HawkHunter

Im installing a new cam into my newly re-built 383 and have two questions...

First, ive got the old cam out and the new one burning a hole in the box... the cam has @ .050 243 intake 257 exaust and 107 degrees lobe separation and .500 valve lift (intake) .486 (exaust). I have been told that you can advance or retard the timing of the cam to produce more torque or more horse power. I wish for more torque as I only have a 2600 stall right now and dont really want to step up to a 2800/3000 stall due to my RPMs on the way to the race track... ie. on the street ;p I have gear drive... how many teeth should I move my cam while installing it and in which direction to tweek the maximum amount of torque out of my stroker and lockup at highway cruise speed. (top gear is my cam)


My second question is related. I have heard that I could get a lot better power out of a Holley carburettor than a Edelbrock. I've looked at a few application charts and Holley's mechanical double pumper application chart suggests a 1050+ which I think is way out to lunch... So from what I've read it appears that an 800 would work great for me? A friend recommended that I go with a 750 MAX... He even said that the Edelbrock 600 that's on there right now would be fine. According to the volumetric efficiency charts and equations, I've come up with numbers anywhere between 599 and 1050... So any insight here would be much appreciated (similar setups?)

Engine parts so far which may be helpful for answering my questions
350 csb (obviously)
76cc smogger heads
30 over dome top -6.26cc forged aluminum pistons (should make 10.259:1 static compression with a .015 head gasket 4.1 bore size and 6.731 dynamic)
570 connecting rods
scat crank 375 stroke with 350 main journals
compcam springs and lifters (p/n 986-16 and 858-16)
2600 stall converter on a turbo 400
my 350 was running before i took it apart with a 600cfm edelbrock carb and a rpm performer intake. I plan to re-use the intake. I plan on replacing the carburettor with a Holley or Demon with mechanical secondaries instead of vacuum.

cheers,
Trev

Sonix

iTrader: (1)

I don't have time to read or comment now, but what the heck cam is that? That looks like the perfect setup for me, (if I didn't buy the z-25 from isky...)
cough up a brand and part number

HawkHunter

here's the cam spec card that came with it

Sonix

iTrader: (1)

oh, a thumper, nevermind....
Still, decent specs for my setup, especially if I go with nitrous. Too bad it's just a "show" cam.

Yea, you'll want something in the range of 800cfm. You probably won't make use of the full 800cfm, until you replace the heads, but no sense in replacing the carb twice.

Look at a holley, demon, etc, mechanical double pumper carb.

HawkHunter

yeah - a "show cam" with 243 intake duration and 257 exaust. (295/313 advertised) I guess the only thing that could be improved is the lobe seperation to give it a little bit more "real cam" power.

anyways - back to the camshaft installation - I phone an engine shop and got the answer to my first question. I thought I'd share the response for all. If you install the camshaft counter clockwise a few degrees, you can increase your torque output. If you install it clockwise a few degrees, you can increase your horsepower output. We're talking extreme tweaking here... 2-4 degrees... You need to buy a timing gear or chain/sproket set that allows you to advance or retard the timing a bit. It is done with an offset hole in the bushing that the gear lines up with. There should be enough play in the bolts and holes that fasten your gear or sprocket to the cam.

Thanks for the advice on the carburettor!

have fun!
Trev

SpitotRs305

well a thumper is a show cam... especailly with smogger junk for heads ahd a 6.731 dynamic... they only way to fix that thumper cam would be to switch iit with a cam designed to make power instead of sound cool...

get some new 64cc heads
lose those domed pistons
get your CR into the 10.5:1 area
and get your self the XE274-284
and a 750DP

just a suggestion... i am SURE that engine will rip on the butt dyno but you might be dissapointed if you ever show up at a real one...

HawkHunter

The camshaft you suggested would provide 7.266 dynamic... we're talking 0.535 difference in dynamic compression ratio (same static of 10.3:1)... Which could make the difference of me being able to run on pump gas vs race fuel. Mind you, if I went with 64cc heads also I'd be in the 12:1 CR area and then should probably switch to alcohol, forged crank, stainless valves etc... I would like the car to run on pump gas... Appreciate the input, but I think ill pass.

Cheers,
Trev

Edit: your durations are pretty crappy on that cam too, 230/236 @ 106 lobe sep isnt even compairable to a 243/257 @ 107 lobe sep... sorry... The 1108 summit racing cam would be a far better example of a "real cam" but they dont show their intake close ABDC timing, so i cant calculate the dynmaic compression.. it has 244/254 durations @ 117 lobe sep and 510/533 valve lift instead of the 326/326 on your suggested cam and the crappy 334/324 on mine

SpitotRs305

what are you talking about?
the XE274 with 10.5:1 CR gives like 8.3:1 DCR
and a change in dynamic is much greater than the same change in static...

and if you noticed i told you to junk those domed pistons... in favor of a flat top so that you would be able to get CR down into the 10s with a 64cc head and get rid of the dome pistons tendency to detonate...

you understand that the engine you have there will be a dog below 4k and fall off about 5k...

you need to read the cam shaft article then maybe you would understand what those specs really mean
heres the xe274 http://www.compcams.com/Cam_Specs/Ca...y.aspx?csid=87

no kidding the durations are lower... shorter durations help build cylinder pressure which makes POWER!

i mean jeez this is the 21s century here you seem to be stuck in the 70's with those cams you wont like either of your cams on the street and i doubt you could even drive that on the street without 4.56s and a 3500 stall

but then again i am just some dumb sweaty rednek to interested in making power than blowing money on a cam just to swap it out once i realize i made a mistake

Sonix

iTrader: (1)

The thumpers are made and sold as "show cams". They are sold (and designed) to make your car sound racey. They will make a car good and fast, but you need to set up the rest of the car to match. It'll have good midrange with that LSA, but the idle will be TERRIBLE.
I'm pretty sure our camshafts spin clockwise, so if you *advance* it clockwise, you'll get it to "come on the cam" earlier, and get a bit more torque, vs "retarding the cam" back a few degrees CCW, you'd get more top end.

