camshaft choice

[Jesse OBrien]

I know this is kind of a newbie question, but bear with me. I'm in the market for a new cam for my 350 in my daily. It's probably going to see more time on the track than on the street, but I want to keep it driveable while improving power and getting that scary lopey idle that always gets me off.

 

I'm planning on using a rochester carb that came off my 350ci, and I honestly don't know what cfm it's rated for.

 

Now, my question then becomes:

• What is a reasonable lift and duration for stock fuelie (camel-hump) heads?
  
• Is it necessary to upgrade the valvetrain for a cam upgrade, or only for serious builds?
  
• At what point will I need to upgrade my fuel system from the mechanical pump I'm currently using?
  
• Is there anything I'm missing?

Now, I did search and found a bunch of info, but very very little of it was geared toward the sbc specifically. What have you guys used for your builds? How successful did it turn out?

 

Any info you guys can offer with all your collective experience would be greatly appreciated, and any questions that I should be asking myself would also be put to immediate use. Thanks in advance!

[grumpyvette]

I know this is kind of a newbie question, but bear with me. I'm in the market for a new cam for my 350 in my daily. It's probably going to see more time on the track than on the street, but I want to keep it driveable while improving power and getting that scary lopey idle that always gets me off.

 

I'm planning on using a rochester carb that came off my 350ci, and I honestly don't know what cfm it's rated for.

 

Now, my question then becomes:

• What is a reasonable lift and duration for stock fuelie (camel-hump) heads?
  
• Is it necessary to upgrade the valvetrain for a cam upgrade, or only for serious builds?
  
• At what point will I need to upgrade my fuel system from the mechanical pump I'm currently using?
  
• Is there anything I'm missing?

Now, I did search and found a bunch of info, but very very little of it was geared toward the sbc specifically. What have you guys used for your builds? How successful did it turn out?

 

Any info you guys can offer with all your collective experience would be greatly appreciated, and any questions that I should be asking myself would also be put to immediate use. Thanks in advance!

 

"[*]What is a reasonable lift and duration for stock fuelie (camel-hump) heads?

 

UNTOUCHED STOCK, about .475 lift is maxId suggest

 

[*]Is it necessary to upgrade the valvetrain for a cam upgrade, or only for serious builds?

 

ITS always a good idea on 40 year old cylinder heads and springs and making sure the clearances and spring load rates match the cams only reasonable, plus your LONG over due for spring upgrades on 40 year old heads

 

[*]At what point will I need to upgrade my fuel system from the mechanical pump I'm currently using?

 

generally either when you experiance problems or intend to exceed about 400 hp with a stock system

 

[*]Is there anything I'm missing?

Now, I did search and found a bunch of info, but very very little of it was geared toward the sbc specifically. What have you guys used for your builds? How successful did it turn out?

 

 

 

well the first thing ID point out is that (LOPE)& (RUMBLE) in the idle that you crave is due to reversion pulses at low rpms and too much durration and overlap too allow the engine to run well at low rpms, AND a HIGH COMPRESSION RATIO cylinder, bleeding off exhaust pressure, and if the compression and head flow rates won,t support the intended HIGH rpm opperation the cams designed for, youve just screwed up both ends of your power curve potential installing a high rpm cam in a low compression ratio flow restricted engine

 

 

read thru this,theres a good bit of useful info...slaping a radical cam in an otherwise stock engines, to get it to lope noticably, is basically not going to do much good for the combo

 

 

http://www.chevyasylum.com/chp/

[Jesse OBrien]

Ok, I just did a BUNCH of reading (not just the article you linked to, but all the questions that stemmed from that).

 

You've basically confirmed what I figured to be true. The lope just isn't realistic unless I go hardcore build. However, I did a little math, and based on the heads I'm using (64cc), I should be running around 11:1 compression, depending on the head gasket I decide on. That should put me in the lopey area.

