400 sbc cam swap.... help on choosing a cam ?

[awsomeears]

Okay folks time for a different cam, current cam is ' Unknow ' but the motor makes 20" of vacuum so its probably stock...

400 SBC rebuilt
Pistons are .40over about 3/16 dish, basically a fresh updated stock short block.
Heads are aluminum Edelbrock RPM 6071 head, 2.02 intake and 1.60 exhaust with a camber of 70cc
Weiand Tunnel Ram and two holley 450's
4-speed
2800lbs
4:11 Gears

As it sits now the car runs great, runs cool and burns ZERO oil :headbang

Friend had a 400sbc and mentioned to stick with small base circle to be safe as the rods can hit the cam, I have never swapped a cam but hey why not. I installed my own heads adjusted all rockers and as I mentioned it runs great. I'm confident, just not CHOOSING a cam

Quick search I can see guys are sticking with .460 lift to no more then .490

Also Comp Extreme Energy or Comp thumper cam KITS were recommended

Any help would be great :thumbsup

MY Goal would be to get a nice sound out of this sweet 3" stainless setup RON welded up and most of all get some more power, I know I'm not working with a high compression motor but any upgrade from a stock cam would be nice.

[Irish]

For flat tappet cams, I am a big fan of Howard's cams.

[Prince Valiant]

Well, a stock cam 400 would actually probably pull mid to high 20's of vacuum...but certainly the cam is smaller than your want/need.

Right off the bat, the thumpr cams are probably the safest bets...they'll give you the sound you desire, while still giving you very good driveability.

But what I'd recommend is getting an idea of what kind of cylinder pressure you're developing right now...also, where does it feel like the cam is making power to right now?

Both questions can help give an idea of what size cam you're running currently (knowing the approx head flow of eddy heads, knowing you've got 400 ci's, can help give an idea of of what kind of power range a given cam will give you...thus it's size), and how much larger one can go without making it an absolute dog (if you're only running 120 psi cylinder pressure, I wouldn't recommend changing to a bigger cam!)

Also, do you know if it's HYD flat tappet or solid flat tappet?

[awsomeears]

There Hydraulic tappet for sure as I installed these heads, I did a compression check sheets in the garage I'll check later...

[Irish]

Prince... it's a small block chevy. Walk away!

[Irish]

Pick a cam that is matched to your induction, converter, and gear. Getting all these parts to match in the same rpm operating range is paramount in a mild sbc.

For instance, I had a healthy .030 327, in my S10. It had an intake operating in the 1500-6500 operating range. The heads were good from 2-7200, the converter was not optimal at the time. (Sold the truck before I addressed it.)
4:10 gears. 26 1/2" tall tire.

The cam I used was good from 3200-7200, .510 lift, 235-240's @.050", 110 lobe separation

http://www.howardscams.com/index.php/chevrolet-v8/chevrolet-v8-262-400-non-oe-hydraulic-roller-1957-1996

Plenty of choices...

Only old men that don't want to have to spend time to pic a legit cam runs that off the shelf thumper bullshit.

[WickedSix]

lower compression ratio will exaggerate the 'lope' sound at idle... iirc the thumpr cams have been shown to provide more torque on street bound machines... something in the 280-290 advertised is probably a same bet for what you are looking for. What is your rocker ratio? Have the edelbrock heads been cut for longer valves and springs? What is max for those heads if they are stock? A Cam like the thumper in the .500 lift range (with stock rocker ratio) can get more lift with a ratio increase if you aren't taking advantage of the lift avalable in the heads.

[Irish]

My compression ratio was roughly 10-1. Truck ran a 13.8 at 104, 2.1 60' due to traction issues, with the above mentioned cam. A good converter and a sticky tire would have put that truck into the 12's, easily.

I wouldn't worry too much about how it "sounds", that is old school "3/4" cam mentality.

Pick the most aggressive cam that you could get away with, that will produce the most power, while still maintaining street-ability.

If you go with a cookie-cutter cam, you may want to look at the Edelbrock RPM cam matched for your heads.

[Irish]

.... DPost

[bikedad]

Pick a cam that is matched to your induction, converter, and gear. Getting all these parts to match in the same rpm operating range is paramount in a mild sbc.

For instance, I had a healthy .030 327, in my S10. It had an intake operating in the 1500-6500 operating range. The heads were good from 2-7200, the converter was not optimal at the time. (Sold the truck before I addressed it.)
4:10 gears. 26 1/2" tall tire.

