Help Me Choose a cam for my Challenge SBC engine

Since I don't expect to really be able to use the mystery cam that my Challenge car's original 350 came with and the TBI cam is laughable for any kind of high-end power, I figure I should be getting to work on selecting a better one. The car has to be streetable and idle remotely well.

Here's the details on the engine so far:

Lower half is AFAIK a stock 1989 TBI 350; I've not pulled the heads off to see what kind of pistons it has. I expect that everything on it is stock though.

Vortec 062 heads. Valve springs can be upgraded as necessary.

Intake hasn't been bought yet, but it will likely be something like Edelbrock 2116 or Summit 226018.

Transmission will be a THM-350 which will be at least as of now using a stock stall converter. If absolutely necessary, I can likely find a higher-stalling converter from a 4.3 S-10.

Fuel delivery will be a Edelbrock 600cfm carb (1405). I may be converting to TBI down the line, but I can worry about changing things for that later.

Misc: Though the engine came with a serpentine belt system on it (and I will be holding on to it for later), I'm almost certainly going to be using the aluminum V-belt pulleys the '79 came with since I don't plan to run either A/C or P/S. The '79 also came with a gear drive in place of its timing chain- I'm on the fence as to whether to keep and use it or sell it off.

From my research and reading so far, the Edelbrock 2102 is what I would pick up if left to my own devices- it seems like it would be reasonably well matched and is a reasonably Challenge-Friendly price. Though one of the sub-$100 cam/lifter sets would certainly be nice from a budget standpoint.

If there's an info I've left off that would be helpful, let me know! Thanks for the help in advance!

For what you'll pay for a different cam you can buy a used nitrous kit. The nawzss will give you much more power.

The TBI engine cam is apparently pretty much useless at anything above 4,000 RPM and badly matched to the 062 heads. A 2102 kit is only about $140, and there are a modest number of others that are less expensive. There may still be room in my budget for a nitrous kit even with a new cam depending on how well my sell-offs go.

And the nitrous will only do me any good on the drag, it won't help at all on the autocross... (yeah, an El Camino is going to suck at autocross regardless, but... )

Something I did notice I forgot- the car is running headers straight through to mufflers (one on each side). I can get the exact piping size when I get back home in a few hours.

The 2102 is too mild. The 2103 is a much better choice (although still very mild) , and you can add some 1.6 rockers if you want a little more.

You forgot the most important info. The final drive ratio.

Zomby Woof wrote: The 2102 is too mild. The 2103 is a much better choice (although still very mild) , and you can add some 1.6 rockers if you want a little more. You forgot the most important info. The final drive ratio.

I don't exactly know what the final drive ratio will be yet unfortunately... that hinges on whether I use the posi diff rear which would be a 3.42 or the original open diff rear which would be a 2.73. Won't be anything more aggressive than the 3.42 unless I go wild and pick up a Ford 8.8 rear and find a way to shove that in (and save a good bit on my budget).

Probabilities are that I'll use the 3.42 posi rear end, though I'm still looking for one at a bit more Challenge-friendly price...

3.42-1 is perfect for those mild cams.

an 89 TBI motor should be a roller cam not a flat tappet cam. That pretty much eliminates ANY cheap new cam from contention

I didn't think the TBI motors were roller until the mid 90's.

Zomby Woof wrote: I didn't think the TBI motors were roller until the mid 90's.

mid 90s TBI was relegated to medium duty trucks. last TBI in a light duty truck was 95.
TBI motors in cars were rollers after 87. Trucks were varying by class from what i can tell

Brian wrote: mid 90s TBI was relegated to medium duty trucks. last TBI in a light duty truck was 95. TBI motors in cars were rollers after 87. Trucks were varying by class from what i can tell

The engine came out of a '89 K1500 truck, if that makes any difference... I thought I'd read that the C/K truck engines were flat tappet from the factory but had the provisions for rollers...

"almost" ALL truck TBI's were flat tappet, car TBI's were rollers.

The provisions should be there to convert to roller, if you so desire.

best way to know for sure is to just pull the intake and look

I'll try and get out and pull the intake tomorrow... spent the time I had this afternoon to wrench tearing down the truck itself to try and sell off the parts I don't need.

According to Edelbrock's site though, they don't recommend any roller cams for the 87-95 TBI engines, so I'm pretty certain they should be flat.

Assuming that's correct, what other cams should I be keeping an eye out for a good deal on? And what general specifications? Are there any 'stock' cams from other vehicles that would work well?

