how much CR with AL Heads, 355 chev, and 91 octane - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 10-31-2011, 06:22 AM
bigalow's Avatar
Registered User
 
Last photo:
Join Date: Oct 2007
Location: chicago IL
Posts: 276
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
how much CR with AL Heads, 355 chev, and 91 octane

With a mild 355 chevy with AL heads can I run a 10-1 CR and still run 91 octane??? 226dur 480 lift cam @50

I have read AL heads disapate heat quicker than an iron head and you can run a higher static CR?

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 10-31-2011, 06:49 AM
TroyBoy's Avatar
Psychomotors
 
Join Date: Jan 2006
Location: East Bonne Terre ,Missouri
Age: 49
Posts: 679
Wiki Edits: 0

Thanks: 14
Thanked 9 Times in 8 Posts
I don't see a problem as long as you have your timing dialed in correctly.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 10-31-2011, 06:54 PM
Registered User
 
Last photo:
Join Date: Apr 2007
Location: Seattle, Wa
Posts: 7,088
Wiki Edits: 0

Thanks: 4
Thanked 539 Times in 455 Posts
Quote:
Originally Posted by bigalow
With a mild 355 chevy with AL heads can I run a 10-1 CR and still run 91 octane??? 226dur 480 lift cam @50

I have read AL heads disapate heat quicker than an iron head and you can run a higher static CR?
Run the DCR equation, you want to be in the 8 to 9 window.

http://www.kb-silvolite.com/calc.php?action=comp2

Yes aluminum pumps heat into the cooling system faster than iron, so you not only can, but need to compensate with more compression. Same kind of thoughts go with bigger cams. The intake closing point makes the engine appear to have less stroke and therefore cylinder volume. Until the motor is wound up enough that the incoming mixture has enough velocity to over come the reverse pumping of the rising piston the engine suffers from low filling of the cylinder and loss of power. To compensate, the static compression ratio is run up to off set this dynamic loss of compression to the forces of reversion.

Bogie
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 10-31-2011, 08:51 PM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 60
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 598 Times in 547 Posts
Quote:
Originally Posted by bigalow
With a mild 355 chevy with AL heads can I run a 10-1 CR and still run 91 octane??? 226dur 480 lift cam @50

I have read AL heads disapate heat quicker than an iron head and you can run a higher static CR?
10:1 is doable. Be sure to keep the quench nice and tight, on the order of 0.040" or so. A tight quench distance is sometimes called "mechanical octane" because of how it lowers the engines need for octane.

The 0.040" quench figure is often used because of the commonly available 0.041" composite head gaskets that are abundant, along w/a "zero decked" block as much as anything- it's not a "magic" number. You don't want to go much tighter than this using steel rods, it's just a good all-around compromise. A 0.015" steel shim HG along w/a stock 9.025" deck height will give you the same 0.040" quench (although the sealing surfaces need to be pristine if using a shim HG), so it doesn't matter so much HOW you get there, just that you get there.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 11-01-2011, 10:09 AM
bigalow's Avatar
Registered User
 
Last photo:
Join Date: Oct 2007
Location: chicago IL
Posts: 276
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I will specify a 0 deck at the machine shop and use the rec gasket.

COULD YOU TAKE A QUICK GLANCE AT MY COMBO? I can't [post a new thread because I know this subject has been beat to death
TAKING BLOCK TO MACHINE SHOP SAT AND I NEED TO TELL THEM WHAT I WANT--THANK YOU!

My 350 is for my 54 pickup.
I am after as much performance as possible but a driver. Truck so torque at a useable rpm range is important. Something i could drive 500 miles to KY if I wanted to and be able to buy gas for it along the way, and not have to take extra fuel containers because my range is only 80 miles

The truck weighs 3000lbs
700r4 trans
convertor ????(I don't know?)
3.73 gear
29 inch tall rear tires

82 chevy 350 2 bolt main stock rotating assembly
1) Have the block R&R'd, bored, O decked, balanced
2).Hyper pistons between 9.5 and 10 to 1 CR
3) Rotating assembly R&R"d
4) Comp X4262 lobe=111, Cent=107, Dur 218/226 lift=462/480 @.050
5) 64cc AL heads $700 nothing fancy
6) stock oil pan and standard pump
7) dual plane Edelbrock intake
8). 600 CFM carb

Last edited by bigalow; 11-01-2011 at 10:32 AM.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 11-01-2011, 12:58 PM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 60
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 598 Times in 547 Posts
Quote:
Originally Posted by bigalow
I will specify a 0 deck at the machine shop and use the rec gasket.

