silverstang84

Hey guys, I'm collecting some motors parts for my 86 iroc build. I have a set of new vortec heads for it which means I have to get a matching intake manifold. My question is... Will a high-rise kind of manifikd work? I'll be running a edelbrock 600 carb and the stock IROC hood. Obviously I don't want to hit the hood.

jwfirebird

iTrader: (2)

would guess it wont vortec stuff tends to be taller, but i would say you want a dual plane anyway. vortecs are low rpm torque engines and high rise manifolds are high rpm. you are also small on the carb which is going to be worse if you intend to make high rpm power. why do you want to use that carb? more details on what you have and want to do?

RedLeader289

iTrader: (2)

Depends on how high of a high rise you go with. For instance - I have a GM vortec eliminator High-rise air gap intake, and a holley 750 dp...it does not come close to fitting under a stock hood.

I've seen people fit them though, so there are some that will work...just depends on the measurements. I think a performer RPM will fit.

midias

I think this without a spacer and a drop base cleaner will fit.

http://www.summitracing.com/parts/edl-7116

silverstang84

Thanks guys. I'll probably just go with a performer type of manifold

silverstang84

Jwfirebird: I'm using the carb because it works fine and I already ran it on the car. I realize there are better options then the edelbrock 600 but it's what I had

Night rider327

iTrader: (13)

Your info is not quite right.

The vortec heads are great flowing smaller port head that will make power up to 6000 rpm easy. I wouldn't call that a "low rpm engine".

Also the cam plays a major role in the engine's power band. Sure a stock vortec cam is small and made for low to mid range power but about the same as any other stock SBC cam.

600 cfm is not on the small size for the OP build by any means. In fact it's the perfect size. Too many people tend to over carb.

I ran 11.40's @ 118 mph 1/4 mile with a 600 cfm on a 355.

The needed CFM is based on engine size, VE % and RPM.
A slight modded 350 running at 6,000 rpm with a VE of 93% only needs 565 cfm. Round up to nearest common carb size and it's perfect.. 600cfm

To the OP.. Not vortec heads on my F body, but I can fit brodix IK heads and a performer intake with a drop base air cleaner under a stock hood. I now have a scooped hood and fit the RPM intake a 1" spacer and a 3" tall filter but thats under a scoop.

My dad has a performer, eddy carb, 3" tall filter in drop base housing under his hood on a 82 firebird

silverstang84

Thanks for the info man. I'm thinking of a comp Thumpr cam.

midias

You can do better than that poser cam.

Night rider327

iTrader: (13)

I agree... The thumper cams are a waste of good metal IMHO. The only thing they do good is give you a "fake" drag car idle. They leave alot of power on the table.

Only things they seem to work good in is a 50 year old man's 2,300 lbs T bucket roadster with a SBC engine with tunnel ram and lake pipes. That he only drives to the car shows on Sat. afternoon and to the ice cream shop on sundays.

If you didn't catch on to that, the above means just for show, have a cool sound, not really any performance or real useable range.

MANY better cams out there. In fact the old speed pro/elgin/summit, etc cam grinds would be better.

I run a speed pro 218/230@.050" hyd. flat tappet in my vortec headed 355 in my S10.
Howards solid flat tappet 249/252@.050" in my Brodix IK200 headed 355 in my camaro

jwfirebird

iTrader: (2)

the vortec 350 is a truck engine, i have one in my yukon, and its all about low end torque in a truck. just because you believe the things people spew like fact on the internet doesnt make it true. i have the opposite experience, if you see quick cars at the track and talk to them the ones in the 3-400hp range have 700-750 carbs. i believe real world alot more than engineer nonsense on the internet.

RedLeader289

iTrader: (2)

For what it's worth, if I was to order the turn-key model of my crate engine it would come from GM Performance with a Holley 750 on it, I think that's totally reasonable considering you can always tune a carb down but it'll only dump so much fuel in past a certain point.

86LG4Bird

iTrader: (1)

Wow......the guy says he's going to use Vortec heads, NOT the tiny production cam that came in the Vortec trucks. The fact that he's using a great set of heads doesn't make it a low-rpm truck engine.
OP, What are your goals and intended use of the car? Gearing? TC? All of that will help you decide on the intended powerband, then pick a cam, then pick a manifold.
Unless you're building a strip-only car, I don't see anything wrong with a 600 cfm carb for a dual purpose 350/355.

