How much boost
 

Anybody running 20# of boost or more and low timing ??

Charlie66 has been running 30+ psi of boost and 27 degrees of timing max for quite a few years.

None of this 36 degrees of timing bs, also I believe his EFI software allows him to retard timing but send him a PM on that deal.
He originally was on pump fuel and went to E-85 fuel some years ago.

Tom V.

Not to start anything, but I run 36 degrees of timings since I put the wide port Edelbrock head on in 2004, but I run alcohol too. Thanks Rusty

Should have stated on v8 Pontiacs

On my B & M blower on gas I ran 34 degrees but only 6-9 lbs of boost. On my 8-71 blower car with alky I run 27, it doesn’t seem to like anything over 28 again only 11 lbs of boost. I am talking about drag racing.



GTO George

We run 42lbs @ 27 degrees on Q-16

After market block ?? I am at 12 # on a cast 455 block with iron heads on E-85 looking to turn in up around 20 -25 # with 23 degrees ...

Yes IAII iron block. 20-25# on a stock is brave.

X2, At some point the stock block just will not take it any longer at the higher boost pressures and the main web area or the main caps will crack.

First #2 cap then #4 cap, and then #3 cap.

Saw it happen on other stock Pontiac 455 Blocks.

Tom V.

Can you hook the car at that boost? if it is a spin feast you won't hurt much except your tires.

Just remember that cast iron heads will not like the timing as it cannot dissipate
the heat. I made 1265 hp at 6000 rpm and 1100 ft lbs from 3800 to 5900 on 15 psi. I ran 28 degreeson E85 and I will lower that to 25 degrees when I get it in the car. This is without intercooler and blow Thru carb on the dyno.. Single 91.5 PTE on IA2 block, wideports and street solid roller.

Ditto!



GTO George

At what compression ratio? Even with E85 you want to be conservative. 8.5:1 range is plenty.

Intake charge temp will also affect amount of boost and timing you can run.
Highly suggest you run a very good intercooler or at a minimum water/methanol injection.
Agree with Tom on timing. CONSERVATIVE !
Watch your rpms too. The stock blocks/cranks that seem to hold together longest are keeping revs low( under 6k).

Its not low or high timing that is the question.

Its what does your motor wants.....

Read the plugs, they will tell you what the engine needs.......

To many variables to know other wise.....

Agree, learn how to read the plugs.
A Air/Fuel meter can get you close but Air/Fuel meters have been known to get contaminated and give false numbers too.

Spark Plugs do not lie (if you can learn how to read them properly).

27 degees of timing is like knowing where the edge of the cliff is. One more step and you fall off or in a engine's case take out a head gasket or have other issues. This is not a Chebby that needs 40 degrees of timing to run right.

One additional degree MAY GET YOU A FEW MORE HP OR IT MIGHT GET YOU A LOT MORE ENGINE WORK. Conservative on timing. Just saying.
Plugs do not lie (if you read them properly).
Some actually cut the plugs apart and look deep inside them.

Tom V.






Tom V.

Ok thanks guys .... I always thought that the reason turbo engines blew up was because they detonated and not because to much boost .. the Buick v6 is a perfect example the stock blocks have been 35 # of boost and if you ever seen the stock block and bottom ends they are very weak in stock form ....mine had a girdle and they have held together as long as they don’t detonate ... but I blew headgaskets from not having enough octane though . Also will a motor make more power on more boost and low timing or low boost and lots of timing ??

I always cut a couple of plugs open to look at the base ring every time I make a fuelling change,small price to pay. I also check the earth strap and porcelain every time I make a timing change.

Jim (twooldgoats) runs 30 or 31 degrees timing with 15 lbs of boost in his blown race car!

GTO George

OK, this is really pretty simple, so let's just put the facts out there:

Mixture burn rate is mainly dependent on fuel type and octane, and cylinder pressure. Simple as that. Increasing octane gives you a slower more controlled burn, and increasing cylinder pressure (more dynamic compression, more boost, etc) speeds it up. There are other factors like chamber design, etc. that can have a smaller effect, but in the interest of simplicity, let's just go with the big ones. Ignition advance is nothing more than the tool used to make the big boom/peak pressure/complete burn/whatever happen at the right point of crankshaft rotation. Most things you read on average/conventional Otto Cycle reciprocating piston engines will tell you that this point occurs 15-20 degrees ATDC.

Every dynamic load and speed state of a given engine will have an ignition timing point that yields maximum brake torque. Also very simple. Advancing the ignition past this point will create pressure spikes, negative torque, and detonation, and retarding it from this point will cause loss of efficiency and excessive exhaust temperatures. Too retarded is mechanically safer than too advanced, but neither is optimal. Running an engine with excessively retarded timing is, well, retarded. There just isn't any reason to do it given modern accurate electronic engine controls, especially those with knock control capabilities.

Retarding timing excessively just to use a higher boost pressure than you normally could for a given dynamic state is counterproductive. No good tuner does this. A book could be written on the how and why, but just think about the things written above and give them careful logical consideration.

Agree Charlie, in Jim's case he is running Methanol, he is at a higher altitude, (lower density air therefore for the same fuel jet he is richer vs a sea level car.)
Finally his boost pressure is 15 psi.

So he has found a sweet spot for HIS location, engine, and fuel. 30-31 degrees. If he was trying to run 38 or 40 degrees I would be posting a different comment: Pack a couple of extra engines in the trailer.

Pontiacs are not CHEBBY engines.

Tom V.