394 pistons
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Joined: Jun 2024
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394 pistons
I'm rebuilding 64 394. Im looking for low compression 0.030 over. I contacted Egge, they got back to me and quoted me over$2900, for a set. So I thought what about 455 pistons and deck the block 0.015 as a better alternative. What is cost approximately for deck job, and what are your professional thoughts on this. Thanks for your time!
Registered User
Joined: Sep 2017
Posts: 5,215
From: St. Paul Minnesota
I'm rebuilding 64 394. Im looking for low compression 0.030 over. I contacted Egge, they got back to me and quoted me over$2900, for a set. So I thought what about 455 pistons and deck the block 0.015 as a better alternative. What is cost approximately for deck job, and what are your professional thoughts on this. Thanks for your time!
How did you arrive at milling .015" from the block and using 455 pistons ?
Registered User
Joined: Jun 2024
Posts: 20
How did i arrive at 455 pistons?
Well 394 piston is 4.125 dia, 1.765 compression height, 0.981 pin diameter.
455 piston 4.125 dia, 1.750 compression height, 0.981 pin diameter.
1.765
1.750
0.015
thanks
455 piston 4.125 dia, 1.750 compression height, 0.981 pin diameter.
1.765
1.750
0.015
thanks
Last edited by Super88guy; Nov 10, 2024 at 09:14 AM.
Registered User
Joined: Sep 2017
Posts: 5,215
From: St. Paul Minnesota
Let me ask a few things. 1. Is your block decked now ? 2. How many cc's in the dish of 455 pistons ? 3. How many cc's in the 394 piston dish ? 4. Whats the combustion chamber cc's ? 5. What are the head gasket thickness ?
Registered User
Joined: Sep 2017
Posts: 5,215
From: St. Paul Minnesota
You need to find a compression ratio calculator online and fill in the blanks and print them out. Unless you know what cylinder head combustion chamber cc's, head gasket thicknesses, piston top below the deck, piston dishes or reliefs, you are just guessing. These measurements are critical to determining compression ratio.
I don't understand why you would mill .015" from the block deck because of the different compression height between 394 and 455 pistons. Milling the deck would actually decrease the volume in the block....by 3 cc's....which would increase the compression ratio.
And MOST IMPORTANT, find a mechanic/machinist that knows Oldsmobile's and what he is doing.
Registered User
Joined: Jun 2024
Posts: 20
Pistons 455
I seriously doubt you'll find low compression 394 pistons. There are many numerical specifications you need before you start mixing and matching engine parts. Exactly what compression ratio are you trying to get ? What are you calling "pump gas" ?
Well pump gas is 87 octane to 91.comp ratio in the 8s or 9's as for figure Comp ratio that will need to be done along with proper head gasket it may not need the total 015 milling.
You need to find a compression ratio calculator online and fill in the blanks and print them out. Unless you know what cylinder head combustion chamber cc's, head gasket thicknesses, piston top below the deck, piston dishes or reliefs, you are just guessing. These measurements are critical to determining compression ratio.
I don't understand why you would mill .015" from the block deck because of the different compression height between 394 and 455 pistons. Milling the deck would actually decrease the volume in the block....by 3 cc's....which would increase the compression ratio.
And MOST IMPORTANT, find a mechanic/machinist that knows Oldsmobile's and what he is doing.
Well pump gas is 87 octane to 91.comp ratio in the 8s or 9's as for figure Comp ratio that will need to be done along with proper head gasket it may not need the total 015 milling.
You need to find a compression ratio calculator online and fill in the blanks and print them out. Unless you know what cylinder head combustion chamber cc's, head gasket thicknesses, piston top below the deck, piston dishes or reliefs, you are just guessing. These measurements are critical to determining compression ratio.
I don't understand why you would mill .015" from the block deck because of the different compression height between 394 and 455 pistons. Milling the deck would actually decrease the volume in the block....by 3 cc's....which would increase the compression ratio.
And MOST IMPORTANT, find a mechanic/machinist that knows Oldsmobile's and what he is doing.
Phantom Phixer
Joined: Dec 2011
Posts: 5,525
From: Apopka, FL
One other problem with using 455 pistons in a 394 is that a 394 has full floating pins with retainer locks.
The 455 pistons have no retainer locks and use a pin that is pressed in the rod with an " interference fit" .
Just buy 10.25 to 1 pistons and use 93 octane gas.
Or get custom made forged pistons from someone like Racetec for less than $1000.
Of course with the forged pistons, the engine will have to be re-balanced.
The 455 pistons have no retainer locks and use a pin that is pressed in the rod with an " interference fit" .
Just buy 10.25 to 1 pistons and use 93 octane gas.
Or get custom made forged pistons from someone like Racetec for less than $1000.
Of course with the forged pistons, the engine will have to be re-balanced.
Last edited by Charlie Jones; Nov 10, 2024 at 07:27 PM.
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Posts: 5,215
From: St. Paul Minnesota
I think you are going to a lot of work for a lower compression ratio. I believe the method for computing octane ratings has changed from the 1960's. I have an "untouched" 1966 Oldsmobile Toronado with 10.25 compression ratio. I run 91 octane, "Non-Oxygenated" (no ethanol). No pinging, no overheating, freeway at 75 MPH. Charlie Jones makes sense.
As I remember, "for export" Oldsmobile engines were all "low compression" (9 to 1). It wouldn't surprise me if they did it with thicker head gaskets.
You may want to call these folks and discuss your needs. I KNOW they custom make 1957-58 Olds pistons but you don't see them listed.
https://www.racetecpistons.com/
https://www.racetecpistons.com/piston-order-form
As I remember, "for export" Oldsmobile engines were all "low compression" (9 to 1). It wouldn't surprise me if they did it with thicker head gaskets.
