Lower octane/high compression? - Team Camaro Tech
Engine General Engine Discussion.

 
LinkBack Thread Tools Display Modes
post #1 of 14 (permalink) Old Jul 20th, 09, 10:40 PM Thread Starter
Senior Tech
AJ
 
Join Date: Jul 2006
Location: AUSTIN TEXAS
Posts: 3,842
Lower octane/high compression?

.040" 327/333c.i.
Block decked to .012/.015 (I cant remember exactly)
.025" composite head gasket
Aluminum heads, 58cc chambers, 190cc runners
Comp cams 286H magnum .236 @.050, .490" lift, 110lsa
Edelbrock performer rpm intake
Edelbrock 750cfm carb (yes, I know it's way too big), stock springs/rods/jets accelerator pump shot adjusted along with idle mixture screws.
I think I last calculated the compression at 10.8:1, maybe lower, can't remember the DCR.
Pertornix h.e.i ignition
Initial timing between 16*-18* initial, 45*-50* with vac advance

Runs well under wide open throttle from 2,000rpm to 6,000rpm

I usually run 93 octane with no problems, the last 2 times I filled up with 89 octane and felt it ran stronger being that the lower octane takes less energy to ignite, I could not hear any detonation? If I did I mistook it as exhaust noise, when I got home I could tell the headers got hot at some point, probably during one of the wot runs, the first 3"-5" of the primary tubes looked pretty hot (ceramic coated headers) and when I shut the car off idling around 1,000rpm it ran on very slightly or kicked back which it never does (water temp 170*). Should I re tune to use lower grade fuel (take some timing out) or run 93? I don't see why you should take timing out with a lower grade fuel since most take some out when using race gas or nitrous? I will check the plugs and post back eventually, what is the best way to check plugs in a manual trans car, I get how to do it but I wouldn't want to run the car hard down the street, shut it off, not be able to start it up and have to push it back to the garage and then pull the plugs...

sorry for the long, descriptive post.

The only Mustang I'd ever own is a Fender.

'68 333" Camaro
'14 5.0 Mustang
ace's68 is offline  
Sponsored Links
Advertisement
 
post #2 of 14 (permalink) Old Jul 21st, 09, 12:22 AM
Senior Tech
Ron
 
Join Date: Nov 2006
Location: North Channel Lake Huron
Posts: 3,934
Re: Lower octane/high compression?

If I read your engine information correctly, I calculate you have at least a 10.54:1 Static Compression with a .015" Deck and specs you have provided using Flat top Pistons allowing 5cc's for Valve reliefs.

With that 286H-10 cam, you would have approximately an 8.1:1 DCR with the cam installed at 106 Degrease, that is 4 degrease advanced, where 8.2 is considered about the MAX for street use on Pump Gas.

With a .012" Deck, the Static/DCR may be 10.6:1/8.15:1. I imagine other members will check my calculations - LOL

I personally would not run that engine with anything less then 91 Pump Octane which has is 95 RON and preferably Pump 93 which is approximately 97 RON.

This new GAS is Sh*T and it is very hard to hear Detonation until it is too late. The Hot Headers and Run On is an indication that you are detonating. Note: Run On can be caused from a vacuum leak, the throttle plates not closed enough and not enough advance; but heed the previous statement regarding detonation. Reports from many say Alu-Heads are better in regards to detonation over Cast.

In any account Pull the Plugs and look for the tell Tale Flecks on the Ceramic which indicate Detonation.

If you do not want to run 93, you may get by with 91 but I would try E5 or 10 as an alternative as the % ethanol will have a cooling effect and you should not have to make any induction changes in regards to Fuel Supply or Jetting (perhaps the next size larger). I'm not sure what the Pump or RON Octane rating of E5 or 10 is but typically rated as 2 to 3 octane higher than regular gasoline. The UK and Aussy E10 Blends are around 99 RON (Nice). Here's a descent article on E Fuels http://en.wikipedia.org/wiki/Common_...5.2C_E7.2C_E10

A 750 is not too big for a Hi-Perf Mechanical Cammed 327 at the strip and no too out of line on the street if jetted correctly where a 650 may be better suited for a lesser revving build. I personally run a Holley 750 Dp/Edelbrock RPM with Jenkin 291's which seems to respond better with the 750 on it then a similar built 350 using a 750. I can't say why but may have something to do with the over square specs and the way the motor demands to breath over 7000rpm - Gotta love the 327 ;o)

That is a nicely Spec'd 327 you have with a .037 or .040" quench and.025" Compo-Gaskets for them Alu-Heads. You might think about Shaft Rockers with a Mechanical or SR Cam in the future.

Z15CAM - There was a Viper in my Rear View
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

This was my 70 1/2 Z28

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Last edited by Z15CAM; Jul 21st, 09 at 04:12 AM.
Z15CAM is offline  
post #3 of 14 (permalink) Old Jul 21st, 09, 06:22 PM
Senior Tech
Steps
 
Join Date: Dec 2005
Location: New Zealand
Posts: 13,316
Re: Lower octane/high compression?

Basicaly higher the compresion the less advance
and higher the octane more advance.
Assuming A/F ratios are within the ball park.