That's a big cam, so be prepared. ie. you will need a vacuum reserve can.

The xe274 is on a 110 LSA. Lower LSA cams are somewhat rare nowadays. They are only suited to carbed cars, and guys who want to make good midrange torque. The wider LSA tends to make the "tabletop" power curve that most guys are after these days. I prefer to have my car screaming bloody murder at about 4500RPM though, so that's why I dipped down a smidge on LSA.

HawkHunter

I am switching to mechanical secondaries for that reason... and i have an electric vacuum pump to run the brake booster and heater controls, which i was considering ditching anyways. Like you said I am setting up the rest of this car to match the cam.

I will talk with the guy at Custom Auto Rebuilders in Prince George here to make sure he understood I wanted to make torque rather than more top end power. Thanks for that.

spitotrs305 - increasing compression with a short cam like that is great for superchargers and turbos, but you want valve overlap especially at high RPMs (natrually aspirated that is) for the top end of the track. I have yet to see a n/a pro street running anything less than a 305 advertised cam... a friend's 55 belair is running a 292/320 @ .050 (advertised 322/360) and runs 8.00's all day long... My point is these cams have their place... i dont want to run a new set of 64cc heads for $500 each when a set of dome tops that do the same thing to my compression ratio run about $400 for the set of 8... + maybe $65 for moly rings... I wasnt trying to start an argument here... i thanked you for your suggestion and tried to politely explain why I wasnt interested... jeez... oh and I plan to have huge secondaries to dump massive amounts of fuel on those dome tops to help combat the detonation - thanks for reminding me to point that out... and about the rednek thing... you said it - not me

cheers,
Trev

Sonix

iTrader: (1)

Prince george?!? haha, now you expect us to believe you *aren't*
a red-neck?? hahaha, j/k, my buddy Collin just moved away from there. Which car did you have up there? Ever take it to the track? Collin said one guy with a thirdgen was running low 12's or something with a 350 and edelbrock heads I think, I wanted to know more about that guys combo.

The domed pistons - they interrupt the flame path somewhat. They are a less than ideal way to achieve a set compression ratio. It's preferable to have

d dish pistons - and small heads
flat tops and medium heads
domes and big heads

in that order. If you have the choice that is.

I think spitot was giving you advice to maximize your torque under the curve, assuming you weren't going to rev it high, and assuming it was a street car. A 292/300 @.050" car isn't a street car, and would be a BEAR to drive around. Everything has it's place, and your current cam is not a daily driver cam. As long as you realize it'd suck to use when driving around a parking lot, then I think we can continue with suggestions, knowing your intended use of the car. oh, also the smogger heads will limit your flow, and kill the top end. So if you cam is meant for top end, and your heads for low end .... well, you get the *worst* of both worlds. That's what spitot was trying to say, in a .... less than diplomatic way

You'll have a great midrange, i'll admit that. But I think you'll struggle with a bit of detonation (domes and low efficiency smoggers make it more det prone) in the midrange. I think your setup isn't quite as optimum as it could be right now. Have you done much port work to the heads at all?

SpitotRs305

this is what i am saying... by running such a large overlap cam with those crappy heads you are losing all of your torque in the way of det. you will have to pull timing which that cam wont like yeah it might make some hp up high if you ever get it up there but those heads will choke it... havent heard of a stock 76cc head that will breathe where you will be spinning this engine...

basically you are taking a stock engine throwing domed pistons in it and a huge cam... recipe for disaster but you know better...

oh and dumping massive amounts of fuel with your already bad quench ontop of domed pistons you will be picking up the pieces for miles....



no your right i am a rednek but i have a/c...

HawkHunter

yeah, no. My daily driver is my S-class 92 Mercedes-Benz 300SEL... I drive this to the race track and back... sometimes i drive it to the odd car show (4-6 times a year 12 times a year maybe including the race track) The car you are refering to is i think "Glen's" car. It was a grey 3rd gen. and i think it's for sale. Ill get back to you on that. It won the NHRA summit series at our track... He was so consistant... it was un-believable... never a breakdown...

my car (seen in this post) runs 14's with the stock cam and a 383 - but it's packing quite a bit of weight. Since that picture I cleaned up the wiring (the red wires that charge the 24 volt hydraulic system in the trunk) and ripped the headliner taking my kids in and out of the back seat (aww crap...)

I'm confident this cam should be building power by at least 3000 RPM and carry up to 6250 RPM where it wants to shift gears now.

edit: forgot to say that the heads have to go to the machine shop for surfacing and some minor work to accomidate the larger dual valve springs. Perhaps i could change out the valves and guides at the same time to help it breath a little better than 2". I remember seeing posts on this subject already - ill look there...

cheers,
Trev