Polky_85

iTrader: (2)

Hi there! I am seeking advice on my options for power adders for my 350. At first, twin turbo looked appealing, but it seems as though it would make the current setup (recently purchased and installed) redundant and have to look at other options. So I got to thinking, a B&M 144, nothing too crazy money wise, fits nicely under the hood, and very simple install. Problem is, my compression ratio. Am I going to be looking at swapping out many more parts anyways with my current build? Ie. heads/pistons? Would there be anything better suited to a higher compression? I currently make 301hp with exhaust open, and I don't really want to add much more, maybe see what 6-8psi gets me and have some fun. Here is my current build;

Heads:
ProMaxx Performance 2180
190cc Aluminum Cylinder Heads•Small Block Chevy
2.02''/1.60'' Valves
190cc Intake Runner
64cc Combustion Chamber
Angle Plug
10.3.1 Compression

Rocker Arms:
COMP Cams 17002-16
Rocker Arm Ratio:1.6
Rocker Arm Style:Full roller

Cam:
COMP Cams 12-268-4
Intake Duration at 050 inch Lift:224
Exhaust Duration at 050 inch Lift:230
Duration at 050 inch Lift:224 int./230 exh.
Lobe Separation (degrees):114

Headers:
Hooker 2460
Collector Diameter:3.000 in.

Any help is greatly appreciated!

anesthes

iTrader: (12)

I ran a powerdyne on my Corvette that was around 10.3:1. I had to pull a LOT of timing out of it, and a powerdyne is a pretty efficient blower.

I'd change the heads to something with a larger chamber.

-- Joe

Orr89RocZ

iTrader: (20)

Good intercooler turbo build for a handful of psi will work. Alot more psi needs race gas or e85. Or also add a water/meth inj kit with the pump gas to handle it. Pull alot of timing out and slowly work it back in to find what it wants

DIGGLER

iTrader: (1)

Turbo setup on e85 if its in your area.

83 Crossfire TA

iTrader: (2)

It might just be me but 301hp for that combination seems kind of low (of course that depends on how you got that number), do you have any track times?

Honestly, with that kind of compression you'll always be fighting it with boost. If you really want to run boost on that I'd keep it as efficient as possible. The old school roots blowers are cool but they are also fairly inefficient, and make a bit of heat which is going to be a nightmare on an already high compression engine.

If it were me and I didn't want to go into that engine to make more power I'd be spraying it, it actually looks to be a decent combination for N2O...

Polky_85

iTrader: (2)

Would I have to worry as much about the compression with a turbo setup? Hmmmm, never thought about nitrous....

jimw67

Run a turbo with one of these

http://www.viatrack.ca/

to keep track of it's knocking. I assume you're running a carb, but if you're willing to run an ECM, then the knocksense can be hooked into the ecm to automatically have your timing reduced if knock is seen.

Or you could just swap the heads. I realize that you said it is a new build, but I'm sure that you could sell the Promaxx heads for a minimal loss from new. Or run Meth injection

Orr89RocZ

iTrader: (20)

If its well intercooled and have enough wastegate to control boost to lower levels, yes i think it will run fine. Just have to watch the timing. Pull more than similar setups that are lower compression.
Meth/water inj should be considered for higher boost levels or more aggressive power goals. But 7-8 psi intercooled wont hurt that motor. Heck 10 will likely work too. It would fly

Street Lethal

iTrader: (16)

Your already setup with exhaust, if you go turbo you will need to make a lot of changes in the engine bay, and if your only looking for 6-8 psi over what your already making, then it really doesn't justify going through all of that work for a turbo charger. I would recommend sticking to your original plan, go with a roots blower. As far as the compression, either get a custom set of gaskets cut from Cometic to bring it down to a more feasible 9:0-9:5, or run high grade pump gas with alky for your existing setup along with very conservative timing, or simply run E85 and don't worry about anything...

Orr89RocZ

iTrader: (20)

I would just be concerned with how much heat soak blowers have. The high iats would be dangerous on regular gas at that compression and just adding gasket wouldnt help with the quench, unless its over .100" piston to head deck clearance. That may lower comp too much

Ideal would be find one of those little paxton or vortech blowers for under 2500$, if you dont wanna rework the exhaust

Street Lethal

iTrader: (16)

Would love to see a roots blower build with a split carb hat running a cold air intake L69 style, just with a much wider in diameter intake tubing and air filters away from the engine heat...

