Stock Intake manifolds

[79blazer]

I just bought a newly rebuilt quadrajet to replace the stock dualjet in my truck. I need a 4 barrel intake to bolt it to. With so many quadrajets made, there are many intake manifolds in the pick-a-part Yard. My primary concern is getting the best mileage I can. Is there any difference in the stock quadrajet manifolds? I do have a left over Edelbrock performer intake, but it is not EGR. I prefer it, but wouldn't a stock small runner intake give me better mileage?

example, Would a Caprice intake be any different than a truck intake?

[BurnoutNova]

EGR hurts your gas mileage... your best bet would be to use your edelbrock

[87 STEPPER]

As long as it's a 350 and i assume that is the size engine you have it really dosen't matter what vehicle it's off of the only thing that will be differant is thing's like vacuum hose locatinos but as long as you return your trucks to the correct location it's all good.

And yes the stock dual plane low rise or short runner manifold is the better choice for fuel economny but will fall short on performance.

[79blazer]

Doesn't EGR cool the cumbustion chamber? i thought without it, you can't advance the timing as much? and the net end result it is helps MPG if you take advatage of advancing the timing.

Its a 305.

[Billla]

EGR does just that - Exhaust Gas Recirculation. Unburned fuel is routed back into the manifold for combustion. Unless the engine is computer-controlled, there is no benefit to EGR, period.

In terms of manifolds, you won't start outbreathing the stock manifolds until you get up above ~325 HP on a 350. The stock cast-iron low-risers aren't bad at all - and you can always make a plate to block off the EGR and put a pipe plug in the manifold.

Most of the '70s 350 300 HP and 350 HP (Corvette) used a cast-iron low-rise intake - the '5577.

The Performer is your best bet from your collection.

[Roper]

For what its worth. My 350 crate lm1 wasnt working all that great. I got the stock carb rebuilt and it still didnt work right.
Then I put a new edelbrock 650 cfn thunder series off road carb and edelbrock performer non egr intake on it.
Now the truck has no polution gear. Absolutely none anywhere, well except for the pcb that runs to the carb. It also has dual 3" exhausts and a huge air filter with 4.11 gears, three speed automatic.
Truck works great now. Way better than stock.
Plus it really cleaned things up under the hood. Also I never really understood the stock quadrajet. The edelbrock is easy to work at.

[Roper]

Originally Posted by Billla

EGR does just that - Exhaust Gas Recirculation. Unburned fuel is routed back into the manifold for combustion. Unless the engine is computer-controlled, there is no benefit to EGR, period.

In terms of manifolds, you won't start outbreathing the stock manifolds until you get up above ~325 HP on a 350. The stock cast-iron low-risers aren't bad at all - and you can always make a plate to block off the EGR and put a pipe plug in the manifold.

Most of the '70s 350 300 HP and 350 HP (Corvette) used a cast-iron low-rise intake - the '5577.

The Performer is your best bet from your collection.

Im not sure of my HP. It was 250 when it was stock. I also dont have a tack so im not sure about rpm. But with my low geared stock motor if I went faster than 115 KPH the motor started moaning. Hard to describe. It didnt have power though. Now you can really wind it up in all gears. Example 120 kph in second gear and besides induction noise the motor sounds great. In third gear it will easily fill the speedometer and keep going. Motor sounds smooth and nice. I need to get a tack!
Im estamating that my truck normally turns at 2600rpm in 3rd gear at 100kph<60mph>

[Slonaker]

FWIW, I have a cast aluminum intake on mine that looks identical to the cast iron one that came off. It is a factory item, and I see them occasionally in junkyards. It saves a little weight if nothing else.

My mechanic buddy, who knows more about smallblocks than anyone I have ever met, says that EGR helps reduce ping. It is the one emission control device that he actually likes.

Slonaker

[Billla]

Originally Posted by Slonaker

FWIW, I have a cast aluminum intake on mine that looks identical to the cast iron one that came off. It is a factory item, and I see them occasionally in junkyards. It saves a little weight if nothing else.

My mechanic buddy, who knows more about smallblocks than anyone I have ever met, says that EGR helps reduce ping. It is the one emission control device that he actually likes.

