alot of questions...performance....hoods....and pumps...need some help.

[vetteKID]

after spending a week on my lack of performance/ignition missing, i splurged and got new Accel wires, cap/rotor, AC Rapidfire plugs, and edelbrock Performer RPM, and a 750cfm holley. i put on the wires and the new cap and rotor, still a miss. changed the plugs, miss went away, but the carb seemed out of tune, had a friend (chevy certified mechanic) "tune" my carb, and wasnt satisfied. since i was hanging with the serious chevy guys i asked what i should do for basic performance cuase i know there is power hiding in my L-48 somewhere. I was told to get a 750 carb and a pack of jets, an edelbrock RPM manifold(they said airgap, but i didnt want to have clearance problems) and a cam with 220* to 225* duration and .460 to .470 lift.first question, does that cam sound right for my set up?

i put on the RPM manifold and holley carb, and have some clearance problems.... which i expected. my question is, how much more clearnace does the stock BB hood of the early 70's have over my stock 74 hood? and how much of a differance(height wise) is the L-88 hood from my stock one? i dont want a large cowl, just something so my mods will fit, what is my best choice for a hood? and wheres the best place to buy and aftermarket hood?

another quick question what are the exhuast hoses that go from my exhaust manifolds to some sort of, im guessing, air pump? and do i need that pump? cuase it gets in the way!

ok enough questions..please help me with what ever you can.

 

[Scott81]

Well I'm a dork when it comes to figuring out all that engine stuff but for your clearance problems get a drop base for your air cleaner, that will probably help and they only run about $10. Any good local speed shop should have them or be able to get one.

 

[69MyWay]

Vette Kid,

L88 hoods are the only way to go for the mods you have noted, even with a good drop base. So, look here and there. New cost ranges from $250-$800 depending on where you buy one. JC Whitney even sells them. In any event, plan on spending at least some time blocking it down before paint to make sure it is straight.

My only concern with your mods is the fact you don't have the best heads in the world. You compression is decent, so no worries there (if the motor is stock inside). Remember, a motor is nothing but an air pump. The more air you can pump in faster, the more power you make.

Consider your final drive gears, stall converter, etc/trans as you make the cam, intake, heads, carb decisions.

Think of it as a comprehensive mod, not just a carb, intake or cam.

The "stock" bb hoods really had no more room than a small block in 1974.

Good luck, and have fun.

 

[DDLS3]

vettekid,

The Edelbrock performer intake will fit under a stock C3 hood with the set-up you have. If you plan on leaving your engine in the stock to mild street modified the performer manifold is more than enough. Just another option for you to consider.

 

[page62]

That 750 cfm Holley is too big for your engine! (Hard to believe, but it's true...) Go with a 600 cfm Edelbrock.

But quite frankly there's nothing wrong with a properly tuned QJet!

Consider this, however: You may be going at this from the wrong the wrong end of the equation. Does the area you live in have smog testing? If not, you should consider desmogging your car (for test purposes only to keep the gov't happy). Pull the AIR pump, get some headers and install true dual exhaust.

If you do have smog testing, you can still upgrade your exhaust to breathe better.

Bottom line: You need the exhaust end of your engine breathing better before you go mucking about with carbs 'n stuff.

 

[smurfvet]

If you don't change the cam, you will be spending a lot of bucks for nothing. Get a copy of the Chevy performance parts catalog froma dealer. This has all the old "powerful" cams listed, and it also shows crossover capabilites for them. The one good thing about a Chevy cam is the fact they were production units, and there is a definite plus knowing that a bunch of the cams were used on the street. Some aftermarket cams are too "aggressive" for me. Maybe not for you, but are you concerned about driveability? My dear sweet wife (call her 1/2 owner) is! So much for the 3/4 race lumpity-lumpity stick.......

Putting a big double sucker and a fancy manifold on the engine will work, with a cam. without, the thing that makes the engine breathe better (to a point) is missing.

One person commented on heads, etc. These are very important as well... the breathing thing again.