Would one like this http://www.summitracing.com/parts/LUN-10120101LK/ be about the same?

Truck TBIs were not roller cam, although some were roller-ready blocks with flat cams in them. I've heard claims that some later ones actually had roller cams, but have never seen one, myself.

If it is a roller block you will have much more area under the curve if you use a roller cam. Big paybacks in reliability and friction too.

Call up a local machine shop. They have access to cheap cams up to the mild performance range. I had an "RV" cam put in a 454 that I did (which spec'd out at 204/218 duration) and it was $34 on the receipt. See if they can hook you up with a nice stick and some lifters on the cheap.

Maybe I missed it, but what vehicle is it going in? Vehicle weight, tire size, rear gears (addressed above), etc would be helpful. also, are you planning on driving on the street after the challenge, or is this a challenge-only vehicle?

Also... when you pull the old heads off, let us know if they are dished pistons or flat-tops. Flat-tops will put you around 9.5:1, dished will put you at 8.7-9.0. That's of course important for the cam choice. A wider LSA can help reclaim low-rpm cylinder pressure and still maintain rpm, but the lower static compression will mean less cam duration in most situations.

Ashyukun wrote: Transmission will be a THM-350 which will be at least as of now using a stock stall converter. If absolutely necessary, I can likely find a higher-stalling converter from a 4.3 S-10.

i know it's slightly off the main topic of this thread, but you won't be able to use a torque converter from a 700r4 that you would find behind a 4.3 in an S10 in a TH350. they are totally different. i know they have all pretty much returned to mother earth, but you could use a torque converter out of TH250 that you would find in a Vega in an early (non lockup) TH350... this will get you about a 3000 stall, but it won't take much abuse.

regarding cam choice: depends. you will have dish pistons and have about 9:1 compression with the vortec heads.. i'd get the Speed Pro version of the Edelbrock Performer (.420/.443 lift) if you are running 3.42-3.73 gears in a 3500 pound car, maybe the next size bigger for deeper gears and/or lighter.

The car (term used somewhat loosely, and only because it makes more sense to me than 'truck') this is going in is a 1979 El Camino. Rough gross weight around 3200 lbs (Challenge weight may be a bit less since the interior will be mostly stripped and running a racing seat, but it will be running a full interior afterward and a bunch seat). The intent is to use the car after the challenge as a 'normal' vehicle for driving around, hauling parts, and potentially some towing. I'm not TOO concerned with worrying about the low-end torque needed for towing in this initial build though- I will likely be pulling the carb off and playing with the TBI and MegaSquirt, putting either the 700R4 or T5 into it, and doing some other work on it, so putting a better cam for towing into it won't be too much of an issue. It does need to be able to drive normally on the street though as I plan to drive it from here (Lexington KY) down to the Challenge and back, but I don't mind being a bit more aggressive with the build.

It will (in both race and driving setup) be running 16" Camaro/Firebird wheels. I'm blanking on the exact tire size they used, but the're a mediumish profile tire. For the Challenge it will be using the R-comps that I used on the 500ci Fiero this year (assuming I don't kill them practicing and buy new VL710s...).

From what I saw of other TBI truck engines in the salvage yard when I found the Vortec heads, the TBIs had dished pistons. I hope to get the intake and heads off tonight, but may get back too late to be able to get into it. I had been thinking about trying to use a thinner head gasket to bump up the compression a bit. If I'm still harboring some thoughts of using the nitrous kit I have access to though, I probably don't want the compression THAT much higher though, right?

Good to know about the 700R4 converter and the THM350. There's still the possibility I'll use the 700R4 I'm getting, but it's a bit of a budget hit that I'm not likely to be able to absorb with everything else (especially it I intend to try and use the nitrous).

Thanks for the tip on the machine shops- I've been meaning to talk to a few anyway about getting head work done on my Saturn anyway, so that's something else I can check on. Getting a better cam and lifters for ~$50 would be GREAT! I can also see if any of them have the gear to spec the Mystery Cam that came with the Elky's 350 (though I suspect one of the more specialized performance shops would be more likely to be able to do that...)

I'm not seeing a 'Speed Pro' Edelbrock Performer cam... It looks like the lift matches up on to the 2102 (Performer-Plus), though?

http://www.ebay.com/itm/New-Speed-Pro-Chevy-SBC-Hydraulic-Camshaft-420-443-/150593703207

Good cam for a truck hauling a trailer, but poor choice for a performance application like yours. 1.6 rockers would help, but it's still too mild.