Quote:
Initial timing between 16*-18* initial, 45*-50* with vac advance
That with or without VA connected?
45/50 thats one hell of a variation....and a hell of a lot of advance with no VA, and very top end most proberly too much with VA

Im running 100/105 octance fuel with 10.8:1 CR with low end torque cam advanced 4 Degs, with 32 deg advance @ 2850 rpms and about 6 deg of VA...

My Spelling is not incorrect...it is creative

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Steptoe is offline  
 
post #4 of 14 (permalink) Old Jul 21st, 09, 06:37 PM
Senior Tech
Chad
 
67 Plum's Avatar
 
Join Date: Jan 2003
Location: Thomasville,Ga.
Posts: 4,386
Re: Lower octane/high compression?

I am confused here you say it runs fine on 87?

Jul 14th, 09, 09:35 PM
ace's68 ace's68 is online now
Senior Tech

john
Join Date: Jul 2006
Location: Deliverance, Texas
Posts: 1,601
Default Re: 327 rebuild 882 heads
For what it's worth I run a 10.8:1 327 on 87 octane all day long with no problems what so ever, I actually think it runs better on 87 vs. 93, not because I'm cheap but why bother when you get more hp out of fuel that takes less energy to ignite?

67 Plum Mist Met. 408 TH350 3.08 posi
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
67 Plum is offline  
post #5 of 14 (permalink) Old Jul 21st, 09, 06:45 PM Thread Starter
Senior Tech
AJ
 
Join Date: Jul 2006
Location: AUSTIN TEXAS
Posts: 3,842
Re: Lower octane/high compression?

It runs well, it's no "flock of geese" when I get on it like everyone says a higher compression street motor will run, Last night was the first time I noticed I could be doing damage, and last night was the first time it ran on, I used gas from a different station also, that could have something to do with it.

Steps, the 40-50 is with vacuum advance, hose from distributor to manifold source.

I'm going to check plugs & ignition timing and post back...

The only Mustang I'd ever own is a Fender.

'68 333" Camaro
'14 5.0 Mustang
ace's68 is offline  
post #6 of 14 (permalink) Old Jul 21st, 09, 08:15 PM Thread Starter
Senior Tech
AJ
 
Join Date: Jul 2006
Location: AUSTIN TEXAS
Posts: 3,842
Re: Lower octane/high compression?

Okay, took it for a good 6mile drive, stepped on it right before my house (private road, private property) didn't have enough room to get a "good" run in, ran from about 2,500rpm-5,500 which isn't where I wanted to stop, put it in neutral and turned key off (ran on) coasted into the garage.

Plugs vary a little, lost my camera. #2 had some brown flakey build up on it, porcelain was showing white, sandy in color, #4 was probably the worst, mostly brown and smelled of oil.

Vacuum unplugged/carb plugged is 18*-20* initial, it was jumping around a little because of the erratic idle.

With Vacuum advance 45*idle and ALMOST 60* when revved, I need to make some changes, that could turn out bad.

I'm surprised I didn't burn anything up considering last weekend a friend and I took a cruise and my rpm's in top gear were a consistent 4,000-5,000rpm.

Open to suggestions.

Oh... and when I was done and pulled t in the garage, shut it off, there was no run on, it was 190* and idling at 1,100rpm, this thing is pretty fickle I'm finding out.

The only Mustang I'd ever own is a Fender.

'68 333" Camaro
'14 5.0 Mustang
ace's68 is offline  
post #7 of 14 (permalink) Old Jul 21st, 09, 11:33 PM
Senior Tech
Steps
 
Join Date: Dec 2005
Location: New Zealand
Posts: 13,316
Re: Lower octane/high compression?

Get it dropped down to around 36 degs with no VA...BEFORE u start doing serious damage...and maybe best to disconnect the VA in the mean time to

And read several recent posts on timing over the last couple weeks.
Get some basic idea of the principlesof timing so we dont have to re explain for the umteenth time

And keep in mind even if just cruising and way over advanced the pistons are still comming up when fires...thats huge loads on crank bearing, rods pistons
AND is the prime reason why LPG has a bad rep as a fuel..its not the fuel its idiot installers.

My Spelling is not incorrect...it is creative

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Steptoe is offline  
post #8 of 14 (permalink) Old Jul 22nd, 09, 06:15 AM
Senior Tech
Tim
 
77wolf10.85's Avatar
 
Join Date: Mar 2007
Location: Oklahoma
Posts: 3,222
Re: Lower octane/high compression?

[QUOTE=ace's68;1255285

I don't see why you should take timing out with a lower grade fuel since most take some out when using race gas or nitrous?

I will check the plugs and post back eventually, what is the best way to check plugs in a manual trans car, I get how to do it but I wouldn't want to run the car hard down the street, shut it off, not be able to start it up and have to push it back to the garage and then pull the plugs...

sorry for the long, descriptive post.[/QUOTE]

Race fuel allows you to chance more advance with less danger o' dets. It has lead and smoother combustion characteristics. Whereas lower octane fuels have less predictable combustion characteristics. Octane is not a power rating, it is a comparison of ANY fuels(be it pure or a mix)combustion characteristics to a reference pure fuel(OCTANE). ie, diesel is 66ish, garse is 87ish to 114ish, propane is 120, natural gas is 140ish. And on natural gas we have several different rating systems, and they home in on detonation characteristics because natural gas is a mix of a pagefull of hydrocarbons.