COULD YOU TAKE A QUICK GLANCE AT MY COMBO? I can't [post a new thread because I know this subject has been beat to death
TAKING BLOCK TO MACHINE SHOP SAT AND I NEED TO TELL THEM WHAT I WANT--THANK YOU!

My 350 is for my 54 pickup.
I am after as much performance as possible but a driver. Truck so torque at a useable rpm range is important. Something i could drive 500 miles to KY if I wanted to and be able to buy gas for it along the way, and not have to take extra fuel containers because my range is only 80 miles

The truck weighs 3000lbs
700r4 trans
convertor ????(I don't know?)
3.73 gear
29 inch tall rear tires

82 chevy 350 2 bolt main stock rotating assembly
1) Have the block R&R'd, bored, O decked, balanced
2).Hyper pistons between 9.5 and 10 to 1 CR
3) Rotating assembly R&R"d
4) Comp X4262 lobe=111, Cent=107, Dur 218/226 lift=462/480 @.050
5) 64cc AL heads $700 nothing fancy
6) stock oil pan and standard pump
7) dual plane Edelbrock intake
8). 600 CFM carb
Have you played around w/Comp's "Cam Quest" yet? It'll give you some idea of what the different cams average and peak at, power-wise and at what RPM. The 262 cam's average HP was 192, avg. TQ was 267. Peaks were 333 HP/@ 5000 rpm and 411 TQ @ 3500 rpm. Now, these numbers may or may not hold true, but they will work for comparison's sake when trying different grinds from Comp Cams.

The difference in HP between 10:1 and a safer 9.5:1 was just 3%. For that small of a gain I'd much rather have the added safety from detonation that 9.5:1 will provide. Not to mention that if having a 10:1 CR were to make you back the timing down, the 9.5:1 CR "version" would slay the 10:1 version w/the timing backed down to avoid detonation. Besides that, the DCR might be on the high side w/that cam and 10:1 CR, although I didn't actually run the numbers. If you did want to push the CR, check to see what the DCR comes out as, just to be sure.

A stock converter will work, best acceleration will come from a 3000-3500 stall speed.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 11-01-2011, 01:05 PM
Registered User
 

Last journal entry: 1983 GMC
Last photo:
Join Date: Sep 2011
Location: South Texas
Posts: 23
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Great Info

GREAT INFO GUYS

Last edited by BIG TEXAS BULLIES; 11-01-2011 at 01:09 PM. Reason: WRONG SECTION
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 11-01-2011, 01:59 PM
Registered User
 
Last photo:
Join Date: Nov 2006
Location: Woodstock
Posts: 990
Wiki Edits: 0

Thanks: 2
Thanked 89 Times in 81 Posts
If running a stock converter, look for a DCFL code Tc from a V6 Blazer/S10. Behind my Vortec 350 truck I get a stall rpm of 2800rpm.

peace
Hog
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 11-01-2011, 02:13 PM
bigalow's Avatar
Registered User
 
Last photo:
Join Date: Oct 2007
Location: chicago IL
Posts: 276
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by Hogg
If running a stock converter, look for a DCFL code Tc from a V6 Blazer/S10. Behind my Vortec 350 truck I get a stall rpm of 2800rpm.

peace
Hog
Why such a high stall in a truck? I get it with a high rpm HP,torque motor but with a a low RPM HP,torque motor would you want a lower stall?
ie: say your cam selection is 1800 to 5000rpm.
would'nt you want a 2000 stall convertor?
I know there are variables that effect were the convertor actually stalls at, torque ect... but i am asking "rule of thumb"???

