increasing compression on 350 chevy?

Look at a chart of a carnot cycle. All parts of the engines cycles only absorb/rob/steal energy from the engine except for one. Expansion. The amount of energy you convert from gas pressure to mechanical torque on the crankshaft depends exactly on the amount of expansion you are able to perform on this gas mixture. This expansion is the only way an engine is able to extract energy from the fuel/air mixture you've burned. The combusted mixture has potential energy stored in the form of pressure and heat. As it expands, this mixture under goes a cooling as the volume increases. The amount that the temp is decreased by, and the volume is increased by directly relates to the amount of energy converted to mechanical energy at the crankshaft. The great the expansion ratio, the greater the amount the engine can cool the mixture, and hence the greater amount of power can be extracted.

You can use cam profiles with very late IVC events (or very early IVC) to create an imbalance between dynamic compression ratio vs expansion ratio. This is called a "miller cycle" engine. It is able to lessen compressive losses while keeping high expansion power extraction from the mixture. It improves economy at the cost of performance, as it functions as though its a smaller displacement engine than it physically measures. They are often supercharged to recover this loss of power, and a positive displacement blower acts as a check valve to harness the returned intake pulses from the 30-40deg late IVC events

Tighten the piston to head squish clearance to achieve a total clearance of .025 This will not only raise compression, it will lower octane demand, spark advance requirements, greatly reduce detonation propensity; etc.

You can zero deck your block. Or you can just install a Fel Pro 1094 head gasket. That alone is not going to get you there because right now, the pistons are about .025 negative deck clearance at TDC.

I'd put a pair of factory Vortec heads on there.

You have to work the Quadrajet over. It came with BIG air bleeds in it during their first couple of emission years they were trying to figure things out. It is a superior fuel vaporizer. Fuel vaporization is a crucial factor in performance, mileage, emissions; etc.

You can also pick up cylinder pressure with the right cam. I can help you there.

Keep a single exhaust on the truck, as it will make more torque and HP than it will with a dual exhaust, and it will also reduce the exhaust cam duration requirements to get the job done. That keeps 'early' torque AND mileage in it.

Install a one inch or a two inch thick 4 hole carb spacer.

camshaftshaun@gmail.com

Changing the compression ratio will do nothing for MPG, it will give you better performance and require that you use a higher octane fuel but that's about it, your dealing with an old heavy chassis with a carburated V8 engine, new truck manufactures get around this with lighter chassis and redesigned engines using ported fuel injection, hell Ford is using direct injection on there Eco boost, and those MPG numbers are really good, they might be onto something so expect the others to follow suit, so here's how you do it, pull that old engine out and box it up, put it somewhere safe in case you want to reinstall it at a later date, buy yourself a new crate engine with port injection and the ECM that goes with it, many after market company's sell the package ready to install, although you will still have weight as an issue your MPG will dramatically improve.

Since you are not looking for performance but efficiency, look at changing the rear axle ring and pinion gear ratios. Chevy had various ratios for various cars and truck ranging from 4.88:1 to 2.73:1 with the 2.73 designed for better mileage at the cost of performance. You can also go to larger size tires (of the same rim diameter). Your speedometer will have to be re-calibrated if you go this route.

But you mention that the truck is gutless with the 8.6:1 compression. That's a performance issue.

you could desire to spend a boat-load of money and improve performance a dozen distinctive methods and that i doubt you will get one extra 2-3 mpg. maximum attempt performance positive factors then lose it with a heavy precise foot. save the great plans for later. shop that truck and on no account permit it pass. do no longer pass loopy with differences by way of fact maximum of will seem and say; "i'm going to guess it replaced into intense-high quality in the previous he began messing with it". A undeniable Jane gasoline guzzler is a few distance cool over a toyed up truck. positioned some Headers and FlowMaster 40's, possibly some extra suitable heads and a intake manifold.

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