I’m embarking on my first ever engine rebuild of the stock 350 SB. I want to change the Cam to a nice choppy Cam and I’m looking at comp cam motha’ thumpr. Since this part is so deep in the engine i only want to do it once. Are comp cams good, specifically the motha’ thumpr

?

 

I see zero point in the Mother Thumpr cams.......they make a chop but at a serious vacuum loss.....just like any other cam......
I can see the dish pistons in your photo and can tell you that a seriously "choppy" cam is not in the cards......you will tank the DCR and end up with an engine that runs like a slug......
The Comp 268H or XE262 is as much cam as you can really use on an 8 to 1 compression engine......

Jebby

 

Listen to what Jebby is saying. You do not want a ****** thumper cam unless you want a slug of a car.

 

I’m def listening. I appreciate the knowledge. I’ll look into those 2 other cams.

 

Thumpr cams are 100% sound over power. Do you want a fast car or one that sounds bad but gets smoked by every little POS out there?

 

What can i do to this 350 to get the power and the sound that I’m looking for?

 

You're gonna have to tell us how much you're looking for and what kind of budget you're looking at.

 

i have a budget of like $2k for parts, and im looking for the most i can get out of it. Reliabilty, power and throaty growl

 

Are Comp Cams good? Yes. Number one seller in the world.
Are the Thumper Cams any good? Meh! All sound and no go. The Thumpers are the best stereo cams. Great sound but not enough watts for performance..
Serious builders do not use these. (or they wish they didn't)

What others are saying is the camshaft needs certain compression ratios, certain rear gearing, looser torque converter and better head flow numbers to make it operate correctly. Your bone-stock mill, has none of these..

Just about every cam in any camshaft catalog will state the prerequisites needed for the series of camshafts. Choose wisely.

Two thousand dollar budget? H - m - m - m
Flat tappet cam, lifters, timing chain set: $240 ish
Headers, ceramic coated, true dual exhaust: maybe $600
Used Edelbrock Performer 2101 Intake Manifold from EBay $75.
Budget minded aluminum heads $1,000 +
All gaskets, distributor up grade, moneys gone.

 

headers will help with sound and actually help get power but it will
eat into 2k.
Headman makes good ones.
What engine? L-48 or L-82
post your engine pad stamp.

 

Swap your factory 76cc heads for a set of rebuilt 64cc L31 5.7 Vortec heads(Ebay $650-ish), add a Summit Racing spread bore dual plane Vortech pattern intake($180), one of the smaller cams Jebby suggested with new lifters($400) and put a rebuilt non-computer Q-Jet($???) on top. Total price should be around $1500, leaving you with money for headers and a better exhaust. You'll definitely feel the difference. Of course that's assuming your $2K budget is just for upgrades and not any block machining or internal parts.

 

https://www.streetmusclemag.com/tech...ound-of-power/ read this

 

I replaced mine with xe262 cam,I haven’t driven it much but cranked it up several times,and it sounds great.

 

And while they're off the engine, cut them a bit for more compression... as much as 9.5:1 (not sure how far you can go with these heads though). Do ALL your math and know for sure. Then you can use a bigger cam, and make more power more efficiently. Personally, i'd just drop in a complete Vortec 350. I see them running here (where i live) for $5-600, and this is NOT the place to buy cheap stuff. You guys have yards down there with like, 5 to choose from...

And headers dont have to be expensive. There are 4 sets ov used SBC Corvette headers here for $100-600, including a set ov Super Comps for about 1/3 new price. Everything you need is available used, though i'd definitely go with a brand new cam.

 

The author of that article is a salesman. He makes money selling bogus stories. (from 13 yrs ago no less)
That is about the time (2010) Thumpers took off in the industry. Then customers figured out there are much better choices.

Note the sentence about the dyno that says:
Unless noted all parts are stock.
So, you read down the list of parts and everything is not stock except the dizzy.

 

Some dirty back of the napkin math puts its around there without any cutting though there will be some variance based on head gasket thickness.
5700/8/8.2 = 86.8cc(chamber + gasket + deckheight)
86.8 - 12(head cc difference)= 74.8
5700/8/74.8 = 9.52:1 compression

Again, not super scientific but a close estimate.

In either case, without a spring upgrade and additional machining, the limit is <0.500 lift with the Vortec heads. Since we have no specifics of 4 speed or auto I'd stick to a cam around the size Jebby mentioned. The big advantage of a full Vortec swap is those are factory roller blocks. Without sacrificing drivability, or introducing vacuum & converter stall speed issues, you can get a good bit more power out of a roller cam vs a flat tappet that have similar lift/duration specs thanks to the rollers potentially more aggressive ramp.