 

As far as intake and exhaust go, I don't see much restriction there at all. I have the edelbrock performer intake mani, and what amounts to open headers (dual 4.5" side-dumps), so my plan is essentially to let the engine breathe as nicely as the bottom end will allow. That probably means carb rebuild (possibly rejet), valvetrain rebuild/upgrade, and new cam. I was hoping that'd get the scary lope I've only seen in firebirds and camaros (and sometimes even mustangs around here) but that's starting to sound a little unrealistic for a daily driver.

 

In any event, thank you very very much for the info, I'll be digging around the net looking for a few more reviews and re-reading the Goodwrench build a few more times.

[grumpyvette]

if youve got at least a TRUE STATIC 10.5:1 cpr,and your determined to have a lopey idle....you can run this cam

 

 

http://www.cranecams.com/?show=browseParts&action=partSpec&partNumber=110921&lvl=2&prt=5

 

and get the lope you want,

but! .....to do that youll need a few MINIMUM other components to match or be modified

(1) the proper valve springs and clearance work on the heads for a .600 lift, (remember you need a minimum of .050 over valve lift)

 

(2)a 3000 rpm stall converter

 

(3) a decent performance rear gear ratio, in a 3.73:1-4.56:1 range

 

(4)real HEADERS would be a BIG help, as would 1.6:1 roller rockers

 

(5) the heads @ lifters I suggested in the other thread would be as huge help,with your build, but at least use the lifters, correct clearances and springs and get those fuelie heads re-worked (pocket porting your fuelies won,t hurt either)

 

 

 

heads

 

http://www.jegs.com/i/Brodix/158/102...760699%7C10187

 

 

 

lifters

http://www.competitionproducts.com/p...umber=651080DL

 

 

 

(6)youll need to learn how to tune an engine and correctly lash solid lifters

 

if you do that, the car won,t run well below about 3000 rpm so youll need the high stall converter, but from 3000-6500rpm youll notice it pulls a bit better

[sstallings]

Drummingpariah,

In the last six months in Street Rodder magazine, Comp Cams www.compcams.com has been advertising a new line of "Thumpr Cams" that claims to have the nasty lope that everyone wants with streetable performance. I don't know anyone using one yet, but Comp is a reputable cam manufacturer, so you may want to check it out.

 

Personally, I like performance and stealth, a sleeper that catches people off guard, but I have to admit that I always take notice of a car with a healthy cam lope at idle. It suggests more than stock muscle under the hood. Good luck finding your cam.

Steve

[Jesse OBrien]

Thanks for all the extra reading, guys. At this point I'm planning to rebuild the heads from the ground-up before slapping them on the 350, and I had been looking at Comp cams already.

 

@Grumpyvette:

 

I didn't want to give you the impression that my whole goal was to get a lopey idle. That was meant as a target goal, done correctly. I'm really just hoping to make some respectable power without putting gobs and gobs of work into this engine, and from what you've explained, that sounds completely doable.

[grumpyvette]

yes ITs completely within the realm of possibility and done correctly the combo above should easily exceed 400 plus hp, depending on the components used and the care of assembly.

my personal opinion, is those THUMPER cams are a bad JOKE for WANTABEES...even COMP CAMS will suggest some of thier OTHER designs if MAX HP/TQ is the goal rather than building an engine solely for cruiseing around the local car show parking lot in idle, with a lopey sound

 

you don,t need to get all "HIGH TECH & expensive" to make a decent engine combo, but you do need to match the cam timing to the compression ratio, rear gearing, head flow rates and trans stall speed if you hope to have some combo thats reasonably effective

light weight cars using reworked fuelie heads on decent combos have occasionally run fairly well, now those heads are 40 year old technology and restrictive by todays standards but they still have some potential with a high compression ratio and a cam like that listed above with the mandatory matched , engine & drive line components and its MANDATORY too have the correct clearances on the heads and correct springs and valve train geometry, having a car that can run in the 12s should be easy, and faster is certainly possiable

 

let me know what your thinking and Im sure that with a few tweaks we can get that combo to run decent times once the heads are reworked, and youve got the combo set up, but to run a killer cam like that youll need the rest of the combo to match its effective opperational rpm band.