The hoses" on the exhaust manifolds are air injectors that should be hooked to an AIR system. There's a bunch more stuff that goes with it- a pump, control valve, rubber hoses, check valves, etc... Look on a parts website such as Rik's for a picture. Better yet, get a factory service manual- they go into gory detail.

The AIR pump system is an emissions issue. If your state requires a test, be careful. The vehicle may not pass without the pump. The smog police haven't made it to upper New York state yet, but they made it to downstate!

Last but not least- remember the engine (25 to 30 years old or so) wasn't made for that kind of horsepower. Parts like the crankshaft, bearings, connecting rods and pistons take poorly to increasing loads on them 40 to 70%. Like break. Big. I have two Corvairs as well as the Vette- both turbos. I learned a WHOLE LOT about lower ends vs. horsepower on a weenie 180 hp. air cooled engine.

 

[Evolution1980]

Vette Kid,

L88 hoods are the only way to go for the mods you have noted, even with a good drop base....

...Remember, a motor is nothing but an air pump. The more air you can pump in faster, the more power you make...

Two notes I'd like to make here. The hood I have will also work for his app and (I believe) has the same clearance. My hood is the stock hood with a raised 2" cowl.

As for the engine being an air pump...remember though, for it to operate efficiently, the air in needs to match the air leaving. If you are going to be flowing more in, make sure you have the exhaust is unrestricted enough to expel it...this shouldn't be a major issue though unless all the smog AIR stuff is choking it.

Because one of us will eventually ask after this thread likely ends up 5 pages long... What are looking to do with your car, performance-wise? hopped up street car? Drag? or daily driver?

 

[vetteKID]

well i took back the RPM and got a performer and used the stock Q-jet, why....becuase i just want to drive again. what my goal for this car is- a stock looking, stock piston/8.5 comp, 300+ hp, cruiser that DEMANDS respect and all on a relatively tight budget.

im still looking for a cam though. arent blue print cams more expesive than the other aftermarket cams? i dont mind a nice lope at idle, infact i want one, something that says "IM moded" when you are at a stop light. i wouldnt have to worry about TC stall because its a 4speed.

there are no emission on historic cars in MD, so how much are a good set of headers?

 

[Hib Halverson]

First, your post mentioned an aftermarket camshaft but it also kind of implied that you never installed that cam, only the 750 and the Performer RPM.

If you're still running the stock cam, heads and valve gear, get rid of the 750 cfm carb and the Performer RPM. The carb is way too "big" and the intake manifold only works well at RPM your L48 will never see.

Go with a small Quadrajet and the Performer intake.

On the hood issue, you'll need an L88-style hood or other hood with similar increased clearance to fit the Performer RPM, Holley and a decent air filter. If you use a QJ and the Performer, they'll fit under your stock hood.

You don't need the AIR pump unless you have to pass an exhaust emissions test in your state to register the car. Remove the pump, brackets and AIR manifolds and plug the holes.

As for the camshaft (220/225 deg. duration and .460/.470 lift), it's kinda right on the line between somewhat mild and somewhat wild.

What I'd do, if you don't want to change the hood, is use the Edelbrock Performer cam and manifold package with the Quadrajet carb. If you do want to change your hood, I'd use the Edelbrock Performer RPM cam (which is actually more radical than what you planned) and manifold and a QJ carb. Now, if you use the Performer RPM cam, you'll need to change valve springs. Also, as that cam is good to 6500 rpm, you might want to consider forged pistons and better connecting rods as the L48 stuff is pretty marginal for that kind of use. If you do use the OE L48 rods and pistons, start saving money because, if you start running that L48 to 6500 rpm, she'll kick a rod out fairly soon.

 

[smurfvet]

The Q-jet IS a 750 cfm carb- you already had one in the car! GM did a good job designing the carb- most "smaller (327, 350) engines" don't need much more than 600 cfm or so. The carb is a variable flow design- not the same as others on the market. They used this capability to put the same size carb on everything from a 265 to a 454. The only difference is the jets and metering rods. The BIG problem is that they are a bi_ch to get set up the first time. I know a guy who worked at the plant setting these up as OEM parts (Rochester Products-get it?). He set mine up when I first got the car- what a difference! Have an expert do it.