Gsoleski

If it's any help i'm using vortec heads and an RPM intake with a 3/4" adapter for a qaudrajet and a drop base air cleaner. Just barely fits under the hood but it does close

Night rider327

iTrader: (13)

LOL.. Yeah I have a vortec truck engine going into a '81 monte carlo, vortec headed 355 in a S10 (that makes peak HP at 5700 rpm), and a Brodix IK 200cc headed 355 in my camaro (that makes peak power at 6800 RPM) ... Point is????

I do not believe internet BS. I dyno and track test.. Sort of seems like you are the one that buys into internet BS.

I ran 11.40's @ 118 MPH, with a 1.61 second 60' time, 0-60mph in 3.2 seconds.. That's right at the 500 HP range.. Done it with a 600 cfm carb. At that point my car was a daily driver, full interior, sound system, etc. Not just a track car. Now have more head, cam, and gear and run a 750 cfm carb.

Also there is a big difference in track cars and street cars and street/strip cars. Sure at WOT down the track you can use a much bigger carb than needed and not hurt anything and alot of time go faster.. That's on a car that will never sit a tire on the public roads though.. Same with all other parts.. Sure 4.88 gears will get you better times at the track, but would you ever use a 4.88 gear on the street? Same with a spool, sure it works GREAT on the track but do you use those on the street?

A drag car don't have to worry about part throttle, idle, fuel mileage, etc. Just WOT

I'm a professional engine builder by trade. I build engines in the range of stock street to 1200+ HP. I have contracts with dirt and paved circle/oval track race teams. I build for all lower classes of NHRA (not top fuel). I can tell you more about a SBC engine in an hour than YOU will ever read on the internet. I have dynoed many engines, I have flow tested many heads and have track results.

I build my own cars. My street/strip camaro is a close to 600 HP 355 N/A engine.


The FACTORY stock vortec 350 made 255 HP @ 4600 RPM, 330 lb ft torque at 2,800 RPM. How is that just a low rpm torque engine?

Would you call all factory third gen F body engines "low rpm torque truck engines?

Have you ever looked at the RPM at which they make peak #'s at?
1991 camaro/firebird LO3 170 HP @ 4,000 RPM, 255 lb ft @ 2400 rpm

Peak HP at 600 rpm less and peak torque at 400 rpm less than what you call a low rpm truck engine.

Even the L98 350 has a 4400 rpm peak HP point and 3200 RPM peak for the torque.

It's NOT the heads that really sets the engine's power band. Yes they do have something to do with it but the camshaft plays the biggest role.

The Vortec heads will make useable power up to 6,000 rpm. They are based on the Gen II LT1 heads, in fact the intake ports are almost the same as the LT1 heads. The vortec heads are the most efficient factory gen I small-block Chevy cylinder head ever created.

They have 170cc intake ports, 61cc exhaust ports and are listed at 64cc chambers (but every one I have CC'ed has came in at 62-63cc) and flow flow 230 cfm on intake side and 151 cfm on exhaust side. 1.94"/1.50" valves.

This is a higher flow rate than ANY other stock GeI head and in fact better than a lot of the aftermarket heads.

silverstang84

86lg4bird: my goals for the car are nothing more than just a street cruiser. I have a supercharged mustang for going fast... The iroc will be something I can cruise to car shows/drive to work in the summer/let my wife cruise around with the t-tops off. It needed a motor when I bought it, and a friend happened to have a set of new vortec heads so I figured why not..now it's just a matter of selecting a can and intake manifold for it and I can start building.

Night rider327

iTrader: (13)

With the above comment I would toss a summit brand stage I intake on it with a mild 214/224 @.050" .443"/.465" lift, 112 LSA cam and have at it.

silverstang84

^ that intake will work, but I'd like a cam that not only performs decent but it has to sound nice too

Night rider327

iTrader: (13)

See now that's where it gets complicated. The valve overlap is what gets you the rougher uneven idle. The only way to get that is with more duration or less lope sep angle.

