Average Safe Boost level for a LA eng

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Cudafever

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I realize that 4 bolts per cyl is NOT the best design for High compression or boosted engs.

I'm not talking about fire ring head gasket or wire grooved head/cyl.

I also realize that detonation will destroy any head/ gasket/ piston.

If detonation was not a issue.......like a diesel eng. head and deck cut straight, standard gasket. standard head bolts.
And air fuel ratio was kept in check.......what would be the average boost level that would hold for years in LA
small block.
this will be a 9.xx compression ratio 340 or 360
 
i would think 9.xx compression would be a little high...you wanna be around 8.0, but if you must, id say 5 or 6 psi...
 
I haven't build this eng just doing research on it. maybe next winter. but I'm learning fast, that there is a LOT to learn about turbocharging a eng........and making it survive!!!!!!
I was told that 8.0 is low these days, and that 9 to 9.5 is a better base.:study::dontknow:

NOTE: This eng would live at 6800 feet most of it's life.
 
a standard production small block mopar only using 10 head bolts wit h a lot of boost the deck tends to move around,,same problem with the buick motors,,
if you plan on making any type of boost and plan to beat on it, you should look in to o -ringing the block with a reciever groove in the heads,, or use a gasket that has a good track record,,

a mopar performance block will have a more stable deck then a factory production block,,
 
If you are using closed chamber heads, simply radiusing the sharp edges of the deck could dramatically improve the engine's tolerance to boost. Part of it comes from the reduction in compression ratio from the material removed, and part comes from the improved combustion characteristics of the radius.

FinishedCC1.jpg


Although a Chrysler 2.2 Turbo head, the principle is the same.

Mike
 
I ran 6PSI of boost on a Fel-Pro 1008 gasket with ARP bolts.

I did get tired of "pushing" the gaskets out, I have since O-Ringed the heads and cut receiver grooves in the block and run SCE copper head gaskets.

I dont think my tuning was off or detonation was to blame as I have whacked stock pistons with 6PSI off boost WITH upto a 200 shot of N2O and never broke a piston from detonation. LOL However it is real bad for stock pistons when the needle on the tach goes past 8,000...
 
Thanks 440, that's a nice chart!

Mike i will deburr everything in the combustion chamber!
Sooo, what's with the dimples???
 
Cudafever said:
Thanks 440, that's a nice chart!

Mike i will deburr everything in the combustion chamber!
Sooo, what's with the dimples???
Click to expand...

On the 2.2 heads, the dimpled area is a "dead zone". The dimples act like golf ball dimples and induce activity to help keep fuel from separating.

Mike
 
its all in the tune... cars have blown up with 1 psi and others not till 30.. and different sized turbos flow differents amount of air, so just saying 8 psi is a good number is inaccurate..
 
member turbocuda use to run up to 25PSI with Twins and I believe his compression was 9:1. Still a 10 Bolt Head configuration. 895 RWHP He did have a very good Air/Water set up though. Keeping the intake charge as cool as possible will deter detonation.
 
Granted it is a big block but he was over 9 to 1, used meth injection and ran a truck load of boost....
[ame="http://www.youtube.com/watch?v=oRBC7cZ-JiU"]Matts turbo dart - YouTube[/ame]
Will look for the emails with the specifics.....
He said it used to be 7.7:1. Upped it to 9:1 and it makes more hp/torque per pound of boost than at the lower compression, and as long as the tune is right it runs on pump gas with water/meth injection, no intercooler necessary.....
 
I think that chart is out of date or WAY on the safe side with today's technology. Some guys are running 20 PSI with all stock parts, no studs or fancy head gaskets and smacking it with some JUICE on top of that.
 
I would look into ARP head studs over bolts. Look into Snow water-meth injection this is what the diesel guys do to run big boast. Fuel qualty is a big if maybe look into E85.
 
I also favor the Cometic MLS head gaskets. They work about as good as O-ringing.

Mike
 
do ya have to pull the engine apart and have both the deck and head surfaces machined to use the cometic MLS gaskets?
 
mopardude318 said:
do ya have to pull the engine apart and have both the deck and head surfaces machined to use the cometic MLS gaskets?
Click to expand...

They recommend it but I have got away with NOT doing that several times with no problems at all "Water Weepage".. On the TT Engine I used Studs and the block and heads were surfaced smooth per cometic specs. I also sprayed them with copper coat before install and torqued the heads to 105lbs using ARP Lube. I torqued them in about 8 gradual steps. That was a flipping work out!!
 
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