.420" at the intake valve is pretty mild. Something like this might be a bit more well-rounded;

http://www.summitracing.com/parts/TFS-31401000/

$102 + shipping etc thou, so there is that budget impact to deal with, or look for it elsewhere.

I ran a 440/460 in my Malibu ,flat top pistons ,882 heads headers, turbo 350 stock converter. 650 holly victor jr
2.20 gear full interior ran 15.3 all day long. Pulls good from take off ran on 87 octane.

Ashyukun wrote: The car (term used somewhat loosely, and only because it makes more sense to me than 'truck') this is going in is a 1979 El Camino. Rough gross weight around 3200 lbs (Challenge weight may be a bit less since the interior will be mostly stripped and running a racing seat, but it will be running a full interior afterward and a bunch seat). The intent is to use the car after the challenge as a 'normal' vehicle for driving around, hauling parts, and potentially some towing. I'm not TOO concerned with worrying about the low-end torque needed for towing in this initial build though- I will likely be pulling the carb off and playing with the TBI and MegaSquirt, putting either the 700R4 or T5 into it, and doing some other work on it, so putting a better cam for towing into it won't be too much of an issue. It does need to be able to drive normally on the street though as I plan to drive it from here (Lexington KY) down to the Challenge and back, but I don't mind being a bit more aggressive with the build. It will (in both race and driving setup) be running 16" Camaro/Firebird wheels. I'm blanking on the exact tire size they used, but the're a mediumish profile tire. For the Challenge it will be using the R-comps that I used on the 500ci Fiero this year (assuming I don't kill them practicing and buy new VL710s...). From what I saw of other TBI truck engines in the salvage yard when I found the Vortec heads, the TBIs had dished pistons. I hope to get the intake and heads off tonight, but may get back too late to be able to get into it. I had been thinking about trying to use a thinner head gasket to bump up the compression a bit. If I'm still harboring some thoughts of using the nitrous kit I have access to though, I probably don't want the compression THAT much higher though, right? Good to know about the 700R4 converter and the THM350. There's still the possibility I'll use the 700R4 I'm getting, but it's a bit of a budget hit that I'm not likely to be able to absorb with everything else (especially it I intend to try and use the nitrous). Thanks for the tip on the machine shops- I've been meaning to talk to a few anyway about getting head work done on my Saturn anyway, so that's something else I can check on. Getting a better cam and lifters for ~$50 would be GREAT! I can also see if any of them have the gear to spec the Mystery Cam that came with the Elky's 350 (though I suspect one of the more specialized performance shops would be more likely to be able to do that...) I'm not seeing a 'Speed Pro' Edelbrock Performer cam... It looks like the lift matches up on to the 2102 (Performer-Plus), though?

yeah.. Speed Pro sells the same cam as the Edelbrock piece, only without the Edelbrock premium and with an extra .001 listed on the lift.. i put that cam in my 74 Monte Carlo along with a new set of Speed Pro lifters, new oil pump and screen, and all the gaskets to do it for around $120 from www.northernautoparts.com , but you could use pretty much any other Speed Pro cam for the same price.

Just stay away from the Thumpr series of cams. Lots of noise, not a lot of power.

That being said, Comp cams have never done me wrong, I would trust them over an Edelbrock to deliver the numbers.

Find your local roundy-rounders and get a used cam from them, they should be cheap.

Pulled off the intake manifold and confirmed that it is indeed a flat tappet cam, but that it is a block with provisions for rollers (at least I'm assuming that's what the threaded-hole posts in the center of it are for).

Halfway wonder if I shouldn't go back and grab the cam and lifters from the engine I pulled the heads from- or at least the roller hold-downs. :P

I've looked up a few of the local machine shops, but haven't gotten in touch with them yet. I unfortunately don't know much of anything about the local racing scenes here in Lexington, though I know they have to exist...

Ashyukun wrote: Pulled off the intake manifold and confirmed that it is indeed a flat tappet cam, but that it is a block with provisions for rollers (at least I'm assuming that's what the threaded-hole posts in the center of it are for). Halfway wonder if I shouldn't go back and grab the cam and lifters from the engine I pulled the heads from- or at least the roller hold-downs. :P

Don't even halfway consider it, go NOW. Get the spider, the dogbones, and the lifters. New lifters aren't cheap and there are no aftermarket lifters that (IMO) that are worth spit. I'm fine with buying cheap chinese stuff for some things, but not valvetrain parts. Heck, many of the GM lifters were chinese from the factory.

