Author Topic: '86 305 Performance Upgrades?  (Read 3647 times)

Offline rockable

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'86 305 Performance Upgrades?
« on: January 18, 2009, 06:57:13 PM »
I have a stock '86 305 w/Quadrajet and 83k miles.  What are some bolt on options I can do to get an improvement in performance without giving up my ability to pass the emissions tests?

Thanks!
'86 SWB Silverado

Offline 84chevysilverado

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Re: '86 305 Performance Upgrades?
« Reply #1 on: January 18, 2009, 07:32:53 PM »
put headers on it. and some high flow cats
I'D RATHER PUSH A CHEVY THAN DRIVE A FORD

Offline rockable

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Re: '86 305 Performance Upgrades?
« Reply #2 on: January 21, 2009, 06:53:54 AM »
Any other ideas besides improving the exhaust?  Would a change of intake manifolds make a difference?
'86 SWB Silverado

Offline dustystrucktoo

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Re: '86 305 Performance Upgrades?
« Reply #3 on: January 21, 2009, 06:55:17 AM »
 ;D
OK, firstly you want the iron center bolt heads.  Those are 64cc and flow great.  87 and up.
Next to bolt onto the heads, you want either Tri-Y long tube headers or at the least, long tube headers.  You can either get a set with the Oxygen sensor hole, or have the reducer with the hole for  the oxygen sensor.  You want to run either a 2 inch or at the most a 2 1/2 inch exhaust.  H conncetor, or if you can afford it. get the X which is far superior.  If going with the H, then double up on the H.  Run your mufflers as far back as possible, and if you have cats, put them as close to those headers as possible.
Next up is your intake.  Summit has a less expensive model of the Edelbrock air gap RPM, though I would advixe the Edelbrock Performer Air Gap.  Next up, is also your carb.  with the equation of engine size multiplied by max rpm, divided by 3456 and multiplying it by the intake volumetric  efficiency (Performer Air gap I would rate at 90, A normal Performer at 78 and they come in between those.  Stock intake I would rate for that year at about 72 percent, if Iron.  If aluminum, then about 76.    Meaning that if you plan on putting your engine up to 5500 rpm with that engine, then make sure your carb is no larger than a 500.  You figure out the exact cfm for yourself.  too large a carb, will mean that your lower rpms will suffer.  You go with a single plenum opening on the intake manifold, your lower rpms will be like crap.
On the header gaskets, use the reusable aluminum manifold gaskets.  Header size is 1 5/8 primaries. running into a 3 inch collector.  Hopefully you purchase the cats that bolt on to the headers.  After the cats, run your reducer, unless you need the hole for the oxygen sensor at the reducer, then go with reducing the size there and get the cat that matckes that size.  For that 305, I would think that the 2 inch pipe would be better, but 2 1/2 inch aint gonna hurt much.  Up to you.
Make sure you are using the 8mm wires at the smallest.  I prefer the 8.8.  I gotta have good insulated wires, especially with the heat of the headers.  Sprial Core.  I use the Bosch single at the least and double prong for me is preferred.  Mind you, that you might really want to wrap that starter with a heat reflector shield or the insulator material.  It looks like what you have on your water heater at home.
Roller Rockers will help.  If you 4X4 with your truck, then get a carb with dual floats.  If you don't 4x4, then a single float system should do just fine.  I have a two truck and a 600 on my 400 small block does more than I need.  It is a 4160 Holley, though I would have been better off getting the 4150 for any future uses in difference, like on a different vehicle.  Make sure you run a fuel filter in the fuel line and also one before the carb.  Stay away from 87 octane, and use the best oil you can afford for better lubrication ability and less friction.  I myself use Redline 15w50, change it once a year and only use 93 octane.  My truck weighs 6750 lbs with me in it, with just the bare essentials.  Let's add on a vehicle being towed.  I have power.  What I just advised is a correct format area to follow.