A friend of mine has the same setup presented in the previous reply- the Performer with Q-jet. It works very well. He used Hooker headers with the ceramic coating ($300-$400?) and ran 2-1/2" pipes to DynoMax mufflers in the original location ($1500 for side pipes was too much). Sounds good, and the exhaust hides under the car. Stealth mode. He ported the intake and exhaust on the heads when putting in the 365 hp cam. Dyno test shows about 370 real hp.

I had a new set of undercar "side pipe" mufflers on my car when I bought it. Took them off- too loud when accelerating. You might want to look at these- low restriction, for sure!

I couldn't find my GM performance catalog to get a cam number. I know they sell cams with the 350 and 365 hp. grind as installed in the 60's 327 engines. Get a good set of lifters, pushrods and rocker arms, you're good to go.

The AIR system could be removed if you don't have emissions issues. Plug the ports, or better yet, get the headers without them.

 

[Evolution1980]

what my goal for this car is- a stock looking, stock piston/8.5 comp, 300+ hp, cruiser that DEMANDS respect and all on a relatively tight budget.

Hmmm...so you want your cake and you want to eat it?? Hmmm...

Well, what exactly is demanding respect? Do you just want a cool sounding car? Or do you want something to back up that sound?
Realize that trying to put all all these requirements together is a tall order. Can be done...but....

Personally, I don't think you're gonna get everything that you're looking for on a "relatively tight budget". These are still Corvette's, and are still gonna cost you a pretty penny to do things correctly.

There are minor things you can atleast do for the sound though. Start by running headers straight back to open exahust ending in some Cherry Bombs (like myself), or DynoMax Bullit exhaust. You can change the cam to something a bit more mild to give you that 'lumpy' sound. That right there is gonna run about $600, give or take a few bucks.

Stick with your 750cfm Q-Jet. Get it tuned by someone that knows 'em and you'll have plenty of room to grow with it. I have no problem feeding my ZZ4 all the fuel it needs, and as Smurfvet said, it's good all the way up to a mild 454 block.

Going to an open-element air filter such as a K&N will also help, as you'll get that 'whirrr' under the hood as it's sucking in air.

Dumping any emissions you have on the engine (the heavy cast iron headers, AIR pump, cats, etc.) will also give noticable power differences.

Again, I'm not sure what demanding respect means in your terms, but you'll get plenty of suggestions on what you can do, which is a lot. Just remember this saying... How fast do you want to go? How much money do you have?

I believe Scott81 has some sound clips of my car on his site. Or you can ask anyone from the SharkFest thread http://corvetteactioncenter.com/forums/showthread.php?threadid=15755 as to what my car sounds like. I'm guessing that you'd probably like it...

As I used to say..hell, I still say it to customers, "You tell me how much money you have to spend, and I'll build you the best computer for the buck." Same thing here. Give us a dollar idea, and everyone will chime in with suggestions. Just give us a clear-cut idea of what exactly you are going for.

 

[vetteKID]

anyone can make a car sound mean, i want it to be fast, like corvettes should be.

so far, this is set up im planing-
Edelbrock Performer already on
summit 1.5 steel roller rockers 100$
comp cams pushrods 30$
blue print cam 350hp 327 --222*/222* @ .050 int/ex 96$
matching springs 75$
summit headers 80$
custom side pipes 300$

so thats 700$ give or take. my buget is about that, im kinda going from paycheck to paycheck right now.

do you think that this set-up will give me a decently fast street car?

 

[Stingray6974]

Change the cam to a Crane Energizer 272.