Orr89RocZ

iTrader: (20)

Thats not a bad idea there or plus pre blower meth water inj if thats ok to do on the roots rotors

Polky_85

iTrader: (2)

E85 would be a problem.....I'm in Canada and we have about 2 gas stations that sell it . I think the head gasket might be a feasible solution. 0.120" and then go with my B&M for now? (The price is really appealing) Of course, I would love to save up for a Vortech system down the road. Please excuse my total new guy question too, but what is the best way to test for compression? Is there a calculator anywhere online that would indicate a rough idea with different gasket thickness? Thanks again for all the help guys!

Street Lethal

iTrader: (16)

Custom gaskets made to your spec...;

http://www.cometic.com/custom-gaskets.aspx

Compression Calculator...;

https://www.rbracing-rsr.com/compstaticcalc.html

Polky_85

iTrader: (2)

Brilliant! Thanks Lethal

83 Crossfire TA

iTrader: (2)

Maybe with the turbo setup. It depends on your compressor choice, Turbos can get quite efficient (not heat the air as much while forcing it into the engine) but typically that's in a rather small range, and outside of that range efficiency drops off, so the farther off you are from the sweet spot of the compressor map the worse things get.

Relatively low boost with a turbo means a relatively BIG compressor and trying to get the turbine in exactly the right range to spool it but not go into surge.

It depends on what the blower is built for. It should be fine if it was built to have a carb on top of it, if it wasn't it will wash out the bearings in the case. Honestly, if this thing is really 10.3:1 I wouldn't put an iron lung on it. I've done Eaton's and a KB on similar compression engines and they weren't fun to tune, and they're much more efficient positive displacement blowers than traditional roots blowers. They will heat the air more which will be harder to keep out of detonation.

If you go with a really thick gasket and loose all quench you could end up with an engine with low compression and still be detonation sensitive. Not a great answer. If your quench is like .035" now and you can get a .010" thicker gasket so it's like .045", that would likely drop your compression around a point and that would be a more reasonable combination for boost, but more likely your quench is around .050" and that .010" thicker gasket will put quench around .060" and in a lot of cases the loss of quench will be worse for detonation control than the lowered compression is worth.

I'm honestly still where I started, high compression, don't want to change much with the motor/nice setup = N2O. If it's a well built setup hit it with a 250shot any time you need power... Use a progressive shot and it will feel like you just stuck another 200cubic inches under the hood (300 if the engine is really only making 3xx hp).

Orr89RocZ

iTrader: (20)

A 0.010 change in gasket will only move compression .3, no where near a full point and not exactly worth the effort imo

Some engine builders report the detonation sensitive zone seems to be in the .060-.100 range for piston to deck. After .100, its not as sensitive.

A 11.1:1 motor at .041" piston to deck will go to 9.68:1 with a .100" gasket
Question is can you get one that thick and will it seal?

I honestly would chance 10.3:1 with larger ring gap, alittle cam and good tuning and intercooling

junkcltr

iTrader: (1)

Head cost is minimal compared to the power adder. If you really desire forced induction, put it on. Running 6 PSI would probably squeak by. If you like it and want more, change the heads. If you don't care how the power is made, then leave it as is and put a 200 shot on it.
I wouldn't put a thick head gasket in it. Don't see much gain in that.

83 Crossfire TA

iTrader: (2)

Yea, I had 3 year old twins bouncing off of me when I wrote that, no idea what I was thinking but my basic point was that unless the current quench is super tight changing gasket thickness is unlikely to make enough of a change and still maintain reasonable quench.

I've seen it tested showing both ways, that that is the range where it's worse, and that's where it gets worse and over .100" it just doesn't matter if you increase quench more, that's typically as bad as it will get. The fact is that quench distances in that range are big enough that chamber shape doesn't effect much.

I've also seen chamber and piston mods that supposedly work best with quench distances >.070" but I suspect that some of the results were because of how the testing was done (small flathead/L-head engines).

I haven't looked recently but you used to be able to get shims for this kind of thing, or to use with excessively decked blocks... I have no idea what they would do with significant boost.

I would too, but if you're going to go as far as pulling the slugs to re-gap the rings, why wouldn't you sell the heads and get ones with larger chambers at the time? Or swap the pistons out?

t-top89

iTrader: (3)

The price on .120 gaskets are very high. Might want to include that cost.
I just priced a new set of Cometic MLS .120 and they were gonna run me around 500. And thats for a little ol V6.

Orr89RocZ

iTrader: (20)

At that point you work with what you have or look to buy new heads imo

Or buy a drum of e85

junkcltr

iTrader: (1)

250HP shot with PWM control. Can make it act just like a turbo or supercharger with a little programming.

anesthes

iTrader: (12)

Sell me the heads so I can put 'em on my vette. Then you can buy large chamber heads and turbo it up.

-- Joe