing with fire regarding that crank.
Pull it apart, put the right piston in it, a Nodular or aftermarket crank, THEN put your top end kit on it. You’ll be glad you did it that way I promise.
Last edited by cutlassefi; March 21st, 2018 at 05:34 AM.
March 21st, 2018, 02:43 PM
#4
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Thread Starter
Join Date: Mar 2018
Posts: 19
There are some other differences, both good and bad.
First the good. The drain backs at the ends of the decks are scalloped away vs just having a 5/16-3/8” hole there.
Secondly I’ve found the cyl walls to be every bit as thick in the later blocks as the early ones.
Now the bad. That short block most likely has a true cast crank in it, not a Nodular one, and large dished pistons. If you’re planning on putting an aftermarket top end kit on it you’ll need to mill the crap out of the heads to get any decent compression with the stock pistons. And with the improved power level you’re playing with fire regarding that crank.
Pull it apart, put the right piston in it, a Nodular or aftermarket crank, THEN put your top end kit on it. You’ll be glad you did it that way I promise.
First the good. The drain backs at the ends of the decks are scalloped away vs just having a 5/16-3/8” hole there.
Secondly I’ve found the cyl walls to be every bit as thick in the later blocks as the early ones.
Now the bad. That short block most likely has a true cast crank in it, not a Nodular one, and large dished pistons. If you’re planning on putting an aftermarket top end kit on it you’ll need to mill the crap out of the heads to get any decent compression with the stock pistons. And with the improved power level you’re playing with fire regarding that crank.
Pull it apart, put the right piston in it, a Nodular or aftermarket crank, THEN put your top end kit on it. You’ll be glad you did it that way I promise.
March 21st, 2018, 05:17 PM
#5
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Join Date: Nov 2008
Location: Central Fl
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If you want to raise the compression first then that’s ok. But why do two cams?
And if you go with aftermarket heads then the added lift would be beneficial.
And there aren’t any forged cranks for a 455 for less than $800.00. Overkill for your application.
And if you go with aftermarket heads then the added lift would be beneficial.
And there aren’t any forged cranks for a 455 for less than $800.00. Overkill for your application.
Last edited by cutlassefi; March 21st, 2018 at 05:28 PM.
March 21st, 2018, 08:22 PM
#6
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My train of thought was to build it with good internals and put it back together with the stock everything else due to budget.. But now that I think of it I don' know if I would want to put in all the old cam, push rods, etc.. Might have to consult with an engine builder..
March 22nd, 2018, 05:24 AM
#8
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Location: Bradenton, FL
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Just for clarity....you want to take it apart twice? Do it once, enjoy it...you'll be glad you did. Most of us have been through the "oh I'll just do it later" and our cars are still in pieces years later... If the car runs and drives now, run it and build the motor on the side.
March 22nd, 2018, 08:14 AM
#9
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Just for clarity....you want to take it apart twice? Do it once, enjoy it...you'll be glad you did. Most of us have been through the "oh I'll just do it later" and our cars are still in pieces years later... If the car runs and drives now, run it and build the motor on the side.
March 26th, 2018, 11:50 PM
#12
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SY2455: I still have a a couple of months. Lucky I'm stationed where my attire family lives so if I didn't get it running I could at least leave the 455 here cut my losses and sell ...which I'm pretty sure I can make money from. But your absolutely right! It would be a safer idea to run it with the 350.
hurst68Olds: I'm aware of the drive shaft issue. I will have to adjust to length once if I decide to put it in the car. I have done my research and know what is tangible and what is not. There is a lot of ideas I want to do the my Cutlass but I'm still really just in thinking phase... and that's also why I joined this forum so I can chat with experienced wrenchers like you all and get some good insight.
Thank you all for the replies btw.
hurst68Olds: I'm aware of the drive shaft issue. I will have to adjust to length once if I decide to put it in the car. I have done my research and know what is tangible and what is not. There is a lot of ideas I want to do the my Cutlass but I'm still really just in thinking phase... and that's also why I joined this forum so I can chat with experienced wrenchers like you all and get some good insight.
Thank you all for the replies btw.
March 27th, 2018, 07:00 AM
#13
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Join Date: May 2014
Location: Swanton, Ohio
Posts: 126
When I was in the service, we had a guy get permission from the Captain to bring his car on board and do a complete overhaul on the engine while deploy and passing Ammunition all over the place. The rest of us left our cars with love ones or friends. Maybe you can do that if you plan on keeping the car, that way you will have a fresh engine when you get back.
March 27th, 2018, 10:31 PM
#14
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Join Date: Mar 2018
Posts: 19
When I was in the service, we had a guy get permission from the Captain to bring his car on board and do a complete overhaul on the engine while deploy and passing Ammunition all over the place. The rest of us left our cars with love ones or friends. Maybe you can do that if you plan on keeping the car, that way you will have a fresh engine when you get back.
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