Bench Racer (BowtieBandit)
Bench Racer (BowtieBandit) Reader
3/15/11 5:31 p.m.

I'm wanting to build a Vortec headed 350 to place into the Camaro. Basicly a mid ninties truck motor, with a roller cam and one piece rear main. I've got a line on one, actually three, four bolt main roller cam blocks, $150 a piece. I want a choppy idle, and really like the Comp Cams Thumpr, but according to their website, it is designed with flat-tappet motors in mind, and has an eccentric cam lobe for a mechanical fuel pump. My question is that , I know the block is the same, but if I were to run some sortof EFI, like a factory TBI or whathaveyou, will the eccentric lobe interfere with anything? Since money is always an issue, I may wind up carbing the thing anyway, although electric pumps are always an option too.

This same seller has a new "take out" cam, from a new engine, that specs out to 208/221 and .474/.510. I'm still learning all these numbers, but that's a pretty big cam. Comes with no lifters and the price is $125, has a identical cam slightly used at $100. Now, as much as I would like to buy a cam/lifter set, I just can't afford to dish out $500+ for one, although I know I would be pleased with the results. The fact is, I'm in the real world, and we're doing things the GRM way. Would stock lifters be okay with that big of a cam? I know I'll have to run different springs, as the stock Vortecs have a bigger perch and require machining to accept a traditional style spring. I was wanting to run some sortof beehive spring, something that will survive a decent-sized cam.

As much as I love LS engines, and the fact that you can get a 5.3 LS for cheap, and make similar if not more power, this engine I'm bench-building will drop right inplace of my tired 305, and all my accesories will go right back in place as well. If I were to LS swap, I'm sure I would have to change my assecories, mounts, and all sorts of stuff. In the long run, the ol' mouse is still cheaper.

I've yet to purchase anything, so I'm still shopping for cheap stuff, cause I know it can be found, these motors were built in the seven digits. I've bought stuff from this guy before, he's pretty legit, even though I sold that engine without ever doing anything to it, or assembling it.

I know there are several SBC guys here, and basicly I was wanting a stout engine that's cheap, and reliable as all get out. Maybe a .30 over, flat top pistions, compression ratio around a high nine or maybe a low ten, running on 93 octane. The downside to Vortecs are their special manifolds, now I don't have my heart set on them, but their flow-per-dollar is very tough to beat.

I don't plan on racing the thing much, just wanna dive elbow-deep into a short block, make some okay power, and say "yeah, I built that" when I pop the hood.

Input is expected and appreciated!!!

itsarebuild Reader
3/15/11 5:53 p.m.

i know there are others out there with bmnore experience, but here is my $.02

a fuel pump lobe wont hurt anything if you dont use a mechanical pump. they have been making block off plates for motors that dont use the lobe forever.

as for the grind of the cam, it sounds like you could go as far as something in the 262 range. these grinds are often advertised as being good for street strip applications and are compatible with some computers but you will probably need a new chip if you are using a stock efi set up. this also may be too aggressive for your power accessories like power brakes as they dont tend to make good consistent vacuum. 212 is pretty tame by comparison and definitely shouldnt be a problem to run in stock motor. the biggest thing i think you will run into with stock unmodified heads is the lift. i think anything above .5 is going to challenge your springs so you are on the right path with new ones. but you are correct that this costs money and you may be better served with a new cam of a 252 ish grind and less than .5 of lift. they are out there. vortec manifolds are worth the price of the better vortec heads in my opinion.

Zomby woof
Zomby woof Dork
3/15/11 6:16 p.m.

That's a mild cam. You won't be happy with it.

Look for something with at least 220 duration at .050" on the intake, 10 more on the exhaust (+/-) and as much lift as you can handle. Idle will be good in a roller application up to this point.

pres589 HalfDork
3/15/11 7:20 p.m.

Comp "Thumpr" for 350's with roller lifters. Plenty of duration on this thing, over .500" of lift at the intake valve and just under at the exhaust, I assume with a factory 1.6 ratio rocker. There's two more camshafts above this thing in terms of aggressiveness but for street this seems like plenty.

Zomby woof
Zomby woof Dork
3/15/11 9:38 p.m.

That's a nice street cam, and would be perfect with a 3.73 - 4.10 gear

Bench Racer (BowtieBandit)
Bench Racer (BowtieBandit) Reader
3/15/11 9:54 p.m.

That's the exact cam I have in mind, I was just wondering if the cheaper used one would come closer to my budget requirements, but be still closer to what I'm after.

Also, would that exact Thumpr cam require different lifters?

SkinnyG Reader
3/15/11 10:01 p.m.

