Running a larger cam to lower your dynamic compression ratio will push your HC emissions way up. Your cats may clean it up but maybe not. Increasing your compression ratio will also increase NOx.
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If I install a .060" copper head gasket this will lower my compression to 9.5:1. This would bring down the effective compression ratio to 7.919. would this help in regards to emissions?
Quote:
Originally Posted by Torque1st
Running a larger cam to lower your dynamic compression ratio will push your HC emissions way up. Your cats may clean it up but maybe not. Increasing your compression ratio will also increase NOx.
Jolbca...I would have to say your best bet is to make sure your cam is CARB approved, this should be #1 in California. If your vehicle doesnt pass smog in CA and is over a certain limit it will get tagged as a gross polluter. If this happens you would have to take it to a state referee where they will go over the vehicle with a fine tooth comb. This would have to be done everytime it needed smogged, for as long as that vehilce remained registered on the road in the state of CA.
Second best bet is to lower your compression ratio by installing pistons the first time that will be compatible with pump gas ...doing this now will save you possible engine destruction from detonation, this can happen fairly quickly and easily, and should be taken into serious consideration considering you want to use this vehicle for some towing also.
As Eric has said in his post, you could end up with emissions issues with this.
I would seriously try to build this so that you can register it and drive it on gasoline you can find anywhere out west. Your looking at several possible nightmare situations vs doing it right the first time and enjoying your ride....
I called KB Pistons and they told me to not exceed 0.055" for the quench on these pistons. If I use this calculation this would bring me down to 09.568 STATIC COMPRESSION RATIO with a 07.996 DYNAMIC EFFECTIVE COMPRESSION RATIO. Also I am going to polish the combustion cambers as well. Please let me know your thoughts and I am contacting Isky about there cam exemption.
It seems the only manufacturers that carry CA CARB EO's is Edelbrock and compcams.
If you want to regulate your compression ratio, KB-Silvolite carries a multitude of pistons that will help you aqcuire the right deck height clearance and quench with the right head gasket.
You are right about the CARB issue. The quench KB pistons recommends is .040" but the max is .055" before you would get into the problem associated with detonation according to KB Pistons. Since the compression will be around 9.5:1 this should run on premium gas out here in california. The cam I am using is mild and as far as I can see this combination will work as long as I don't do any heavy towing.
I want to thank all who have recommended many great options and know how.
Detonation is is the devil! I have a 390 .040 over, stock with the exception of a bigger bump-stick, and from what I understand, somewhere around 10.5 - 11.1 flat tops. I really enjoy driving my truck, but I have to do a sorta prep session before I take it out for a spin. If I want to just drive it around then I'll put her in advanced mode, with the vacume advance hooked directly to manifold vacume. This allows me to cruise around with out worries of running warm but I not dare try to even accelerate hard, let alone WOT. If I want to pull or haul somthing, then i'll either run the same timing and use no V.A. or that and pull the timing down. Depends on how heavy my load is. I can accelerate fairly well in this mode, though I do have to watch my temp. My Final mode consist of pulling the timeing way down to avoid detonation at WOT. This mode I get the best non-detonation performance, but far from optimum (unless I used avgas or so). Also there is a bit of fine adustment to the carb between these timing adjustments. As you can see my high cr engine is quite a hassle for me. It would be impossible for me to live were I had to pass a sniffer with my lack of patience. So I would highly recomend going with a lower cr as I believe it would be more enjoyable and less hassle.
I have rebuilt this engine just a short period ago, but my financial situation wouldn't allow me to purchase lower cr pistons. I had to re use these from the previous build which I didn't perform.
It sounds like a couple of fish tank air valves mounted in the interior or one of those old JC Whitless cable operated distributor advance mechanisms are needed.
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