Offline Blue 82

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Re: '86 305 Performance Upgrades?
« Reply #4 on: January 21, 2009, 05:15:14 PM »
3.73's or 4.10's if you have the 700R4
82 stepside 2wd 355/th350/3.08 posi

Offline rockable

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Re: '86 305 Performance Upgrades?
« Reply #5 on: January 21, 2009, 09:12:41 PM »
Dusty, I don't think all that's gonna be emissions legal in NC.  I appreciate the detailed information, however.  I just wish I could figure out how to get around the restrictions.
'86 SWB Silverado

Offline dustystrucktoo

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Re: '86 305 Performance Upgrades?
« Reply #6 on: January 21, 2009, 11:34:01 PM »
OK...  EGR.    Weind Action , Edelbrock Performer, or Summit Stage 1 for intake.
Holley starting at 390 going up and not to exceed in my opinion a 570.  390 carb will do great up until 4000 rpm.  570 will perform past 5000 rpm.  I say a 500 or close to it.  The smaller the carb, the better low rpm response and perfomance, not to mention better fuel economy.  The larger the carb, the better the top end, worse on the low end and bad on the fuel economy.
Cats are cats and a larger exhaust will only let it breath easier.   Better oil will lubricate better causing less friction which increases horse and torque, as well that higher the octane level the bigger the boom.  Bigger boom means less fuel to create a certain size boom.  Less gas, minor but important.  More of the fuel exploding and less going out through the exhaust.
Spiral core wires that are well insulated allow for more of the current to get to the spark plug and less to pass through the insulation.  Meaning the spark is going to be a little longer and a little more powerful.  Don't believe me, grab onto one of your spark plug wires while the engine is running.    ::)
better spark plug design allows for a more pinpoint spot which creates more of a high powered boom.  The BOOM is the explosion that is caused when the air and gas are compressed and ignited. 
Heads, you are running 72 cc chamber heads.  the air and fuel are getting squeezed only so much.  With a smaller cc chamber head, you will create a tighter squeeze and which will allow for more of the air and fule to explode, rather than sit in the chamber and go out through your exhaust. 
 ;D
If you can't afford another carb, then have your existing one brought down in size by reducing the jets in the carburetor.  As well, you don't have to worry about the smog lines, though I do believe Has Smog compliant carbs. 
tranny fluid, not a stick.....     change your fluid and filter, do not have it flushed, or inside ports might get clogged and as well that there is a magnet on that pan with any metal shavings.  I would clean the pan and the magnet.  If you saw it and know what hydraulic fluid has to pass through in that tranny, you would quickly drop the pan and wipe any thing and everything , as well as change that filter and fluid every two years without  batting an eye.  Same with the rear end, that if a sliver of metal gets smashed in between two metal pieces that have a smaller clearance than the fragment of metal, then something is going to chip.  Better fluid, the less friction.  The less friction, the easier it is to move.
Polishing and porting your heads costs a little, though changing your  heads would probably be cheaper and more effective.  Right now you have about an 8.2 or 8.4 to 1 compression, I am guessing and a set of better heads would get you about 9 to 9.5 to 1.  Tighter squeeze, bigger boom.  Qite legal and will improve emissions, as well as horse power and torque.
I wouldn't have to type so much, if you had my auto shop teacher in High School.  You wouldn't have asked that question. ;D

Offline rockable

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Re: '86 305 Performance Upgrades?
« Reply #7 on: January 22, 2009, 06:55:58 AM »
Thanks, dusty!  I know a lot about hot rodding engines, I just haven't been keeping up with Chevy's for a long time and the hot rodding I was doing didn't have to be smog legal.  Thanks.
'86 SWB Silverado

Offline rockable

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Re: '86 305 Performance Upgrades?
« Reply #8 on: February 07, 2009, 07:04:19 AM »
If I were to go with the following setup on my '86 305, what sort of HP gain could I expect?
-Stock engine/cam/heads/carb/EGR/AIR
-Edelbrock Performer Intake
-Edelbrock Shorty headers
-Dual exhaust, low back pressure cats, turbo mufflers

Thanks for your estimates.
-
'86 SWB Silverado