455 Build question - Pontiac GTO Forum
User Tag List

 2Likes
Reply
 
LinkBack Thread Tools Display Modes
post #1 of 20 (permalink) Old 01-11-2018, 07:05 PM Thread Starter
 
Join Date: Feb 2014
Location: Lake St. Louis Missouri
Posts: 29
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
455 Build question

Hey guys, my mild 389 build is just a little too mild for my liking and I was able to find an untouched 455 short block. I need to do this on a budget, so I want to use as much of it as possible, but willing to upgrade a few parts for better performance and reliability. My question is what parts made a strong pulling, 455 cruiser that can still PASS a gas station? Looking for known combos that like 90 octane.

Thanks in advance!!

My setup is:
73 455 from a big car
6X-4 heads 93.5cc already redone
Performer RPM intake
FiTech EFI
RAM AIR exhaust manifolds
Vapor Locker USA is offline  
Sponsored Links
Advertisement
 
post #2 of 20 (permalink) Old 01-11-2018, 08:25 PM
 
PontiacJim's Avatar
 
Join Date: Dec 2012
Location: Gastonia, NC - Born & raised in Connecticut - 31 years
Posts: 3,451
Mentioned: 0 Post(s)
Tagged: 1 Thread(s)
Quoted: 347 Post(s)
Garage
Quote:
Originally Posted by Vapor Locker USA View Post
Hey guys, my mild 389 build is just a little too mild for my liking and I was able to find an untouched 455 short block. I need to do this on a budget, so I want to use as much of it as possible, but willing to upgrade a few parts for better performance and reliability. My question is what parts made a strong pulling, 455 cruiser that can still PASS a gas station? Looking for known combos that like 90 octane.

Thanks in advance!!

My setup is:
73 455 from a big car
6X-4 heads 93.5cc already redone
Performer RPM intake
FiTech EFI
RAM AIR exhaust manifolds

If you already have all that on your 455, what else do you need or are looking for? Need to be specific. High performance & gas mileage don't mix - either one or the other.
PontiacJim is offline  
post #3 of 20 (permalink) Old 01-12-2018, 12:27 AM
 
60sPontiacs's Avatar
 
Join Date: Jul 2016
Location: St. Louis
Posts: 30
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Assuming you'll be 30 over/all else standard with new pistons, your static CR with 93.5cc heads will be about 9.64:1 (9.59:1 with stock bore), which is said to require higher than 90 octane for best timing. Cam choice can drop Dynamic CR which is what matters. I'm at this learning point with a 9.56:1 400 but don't have time to mess with it now (but am reading...).

What kind of car is this going in [ah, i see a 67 GTO/3400lbs]? Rear axle ratio? transmission?

These are interesting articles, and people on this forum know their stuff/can point you to other info.
http://www.crankshaftcoalition.com/w..._compatibility
http://www.crankshaftcoalition.com/w...EI_distributor

Also read what Jim Hand did. He ran 87cc heads (10.2:1) with his 455 on 92 octane.. well under 12 second 1/4 miles in a 4000 lb station wagon.
Jim Hand's 455 Pontiac Power

----just noticed the EFI on your list... now I understand what PontiacJim means...
Also just noticed you're in my town... when I'm there. Am in CA now - we both had high of 63F today, but tonight goes down to 49F here while LSL nosedived to 14F (the old STL 50 degree drop...). You can get 93 octane at U-Gas just off 70 on Hwy-Z so your engine will be okay.

Chris

Last edited by 60sPontiacs; 01-12-2018 at 04:18 PM.
60sPontiacs is offline  
 
post #4 of 20 (permalink) Old 01-13-2018, 11:09 AM Thread Starter
 
Join Date: Feb 2014
Location: Lake St. Louis Missouri
Posts: 29
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Thanks for the responses. I think I worded the question wrong. My goal is to run on 90 octane because I can get that at any gas station. The main thing I am looking for is a known cam / piston setup for a nice running motor. Itís not going to be raced but I do want enough power to have some fun.

The other variables with the car not stated above.
373 rear end
200r4

These are the cams that I am looking at and looking for piston recommendations.

255DEH
51-206-4 - DUAL Energy? Hydraulic Flat Tappet Camshafts

XE250H
51-220-4 - Xtreme Energy? Hydraulic Flat Tappet Camshafts

XE256H
51-221-4 - Xtreme Energy? Hydraulic Flat Tappet Camshafts
Vapor Locker USA is offline  
post #5 of 20 (permalink) Old 01-13-2018, 02:28 PM
 
PontiacJim's Avatar
 
Join Date: Dec 2012
Location: Gastonia, NC - Born & raised in Connecticut - 31 years
Posts: 3,451
Mentioned: 0 Post(s)
Tagged: 1 Thread(s)
Quoted: 347 Post(s)
Garage
It is kinda hard to suggest a piston for any combo without knowing some exact numbers. Most piston choices will be forged, and you can get differing out-of-the-catalog over sized pistons depending on how much the block may need to be bored to clean it up - typically .030" over, then .040", then .060".