The cam I used was good from 3200-7200, .510 lift, 235-240's @.050", 110 lobe separation

http://www.howardscams.com/index.php/chevrolet-v8/chevrolet-v8-262-400-non-oe-hydraulic-roller-1957-1996

Plenty of choices...

Only old men that don't want to have to spend time to pic a legit cam runs that off the shelf thumper bullshit.
^^This is pretty much what you need to look at.
Also determine, are you going to race it once in awhile? Drive it mostly on street? Etc. Low end torque is fun off the line but maddening when it falls flat on it's face when you get to third gear (auto or stick). If all you want is rumpity rump then the Thumper cams will accomplish that. I will say this, once addicted to Horsepower Crack it's tough to get off it. :durr

Howards is made right here in Wisconsin and have been doing grinds for a long time. (I have Howards rods in my motor) You can call them and go over what you want to accomplish and what your current specs are and they can recommend something for you.

[Prince Valiant]

Prince... it's a small block chevy. Walk away!Don't worry, I won't :)

Brad can choose to consider my advice or not...it's his call. He can simply take a ride in my junk to see what my knowledge is worth.

Here's the thing...we know what brad's induction (tunnel ram), converter (none...it's a 4 speed), and gear (4:10's) are (and for the record, we also know his eddy heads are equipped w/ valve springs that allow for cams with as much as .575 lift, so no need to consider springs as a limiting component) as well as the number of cubic inches we're dealing with (all cam rpm's ranges are based on 350 ci engine size, smaller or larger affects operating ranges). But we're missing two things to make the best recommendation for a cam given his stated goal (a choppy idle)...and that's his current cylinder pressure and what he in fact has now in there for a cam.

This is a combo that with the right compression could easily live with 250+ @ .050 duration with narrower LSA's in the 106-108 range...but given that it's almost certain he's got a small cam, he probably doesn't have a ton of compression (a small cam w/ 10.5:1 compression would probably have cylinder pressures in the 210+ range, ie, race gas territory).

Brad, perhaps the BEST way to go forward is that you know you want to change the cam...get the cylinder pressure you're currently making, and go ahead and pull the current cam you know you don't want. Measure the lobe lifts and get an approximate idea of what cam you've got (based on the lifts, it wouldn't be hard to go out and find a cam w/ the same lobe lifts and from there figure out what you've got) and go from there.

It means more down time, which sucks, but ensures a much better result for your dollar.

[WickedSix]

he can run a dial indicator on a rocker to get the cam specs without pulling whole engine apartto get a baseline

[Prince Valiant]

he can run a dial indicator on a rocker to get the cam specs without pulling whole engine apartto get a baselinewith HYD cam, he'd have to do it on the lifter or find a way to get a solid lifter in place of a hydraulic...either way, he's taking off the intake manifold. I guess you could just try to bleed out the lifter....not sure how accurate it would be....

But since he know he doesn't want the current cam, why not get it out and measure it with a micrometer?

[jbiscuit]

Those thumper cams are designed for fiberglass hot rods that want to add rumbly idle to a ZZ4 crate engine.

[WickedSix]

he could also pull the cam and find out it has flat lobes from a bad break-in....

I'm just advocating the least invasive method of 'generally' defining what the bump stick is... I'd rather pull a valve cover and have the choice to keep the vehicle running..but that is my preferance

[Irish]

Yea, didn't read your book PV...

I would contact the cam manufacturer of your choosing, tell them what you have, what you want the car to do, and go from there.. Clearly, there are no "experts" in this thread..

That would be the best way to go.

[Prince Valiant]

Yea, didn't read your book PV...Since I didn't write it for you, why would I care? :)

[Irish]

Since I didn't write it for you, why would I care? :)

Man, go fill a balloon with that hot air..

[awsomeears]

Re-did my compression to double check.

All 8 are between 175-180psi all are super close. I was expecting lower to be honest because of my heads being 70cc

I'm going to get #1 cylinder to TDC and remove my rocker and take a reading with no hydraulic load on it to get an exact measurement, but I did get a measurement from my magnetic dial indicator, I got 2.20 rough or two full rotations on my indicator and and extra 20.

Hope that makes fucking sense :)

Thanks for the info so far !

[-stew-]

Don't worry, I won't :)

Brad can choose to consider my advice or not...it's his call. He can simply take a ride in my junk to see what my knowledge is worth.


Or he can read all about your knowledge and motor building skills in this thread...

http://www.brewcitymuscle.com/forum/showthread.php?53593-Oil-Leak-carb-tune-etc/page6&highlight=rings

[73MACH]

:popcorn

[awsomeears]

Lets keep this clean, I know Chris outside of BCM and I think highly of him regardless of any BCM shit storm...

