usmechanix

Hey there everyone! I have a quick question about Quick Fuel Carbs. Has anyone had any real experience with them? Some of you all have responded to pleas for help as I am a complete novice when it comes to Carburetors. Building my first "Hot Rod" engine this year and was looking for a little guidance. I'm building a 327 small journal (not ideal i know but the block was CHEEEAAPPP).
Heads are Aluminum with 210 cc runners with 2.02/ 1.60 valves.
Cam is a Hydraulic Roller Herbert Racing CH7 grind,
Dur: 240/245@.50" .570/.585 lift with a 110 Lobe Center.
All that to say is a 750 Slayer Series going to be what I need to go with Carb wise, or is it a total waste of my time.

http://www.herbertcams.com/sl750vs-q...ors-sl-750-vs/

BTW the guys at Herbert Racing recommended it so I have some faith in it. Just wanting to see if anyone thinks I will be needing to make jet changes or anything like that.

I know that this may not be the exact page or forum in which i should probably be posting this so if anyone as any suggestions where I should post for furter discussion that would also be a huge help thanks.

five7kid

iTrader: (14)

I haven't run a Quick Fuel carb, but I have run some of their Holley carb parts (E85 metering blocks, throttle body). Quality stuff. I do know some racers who run their carbs.

Should be okay, but do they make a 650 CFM?

What compression ratio are you planning on?

That engine won't have any grunt below 3500 RPMs or so, but should scream after that. Your T5 probably isn't long for this world.

usmechanix

OH I know.... waiting for the day to grab third and have a blender under the console, thats why I have an Astro Performance gear set on order for it, as well as a Pro 5.0 shifter, hoping that gives it a long enough life that I can save for a T56. They make a 600cfm in the Slayer series, but they also have a 650 in their Q-Series line. almost twice the price tag though... I forgot to mention the ProComp Electronics Dual Plane Air-Gap Intake... not that it should change anything drastically. Compression Ratio I'm completely open to suggestion on. I was thinking 10.5:1 static compression? maybe a touch more because I understand that Dynamic is more important. Five7kid you may be able to clear this up for me but I've been told by a local engine builder that with that size of a Cam I can go with more static compression because of valve overlap?

A little extra Info about the block. It hasn't been decked (manufacturer stamping in front of cylinder 2 is still there) and the Heads are new. I was thinking a little dome pistion and a Zero Deck? Thanks man

five7kid

iTrader: (14)

SBCs tend to like .040" "quench" distance - deck-to-crown plus compressed head gasket thickness = .040". If you zero deck it, then use a .040" head gasket.

The cam overlap tends to bleed off cylinder pressure. That's why higher compression tends to aid power with bigger cams. 10.5:1 static CR will probably do, but use a dynamic compression calculator with your cam specs to verify.

What's the stated powerband on the intake? Not sure off the top of my head what they offer.

The 750 CFM probably won't hurt you, but the throttle response might be better with a 650. You're probably in single-plane intake territory with that cam, which would handle the smaller carb better; but you probably don't want to tax your T5 any more than necessary. I think you'll be okay with that combo for now.

usmechanix

The intakes advertised rpm range is 1500 to 6500

five7kid

iTrader: (14)

That's as good as you can get with a dual plane intake.

usmechanix

Just so I know is there an "ideal" dynamic compression ratio? Also should I decide not to deck it do I just go with a larger dome and thinner gasket? or for a street car am I just completely overthinking all of this.

86LG4Bird

iTrader: (1)

Stay away from domed pistons for pump fuel use.
I'd want about 11:1 CR with aluminum heads for that huge cam. It has nothing to do with overlap; it has everything to do with IVC event.
You can get close to ideal quench without decking the block. Run a Felpro 1094 .015" head gasket. What's the chamber volume of the heads?

usmechanix

They're 64cc.

usmechanix

Here's a little extra information that way no one is flying blind.

Shortblock
Block: Gen-1 never decked (Manufacturer stamping still there, bored .040 over
Crank: Steel
Rods: Factory style, ARP Rod Bolts
Pistons: KB157 Hypereutectics (looking for 10.5:1 static compression)

Top End
Cam: Herbert Racing Hydraulic Roller CH7,
Adv. Dur. 287 Int. 285 Exh.
@.500. 242 Int. 246 Exh.
Lift .567 Int. .585 Exh.
Lobe Center 110
Centerline 106
@.500 Int. Open 14 Degrees Close 46
Exhaust Open 52 Degrees Close 11

Heads: Herbert Racing
Intake Valve: 2.02
Exhaust Valve: 1.60
Intake Runner: 210cc
Exhaust Runner: N/A (need to email them to find out for sure)
CFM: No clue

Intake: Procomp Electronics
Design: Dual Plane
RPM: 1500-6500

Carb: Quick Fuel Technologies
Slayer Series 750 CFM

Exhaust
Headers: Flowtech
Primaries: 1.5 in.
Collectors: 2.5 in.
Y-Pipe: 2.5 in.
Catback: 2.5 in.