More duration bleeds off massive amounts of cylinder pressure (compression) and unless you have a high compression engine you will end up with a very soft low rpm power. Won't be able to get out of it's own way untill you get to 3000 rpm or high then it will pull great.

The tighter LSA will lower your vac levels alot and this will mean less fuel mileage, higher emissions levels (not sure if that's a prob for you or not, every state is diff) and might even end up with power brakes not working right due to lack of vacuum.

It's really hard to have your cake and eat it too when your dealing with a low to mid compression street engine that you want to have good performance and sound.

Now I see you said you are getting up your parts.. What are you thinking compression wise? If you can get around 10.0:1 then you can go up alittle on duration and tighter on LSA and get the sound you want and the performance from the engine will be right on. Maybe step up to a 220/230 @.050 with a 108 or 110 LSA

Keep in mind though when you go bigger on that cam you will need more converter (if auto) and gear.

I got some cam sounds for you on mine. This 1st vid is over 4 min long and has both mine and my dad's car. Don't count his firebird with ram air hood, we all know it sounds good.. It's a twin T3 turbocharged 327, no mufflers.. My camaro though in this vid from the 3 min to 3 min 29 second range you can hear real clear.
Thats a 10.18:1 355 with a crane powermac 272-2 cam. 216/228 @ .050", 112 LSA. I had 1.6 rockers on it and the higher ratio rockers do not change adv. duration but does add a few degrees to the .050" figure so say 218/230@.050. Exhaust is hooker shorty headers, true dual 2.25" pipes, flow master 2 chamber mufflers.

Here's another one of my same car/engine but has no exhaust on it at that time. Just headers.
And here's the last one. Same car, diff engine. 10.34:1 355 with a 249/252@.050", 106 LSA solid cam. Hedman long tube headers, same dual 2.25" pipes and flowmasters as the 1st vid. (since then I have changed to dual 3" pipes and ultra flo mufflers, but no vid of that system)

I have a couple of MP3 files of my camaro (1st combo, 1st vid I linked too above) I had them on exhaustclips.com but that was years ago.
I'll try to upload one of the mp3 files here. This is the 216/228 @.050" cam, 112 LSA and 1.6 ratio rockers

silverstang84

Your car sounds great dude. That's about the sound I'm going for.. The vortec heads are 64cc combustion chamber and the 350 I'm using has flat top Pistons with relief cuts for the valves, so I'm thinking it could be 9-10.1 compression??

Night rider327

iTrader: (13)

Thanks man. Yeah that's why I wanted you to hear the diff in the 2 cams. The smaller cam does have an off beat idle that clearly sounds non stock, but the bigger cam has that real rough choppy race car type sound.. A cam like the bigger of my 2 will never work good in a milder engine combo.

If that 1st smaller cam sound is good for you then yeah something like a 216/228, 218/230, maybe even a 220/232 @.050" cam with a 110 or 112 LSA would be just right for you.

The vortec heads are listed as 64cc, but every set of stock 906 and 062 GMs I have checked has came in at the 62-63cc range.

What's the valve relief CC size of your pistons? Flat top comes in a wide range from 1.8 to 8.7cc.. Common is 5-7cc though.

All the little details will stack up and will change your compression so to get it dead on you need to have alot of the specs. Like piston compression height. Stock is 1.560" but they sell pistons for the 5.7" rod 350 that ranges from 1.455" to 1.568". This is gonna change how far in/out of the block at TDC that the piston will set in the hole.

The stock specs is a 9.025" deck and with the 3.48" stroke, 5.7" rod and a 1.560" compression height your piston is .025" in the bore at TDC. Just look at how bad a 1.455" compression height piston would screw you up. That would put your piston 0.13" down in the bore at TDC. Even the 1.54" ones are bad as it moves you .020" deeper into the bore. This kills your compression and quench

What bore and thickness of head gasket you will be using? This changes compression
Along with if the block has been decked/milled or not.