Carry on !

[Prince Valiant]

Or he can read all about your knowledge and motor building skills in this thread...

http://www.brewcitymuscle.com/forum/showthread.php?53593-Oil-Leak-carb-tune-etc/page6&highlight=ringsah, but it's cam picking skills brad wants...the dude still still running the basic combo I picked (even though it goal for the combo and gears were considerably different than as the car sits now...). Oh, and who was the first one correct (by a long shot) while picking against himself saying that something was very wrong with the short-block? Um, me. My knowledge (and honesty) is just fine...

Brad, as far as your cam selection goes:
1) I have no idea what you measured, lol. Maybe someone else knows...but let's assume it is a small cam.
2) Your cylinder pressures not horrible...not terribly high, but not godawfully low...good news is, you can probably fairly safely go to a decent size cam without too much worry.


As far as the comp XE series goes (and other similar aggressive ramp cams like voodoo, etc), while they're among the best HYD flat-tappet cams to make power with, it doesn't take much to get to your self-imposed .490 lift limit. Basically the comp XE 274 and you're there at the limit. The comparable voodoo cam of that size and you're over .500. But even if power was your only goal, you'd probably still be better off going with a less aggressive ramp given your lift constraints.

I still don't understand the thumpr hate...and still see them as a reasonable alternative. They're not the most powerful cam, but for a given size, they're likely to sound the best while still giving you considerably more performance than you've got now. For a comparable sized XE/voodoo type cam, you'd probably give up 10-15hp (prob ~3% less power) with a thumpr, but sound much tougher. If sound is important, these are real alternatives. Also consider the nostalgia cam series...they more or less try to recreate the sound of classic cams from the past, while maintaining modern cam drivability.

Looking through both Howards and Comp cams, here were two I liked the most based on your goals:

Howards cam 112591-08, CL112591-08: total duration: 285 295 Dur @ .050: 231 241 valve lift: .470 .470 LSA:108
Should give a good lopey idle and works with lower compression of less than 10:1

Comp Cams 280 AH-8, part #12-325-4: total duration: 280/288 dur @ .050: 232/237 valve lift: .483/.483, LSA: 108. Even though outwardly this cam looks similar, it'd likely act bigger, lopier, peak later in the rev range since this cam is not ground with a 4 degree advance as the howards is...but you could also simply install this cam w/ 4 degrees advance for similar results....

Basically I think the Howard's cam gives you most everything you want. It should work with the mild engine specs, sound tough, and still deliver good driveability...

[Irish]

What a joke! Glad we could entertain.

*takes a bow

[Irish]

Lets keep this clean, I know Chris outside of BCM and I think highly of him regardless of any BCM shit storm...

Carry on !

I'm sure Korndog did too! :)

[DNT H8]

No experience with Howard, Thumper I wouldn't buy on clearance, Comp's XE line are exceptional cams but love the high RPM's.

If I can offer a humble piece of advice don't waste your $$ on a off the shelf cam... I will never buy one again! Custom grind is the only way to go for $50 more than a high end OTS cam. You get it to your setup and drive style...

Custom cam OP!

[WickedSix]

a quick calculation puts your compression, given ideal conditions, in the 11:1-12:1 range

P1*V1 = P2*V2 becomes V1/V2 = P2/P1 where V1/V2 = CR = 175/14.7 = 11.9 (assuming the intake stroke reaches atmospheric pressure equilibrium)

What did you measure that was 2.2 inches?

[Prince Valiant]

I'm confused on this...

while compression ratio and cylinder pressures are interrelated, I was under the impression that there was no way calculate compression ratio's (as you represent) from cylinder pressures. Given that different cams will yield differing valve opening and closing events, overlap, etc, causing a vehicle with the same compression ratio to have differing cylinder pressures...

[Irish]

Custom grind is the only way to go for $50 more than a high end OTS cam. You get it to your setup and drive style...

Custom cam OP!

This!!! ^^^^



I wish the ignore button was available in Tapatalk, had to go into Safari to use it lol!

[awsomeears]

I just contacted Howards cam for at least a off the shelf cam as a starting point, I should get a response in a day or two...

[MY FYN 79]

You should be concerned with dynamic compression and not static compression. Pat Kelley has an excellent writeup online about the differences. There are also calculators online.

I would suggest buying a cam for HP/TQ and not sound. If your cam is tame now, you'll be happy with the sound of a larger cam that is designed for HP/TQ, not some insulting crap that Comp makes.