Slonaker

Some Corvettes - I think starting in 74 until TBI - came with aluminum low-rise intakes that were an almost exact duplicate of the '5577 manifold. They're in somewhat high demand...so it might be better to eBay 'em

I guess you could look at EGR as enriching the mixture somewhat - but I can't see how that would prevent ping. Interested in his perspective on his experience if you can talk to him a bit.

[Slonaker]

He says that it cools off the air/fuel so detonation is less likely to happen.

When I was researching my intake, nothing indicated it was a Corvette piece. I was even told they came on a lot of El Caminos. I don't know what it came off of. I found it in my Dad's garage after he died.

Slonaker

[Jonboy]

They were found on a lot of the 80's Camaro's,and probably a lot of other 80's V8's too. I would just take a magnet with you to the pick a part, and see what you find. While you are there, pull the thermostat housing to make sure it is not corroded in there, though. On the bright side, most of the factory V* aluminum intakes will have EGR, too.

[Pyrotechnic]

If you already have the Performer, that is your best bet. I ran one on my 78 with a stock 350 without the EGR and it ran great.

[Billla]

Originally Posted by Slonaker

He says that it cools off the air/fuel so detonation is less likely to happen.

When I was researching my intake, nothing indicated it was a Corvette piece. I was even told they came on a lot of El Caminos. I don't know what it came off of. I found it in my Dad's garage after he died.

Slonaker

Hot exhaust piped into the intake charge cools the air/fuel? Nope, not buying that one Does exactly the opposite.

The only place I've seen the low-rise aluminum factory stuff is Corvettes - but I'm not the definitive reference by any means I've seen 'em here and there but not very often.

[BurnoutNova]

yes it does cool the flame front, when i say cool i mean in comparison to the combustion temperature.

research it if you dont belive

[shadetree]

I've seen several mid 70's 305 engines with a stock "low rise" aluminum intake. All had EGR, and all were identicle to a cast iron intake.
As for the reason for EGR, I read that a small ammount of exhaust contamination in the intake charge reduces oxides of nitrogen (smog). That can be accomplished with more cam overlap (can you see Detroit using hypo cams, claiming cleaner air?). Cooling of the burning charge is a residual bennefit of small ammounts of exhaust gas contamination (or so I've read).

[Russell]

Lets put it this way -- If EGR didn't do anything useful, it wouldn't be found on brand new engines being built and sold today. The vaccum smog crap that comes stock on these engines probally worked ok when new, but rarely stood the test of time, hense why very little of it is used anymore.

There is absolutely no reason why EGR would reduce mileage or power, should be doing just the opposite!

[Billla]

I have researched, and I'll continue to disagree that there is any performance, driveability or milage benefit to EGR. The sole reason for EGR is to reduce unburned hydrocarbons - in older engines this was done to meet emissions standards, in newer ones it's done to prolong the life of catalytic converters. All this is "useful" in terms of meeting emissions standards (A Good Thing), but demonstrates no performance benefit. From a thermodynamics perspective (I hope we don't go there the overall efficiency of the engine is higher because the unburned fuel in the exhaust gets a "second chance" and so more is burned...

EGR dilutes and heats the intake charge - which results in lower peak combustion temperatures (as the charge is less dense) but also less specific power.

More cam overlap actually makes the problem worse, as more unburned fuel escapes through the exhaust valve. The purpose of overlap is to allow higher volumetric efficiency - the escaping exhaust gases pull the intake charge in - but significant overlap means significant intake charge escapes at lower RPM.

Good discussion, many viewpoints

[Russell]

I suppose if you look that deep into it, there is a chance that it may not help performance much. I've always been told it re-burns fuel that wasn't burnt the first time around, and also cools the intake charge, which allows you to run more overall timing. In my limited experience, more timing always meant more power, so I'd never considered EGR to be a detrimental device.

[Billla]

Originally Posted by Russell

I suppose if you look that deep into it, there is a chance that it may not help performance much. I've always been told it re-burns fuel that wasn't burnt the first time around, and also cools the intake charge, which allows you to run more overall timing. In my limited experience, more timing always meant more power, so I'd never considered EGR to be a detrimental device.