86LG4Bird

iTrader: (1)

Unless you're going to mill those heads down to a 55-56 cc chamber, then I wouldn't recommend running that cam. Not only will it be a dog down low, torque production will be below what it would be with a better matched cam throughout the rpm range.
Having only 333 cubic inches doesn't help in that department either.
With factory rods, I wouldn't dare spin that thing high enough to even see the bottom edge of that cam's potential.
Your exhaust system appears to emphasize low/mid rpm&airflow rather than high end.
If you're leaving the heads as-is, I'd be looking at a cam with no more than 270 deg adv duration (@.006" tappet lift). That's going to be something like a 218 @ .050". That'll give you a 8.0 DCR, which is the minimum I shoot for even with iron heads.
Those are big heads for a 327/333 ci. so it will still make good power up high with a properly spec'd cam.

Buickstaged

iTrader: (1)

Usmechanix, I run 2 qf carbs. The first is a 950 4 corner idle mechanical secondaries, on a 470 Buick that is a 10.5 cr. Made 560 hp and 590 torque. It ran nearly perfect out of the box. Have never had to reset. The second is a 650 qf, mech secondaries on a 10. Cr. This is a 355 sbc that made 403 hp at 5350 and 423 torque at 4800. I recommend these carbs, out of the box they were nearly spot on. I own 4 older muscle cars, have fooled around with Holley carbs for years - I always had to tinker with Holleys, have had to do virtually nothing with the qf carbs. I am not associated with QFuel in any way. My recommendation is for the Qf. Regards, byron

usmechanix

Thanks a million Byron! That at least makes me feel better about that part of the decision. The rest of it not so much.

usmechanix

Hello again LG4. I apologize for what I'm about to but I need to ramble a bit. Apparently Herbert Performance is no longer responding to ANY forms of communication at all. After repeated attempts to contact by phone and email. I have given up on them. Feeling royally screwed over I have a few questions about other Bumpstick options. I would really like to continue to use everything else I have when I purchased the Top End Kit. I've done some checking on Herbert's website. The Springs have a Seat pressure of 125 and an Open pressure of 340. The Lifters will accept up to 350 Open Pressures and 140 Seat. Will I possibly be needing to change any of these things? Now I read an article in Super Chevy where they built a sinister 327 (.030 over) making 450ish hp and 400ish tq. The stick they used granted it was a solid roller cam was a 236/242 duration with only .501/510 lift and a 110 LSA(COMP Xtreme Energy). Correct me if I'm wrong, but the heads they use seem WAY bigger than what I have already. I guess my question is given the flow numbers of my Heads are lower than the AFR ones tested would you go with something similar to what you suggested? They did also use almost an 11:1 CR. Do you think its still possible to run Pump Gas i.e. 93 Octane with this combo? I really appreciate your input. As far as the Exhaust goes. What would you change to match it better to the engine?

Herbert Heads
http://www.herbertcams.com/dhpsbchea...r-heads-210cc/

Super Chevy Article
http://www.superchevy.com/how-to/eng...62-horsepower/

Five7kid I know by now this thread has absolutely nothing to do with Carburetors or the theory of operation at this point so I appreciate you letting it continue to go on.

86LG4Bird

iTrader: (1)

Most important with the exhaust, go minimum 3" single from the Y on back.
Next would be header primaries: 1-5/8"
2.5" collectors and Y is ok.
Your springs and lifters will be fine with a 218-ish cam. Also, pump gas is fine with 10.5 CR and Al heads with that cam.


Since you're using an old 327 block without factory HR provisions, I assume you have the retro-fit HR cam and lifter setup from Herbert? Keep that in mind when ordering any cam. It's different from a factory HR setup cam.


One more thing. I don't recall seeing your intended use/objectives for this engine, but don't get caught up chasing a hp number with this build. Concentrate on a powerband that will be useable. Think small when picking cam and carb, and I believe you'll be happier in the end.

usmechanix

Thanks again for the quick response! You've been a huge help in unraveling this giant mess I've put myself in. to answer your questions yes I do have retrofit roller tipped lifters with the tie bars. The Car is going to be primarily a street car with some possible trips around an autocross course. Also a couple times a year I am the chase car for a motorcycle trip through the Smokies.