 

I will say that all David Freidburger, Steve Dulcich, and Steve Brule of Engine Masters have all stated that they are surprised how well the Thumpr series performs on their show. You can watch episodes of Engine Masters where they compare a bunch of cams, including Thumprs and Motha Thumprs. With that being said though, there are always cams that would work better depending on your combination of parts.

 

I like those guys, and Rich Holdener... but come on... this is a business. Those are little more than (well-)paid ads. I've seen this **** since i started buying mags in the mid-80's. Those articles and videos are so full ov holes its hard to take anything in them seriously.

The thing is, most guys, as in the vast majority ov people who modify their cars, are just playing around anyways. They're ambling around to car shows, doing occasional 'braap's beside Mr. Civic at the light, and cooking tires for their buds. I would bet my car that the majority ov them would take a wicked looking/sounding car over a slightly less wicked looking/sounding car that is a lot faster. How many times has a guy like Jebby insisted to buy the 268H cam, and yet they go and buy the 285UHLkill-X anyways? I've quit arguing with these types ov enthusiasts. I dont understand it, so i just keep my mouth shut. Its no different than the bodybuilders in a gym. Its the same amount ov work to be big AND strong... as it is to just be big. yet... pretty much none ov them do the former. They just wanna be Arnold... all show. Its ALL about appearances. The Thumpr is a great cam for that. It'll make your car well faster than stock. It allows you to overcam a car (like soooooooooo many people did in the 70's and 80's) without actually ruining your drive. The racers among us bristle, but its what the people want. I wont buy one... i'm that (other kind ov) idiot that will spend an extra $100 for 5 more HP...

Again, like the bodybuilder analogy... if these guys only understood that a truly well-built, powerful engine will sound AWESOME too... they might just try it.

(then again... i doubt it...)

 

Are you MEASURING those chambers? Inputting ALL the little forgotten numbers? I dont know about Chevy, but Mopar was notoriously baked on their chamber numbers... typically about 10cc off, or a point ov compression. Their tolerances were all over the map. Maybe i'm just ****, but i'd be aiming for an exact number (whatever that may be) especially if its pushing the envelope on pump gas.

Thats just the beginning ov the Vortec advantages. I honestly dont know why people even do mild builds out ov non-Vortec smallblocks anymore (numbers matching aside obviously). I want a 454 Vortec in mine...

 

The Thumpr series does make good power......but not real good power......
I tried one in a friends 355 Tunnel Ram/Dart 180 head setup in a 37 Ford about 12 years ago.......it made good power like I say but it had like 6-7 inches of vacuum.....and I was like "Why does this exist"?
There are better cams out there that make a good "Fairgrounds Sound".....the 280 Magnum and 292 Magnum from Comp are the first two that come to mind.......the other is the Edelbrock Torker cam which is sold by Elgin too as Pt# E1180P......this cam makes damn good power and has 69 degrees of overlap for a seriously healthy sound.......
But the key to running all of these Fairground cams is compression....a lot of it......don't even attempt to run a cam that has larger duration than 230@.050 with out at least 10 to 1 compression......
I just built a 350 1982 CFI short block (freshened-hone and rings/bearings) then bolted 1968 64cc heads on it (mild cleanup on bowls) with a steel shim .015 head gasket for 10.3 to 1 with the Elgin E1180P cam.......I also put a small 6.75 balancer and 153 tooth flywheel on it (much lighter) with a 10.5 clutch for a 56' Chevy 4 speed......a small 600cfm Holley on a 54 year old Weiand WCQV aluminum intake.....curved HEI.....this little beast revved quick and would drag that shoebox down the road with authority.......probably a low 14/high 13 second car due to a **** stock gear.......but the sound was pretty damn cool, throttle response was awesome........This is very representative of the small block world pre-1995 when heads were plain unavailable.....and if they were, no one knew about them or had money to buy them......probably made about 380-390hp......damn good power for pile of parts I had laying around.
The point is that the compression made this all work.......guys in the 60's and 70's would stick a healthy cam and intake on a 350/300 and it would run like a raped ape because it had 10.25 to 1 stock (more like 9.9 to 1 actual).........you will note I put a small carb on this.....that is a signature of mine.....small carbs signal better and if you are not class racing you will never miss a larger one.......I took the single feed 600 and added the secondary metering block and a yellow spring for the vacuum secondary....jetting was 69/76 with a 5.5 power valve......
The compression boosts torque throughout the power band and keeps cylinder pressure up at and just off idle to rev quick and signal the carb well.........
In the 80's...we all put hog *** cams in our engines and they ran like turds because by 1987 when I got my license....high compression engines had been dead for 17 years.......during this time, Comp released the 268H cam.....which was designed for 8 to 1 engines by shortening the overlap but keeping a decent duration and lift.......Comp sold 100,000 of these cams and it is arguable that Comp wouldn't exist today if not for this cam......it plain works......

Jebby