 

and before you ask! NO! you can,t ignore doing some of the listed mandatory mods or leave out components and expect it to work correctly

[pparaska]

...

light weight cars using reworked fuelie heads on decent combos have occasionally run fairly well, now those heads are 40 year old technology and restrictive by todays standards but they still have some potential with a high compression ratio and a cam like that listed above with the mandatory matched , engine & drive line components and its MANDATORY too have the correct clearances on the heads and correct springs and valve train geometry, having a car that can run in the 12s should be easy, and faster is certainly possiable

 

My Z had a 327ci SBC in it, with 461 fuelie heads, pocket ported with the correct springs for a Comp Cams XS274S-10 cam (solid flat tappet), and I was running 9.7:1 compression. It had a Holley 300-36 dual plane intake and a 650 double pumper, hooker block hugger headers and 2.5" dual exhaust with X pipe and Dynomax Hemi SuperTurbo mufflers. The car had a very noticeable idle, could cruise at 2500rpm without loading up, HP peaked above 6000rpm (I shifted at 6700). It ran a 12.78@110.4 on 255/40-17 Toyo RA-1s, with a bunch of traction problems (I had to baby it off the line). So that performance and lope is possible. With a 350, that cam would be a bit more tame, and 10.0:1 or more would be better. Look into dynamic compression ratio for whatever engine your are building - this effects static compression ratio that you are going for and the cam you can use, and how far to advance/retard it.

[Jesse OBrien]

I did a little looking around on Summit, and have come up with the following:

• http://store.summitracing.com/partdetail.asp?part=SUM-CEDL402&view=1&N=700+ complete set of alu heads for $1600, includes everything but carb.
  
• http://store.summitracing.com/partdetail.asp?part=CCA-K12-422-8&autoview=sku COMP cams kit for $1k, still requires a valve job (seats, guides, valve resurface)

I could also just rebuild the engine and not build it up, but that's considerably less fun. I've been toying with a few different ideas, but I'm interested to know what you guys would suggest.

[Pyro]

A q-jet will need more than a jet change to run a lopey cam. Just get a holley 3310 750 cfm with vacuum secondarys. They are cheap, dependable, run well, and are easy to tune.

 

forget the performer intake, you need the performer rpm intake

 

heads will need to be machined to hold 1.470" springs and will need screw in studs and guide plates. You will be better off getting a set of dart iron eagles (64cc chambers, 200cc intake ports, straight plugs). They come with springs, retainers, screw in studs, and with a valve job. Plus they flow 40 more cfm right out of the box which translates to about 40 more hp.

 

3.90 gear, 3000 stall, and a compcam 292H would work nicely with 10.5 to 11:1 cr. will make power to 7,000 rpm.

 

Make sure to use engine oil with lots of zinc or use an additive to regular oil.

[grumpyvette]

you WON,t get the results you after with that kit!

[Jesse OBrien]

All right, since I'm really not sure what I've got (and haven't looked up the stamps yet... I'll get to that tonight) I'm just going to throw up some pictures, and maybe you knowledgeable folks can help me out a bit. Please bear with my inexperience, I'm doing my best to pick up all the info you guys are throwing out, and think I'm doing a decent job at it but I just wanted to see what else I can get out of you for advice.

 

Here's the intake manifold. I'm not sure how to differentiate the RPM from the standard Performer (or whatever other models there were). It definitely says Edelbrock Performer on it, though.

 

Here are the two carbs I have, from the bottom. The left is the edelbrock that came on the 283 (probably in a kit with the intake manifold, is my assumption) and the right is the Rochester that came with the 350 (stock, I'm assuming). I don't know what kind of power handling they're going to be good for (or what kind of fuel economy) but it looks like the Rochester could be worth keeping.

