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Old 04-12-2012, 12:43 PM
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More power

I have 1987 Chevy caprice 350 CID, is there anything i can do to get more power? So far I change the whole top end, manufacturer block, distributor, cap and rotor, wires, plugs, headers, exhaust. if you want me to provide exactly what was installed to get better clarification so you can give me adequate answer i will do so?

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Old 04-12-2012, 12:50 PM
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Quote:
Originally Posted by 87sigmabox
if you want me to provide exactly what was installed to get better clarification so you can give me adequate answer i will do so?
Umm... That's usually how it works. Nobody can help you if you don't spill the beans.
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Old 04-12-2012, 01:17 PM
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sounds so far that you did all that you can do. (w/o touching the internals) if it didnt give you the amount of power you wanted then you didn't buy the right parts. examine the specs on your heads and c.r. and since you said nothing about the cam being changed, that would be the next step. you might be able to mill the heads cheaply, or change out rear gears also. peace
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Old 04-12-2012, 01:20 PM
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So you have replaced the engine block (?!), top end (is that cylinder heads and pistons?), headers and exhaust? Assuming you picked the right parts you should have made a lot more power. You did not mention cam and intake though.

How much power were you making?
How much power do you make now?
How much power do you want to make?
What is your budget?
Is this a street car?
Drag car?
SCCA road course car?

You need to include all this info as well as the specific parts you used. More detailed info will get you more detailed responses.
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Old 04-13-2012, 05:35 AM
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Carburetor, Performer, 600 cfm, 4-Barrel, Square Bore, Electric Choke

Cam and Lifters, Hydraulic Flat Tappet, Advertised Duration 292/300, Lift .488/.488, Chevy, Small Block, Kit

Headers, Street, Shorty, Steel, Painted, GM, Car with Chevy, Small Block,

Cap and Rotor, Red, Male/HEI, Brass Terminals, Screw-Down

Fuel Pump, Mechanical, Performer RPM Series, 6 psi Maximum Pressure

2-Muffler, American Thunder 40 Series, 2 1/2 in. Inlet/2 1/2 in. Outlet, Steel, Aluminized

Spark Plug Wires, Super Conductor, Spiral Core, 8.5mm, Red, 90 Degree Boot

Distributor, Street Fire HEI, Magnetic Pickup, Vacuum, Mechanical Advance

Cylinder Heads, E-Street, Aluminum, Assembled, 64cc Chamber, 185cc Intake Runner,

Intake Manifold, Performer EPS, Dual Plane, Aluminum, Natural, Square Bore,

Timing Chain and Gear Set, Performer-Link, Double Roller, Iron/Steel Sprockets,

2.25 diameter x pipe
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Old 04-13-2012, 06:43 AM
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if you have changed all this then there is not much more than you can do, if you want more acceleration then my next suggestion would be to get a set of 3.73-4.10 gears and put a shift kit in the transmission.

with what the parts you listed the motor should be making 400+hp unless you did all this to a motor that needed to be rebuilt and is letting the compression blow-by the rings.
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Old 04-13-2012, 10:41 AM
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Quote:
Originally Posted by 87sigmabox
Carburetor, Performer, 600 cfm, 4-Barrel, Square Bore, Electric Choke

Cam and Lifters, Hydraulic Flat Tappet, Advertised Duration 292/300, Lift .488/.488, Chevy, Small Block, Kit

Headers, Street, Shorty, Steel, Painted, GM, Car with Chevy, Small Block,

Cap and Rotor, Red, Male/HEI, Brass Terminals, Screw-Down

Fuel Pump, Mechanical, Performer RPM Series, 6 psi Maximum Pressure

2-Muffler, American Thunder 40 Series, 2 1/2 in. Inlet/2 1/2 in. Outlet, Steel, Aluminized

Spark Plug Wires, Super Conductor, Spiral Core, 8.5mm, Red, 90 Degree Boot

Distributor, Street Fire HEI, Magnetic Pickup, Vacuum, Mechanical Advance

Cylinder Heads, E-Street, Aluminum, Assembled, 64cc Chamber, 185cc Intake Runner,

Intake Manifold, Performer EPS, Dual Plane, Aluminum, Natural, Square Bore,

Timing Chain and Gear Set, Performer-Link, Double Roller, Iron/Steel Sprockets,

2.25 diameter x pipe
The pistons are what? Add to that question what is the piston crown to head deck clearance and the thickness of the head gasket? The reason for these questions is to get at the Static Compression Ratio (SCR). The next thing is to get at the Dynamic Compression Ratio which needs knowledge of when the intake valve seats closed in terms of crankshaft degrees, so I need the data off the cam's timing card and the connecting rod's center to center length.

The above is to get at the Dynamic Compression Ratio (DCR). A high performance engine needs to have its compression carefully calibrated to the camshaft. The mixture inside the cylinder is incapable of being compressed till the intake valve closes. At low through mid range RPMs especially with over-sized intake ports and valves the velocity of the mixture inside is unable to overcome the forces of reverse pumping caused by the rising piston. Velocity within the ports is a function of RPM and the port size. Bigger ports allow the mixture to expand which in the laws of physics and gas dynamics means velocity is lost and intake ram effect with it. The effect is, also, proportion to RPM which changes the amount of flow required. At the low end of the scale the amount is small therefore the expansion of mixture is great and the loss of velocity large, so it's easy for the piston to reverse the flow and pump mixture back out the past the valve and into the intake tract if not actually out of the carburetor this being called reversion. The popular press likes to attach reversion to a function of not adequately blowing the exhaust out of the cylinder. While not untrue that is the minor cause of reversion. What happens is that the engine needs to spin up fast enough to increase the mixture velocity in the ports and past the intake valve to where it develops enough inertia to overcome the pistons reverse pumping and force mixture into the cylinder this is called ram charging not to be confused with the 1960's era Chrysler's with their super long intakes. That is intended to increase the length and weight of the mixture stream so that at high speeds there is a lot of inertia to continue to fill the cylinder against the rising piston with a late closing intake valve. So it's merely a tool to aid the situation caused by the cam timing. So the DCR is a measure of lost stroke (the engine looks smaller) till the intke closes. While this doesn't change with engine speed there is a point where the incoming mixture develops enough inertia that if overcomes the reverse pumping and ram fills the cylinder. This is the key that allowed the design of high speed engines. Before this was understood, (Sir Harry Ricardo) the gas engine peaked out around a thousand RPM.

OK, that's a lot of rocket science but we're far from finished. Let me digress into the relationship of gearing to all of this before diving back in the DCR. The effects caused by holding the intake valve open till late in the compression stroke is to move the power peaks further up the RPM band and to lesson the RPM spread between the torque and horsepower peaks. Also, this greatly reduces the lower end torque against raising the upper end horsepower. This gets to be a problem as now the engine needs to spin faster to get at a useful power range. The result of this is to require stiffer gearing and in the case of an automatic transmission a higher stall converter. The higher stall converter allows the engine to spin to a higher RPM before putting the load of moving the vehicle on the crankshaft by increasing coupling slippage within the converter. A radical cam is easier to manage with a stick transmission as it's easy to treat engine RPM and road speed as independent of each other, especially with 4,5, or 6 speed gear box. This is tougher to do with an automatic especially with a 3 speed as these things aren't designed to be manually shifted and require a lot of time and money to modify into manual control. A quick and dirty way around this is to use a 4 speed 700R4 which has a deep low compared to the TH350 it is about a ratio deeper. This really improves the launch, but the skip to second is a long one resulting in a large RPM drop. But it gets around running an extremely low ratio rear end which will eat you out of house and home at highway speed to pay for the fuel it burns.

You have what looks to be a rehash of the 1960's era muscle car cams where there is a lot of duration and not a lot of lift. These sound better than they perform. The modern trend is to faster lift on a shorter duration. This mitigates the mixture reversion issue by getting the intake closed earlier and makes better use of larger volume ports to deliver higher flows with less mixture velocity. These older design cams are very rampy, while the ramp doesn't do a lot to improve cylinder filling, unless you really rework the back side of the valve, they demolish the compression pressure by seating the valve late in the compression cycle.

Headers, your choice sucks, no other way to put it. The cam you have demands long tube headers. Here as with the intake inertia is the issue. Long tube headers develop a lot of inertia which leaves a high vacuum behind in the cylinder that is used to get the intake flow started during the cam's overlap phase where the exhaust valve isn't closed and intake is stating to open. The effect is greatly assist the intake flow to minimize the problems you having at lower RPMs with late seating intake valve and lazy port flows. This will brighten up the bottom end coming out of the hole a lot.

I don't think the EPS is nearly as good as the RPM in your situation and the 600 CFM carb is too small mounted over too much cam and port volume. But without stiffer gearing and high stall converter I can't get too excited to recommend the 750 Holley or Holley clone I'd like to. A big Q-Jet in your situation would be better. For the life of me I can't understand why Edlebrock gave up on the Q-jet and kept the Carter as like the Holley it's difficult to size it for a broard RPM and power range.

But first before we do anything we've got to get to what the real compression ratios are for both the Static and Dynamic --- Ratios.

Individually you've got some good stuff here, but they don't play well together yet.

Bogie
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Old 04-13-2012, 08:25 PM
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Quote:
Originally Posted by 87sigmabox
Carburetor, Performer, 600 cfm, 4-Barrel, Square Bore, Electric Choke

Cam and Lifters, Hydraulic Flat Tappet, Advertised Duration 292/300, Lift .488/.488, Chevy, Small Block, Kit

Headers, Street, Shorty, Steel, Painted, GM, Car with Chevy, Small Block,

Cap and Rotor, Red, Male/HEI, Brass Terminals, Screw-Down

Fuel Pump, Mechanical, Performer RPM Series, 6 psi Maximum Pressure

2-Muffler, American Thunder 40 Series, 2 1/2 in. Inlet/2 1/2 in. Outlet, Steel, Aluminized

Spark Plug Wires, Super Conductor, Spiral Core, 8.5mm, Red, 90 Degree Boot

Distributor, Street Fire HEI, Magnetic Pickup, Vacuum, Mechanical Advance

Cylinder Heads, E-Street, Aluminum, Assembled, 64cc Chamber, 185cc Intake Runner,

Intake Manifold, Performer EPS, Dual Plane, Aluminum, Natural, Square Bore,

Timing Chain and Gear Set, Performer-Link, Double Roller, Iron/Steel Sprockets,

2.25 diameter x pipe
I suspected with all the other Edelbrock stuff, your cam is also an Edelbrock product.

It looks like the Torker Plus p/n 5002

http://www.edelbrock.com/automotive_...5002&submit=go

At least the advertised duration and lift numbers match up with what you wrote. And it looks like you followed Edelbrock's recommendations to the letter when it came to the timing set.

Bogie's right. You do have something of a mismatch. Your intake and heads are suggested by the manufacturer for use when you want torque (for the most part) from off idle to 5500 rpm. Your cam is designed not to come alive until 2500 rpm.

There is good news. You can get these things to work better together. You can for instance effect a cam's powerband by advancing or retarding it.

You can only do that so much, though, as you have to worry about piston to valve clearance. Really, you need to worry about that in any case. But it becomes more of a concern as you alter the timing of valve events in relation to the position of the piston. What once was safe can quickly become unsafe if you alter this relationship too much.
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