And congrats on the roller block. In the performance SBC community, that is one of the blocks to get. You have a modestly beefier casting with roller potential.

Rough gross weight around 3200 lbs (Challenge weight may be a bit less since the interior will be mostly stripped and running a racing seat, but it will be running a full interior afterward and a bunch seat). The intent is to use the car after the challenge as a 'normal' vehicle for driving around, hauling parts, and potentially some towing. I'm not TOO concerned with worrying about the low-end torque needed for towing in this initial build though- I will likely be pulling the carb off and playing with the TBI and MegaSquirt, putting either the 700R4 or T5 into it, and doing some other work on it, so putting a better cam for towing into it won't be too much of an issue. It does need to be able to drive normally on the street though as I plan to drive it from here (Lexington KY) down to the Challenge and back, but I don't mind being a bit more aggressive with the build.

You have one benefit here and a couple challenges... The TH350 has a tight ratio spread. First gear is 2.52:1. Tight ratios means you can sacrifice a little bit of broadness to the torque curve since you'll be staying with small gear changes keeping the RPMs in the sweet spot. The 700r4 is one of the worst gear spreads I've ever seen. First is 3.06:1. It has the largest 1-2 ratio spread of any production automatic which means you don't get to stay in the sweet spot and you need a broader torque curve. The T5 has multiple ratio clusters so you should be able to find one that suits most profiles.

It will (in both race and driving setup) be running 16" Camaro/Firebird wheels. I'm blanking on the exact tire size they used, but the're a mediumish profile tire.

245/50-16 was common, so was 235/55-16 on the F-body. Either way, you're looking at 25.5 - 26" diameter.

I had been thinking about trying to use a thinner head gasket to bump up the compression a bit. If I'm still harboring some thoughts of using the nitrous kit I have access to though, I probably don't want the compression THAT much higher though, right?

You can use thinner head gaskets. Shim gaskets can be finnicky, but many companies like Cometic, Victor Reinz, ROL, and FelPro make MLS composite gaskets in thinner sizes.

Don't be afraid to push the compression a bit with Vortecs. The chamber shape is very tolerant to detonation. Depending on your setup, 10.5:1 is easy on 93 octane. I have a very mild cam in mine and run 87 octane with 9.6:1. More cam can reduce the need for octane with higher compression.... but more on that in another episode.

If it were mine, I would shoot for something like this: @.050" duration 225-intake, 230- exhaust, 110° LSA, install it about 2-4 degrees advanced (which for most grinds means just line up the dots). That should net you a good square 400 lb-ft around 3500 RPM, and a good 350 hp at 5000 RPM with headers and proper dual exhaust. Shift at 6000 and smile. Converter will need to be around 2500 stall and rear gears should be pretty deep... 3.90 or 4.10 with the TH350. The torque curve should be fat enough to get by with 3.42s with the 700r4.

For the challenge, the TC can be as cheap as you want. For the street, spend money on a good one. All high-stall converters are not the same. A cheap one feels like you're in neutral until you hit higher RPM. A good one moves the car forward like a stock converter when you take your foot off the brake, and the amount of stall is more proportional to throttle input.

Big point to make here.... With vortec heads, don't assume anything when it comes to valve lift capability. The generally accepted max lift on stock springs/retainers is .470" gross lift. Since you won't be able to use stock springs anyway with an aftermarket cam, you have a few options: 1) buy a common aftermarket spring/retainer kit that will allow .550" lift, 2) buy an inexpensive guide cutter bit and cut down the guides to allow more lift, or 3) only use .470" lift. #3 is a very poor option in my opinion since the vortecs will absolutely benefit from more lift. #1 and #2 are equally fine options and you'll just have to weigh the cost/comfort level of what you feel comfortable doing.

One more big point to make... Don't take the cam manufacturer's word on spring rates. Most of the cam companies make a handful of springs to fit a few hundred cam profiles. They assume that the handful of different spring rates will sorta satisfy "range X" of cam profiles. You may end up with a cam that is at the low or high end of that range and your springs will be either way too stiff, or not stiff enough. Find a trusted machine shop to recommend spring rates for your cam. You'll also save money that way. Instead of buying the expensive aftermarket performance kit, you can buy inexpensive, off-the-shelf, machine-shop parts and get a better result.