[dr_hunt]

That looks like a standard performer to me. What is your budget? All this talk is meaningless if you can't afford the pieces.

[Jesse OBrien]

Budget for the engine is going to be income / 4 - wheels, so assuming I spend around $2k on steel wheels and nice wide tires, I'll have around $3k to spend on the engine. I figure $3k gives me some wiggle room and I can do a moderate N/A build with that, assuming I can reuse as many parts as possible.

 

Correct me if I'm off on that. I can always extend the project by a few months to increase the overall budget but I'd really like to get this back on the road before our short rainy season begins.

 

All this is coming out of my fund that's set aside for it, so I'm hoping to just order all the parts I need at once late next month (when I've nailed down which route to go) and go to town for a few weekends installing stuff.

 

For the time being, my ground-up rewiring project and body work are taking priority, along with trying to find a t56 that isn't beat to hell that is a reasonable price. Does $3k sound reasonable?

[dr_hunt]

Oh yeah, you could do alot with that. You could do a complete build with heads, pistons, cam, rods and crank for that.

[Jesse OBrien]

It seems like choosing heads are a bigger decision than a camshaft. I currently have a set of 3890462 heads and 333882 heads (both came on engines I have now). I'm having a tough time getting the 3890462's off the 283ci (I'll probably buy a torch tomorrow, pb blaster isn't loosening them enough) but I'm considering just tossing those on the 350ci block (that currently has the 3338882's on it.

 

According to the casting number, I think the rochester carb is an 650cfm, but that seems a little big for a stock GM carb. I like the way it works, but it's currently loaded with vacuum messiness.

 

I've gutted the car and found lots of nasty coverup jobs and twisted floorboards, so it looks like a good portion of my budget is going toward a decent welder, some sheet metal, and a creative application of brake lights. I've changed my current engine goals to "get it on the road". It seems like the stock 350 block, fuelie heads, rochester carb, and performer intake manifold will accomplish that goal the best. That way I'll have time to focus on the chassis, and probably build an entirely separate engine on a stand.

 

I've put both th400 transmissions up for sale, and I'm hoping to get a t5 to bolt up for this for now (I've found a few semi-helical gear kits that got me excited about the t5). I need to start a build thread for this car.

 

... off to do that now, but as always, any suggestions will be taken completely to heart.

[jbk240z]

Make sure that you have all the bolts out of the heads before you pry or use the torch. On the SBC engines, there is often an overlooked bolt or two hidden deep under oil & sludge. There are 17 bolts per head.

Good luck.

[grumpyvette]

 

might help

[Z48LT-1]

I don't know whether this is an approved approach to breaking loose stuck heads, but recently, on one of the car programs on Spike or Speed, a guy stuck a couple crowbars in intake ports and gave them upward whacks with the heel of his hand. Mind, I'm not recommending this but perhaps someone who actually knows can advise whether this is as bad an idea as it sounds.

 

Cheers -- Gary

[Jesse OBrien]

Make sure that you have all the bolts out of the heads before you pry or use the torch. On the SBC engines, there is often an overlooked bolt or two hidden deep under oil & sludge. There are 17 bolts per head.

Good luck.

 

 

might help

 

Thanks guys, I've gone through so much pb-blaster on this that there's no sludge/oil left to muck around in. I've been going through the GM service manual, and it seems like I have everything right, the head studs just won't budge. I may just have to buy an impact gun instead of a ratchet and hammer.

 

I don't know whether this is an approved approach to breaking loose stuck heads, but recently, on one of the car programs on Spike or Speed, a guy stuck a couple crowbars in intake ports and gave them upward whacks with the heel of his hand. Mind, I'm not recommending this but perhaps someone who actually knows can advise whether this is as bad an idea as it sounds.

 

Cheers -- Gary

 

That doesn't sound like an awful idea, actually. Since they're iron heads I don't need to worry much about them cracking. I'd be worried about the valve guides more than anything.

 

I let it soak overnight, so hopefully I'll have some better results today.