UPDATE--never mind, I just checked out "CAMQUEST" wow-is that cool and I did not know it existed!!
Thanks COBALT327!!!

Last edited by bigalow; 11-01-2011 at 02:36 PM.
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 11-01-2011, 03:12 PM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 60
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 598 Times in 547 Posts
Torque converter stall can be discussed w/the various manufacturers that modify them. They'll want all the available info on the vehicle- the more accurate info you can provide will help them pin it down. But basically speaking, for best acceleration you'd want the stall RPM to be close to the torque peak RPM. Less stall speed is OK up to a point but if you were to go too low on the stall speed and if using a big cam, you risk having the engine trying to pull through the brakes at a stop, for instance. But w/the cam duration/overlap you're considering, that's not too likely to be a problem, IMO.
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 11-01-2011, 08:16 PM
bigalow's Avatar
Registered User
 
Last photo:
Join Date: Oct 2007
Location: chicago IL
Posts: 276
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I noticed the value of Porting the manifolds and heads with the Cam Quest software. Incredible actually
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 11-02-2011, 11:28 AM
Registered User
 
Last photo:
Join Date: Nov 2006
Location: Woodstock
Posts: 990
Wiki Edits: 0

Thanks: 2
Thanked 89 Times in 81 Posts
Quote:
Originally Posted by bigalow
Why such a high stall in a truck? I get it with a high rpm HP,torque motor but with a a low RPM HP,torque motor would you want a lower stall?
ie: say your cam selection is 1800 to 5000rpm.
would'nt you want a 2000 stall convertor?
I know there are variables that effect were the convertor actually stalls at, torque ect... but i am asking "rule of thumb"???

UPDATE--never mind, I just checked out "CAMQUEST" wow-is that cool and I did not know it existed!!
Thanks COBALT327!!!
2800rpm isnt high at all.
Stock my L31 Vortec 350 was rated at 255 sae net hp@4600rpm and 330 lb/ft torque@2800rpm. On a flat surface I can let off the brake and the truck will creep forwards.
The 4l60e also has very wide ratios. During WOT upshifts with the stock TC I would shift at 5500rpm and the revs would come back down to 3200rpm which cause accleration to halt momentarily until the rpms climbed into the powerband again. WIth the L35 V6 TC the same 5500rpm upshift would result in rpms coming down to only3700rpm which kept the engine in its powerband and acceleration was MUCH better through the shifts.

As stated by others, for best acceleration you want your stall speed to be at peak torque. For street use you want is a few 300-500rpm below your torque peak.

The 1999+ trucks with 4.8/5.3 have torque peaks of 4000rpm and power peaks of 5200rpm. This is why they have bunkly low rpm torque. Slap in a Trailblazer Inline 6 torque converter and these trucks wake right up as they normally stall 2700-2900 depending on if its in front of a 4.8/5.3/6.0.

My next TC will be 3200-3400rpm for my truck. Once you are cruising the TCC locks up so the input shaft of the trans is spinning teh same rpm as the engine which allows fro good fuel economy. The lockup TCC has allowed very agressive stalls such as 4000-4500 stalls to used in a driver. Not locked up economy would be horrible as would trans heat.

In a truck with a TBI engine with torque peaks of 1800rpm you wouldnt want to go too high on the TC.

TC's are hugely overlooked for allowing for great performance on daily drivers. Most stock trucks can benefit from higher stall TC's, let alone any vehicle with an aftermarket performance cam.

peace
Hog
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last 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:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
chev heads prochev12 Introduce Yourself 2 09-20-2010 01:49 PM
What 350 sbc heads to choose for 87 octane eric32 Engine 6 09-20-2008 09:20 AM
chev heads bernie mcwilliams Engine 2 02-20-2007 09:00 PM
Chev crate motor on 87 octane? Blackdog Engine 5 12-28-2004 01:08 AM
chev 250, 292 heads same? godofgsxr Engine 5 05-15-2002 05:48 PM


All times are GMT -6. The time now is 05:02 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.