Your best bet to run on the 90 octane gas would be to shoot for 9.0 compression. You can go higher, but you may be taking a chance with engine detonation, but some feel comfortable going higher and you will read about guys running 10.0 on pump gas which to me is skeptical, but doable if timing is adjusted and everything is in perfect tune.

Things you need to know are specific values that will determine the compression ratio. You will need to know exactly what your head chamber cc's are, not the numbers they are supposed to be or what the internet says they are. Actual head chamber volume can vary from advertised numbers. Head chamber volumes can change by grinding in the chambers to clean-up/improve flow, head milling, the height of the valve as it sits on the valve seat, or even the design of the valve head. That said, you have your heads cc'd @ 93.5.

You will need to know what the deck height is, ie the top of the cylinder measured to the top of the piston. This is the space above the piston and has volume in cc's. Typically a Pontiac piston will sit .015-.020" down in the bore. A block can be milled down to bring the top of the piston flush - called zero deck height. I don't recommend it, but others will. I'll throw off head/intake angle geometry and the intake side surfaces have to be milled accordingly to match any angle changes. I'd rather see a custom piston with the wrist pin relocated, if anything., but have not heard of this being done, so who knows. The 455, .030" over @ .020" down in the bore will calculate to 4.5 cc's as the cylinder volume above the piston (some pistons are made with a piston edge that is beveled which will add additional cc's in an effort to further reduce compression).

Your head gasket, that hole in the center, has a volume in cc's. The thickness of the gasket used can be used as an adjustment to raise/lower compression slightly. The Felpro gasket, as most will list, is supposedly .039" when compressed. For example, 455 .030" over (4.180") with .039" compressed head gasket is 8.7 cc's. Using a thinner .027" compressed gasket is 6 cc's.

So now with these numbers above, you can calculate for your piston and determine the amount of cc's that has to be built into the piston by either the valve relief notches or a dished area cast/milled into the tops of the pistons. So let's use 93.5 + 4.5 + 8.7 = 106.7 as your total number of cc's above the piston.

Using the Wallace Compression Calculator, Compression Ratio Calculator - Wallace Racing , you can plug in the numbers. I used the 455 .030" bore, 4.180", as the Gasket Bore Diameter which will be fairly close. Used .020" for Deck Height. I also used the 6.6 Valve Relief/Dome cc's as a baseline for the compression ratio - which is what you adjust to change your compression.

So, plugging in the numbers, I get a compression ratio of 9.37. Not bad.

You can use a number of different pistons, but in my 455 build I used the Keith Black ICONN pistons which come in 3 different valve relief configurations, 5.5, 11, & 17 cc's. Plugging in the 5.5 cc's in place of the 6.6 cc's and the compression is now 9.44. Getting up into the compression where 90 octane might not be too comfortable.

Plugging in the 11 cc's (which I went with) and the compression is 9.04. Right were you want it.

Pluggin in the 17 cc's and the compression drops to 8.65. Not necessarily where you might want to be BUT, there are options with this ratio.

There is this thing called "Quench Area," the area between the piston and the head when the piston is at top dead center. Many builders like to see this area have a distance of .040 - .045" (depending on piston material used) to maximize the cylinder burning. The tighter measurement can aide in preventing detonation and can sometimes allow for a higher compression. With a deck height of .020" plus a gasket of .039", the Quench is .059". Not really ideal. What I did in my build was go with a Cometic .027" head gasket. .020" + .027" = .047" Quench area. Changing the formula and using the .027" head gasket yields an increased compression ratio of 8.82.

The larger Quench will obviously work because that's factory - .059" - .060", but remember leaded gas was used and leaded gas suppressed detonation. Still, it works with most builds, so not a big problem. So the 9.04 compression will work, but so will the 8.82 compression with the tighter Quench which will reduce the chances of detonation.

Using the 8.65 or the 8.82 compression, you can select a cam with the narrow Lobe Separation Angle (LSA) such as the Competition Cams series with its 110 LSA. These cams have real power in a lower compression engine because they build additional cylinder pressure - essentially acting as higher compression. They are very strong cams, but will peak out in the RPM range early which may not be too much of a problem at all reading into what you want out of your engine and the lower RPM characteristics of the 455. Wider LSA cams (114-116) will provide a broader power range but not have the lower RPM punch of the tighter LSA. The wider LSA cams typically bleed off some of the compression at the lower RPM's and is why they were selected when using higher compression engines. You will pick up the lost compression as the RPM's increase.