Take timing out for juice. Juice adds energy, therefore adds heat, therefore increases risko'dets.

Don't worry with pulling all plugs, just yank 1 easy to get to plug. Don't put much stock in plug reading personally, mainly looking for bad uglies.

I would run my vac advance hose to a dandy little valve I've been hoarding for about 15 years now, build in a tiny leak on the downstream side and flop it to off/bleed to shut off the engine. Or rig up one of my Holley AC idle solenoids to slow the idle for shutdown. Both would be doing the same thing, slowing the engine which you could also do by dumping the clutch or leaving in drive. That's how we used to kill em back in the early 70's when gas went to **** and everybodies junk dieseled at shutdown. Leave it in drive with the AC on. Another good trick was to park with your radiator into the wind, let it idle a minute to cool any hotspots.

Tim Smith
77wolf10.85 is offline  
post #9 of 14 (permalink) Old Jul 22nd, 09, 07:27 AM
Senior Tech
Chad
 
67 Plum's Avatar
 
Join Date: Jan 2003
Location: Thomasville,Ga.
Posts: 4,386
Re: Lower octane/high compression?

Quote:
Originally Posted by Z15CAM View Post
If I read your engine information correctly, I calculate you have at least a 10.54:1 Static Compression with a .015" Deck and specs you have provided using Flat top Pistons allowing 5cc's for Valve reliefs.
I got 10.52 to 1 using 4.155 bore for head gasket.

67 Plum Mist Met. 408 TH350 3.08 posi
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
67 Plum is offline  
post #10 of 14 (permalink) Old Jul 22nd, 09, 07:30 AM
Senior Tech
Ron
 
Join Date: Nov 2006
Location: North Channel Lake Huron
Posts: 3,934
Re: Lower octane/high compression?

Chad - Siish! I guessed with a 4.100 Dia Gasket - LOL

Z15CAM - There was a Viper in my Rear View
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

This was my 70 1/2 Z28

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Z15CAM is offline  
post #11 of 14 (permalink) Old Jul 22nd, 09, 07:49 AM
Senior Tech
Chad
 
67 Plum's Avatar
 
Join Date: Jan 2003
Location: Thomasville,Ga.
Posts: 4,386
Re: Lower octane/high compression?

Quote:
Originally Posted by Z15CAM View Post
I imagine other members will check my calculations - LOL
I just had to it was like a challenge.

67 Plum Mist Met. 408 TH350 3.08 posi
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
67 Plum is offline  
post #12 of 14 (permalink) Old Jul 22nd, 09, 09:39 AM
Senior Tech
Shawn
 
Join Date: May 2005
Location: PA
Posts: 1,339
Re: Lower octane/high compression?

you have to retard the timing so the fuel doesnt all burn up before you reach TDC which causes knocking
victimizati0n is offline  
post #13 of 14 (permalink) Old Jul 23rd, 09, 05:16 PM Thread Starter
Senior Tech
AJ
 
Join Date: Jul 2006
Location: AUSTIN TEXAS
Posts: 3,842
Re: Lower octane/high compression?

Quote:
Originally Posted by Z15CAM View Post
Chad - Siish! I guessed with a 4.100 Dia Gasket - LOL
For the record the gasket bore is 4.040" and the block is also 4.040", the fit was CLOSE.
There was no way in heck I was going to use a shim steel gasket knowing the block has been through heat cycles and I was using aluminum heads, NO ONE stocked a composite gasket that was anything larger than 4.000" so I could not use any of them, and if they were composite they were too thick. A few weeks later and many phone calls I finally tracked one down, scummit, jegs, competition products is the only place I cold find it, it was a Fel-Pro off brand or something...

The only Mustang I'd ever own is a Fender.

'68 333" Camaro
'14 5.0 Mustang
ace's68 is offline  
post #14 of 14 (permalink) Old Jul 24th, 09, 06:05 PM
 
Join Date: Apr 2000
Posts: 21,341
Re: Lower octane/high compression?

Please do a search under Ray T. Bochaz here and find out what I have posted before!

The low octane, high compression combination is like this one.

The now, long gone Mr. Fuelings 454 aluminum, truck engine torque heads on a 502.

1. pistons designed by Mr. Fueling;
2. a fast-burn closed chambered head;
3. min. quench at like .035";
4. as long a rod as you want to buy;
5. CR. up at 12.1 to 1 on 87 octane in said 502.

And w/ a mild street cam.

pdq67

PS., true flat-top pistons, small chambered heads, long rods and a tight quench will get you started.



pdq67 is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Team Camaro Tech 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.
NOTE we receive a lot of registrations with bad email addresses. IF you do not receive your confirmation email you will not be able to post. contact support and we will try and help.
Be sure you enter a valid email address and check your spam folder as well.



Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



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