But yes it's pretty common to be in the 9 to 10:1 range with an engine like your putting together. Just wanted to point out some of the little things to look at/for and think about

jwfirebird

iTrader: (2)

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seems i have a different perspective. i believe the street manners are in the tune, i have a way higher rpm setup gen 1 type and a fully mechanical 4150 750 and higher rpm tc(why i call vortecs low rpm torque, most drag cars have tc ratings over that). my car has 4.10s and a th400 and is driven on the street way more then the track. if its over 40 or 50 degrees it cold starts without the choke and you let it warm up for maybe a minute and go. and my wife has driven it a ton. she just has to have some instruction on how to do a more impressive burnout. but it drives like any other car i had the perf shop make it auto in drive but manual in 1 and 2.

the tune also includes the proper adjustable ign stuff, that plays a big role in big cam/ idle and take off characteristics.

Night rider327

iTrader: (13)

Yeah I guess we have a different perspective. Yes my car is a "street" car but street manners sucks to me on it. It use to be a good daily driver with the smaller cam, heads, etc, lower useable powerband. Now it's just a fun toy to play with on the streets and take to the track.

Yes proper tune is a big part of it, but even tune can not fix an engine that has to idle at 1,000 to 1,300 rpm, only pulls 4-5" hg vac, power brakes don't work, buzzing 3600-4000 rpm at normal common road speeds, 4500-5000 rpm at interstate speeds, etc. That's not what I would call a good street car.

Yeah I have the adj. ign parts as well. Mallory digital box with built in start retard, nitrous retard, top end retard, rev limiter, 2 step, etc etc, MSD pro billet dist., Mallory E core coil, MSD 8.5mm wires.

Holley 4150 HP double pumper 750 cfm, adjustable fuel pressure reg.

Get's 7 mpg on 93 octane fuel, over 110 DB level from the exhaust, power band in the 3500-7000 rpm range. Not really my idea of a good street car.

Most people will want a street car even a performance based street car to opt. in the off idle to 5500 RPM range, idle speed of about 700-800 rpm, pull a min of 11 or 12" of vac with most in the 14" range, cruise down the interstate at 1,000 rpm or lower than what mine (or yours) does, etc

jwfirebird

iTrader: (2)

thats how mine was for a long time, but then i put regular turbo type mufflers on it and got a ratio gauge. leaned out the primaries a ton and now i get 10 probably. and the noise isnt loud as the wind from the ttops(got cutouts but havent put them on the mufflers really didnt slow it very much). it would be way more if i had the money for a t56 or built od but it isnt in the cards right now. i have been thinking about going back to a 3.50 or 3.23 gear just because i dont hardly go to the track very much any more.

Night rider327

iTrader: (13)

Same here. I would love to add a gear vendors unit to my th-400 or swap in a 4L80E but that's just not gonna happen anytime soon. It would be more driveable/streetable with the OD.

My new bigger exhaust is quieter then my old small exhaust.. Go figure, but still over 110 DB.

My 1st exhaust system was hooker shorties, dual 2.25" straight pipes, old flowmaster 2 chamber mufflers for back in like '98 placed before rear axle, tails ran out under axle to rear of car. That read IIRC 120 DB at the rear of car, 2,000 rpm.

The new system is hedman long tubes, dual 3" pipes, 3" X pipe, Dynomax ultra flo mufflers placed at rear or car, under the storage well and about 6-8" of pipe on end as tips. This one reads at 114 DB at rear of car, 2,000 RPM.

With my engine I can't go to a higher gear like a 3.23. The engine would never be in the power band, wouldn't have any low rpm torque, etc. Gas mileage would probably be worse than with the 3.89 gear

five7kid

iTrader: (14)

If you're talking about a cruiser and you're more interested in "that muscle car sound" than you are performance, a Thumpr cam and Performer Vortec would probably be fine. Personally, I'd never do it, because I'm more interested in performance than I am in exhaust note, but for what you've said you want, it would do fine.

While you didn't ask, nobody has mentioned valve springs. If we can assume these Vortec heads you have still have the factory valve springs, they are not up to the task of any aftermarket cam. You have to be a little careful with valve lift, not exceeding .480" at the valve for sure, some Vortec heads don't have enough clearance for .440" with "regular" valve springs because of the top of the valve guide. But, a set of beehive springs & retainers typically solve both the valve control and valve lift issues with a mild aftermarket cam. The other solution is to have a machine shop cut the tops of the valve guides, which will allow you to use "normal" SBC springs, give you plenty of valve travel, and also allow you to use positive-type valve stem seals.