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PrintOSeal Intake Manifold Gaskets and Exhaust Heat Crossover Port

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What is the intention of PrintOSeal intake manifold gaskets ?

Are they for aluminum intake to iron heads, or iron intake to aluminum heads, or all aluminum set up...?

Also, I see a lot of these PrintOSeal gaskets, maybe even all, that don't have exhaust crossover openings and they block off the exhaust crossover ports...

Won't the hi temp heat burn right through the gasket or would that happen with a steel core center (s3 type) ?
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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
 

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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
 

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On a street vehicle that is driven on a regular basis and using a carburator, I always use the carb heat crossover. Especially when using a Quadrajet (my favorite carb). On an older vehicle I really like carbs over F.I., it's about a 1/4 the price and very simple. A plus is if I am in the middle of nowhere, I cab fix a carb. Electronic fuel injection, not so much. Through the last 4 decades carbs have always work for me. The Quadrajet was designed by GM using thousands of hours by engineers. Some think it is complicated, but one you educate yourself they are very simple. I am able to buy used Qjets on the cheap because people think they are junk. The qjet is possibly the best carb ever made, OK maybe a toss up between the Qjet and an Autolite 4100 series, which is even a simplier carb. . Just my opinion.
 

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When you run your finger along that silicone bead at the intake to block line, does it show any oil?
I see blurry spots where there is silicone squeezed out and several where there is no silicone to be seen. Both are potential leakers.
 

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Discussion Starter · #17 ·
I see blurry spots where there is silicone squeezed out and several where there is no silicone to be seen. Both are potential leakers.
That's what I seen too... I didn't feel for any oil on the block, but I'm at home today with the car and I can go outside and do a quick check on that. I did see that there is some older oil or grime from that area and where it meets the transmission bellhousing, (which is oddly shaped)...

Tire Automotive tire Helmet Bicycle tire Tread
 

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Discussion Starter · #18 ·
I'll have the intake manifold taken off today...

I have the 1256 Fel Pro PrintOSeal gasket kit, but I don't have the new bolts or ultra black silicone gasket maker until tomorrow or Saturday, to put it all together.

So in the meantime, I will be removing rocker arms, pushrods, and lifters one at a time to inspect for any damage.
 
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