Now my next question is the heads that they used in that article flow massively more air in that lift range than the Herbert ones. Do I prop up whatever stick I choose with a larger rocker ratio to compensate? or would I be going backwards. What do you think of these? Do I at least seem be heading in the right direction?

http://www.compcams.com/Company/CC/c...?csid=160&sb=2

http://www.compcams.com/Company/CC/c...?csid=159&sb=2

http://www.compcams.com/Company/CC/c...?csid=157&sb=2

86LG4Bird

iTrader: (1)

I''d go with this one:
http://www.compcams.com/Company/CC/c...?csid=158&sb=2
It will fit the variety of uses you want from the car.
Run 1.6 rockers if your spring/retainter/valveseal setup permits it.

usmechanix

Well I guess the question now what does that consist of. The spring pressures are as such. Does the rocker ratio really change the pressures that much? Another random question rocker ratio only effects the valve lift right? or does it also effect duration?

OD:1.437
ID:.750
Hyd./Solid
Max Lift: .675
Spring Type: Dual W/Damper
Seat Pressure: 125/1.750
Open Pressure: 340/1.150
Coil Bind: 1.050

86LG4Bird

iTrader: (1)

Those springs are good. Set them up no more than 1.750 installed height. I'd shoot for 1.700, since your valve lift of .535" with 1.6 rockers won't push them near coil bind.
Here's an illustration from Lunati's website on seal-to-retainter distance. Their suggestion of .090" minimum is very conservative. You can cut that in half IF YOU MEASURE EVERY ONE. Their number also considers possible valve float, which you're not going to get with that Comp XE cam if you set your springs up as suggested. Same goes for their coil bind "minimum". With no float and measuring for every valve, some people run all the way down to .020" clearance to coil bind. It actually helps damp out damaging valvetrain harmonics. Not a concern here though since the setup we're talking about won't push the limits of the valvetrain.

1.6 rockers will not exceed that 340 lb open pressure, since lift will still be below their assumed max lift.
Seat-to-seat duration isn't affected. Duration measured at .050" changes by maybe 2 degrees.

usmechanix

Well I called Comp today and I spoke with Alex. He recommended the XR282HR grind, 110LSA, .510/.520 lift with 1.5, 230/236 dur. at .50? what are the major differences between this grind and the XR270HR 110 LSA .495/.502 lift with 1.5, 218/224 at .50? Besides the obvious specification differences I guess I don't understand How all this applies to the power curve. Does it Shorten it? Broaden it? Move it Higher in the RPMs or drop down to more pedestrian levels?

86LG4Bird

iTrader: (1)

Oh dear... :facepalm: The LAST person you EVER want to take advice from when selecting a cam is from one of those "tech specialists" at Comp Cams that are given their first job at the "customer service" phone desk! You might as well throw darts blindfolded or ask a 5th grade girl.....I'm serious! Comp makes some quality parts, but unless you know of someone by name who is far far away from the "customer service" phone lines, you stand very little chance of getting what you really need. I know of one person by name there that I would trust to give me any sound advice on cam specs, and for all I know he's retired by now.
What this "Alex" suggested to you is just dead wrong, unless you told him you want a high-winding track motor and don't give a rat's @ss about having any useful powerband in an actual street car. He definitely didn't absorb much if any of the information that you've shared in this thread. Hopefully you didn't even share those original Herbert cam specs with him as a reference point. If you did, he's probably a newb but still realized the Herbert would be a disaster, but not quite experienced enough to know he isn't even playing in the right ballpark.

usmechanix

This is why I bring this information before the people I trust to steer me in the right direction. Is it true that for every 10 degrees of duration it moves the power band up or down about 500 RPM? If so that basically means that its a 750 RPM difference between the two of them minus the lift differences right? I pulled that data from Comp Cams website as well. I'm just trying to make sure I understand how this whole process works. Camshafts can be very very mysterious at first but I think I'm starting to figure this out.

86LG4Bird

iTrader: (1)