Mike

 

[vetteKID]

the energizer 272 has the same duration as the 350/327 blueprint but more lift, correct? wouldnt that make it sound more radical?

well tomorrow im ordering my mufflers and summit headers, and then i will order all my cam stuff (cam,rockers and rods and such) next paycheck.

quick question about headers....i know im probably annoying you guys but hey im young and eager to learn about vettes. ok.....will getting full long tube headers interfier with placing my side pipes correctly? in other words do the long tube headers exit before the turn towards the side pipe skirts, so i dont have to back track? if so can i use shorty headers?

you guys have been a HUGE help and i thank you guys for steering me in the right direction and sharing your knowledge.

 

[smurfvet]

Look at your present exhaust pipes to see where they turn horizontal and start to bend inward toward the "holes" in the transmission crossmember. The repro side pipe setups are made to fit in the same area. I THINK (???) that the "long tube" headers with a long collection tube will be too long- you will have to backtrack to get the sidepipe to exit just behind the wheelwell like the originals.

If somebody has a set of the shorter variety, they could verify that they do bolt right up to existing pipes, side pipes included.

Do you know what side pipes cost, complete? If you're on a budget, this isn't the way to go....... do what evo1980 said- much less bucks, which can be put in the engine.

 

[Evolution1980]

the energizer 272 has the same duration as the 350/327 blueprint but more lift, correct? wouldnt that make it sound more radical?

well tomorrow im ordering my mufflers and summit headers, and then i will order all my cam stuff (cam,rockers and rods and such) next paycheck.

Since I'm too lazy to go back and check your original threads when you first came around... How many miles you have on your engine thus far? I've come to be hesitant about building up the top end of a high-mileage engines. Anyways...

When putting together your cam, rockers, (lifters, if any), make sure they will all work together first or you run the chance of punching holes your pistons.

As for your headers and mufflers....First, you'll want to check with Summit to be sure that the headers you're getting will match up with your side exhaust. As far as mufflers, you going rear-mufflers or side-exhaust? I'm a bit confused now.

One word about side exhausts. If you are going to aftermarket side exhaust, like Hookers or something, you'll lose a little power over straight back exhaust. Your backpressure won't be as much as with straight-back exhaust (plus straight back is going to be much cheaper.) Also, with side exhaust and wanting your car to sound mean... if someone is standing next to your car (or you're blowing by 'em), they're only going to hear 4 cylinders. When you have dual rear exhaust, they get ALL 8 cylinders firing. That's loud!

(As I always note when posting pseudo-mechanical advice: I only know what worked for my car, a 1980. I don't know the exact setup of a '74 and what all it can accept and not accept in the way of parts and mounting and whatnot... But that's why you're here asking questions, right? I know I've asked my fair share... :L )

 

[vetteKID]

Evo- i have 58,000 miles on the engine, its all orginal...when i bought it the only none OE things were the water pump and wires.

i have a friend in the exhuast business and does custom work for me, and i purchased the flow through chambered style mufflers (like the ones on mid-americas chambered exhuast system), for 35 bucks a pop, and i can use them for side pipes or straight back. I was planing to do some sort of H pipe right at the bends, but i havent really looked into that too much might have clearance issues. i already have the skirts, he qouted me 300 for the work. im not buying a midamerica or ecklers version they are WAY too expensive.

im waiting for a few days to get the shorty headers. quick question.... what are the pros and cons of block hugger shorty headers? how much power (or torque) will i lose compared to long tubes.

 

[Tom Bryant]

Headman used to make a header that turned out before the collector for use with the Corvette side exhaust. Had to cut the down pipe off the side exaust and weld on the collector adapter. Maybe they still make them.

Does MD have a 25 year law for emissions checks? Even California exempts 1974 and older cars.

Tom

 

[vetteKID]

any historic car or street rod does not need to pass emissions. the car needs to be 25 years old(historic) or have significant engine and frame modifacation(street rod). my car is 28 years old and is registered as a historic, so no emissions.

thanks for the heads up on the headers, good thing i waited. just checked with summit, found just what i wanted and they arent going to break the bank, thanks Tom.

 

[Stingray6974]

vetteKID,
With the shorty headers you lose the "tuning" performance gains. But they still outflow the stock manifolds.

Mike