I'm in a similar boat for one of my current projects. OE roller SBC, and I want something ragged and choppy. Summit sells "Howards Cams" and I like these two (both 108° lobe centers):

180305-08 - Essentially a roller version of Lunati's Bracket Master II, probably gentler on your valvetrain.


180325-08 - a split grind, looks to be more aggressive valve opening, with some hefty lift.

I have not run either of them, however I will be buying one of them. I'll be running my factory roller lifters assuming they're any good. If it eats the cam, I'll cross that bridge when I get there.

Zomby woof
Zomby woof SuperDork
3/15/11 10:10 p.m.

Application? I like the second one.

We used to use that Bracket master II back in the 80's in everything. It was a great limited street stock track cam, and good on the street if you were light, or had the gear. Well, that, and they were only about $75

SkinnyG Reader
3/15/11 10:11 p.m.

Um..... application is an '87 Chevy Sprint. Shhhhhhhhh. It's "secret."

novaderrik HalfDork
3/15/11 10:13 p.m.

the only proper answer for a good all around street cam with a small block Chevy with Vortec head is "HOT cam".. go buy part number 12480002 from either your local GM dealer or any number of mail order places like Summit or Jegs..

build it with flat top pistons and steel shim head gaskets for about 10:1 compression, and you can indeed have it all. it will idle silky smooth at 800, but starts to get choppy at 750 and lower. it pulls like a fresh stock 350 from idle to about 3000 rpm, then just absoluutely takes off from there up to past 7000 rpm.

i had it in my 71 Nova, and it did just fine with the auto and 2.56 gears.. later, the T10 4 speed woke it up some, and then when i finally got the 3.70 gears in it, that car was an absolute riot. i could have all the fun i wanted, and still knock down 17mpg in daily driver mode with 89 octane in the tank. i think that if i'd ever gotten a TKO 5 speed for it like i wanted, well over 20mpg would have been easily doable.

i had a quadrajet carb but that cam was designed for the 96 Corvette LT4- so it's good to go with efi.

Gimp GRM+ Memberand Dork
3/15/11 10:19 p.m.

I admittedly didn't read anything above me.

I had a Comp Cams 268xe with the Vortec heads, and the motor was a blast.

Zomby woof
Zomby woof SuperDork
3/15/11 10:24 p.m.
SkinnyG wrote: Um..... application is an '87 Chevy Sprint. Shhhhhhhhh. It's "secret."

Light car, you don't have to worry about duration as much, but I like that second one. The "hot cam" is similar, but a half dozed degrees milder.

My Sprint still has the turbo 3 in it

Travis_K Dork
3/15/11 11:00 p.m.

The Thumpr cams seem like the muscle car version of hellaflush or body kits with big aluminum wings, etc. In other words, kinda dumb. I agree for what it sounds like you are looking for, the HOT cam sounds like a good idea. And at least last i looked, they were pretty cheap for a roller cam. Just do that, with vortec heads, good pistons and ARP hardware and you will have a decent engine.

Bench Racer (BowtieBandit)
Bench Racer (BowtieBandit) Reader
3/15/11 11:04 p.m.

In reply to Travis_K:

That's what I love about htis forum, you can be blunt, but never come off as being harsh.

Thank you.

Zomby woof
Zomby woof SuperDork
3/16/11 12:40 a.m.
Travis_K wrote: The Thumpr cams seem like the muscle car version of hellaflush or body kits with big aluminum wings, etc. In other words, kinda dumb.

Care to explain what you mean by that?

Travis_K Dork
3/16/11 2:08 a.m.

They are designed to make the engine idle rough on purpose, to me that is rather ricerish.

Zomby woof
Zomby woof SuperDork
3/16/11 3:31 a.m.

Back it up.

How do you figure that?

Rob_Mopar HalfDork
3/16/11 7:34 a.m.

I get what Travis is saying. It's not necessarily a 1:1 example, but I get it.

The Thumpr line was initially designed for cruise night guys who wanted the rumpity rump idle out of a big cammed motor but they didn't want the rest of the bad habits of an overcammed motor. The difference is Comp managed to make the Thumpr cams deliver some good power.

So from Travis' perspective somebody stuffing in a cam just to get the choppy sound but not building the rest to back it up isn't any different than guys tacking aluminum park benches on their trunk lids and slamming their suspensions to "look like a racecar" but the car not being able to live up to the look.

Or at lease that's what I took from it. And for full disclosure, the sound of a choppy cam in a high compression motor is music to my ears.

pres589 HalfDork
3/16/11 9:03 a.m.

Dyno plots of motors with the Thumpr cams seem to spell out that these things do make good power. Maybe that isn't good enough somehow...

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