So selecting a cam to match your compression is just as important as the compression itself. This is where the difference between Static Compression (your actual number) versus Dynamic Compression (cylinder pressure derived by the camshaft specs, namely the Intake Valve closing degrees After Bottom Dead Center (ABDC) ). This number is found on most cam manufacturers Cam Card. That said, you can use the 9.04 compression ratio or the 8.82 compression ratio to determine your Dynamic Compression by obtaining the cam manufacturers cam spec for the Intake Valve closing point at ABDC. From what I have read, and what I shot for in my 455CI build, it to keep the Dynamic Compression below 8.0. Use this calculator to get your Dynamic Compression ratio Wallace Racing: Dynamic Compression Ratio Calculator

AND, as a DISCLAIMER, because I am not an expert on this, just advising, you want to talk with your engine builder and also get cam manufacturers recommendations to zero in what you want the engine to do as the final voice in your engine build. Keep in mind that a cam that may be strong in a 400, will be milder in a 455 due to the bigger cubes. The Comp Cams XE cams, 262, 268, or 274 would be a good choice with the lower, under 9.0 compression. https://butlerperformance.com/c-1234...ppet-cams.html
PontiacJim is offline  
post #6 of 20 (permalink) Old 01-13-2018, 02:53 PM Thread Starter
 
Join Date: Feb 2014
Location: Lake St. Louis Missouri
Posts: 29
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Thanks for the info. I am just worried about buying the wrong stuff and spending good money to build a bad engine. You have made some good points and it looks like I need to wait till the block gets done so I can get the exact numbers to punch into the calculator to help figure out what is needed.

Thanks again!

Mike
Vapor Locker USA is offline  
post #7 of 20 (permalink) Old 01-20-2018, 01:48 PM Thread Starter
 
Join Date: Feb 2014
Location: Lake St. Louis Missouri
Posts: 29
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
I was tearing down the 455 and saw that it had these rods. I cant find any info on these. Does anyone know what these are and are they any good?
Attached Thumbnails
Click image for larger version

Name:	455 old rods.JPG
Views:	75
Size:	896.2 KB
ID:	102361  
Vapor Locker USA is offline  
post #8 of 20 (permalink) Old 01-20-2018, 02:11 PM
 
PontiacJim's Avatar
 
Join Date: Dec 2012
Location: Gastonia, NC - Born & raised in Connecticut - 31 years
Posts: 3,451
Mentioned: 0 Post(s)
Tagged: 1 Thread(s)
Quoted: 347 Post(s)
Garage
Quote:
Originally Posted by Vapor Locker USA View Post
I was tearing down the 455 and saw that it had these rods. I cant find any info on these. Does anyone know what these are and are they any good?
Reading the obvious, a reconditioned(rebuilt) rod for TRW. Standard Pontiac cast rod - has a narrow pencil line thin casting flash on the side of the rod beam as opposed to a wider 1/16-1/8" wider casting line ID'ing the rod as a forged rod. Here is one on Ebay: https://www.ebay.com/p/TRW-CR1459-Co...p2047675.l2644

Would not use a cast rod in any performance build, get a forged rod.
PontiacJim is offline  
post #9 of 20 (permalink) Old 01-20-2018, 02:17 PM Thread Starter
 
Join Date: Feb 2014
Location: Lake St. Louis Missouri
Posts: 29
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
So that is what that first word is.... damn, i was hoping to save a couple bucks.

Question on the quench. is it really a big deal, or is it just to squeeze a little extra power out of the motor?

Last edited by Vapor Locker USA; 01-20-2018 at 04:29 PM.
Vapor Locker USA is offline  
post #10 of 20 (permalink) Old 01-20-2018, 07:21 PM
 
PontiacJim's Avatar
 
Join Date: Dec 2012
Location: Gastonia, NC - Born & raised in Connecticut - 31 years
Posts: 3,451
Mentioned: 0 Post(s)
Tagged: 1 Thread(s)
Quoted: 347 Post(s)
Garage
Quote:
Originally Posted by Vapor Locker USA View Post
So that is what that first word is.... damn, i was hoping to save a couple bucks.

Question on the quench. is it really a big deal, or is it just to squeeze a little extra power out of the motor?
Not a real big deal, but it is not so much about extra power as it is about detonation.
PontiacJim is offline  
Sponsored Links
Advertisement
 
Reply

  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, LeMans & GTO Engine Tuning and High Performance

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Pontiac GTO Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
LS2 build question.... 06BOMGTO Engine Discussions 2 07-06-2014 06:46 PM
455 Motor build opinions speedracer25f 1964-1974 Tempest, Lemans & GTO Complete Engine Compartment Discussion 8 08-09-2012 01:03 PM
Build Question GuatoLT1 2004-2006 GTO General Discussion 18 07-01-2011 06:19 PM
??? 455 build??? SWOOSH 1964-1974 Tempest, LeMans & GTO Technical and Electrical Wiring 16 04-23-2011 03:41 PM
build sheet question ? abodybrad 1964-1974 Tempest, LeMans & GTO Technical and Electrical Wiring 3 03-27-2010 09:37 AM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome