[BogiesAnnex1]

They are good for making a positive seal on older and usually distorted mating surfaces or where milling has been on some but not necessarily all of these surfaces to correct flatness and angles.

No the exhaust plug won’t last long, it takes serious amounts of metal to close those passages even the thin stainless steel of some gaskets won’t last for very long. I find a quarter inch thick aluminum plug driven into the intake side and flush with the intake mating surface to be long term survivable and removable if you don’t like the result. This takes some fabrication time to get a good fit into the passage so it also backs up the gasket preventing it from burning through.

A consideration in this is how the automatic choke if used gets its heat. Electric not considered here since it gets heat by converting voltage to heat. But exhaust heated come in one of two variations on the Chevy engine. One is the divorced choke where the bimetal heated element is in or on and covered mounted to the exhaust crossover of the intake. The second is integrated on the carburetor and uses a steel tube in the crossover of the intake such that it is heated by the exhaust gasses thusly heating air drawn through the tube that is discharged into the thermostat housing as it passes as a tiny air leak into the intake system. So if your set up uses one of these two exhaust heated systems you will need to make suitable modifications to this system.

If you live in a cold climate the exhaust heat cross over is very necessary to get running quickly without drowning the engine with excess fuel for long periods of time especially with a cast iron intake. Aluminum is a bet better without a functional cross over because it picks up engine heat quickly. But the issue for day to day driving is to get the cold start mixture enrichment off as quickly as possible so top end cylinder lube isn’t washed off by the rich fuel mixture which shortens bore wall, piston ring and skirt life.

Bogie

 

[BogiesAnnex1]

If you don’t have problems now you don't need to worry it. Iron intakes don’t move near as much heat into the manifold as aluminum. If your intake is aluminum then in a moderate climate adding exhaust heat can result in cooking the fuel out of the carb, so called percolation which is just boiling standing fuel out the vent. The Carter derived Edlebrock AFB and AVS are more sensitive to this than Q-Jets and Holley’s. In fact factory Q-Jet intake often put exhaust heat around the primary side throttle bore of the carb.

The big reason for cutting off exhsust heat from the hotrodder perspective is to increase mixture density which increases power. The down side is unless you operate at racing RPMs all the time there isn’t enough manifold velocity to keep the wet fuel mixed with air so the engine acts rich when it really isn’t. This wastes a lot of fuel unburnt into the atmosphere and at your wallet as your not getting distance travelled for the fuel run through the engine and back to an already discussed subject is the wet fuel going unburnt washes the already thin upper cylinder lube from piston, it’s rings and the bore wall accelerating wear of these parts.

These are trade offs racers make but on a competition engine that is run flat out the intake velocities are high which tears the liquid fuel into fine droplets but are a liquid not a true gas. Anything in its liquid state occupies less space than the same liquid does in its gaseous state. This is fundamental physics and perhaps chemistry. So as long as the fuel can be kept in finely divided liquid or a mist as a liquid state there is space to pull more air so the reactive weight going into the cylinders is higher. The more product to be reacted in the confined volume of the cylinder the more power can be had from that cylinder.

Once the fuel undergoes the phase change from a liquid no matter how fine its particles at the phase change it occupies about 20 times the volume for the same weight of product. This expansion taking place in the intake reduces the weight of the flowing mixture within the intake and therefore less weight of reactants flow into the cylinder. Thankfully gasses being compressible the weight of reactants in the port and runner volume is not reduced anywhere near the expansion ratio of liquid to gaseous fuel so the power impact is only a few percent but if your racing for cash, cases of oil and or glory a few percent less horsepower keeps racers up at night.

On the street the engine is not operated as it is on the race track. Here most of its life is operating at 2000 RPM or so not 6 to 9 thousand so port flows are pretty lazy to where liquid fuel is not being consistently misted and may actually be tossed out of flows at turns to condense and run as liquids along the bottom of the intake. Liquid fuel running running into the cylinder unless you have a modern chambered head makes the engine run rough, burn more fuel than needed and accelerates top end wear. So what’s an engineer designing these Monte Carlos for grandma and grandpa to do well before electronic fuel injection and better combustion chambers you would apply exhaust heat to vaporize the fuel into a gaseous state where it mixes nicely with the incoming air, isn’t slung out against manifold and port walls at every turn to condense and run as a liquid into whatever cylinder is handy; as well as to get reliable consistent operation (drivability) combined with decent engine life. So heating the intake with a carburetor was done across the board by all manufactures, exclusive of intentional high performance models which never sold enough vehicles to justify the bulid expense of making them. Figure in all the Barracuda production at Chrysler they never made a thousand hemi-Cudas, so racers and hotrodders is far from Detroit’s focus where needing to make and sell vehicles by the millions to the masses to pay for the facilities and tooling.

Basically fuel injection and specifically port and direct gets around all this carburetor mess. Initially port injection provides a high pressure spray of fuel into the valve pocket. With port EFI came the return to the pre smog dual quench combustion chamber to do the fuel and air mixing in the chamber since the intake was dry. For less expensive throttle body injection everybody concocted some form of swirl port to spin the mixture as it entered the cylinder. Hitting into 1995-96 this needed improvement so low pressure TBI injection at the factory was eliminated in favor of high pressure sequential port injection across the board. This lead to high swirl being a function internal to the combustion chamber thus Chevrolet introduced the Vortec head, Chrysler the Magnum head, and Ford the GT and GTP head. Head and chamber design has gone on from there. These heads make power period! A nice fall out for the racing and hotrodding communities is these heads are designed to work with fuel in its liquid state without port flow obstructions designed to create high swirl, all of that being done with chamber shape without restriction to flows at the valve. These heads are as happy to do this mixing chore for a carburetor or throttle body injector as they are for a port injector. This alone is reason to put your cash into building a 350 instead of winnowing dollars into the 305.

A Vortec headed 350 will rock you in ways the 305 can’t really get to, not that you can’t put L31 Vortec heads on a 305 but for the money spent your always power behind not only from the lack of 45 more cubes but the small bore of the 305 just doesn’t let the Vortec head breath bigger valves not withstanding. This is just a fact of life with bore diameter. You’ll find that nearly all flow bench numbers are with a 4.030 diameter. The reason is this allows the port delivery freedom that smaller bores don’t regardless of port volume and valve size.

I guess this should be enough to leave you blurry eyed and brain numb so I’ll hang it here for a while. Besides it’s time to feed the dog and cats.

Bogie

 

[BogiesAnnex1]

Placing a straight edge across the bottom the surface should be slightly convex, that is higher in the middle than the perimeter with a smooth gently bulging surface toward the center surface. This combines with a slight angle across the width of the lobe that causes the lifter to rotate in its bore. Anything else is grounds for replacement. The cam lobe condition is harder to see without removal, but by rotating the crank to turn the cam with a strong light you can see the surface of the lobes. Pits, gouges, worn or wearing round says the cam is toast.

Used lifters need to go back on the lobe they were mated with otherwise the wear rate goes insane.

Bogie

 

[BogiesAnnex1]

Dirty pushrods are mostly a sign that the engine has many miles of cold and slow operation mixed with infrequent oil changes. Crud on these parts is probably reflective of the entire inside of the engine, it isn’t a big deal especially on a 35 year old engine.

The concave shape on the lifter presents as worn out again not unexpected on an engine of this age. Chevy and others made decisions about the materials and post machining treatments used on camshafts and lifters in-order to reduce manufacturing costs which led to increased wear on these components as well as the EPA mandating lower amounts of zinc phosphate Extreme Pressure (EP) additives in engine oil that offered some wear protection. This and the discontinuance by the manufacturers of nitriding camshafts and hard facing of lifters in the mid to late 1970’s greatly increased cam and lifter wear. It is important to remember that treatments like nitriding or Parkerizing or Melonizing are all sacrificial surface treatments that don’t last forever. After these were cost cutting eliminated the reduction in EP additives to engine oil became the straw that broke the camel’s back on these highly loaded components of cam lobes to lifter feet directly leading to the manufacturers going to roller cams of with flat tappet cams just totally neutering durations and lifts as in GM’s 1987 through 95 truck engines while passenger cars got roller cams since 87 and trucks finally with the 96 Vortecs.

You are at the decision time I warned you about at several points and ways as whether to keep throwing money at the small displacement power limited and technically obsolete pre roller 305 or move into at least a 350 with a lot more capability power wise and in that decision wheter to make the change to the factory or OEM roller cam engines.to just get out of the fight with keeping a flat tappet cam alive for many miles any more. Plus the post 86 engines came with a one piece rear seal that is so much secure against oil leaks, this would require a matching flexplate as the one piece rear seal drives a different (smaller) crankshaft bolt circle and a bit of counter weight moved off the crank and onto the flexplate.

You are headed to considerable down time and expense with either way you jump. The least expensive in the short term is replace the cam and lifters with a flat tappet. That does require getting the engine up so the pan can be removed so the front cover can be removed and it’s gasket with the pan renewed.

The longer term investment is to put the money and time into a roller cam block.

Fixing old cars, hot ridding and racing are expensive hobbies, nothing new here they always were. A sign high on the back wall behind the counter of the speed shop in my home town read “ Speed costs money. How fast can you afford to go?” Nothing about this has changed in the intervening 70 some years since I was a teenager.

Bogie

 

[BogiesAnnex1]

Push rods on your engine are the hardened type as they are guided by a slot in the head. Standard pushrod length for the flat tappet cammed SBC is 7.8 inches.

Rockers are NOT the self guiding type on this engine so be careful here you can’t or shouldn’t run self guiding rockers with head guided pushrods else they will bind and the conversion to self guided gets you into drilling the slot guide out of the head, so regular pre 1987 parts are what you want.

Generally for a factory build engine push rods and rockers wear a long time but you want to examine them a polished surface where pushrods meet the rocker is good for either part pits and gouges not good. Check in the ball and socket, pretty much looking for the same qualities as the push rod ends of things. The ball and socket is also subject to over heating if pushed hard, here you’re looking for bluing of the metals. The rocker tip is hardened for wear against the valve stem, here your looking for a linear groove worn into the tip of the rocker which indicates the surface hardness is worn through this is a cause for replacement even if everything else looks good.

Bogie

 

[BogiesAnnex1]

Yes.

The only exception would be that L31 Vortec heads would not bolt to your current intake. Also, the 1987-1995 heads would not bolt to your current intake. The bolt pattern of the 87-95 intake looks like the 55-86 pattern but the 2 bolts on each side of tge plenum meet the head at a different angle.

There are many aftermarket heads in aluminum and cast iron that do accept your current intake. Most aftermarket aluminum heads are .1 inch taller from their head gasket surface to the valve spring pocket; this requires a .1 inch longer than stock stem valve. Everything else is the same dimension as production except that the push rods also need to be .1 inch longer.

The 350 including the 86 and up with the one piece rear seal bolts to your 350. However, the 86 up crankshaft requires a same date period flex plate because the crankshaft bolt circle is smaller than that of the two piece crank flange of 1955-1985. The converter bolt pattern and the starter ring gears remain the same as 55 through present crate engines. There are two ring gear counts at 153 for the 10.75 inch dia. flex plate and 168 for the 11.5. Most blocks are drilled and tapped for the straight bolt starter pattern of the 153 tooth and the slightly angled bolt pattern of the starter for the 168 tooth flex plate.

Chevy V8’s big or small block excepting the 2000 Gen-III and up series that replaced the classic SBC use the same bellhousing bolt and depth pattern since 1955. The 90 degree V6 derived from the Chevy V8 and the inline Chevy 6 and derived inline 4 use the V8 pattern since 1963. So all Chevy transmissions easily interchange through these dates in terms of mounting to these engines.

Probably a good idea to start copying the data that’s been coming your way to paste together a data book of what goes with what. Chevy makes several twists and turns so there are things that easily interchange and places where it gets tricky.

edit addendum:

I was going to add before getting interrupted by wifey that transmissions also get tired with age. There is a strong possibility that it will need an overhaul as well as you either drive more aggressively an what you currently have, or beef up the performance of your current engine or go to a larger engine. All of these possibilities add stress to the transmission actually the entire drive train.

Bogie

 

[BogiesAnnex1]

A couple likely choices of what’s going on:

1. If it is an issue of cam lobe and lifter foot wear and the lifter ticks this would indicate that the wear has reached a point where the plunger trying to maintain the zero load setting has run out of upward adjustment distance. In this case the plunger would be positioned against the retaining clip at the top of the lifter body and the push rod would be loose.

1.a. Running the engine with a stethoscope should pinpoint which rocker is clattering. Removing that valve cover should reveal that the rocker does not open this valve as much as those adjacent to it.

1.b. Not taking action can result in the push rod uncoupling from the rocker or being bent if it gets bound in its guide. Adjusting to the point of quieting the tick will forestall that failure for a while.

2. The other most likely possibility fit the lifter tick is the check valve on the bottom of the plunger is leaking, therefore, not holding the plunger in its preset position as the lobe lifts the body of the lifter against the pressure of the valve spring. This check valve will be a lightly loading spring against either a ball or a wafer in a cage on the bottom of the plunger. If this valve is leaking the plunger will bleed down as the cam lobe raises the lifter body and valve spring force opposes the plunger being lifted with the lifter body because the oil trapped beneath the plunger is leaking back into the oil reservoir in the upper section of the lifter. Engine oil pressure is no where sufficient to oppose the valve spring force. The oil inside the upper part of the plunger is only a feed puddle to the chamber beneath the plunger that is fed or vented by the metering valve riding on the underside of the plunger or internal “piston” of the lifter.

2.a. There could be trash that circulated with the oil has become caught in the bottom check valve of the lifter in which case disassembly and cleaning might restore operation.

2.b. Or that this valve or seat has worn to the point that it leaks. Either way this valve is what maintains the plunger adjustment.

3.0 Excessive clearance allowing oil to escape the lifter.

3.a. The oil from the compression pocket in the bottom is leaking around the plunger due to wear or damage to the interior wall of the lifter body or that outside wall of the plunger.

3.b. Wear between the lifter body and its bore in the block is excessive to where the timing of the reservoir feed hole is off and the reservoir is leaking or not filling properly. This is pretty rare but does happen.

4.0 A link to a cut away lifter so you can visualize how there parts are nested and work together.

http://www.crankshaftcoalition.com/wiki/images/thumb/9/90/Hydraulic_Lifter.jpg/200px-Hydraulic_Lifter.jpg