You may want to call these folks and discuss your needs. I KNOW they custom make 1957-58 Olds pistons but you don't see them listed.
https://www.racetecpistons.com/
https://www.racetecpistons.com/piston-order-form
Registered User
Joined: May 2008
Posts: 830
From: Bradford, Ontario
Hi 394,
The last 394 I rebuilt the guy wanted the block bored .030 over and I sourced inexpencive pistons on E-Bay from Falcon Global ( Falcon Sales e-Store)
You can buy the complete rebuild kit for $1264.21 item number 151107034985 or buy seperate pieces.
I also used this set several years back for one of my cars and the engine runs like new because all the inners are new.
Before assembly I mic'd the diameters and they were all within tolerances in the manual.
Check them out and if you can't find what you are looking for then call them and they will find what you need.
Steve
The last 394 I rebuilt the guy wanted the block bored .030 over and I sourced inexpencive pistons on E-Bay from Falcon Global ( Falcon Sales e-Store)
You can buy the complete rebuild kit for $1264.21 item number 151107034985 or buy seperate pieces.
I also used this set several years back for one of my cars and the engine runs like new because all the inners are new.
Before assembly I mic'd the diameters and they were all within tolerances in the manual.
Check them out and if you can't find what you are looking for then call them and they will find what you need.
Steve
Registered User
Joined: Jun 2024
Posts: 20
Thanks all
[QUOTE=Oldskeeper;1602448]Hi 394,
The last 394 I rebuilt the guy wanted the block bored .030 over and I sourced inexpencive pistons on E-Bay from Falcon Global ( Falcon Sales e-Store)
You can buy the complete rebuild kit for $1264.21 item number 151107034985 or buy seperate pieces.
I also used this set several years back for one of my cars and the engine runs like new because all the inners are new.
Before assembly I mic'd the diameters and they were all within tolerances in the manual.
Check them out and if you can't find what you are looking for then call them and they will find what you need.
I wondered about falcon also will find race tech. If you look in 63 service manual they show three types of pistons so they did have lower compression pistons. As does eggs for 2900$
The last 394 I rebuilt the guy wanted the block bored .030 over and I sourced inexpencive pistons on E-Bay from Falcon Global ( Falcon Sales e-Store)
You can buy the complete rebuild kit for $1264.21 item number 151107034985 or buy seperate pieces.
I also used this set several years back for one of my cars and the engine runs like new because all the inners are new.
Before assembly I mic'd the diameters and they were all within tolerances in the manual.
Check them out and if you can't find what you are looking for then call them and they will find what you need.
I wondered about falcon also will find race tech. If you look in 63 service manual they show three types of pistons so they did have lower compression pistons. As does eggs for 2900$
Registered User
Joined: Sep 2013
Posts: 2,924
Ross Racing engines in Ohio or Ross Racing Pistons in California? be Leary of the Ohio one
if you went with 455 pistons, you wouldn’t need to cut the block deck at all. You would get your desired lower compression because the 455 piston sits lower by .015” to 025”
you had the right idea in the first place
if you went with 455 pistons, you wouldn’t need to cut the block deck at all. You would get your desired lower compression because the 455 piston sits lower by .015” to 025”
you had the right idea in the first place
Last edited by CANADIANOLDS; Nov 19, 2024 at 03:54 AM.
Registered User
Joined: Jun 2024
Posts: 20
No rebuttals
Ross Racing engines in Ohio or Ross Racing Pistons in California? be Leary of the Ohio one
if you went with 455 pistons, you wouldn’t need to cut the block deck at all. You would get your desired lower compression because the 455 piston sits lower by .015” to 025”
you had the right idea in the first place
if you went with 455 pistons, you wouldn’t need to cut the block deck at all. You would get your desired lower compression because the 455 piston sits lower by .015” to 025”
you had the right idea in the first place
Registered User
Joined: Sep 2013
Posts: 2,924
yes Ross Ohio. I'm surprised nobody had a rebuttal to you agreeing with me using 455 pistons. Im glad to hear i wouldn't need to trim the deck. I am wondering if id need a different size push rod not that thats a big deal. Getting the 455 pistons would save money. Thanks for everyone's input I appreciate it. It keeps options open!!
if the 394 are floating rods, you get floating ones when you order them.
and like I said about the Ohio guy..run away, very fast. Unless you can physically go there, see the parts, feel them in your hand and measure them. That’s ok..he’s a crook
Thread Starter
Registered User
Joined: Jun 2024
Posts: 11
different pushrod? if you meant connecting rod , no. If they are the same pin diameter and top end width clearance you’re ok.
if the 394 are floating rods, you get floating ones when you order them.
and like I said about the Ohio guy..run away, very fast. Unless you can physically go there, see the parts, feel them in your hand and measure them. That’s ok..he’s a crook
if the 394 are floating rods, you get floating ones when you order them.
and like I said about the Ohio guy..run away, very fast. Unless you can physically go there, see the parts, feel them in your hand and measure them. That’s ok..he’s a crook
Registered User
Joined: Jun 2024
Posts: 20
Ross Racing engines in Ohio or Ross Racing Pistons in California? be Leary of the Ohio one
if you went with 455 pistons, you wouldn’t need to cut the block deck at all. You would get your desired lower compression because the 455 piston sits lower by .015” to 025”
you had the right idea in the first place
if you went with 455 pistons, you wouldn’t need to cut the block deck at all. You would get your desired lower compression because the 455 piston sits lower by .015” to 025”
you had the right idea in the first place
Registered User
Joined: Sep 2013
Posts: 2,924
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