usmechanix, unless you filled in more profile info since you started this thread, I've been totally blind.....we're practically neighbors! I work up the road from you in Middletown.
Anyway, back to the subject...... 500 rpm per 10 deg intake....meh, yeh, that's a decent rule of thumb. Not a constant though; it depends on so many things: intake type, exhaust, cubic inches, heads' port quality, and others.
Nearly all of the SBC "rules of thumb" are based on 350 cubic inches, and for some reason Comp's charts that the newbs are given sure seem to result in too-aggressive cam specs over 75% of the time.
Here's a reference point for you: The LT1 350 in my Impala (the avatar at the left) runs a 228 duration HR cam, 200 cc intake runners, and I shift at 7100 rpm for best 1/4 mile performance. Now granted that LT1 manifold is a single plane type that favors high rpm power production, so....knock it down about 500 rpm for a 2-plane RPM type manifold and it still would want to shift around 6600. As as you go down in motor CID, the powerband moves higher in the rpm band. That 230 cam Alex suggested, in a 333 CID motor, would want to be shifted quite a bit beyond 6500 rpm to get the performance out of it. Is that what you want? I don't think so! That poor old stock rotating assembly might survive that 2 or 3 times and then you'd have a pile of junk on your hands. And meanwhile, you've been deprived of all of your performance down in the rpm band that you could have used in a real car.
That 218/224 cam I recommended will make power beyond the 6000 rpm that I would suggest you set as a limit on your rotating assembly.
More lift won't affect the rpm range much at all. It mostly affects torque, maybe a little, sometimes not, hardly EVER hurts it.

usmechanix

HAHA thats hysterical. Yeah I did update my profile a little. Yeah I'd prefer not to have a hole in anything thats not supposed too. Any suggestions for beefing up the Bottom End? Maybe a better set of Rods?

86LG4Bird

iTrader: (1)

Nope. That old bottom end is only a deal if you can leave it alone. Before I'd spend a dime on "beefing" it up, I'd just go get a junkyard 96-00 5.7 Vortec roller longblock and work from there.

usmechanix

I bought the motor off a buddy of my step-dad's who was strapped for cash. It was already assembled. Had maybe 2000ish miles on the rebuild. So you're saying ditch the bottom end in its entirety before throwing rods at it?

86LG4Bird

iTrader: (1)

No, I'm saying work with what you have. If you don't, whatever you paid for the motor is pretty much flushed. You could have bought a roller block for rebuild for $200 instead. The fact that it has survived 2000 miles gives me more confidence in it than I would have in any rookie rebuild.
You can't just "throw a set of rods at it". Done correctly, that will most likely lead into machine work, rebalancing, replacing components, and where does it end...., disassembling, re-assembling (do you have all the tools and know-how to give it a fighting chance of making it 2000 miles?) Rough guess says you'll add $1500 to what you already have in the motor ??

usmechanix

I don't but my machinist does. Apparently the rotating assembly was balanced beforehand. If the new rods are within a gram of each other I can't imagine it would change drastically enough to need rebalancing? I'm putting new pistons in anyways so rods aren't really that big of a deal at this point.

86LG4Bird

iTrader: (1)

OK, We seem to be chasing a moving target here.
You'll need to decide not only what the rpm limit of your engine is going to be. Don't forget the valvetrain; beyond 6500 rpm you're not talking cheap and low maintenance anymore. And.....consider your vehicle and your objectives for it: weight, gearing, trans, TC.....are you dreaming of a a high revving powerplant that your vehicle can truly utilize? Do you care about low rpm driveability/manners.
Figure out what you want and then we can get back to the cam discussion.

usmechanix

Well we haven't been all over every detail yet. It's going to be a built T5 manual. Astro Performance A5 gear set good to over 500ft lbs of tq. Eventually 3.73 gears, maybe 4.10 and a posi unit. If the valve train that's in the heads can't take it over 6500 or even 6000 it's not worth it to me to blow it up. Low rpm manners don't matter too much to me, I guess I dont know what a car thats not streetable is like to drive... im used to a doggish 305tbi car. I also know that long term reliability goes down the toilet the longer it lives in the upper stratosphere of rpms. Honestly the car will get pounded on from time to time. I just want to make sure everything will stay together at 6500. I'm planning on putting the limiter there with as much power as I can possibly utilize on the street.

86LG4Bird

iTrader: (1)

Allright, it seems I took off on the wrong impression going on the "CHEEEAAP" remark in your first post.
If you're rebuilding the bottom end, and the valvetrain (from Herbert?) is good to 6500 rpm, then you'll be able to use the upper limit of that 218/224 cam I suggested.
And depending on the internal ratios of the T5 (somebody help me out here; I only know T56's and autos), I could be convinced to agree to the Comp XE 224/230/110 cam -- it would probably be slower even though it would make more peak power, but would impress people with even more rumpity rump

usmechanix

Yea I bought the whole motor with an MSD Billet Distributor sitting it for 600 bucks. It was supposedly set up as a 327/300 from back in the day with flat top pistons and 1.94/1.50 valve cast iron heads and a edelbrock torker 2 intake. But I wanted more out of it. I don't care to spend the money as long as the results stack up. I will see if I can dig up the gear ratios for ya.


Gear Ratios
Ratio........1st.............2nd.........3rd.........4th............Rev.......5th
T5U..........2.95...........1.95.......1.36........1.1............2.76...... .64