Absolutely correct that it burns unburned fuel - the exhaust always has some unburned fuel (hydrocarbons) in it due to cam overlap. The unburned fuel undergoes partial combustion in the exhaust manifold, and the output from that partial combusion is NOx - the nastiest of the emissions gasses. If you remember the AIR systems from the early '70s the intent was to inject air into the exhaust manifold to provide better combustion in the exhaust manifolds to reduce NOx generation.

If you think about it a bit, you can see absolutely that it can't cool the intake charge - compare the temperature in the exhaust to the temperature of the intake charge which is typically ambient + ~80 degrees. How can an injection of hot exhaust gas, albeit with some fuel, cool a 140 degree intake charge?

The combustion does occur at a lower temperature due to the diluted charge which may allow for more timing - but the energy present in the charge overall is lower. Trade-offs, but the net is less performance - especially on non-computer controlled engines.

In no way am I encouraging anyone to disable their EGR, especially on a computer-controlled engine. The computer allows those engines to maximize the benefits of EGR and minimize the negatives - and is calibrated for EGR. On a GEN I engines that exceed ~1 HP/CID, EGR provides no real benefit (other than emissions) and works against power levels that we're working to achieve.

[SSC's76]

It's a double edge sword kind of deal. The inert gas from the EGR system does increase intake charge temp but decreases combustion chamber temps. This cooling effect of combustion gases allows more spark advance under cruise and increases combustion efficiency. That’s why the auto manufactures went with electronic spark control and an array of sensors to monitor and adjust for proper operation. In pollution controlled vehicle with all the sensors intact it does work especially with a computer controlled carb or fuel injection system. In a dumb system it does very little to effect fuel economy but can hurt drivability since the EGR will only be metered by vacuum and the levels of advance that would yield better cruise economy will bring detonation without constant adjustment. So for performance or non emmision use toss it. If your running a CCC or FI setup keep it.

BTT.

Lots of GM cars came with an aluminum intake manifold. For weight savings it might help but for a good seal your not going to beat a cast unit and there is no flow difference between the peices unless you get ahold of a ZZ3/ZZ4 intake which are both nearly identical to a performer.

[79blazer]

Yeah I noticed I can have the timing more advanced at night when it is cool, but during the day, It will knock a lot easier. Now I am seeing why they had CCC. I have a year to go before It has to be emission tested, So I think I'll go with the intake I have. And will be keeping an eye out for a #3701 intake.

[jimfulco]

I wouldn't use a Performer on a stock or nearly stock 305. Too much volume in the runners that you can't use, and which can diminish the signal to the carb, causing poor driveability and, I suspect, gas mileage. The Performer reduces the performance of even a 350 up until 3000-3500rpm, according to an Edelbrock graph I saw a few years ago. Bigger is not always better.

EGR or non-EGR depends on carb calibration, and vice-versa. Disconnecting EGR with a carb that's calibrated for use WITH it can cause pinging at part-throttle due to a lean mixture. You can recalibrate the carb to be a little richer at part-throttle, and the pinging will disappear. EGR is not in the circuit at full-throttle, so WOT performance might not be diminished by it, but part-throttle efficiency is a different story. I'd be tempted to use a pre-'73 intake and carb, if possible, just to keep away from EGR problems.

Be sure of a couple of things when you go to pick a manifold. Does your air conditioner compressor use a rear brace that mounts to two holes straddling the crossover port on the driver's side of the intake? Not all intakes have those holes. The alternator brackets have a rear hole that mount to a hole near the top front of the intake. Early long-water-pump engines had the hole in a different place than the later ones. This may be addressed by getting an alternator bracket that matches the intake. The changeover was sometime in the '70s, but I don't know which year. I found a late-style non-EGR cast iron intake without EGR but with A/C bracket holes on a '77 Chevy van.

I'd be a little leery of the factory aluminum intakes, what with the fine quality control they had back then. Not to mention they didn't use any kind of anti-seize compound when they bolted stuff to them. Check all the bolt holes for threads, and hope like heck it's not warped.