[WickedSix]

Prince,

often the valve opening and closing events in a engine will yield lower cylinder psi than the actualy static compression ratio. Inaddition the cylinder may not be completely sealed during the compression test which leads to lower numbers, sometimes this is counteracted by cranking several revolution in order to obtain the highest number. The quick calculation is a representation of ideal gas law where temperature is held constant (isothermal). It is a bit of an oversimplication of thermodynamics involved and is not as reliable as calculating the comp ratio using the blueprint of the engine...but if you don't know what all is there it can give you an idea of where the engine sits.

[WhatsADSM]

I'm confused on this...

while compression ratio and cylinder pressures are interrelated, I was under the impression that there was no way calculate compression ratio's (as you represent) from cylinder pressures. Given that different cams will yield differing valve opening and closing events, overlap, etc, causing a vehicle with the same compression ratio to have differing cylinder pressures...

There isn't.

[awsomeears]

Howards cam for there off the shelf recommended this : http://www.summitracing.com/parts/hrs-cl112431-08

Hydraulic Flat Tappet, Advertised Duration 277/277, Lift .450/.450, Chevy, Small Block, Kit

[Prince Valiant]

Are you going to order this?

It's specs aren't too different from what I first ran in the valiant...should give you a great midrange pull...

[awsomeears]

Not sure really, just doing a bunch of research, definitely understanding this stuff...

[Prince Valiant]

what other cams are you leaning toward/looking at?

[awsomeears]

what other cams are you leaning toward/looking at?

The Howards that I just mentioned and the ISKY http://www.summitracing.com/parts/isk-201281

Now I have the 1.6 ratio rockers so that adds a little bit and my math should be correct .


Isky .485/1.5 = 323.33 / 1.6 = .517 Lift

Howard .450/1.5 = 300/1.6 = .480 Lift

Talking with all sort of people/threads, and were all in the same ball park,

[Prince Valiant]

b/w the two, that isky should definitely be a bit rowdier...and without knowing what you've got now, other than it making 20 inches of vacuum, it's a pretty safe bet to be a bit bigger than what you've got now.

looking at the two cams, though they may seem fairly similar, one needs to keep in mind the intake centerline as well when making comparisons b/w two cams. This gives one an idea of whether the cam is ground with advance (or retarded) already ground in or not...most cams are ground with some advance when installed "straight up".

Basically to figure out whether or not advance is ground in or not (it commonly is), of if it's ground with the cam retarded (very rare), subtract the LSA from the intake lobe's centerline. So if a cam has an LSA of 108 but a lobe centerline of 104 degrees, then you have a cam with 4 degrees of advance in it installed "straight up".

For every 4 degrees of advance, you move the powerband up (sooner) ~ 500 rpm. Likewise, for every 4 degrees of retard, you move the powerband back ~ 500rpm. And of course, advance or retard will not only affect the power curve, but the sound as well...advancing a cam smooths out the idle, retarding makes it lopier/choppier.

But in this case, not only is the iskier bigger duration wise, while ground on same LSA (giving it more overlap which will contribute to a "tougher sound" and generally more, but peakier power), it's also ground with 2 degrees less advance than the howard's cam (106 intake centerline w/ 108 lsa vs 104 intake centerline w/ 108 lsa).

So not only will the isky act bigger and give more top end power because it's bigger...but because it doesn't have as much advance ground in either.

This isn't to say the isky is the best choice though...avg power/tq may go down due to decreased low-end, etc....

One option might be to go with the howards and if you don't like how it behaves installed "straight up", then retard the cam timing a bit and see how you like it then (not exactly an easy, straight up thing). There are some timing chain sets that have matching marks that correlate to 4 degrees advance, straight up, or 4 degrees retard (these are all relative since the only way to KNOW if the cam is installed as such is to degree the cam). There are also offset keyways that allow for advancing/retarding a cam. I would imagine that there are also advanceable/retardable timing chain sets frequently seen in the sports compact world.

Given, again, I assume, that you don't have power brakes, pretty short gears, lightweight vehicle with aggressive intake/etc and a manual trans, I don't think you'd be too poorly off going with the isky. You're low rpm/bottom end might be a little soft, but that's what the gears are for, and the power you need to get off the line can be stored nicely in your flywheel anyways. And it'll certainly sound pretty tough to boot.

[jbiscuit]

Don't forget he is running a tunnel ram on this car also. Which will also factor in to the lack of low end power. If it were me, I would want to up the compression quite a bit before going through all this work for just a cam swap. If you just want more "lump" from the cam, then thats fine. But if you want more performance, then I would want this thing around 11:1 on pump fuel and lots more cam. Thats just me. Pistons are cheap for a SBC since there are lots of options