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New cam/heads vs Supercharger $$$$$$$

S

sscam69

Guest
Well you can read about the supercharger on the "supercharger post"

Here is my delima.

I have close to $800 for some upgrades to the engine and can have $2k by the end of summer.I am getting the feeling the cam is more feasible than the supercharger as you might of have read in the post.

The engine has just been rebuilt but it does not put out enough power. I had asked for a hi lift cam didn't happen. There was confusion at the shop. Anyways I am really happy with the build as they did a good job. I am seeking at least 400hp--400ft-lbs of torque on a streetable engine.

I have a lot of good components already.

Dual exhaust
Single plane manifold (can purchase a dual plane if necessary for streetability)
Headers
Holley street avenger carb (670 cfm)
and other goodies.....

rpounds changed out the cam with the block inside the engine. I had never heard of anybody doing this and a big light bulb went off in my head.

I can afford the cam, lifters, springs and pushrods necessary for the performance of the cam. I figured while I was at it put in some new (better I think) heads but not necessary. What I mean by this is I think the heads are the stock heads but not sure (where can i find the casting #'s). What I do know is that they are ported and have 2.02/1.6 valves. The heads are going to require machine work for the springs anyways so I figured get some better flowing heads.

Does anybody know the flow numbers for stock heads? I would change the heads under the assumption that they flow better than the originals.

Obviously Vortech heads are the way to go on my budget. They can easily get expensive with the machine work though. 3-angle back cut, pocketed and ported, new valves 2.02-1.6, and machine work for the springs. I figure these heads will cost me the $800 alone.

As far as the work is concerned I will be doing it myself to save cash and can get some help from some gearhead friends. Thier payments consist of a few six packs.

reminds me just like the commercial

New camshaft for your engine $200 dollars

Beer for your friends as payment for their help $50

400 horses at your command PRICELESS.....LOL

Ok back to the post

Camshafts I am considering

Comp Cams
#Magnum 292H
Hydraulic flat tappet duration 244int/244exh @.05" with .501/.501 lift respectively.

#Xtreme Energy
Hydraulic Flat Tappet duration 240int/246exh @.05 .507/.510 lift respectively

any suggestions or comments on what I should do. I am always willing to hear out experienced folk.

sscam69
 
S

sscam69

Guest
Oh as for the selection of the cams I used the Dyno desktop software and looked at the performance curves. The magnum cam will get me closer to what I am looking for. I will post picks of the curves tommorow as I have some homework to do.

sscam69
 
B

Bullitt

Guest
Well, being that you live in Texas and face emissions testing, perhaps the heads/cam combo would be easier. I can already see the inspectors face when eyeing the blower, especially if it's polished. :eek I'm thinking of a supercharger, as well. First, being a big-block owner, aluminum heads are running about $1800 for me. Seond, is that with a lower compression ratio, I will be able to run more boost than those with higher ratios. Third, is dollar per horsepower. With a valvetrain upgrade, heads and the associated parts and supplies, I might be spending the same or more as compared to forced induction. I have to crunch the numbers, but I doubt I'll see the boost power I could gain.

On camshafts, I also am considering the Magnum series from Comp Cams, albeit for a 454. They seem to have a broader RPM range that I want to operate at. Though, I'm looking at the 280H versus the 292. Talk to Comp and get their opinion, also. Like you mentioned in the other post, I have to look into space limitations and hood clearance. Then again, I don't have A/C or smog equipment.

Sorry for not being any help. Decisions, decisions.....

--Bullitt
 
S

sscam69

Guest
More help than you know

NO bullit you are help. We are both in the same position looking at the same options.

As for emissions at an extra $30 and the car is passed garaunteed! The fellow who owned the car before me stripped all that stuff off anyways so it doesnt matter.

Here are the specs and the curves for the simulations I ran

sscam69
 
B

Bullitt

Guest
I like the torque span of the 275DEH the most. You give up horses to the 284H, but you beat it everywhere on torque with the 275. The 292 was not as impressive, as I would have hoped. Does the calculating software take into consideration the altitude elevation of El Paso? I'm sure that will be of great concern. What's the percentage of volumetric efficency that it calcualates at, also?

--Bullitt
 
S

sscam69

Guest
I have to check that out but what I did do was input the data from an engine that chevy hi-performance put together and the simulation was off by about 5-10Hp and same on the torque. They peak power and torque were off by 200 rpm. Though its not exact its kinda hard to be with so many processes going on in these engines.

But the software does get close enough that you can get a REALLY good idea of what its going to do.

Give me the specs on your big block and I will input the data see what it does.

OH one thing I was not to sure on what the intake centerline is on these cams just the lobe separation angle.

The dual energy was a last minute addition to the simulation. I was just curious and it turned out to be the probably the most streetable of the three with that low end torque. I will never see anything above 6k so thats my window for me.

sscam69
 
R

rpounds

Guest
Changing out the cam is not a difficult job (in my humble opinion) and can reap some rewards as long as it is matched with the other components used in the build. The hottest cam you can buy will do you no good if the engine can't breathe. Therefore, I would take a long look at swapping out the heads. If you want a really noticable difference in power, the heads are the key.

I am not sure of the flow numbers for stock 79 heads, but I doubt that they flow as well as aftermarket heads. May I offer a couple of tips for head selection? Okay, here goes . . .

Remember that, as in the case of camshafts, bigger is not always better. It really depends on where you want to develop power. Realize that a cam with long duration and a lot of overlap will cause your power band to move higher in the RPM range. The same is true of cylinder heads . . . larger intake/exhaust ports will usually move the torque curve higher in the RPM range. This is because at lower RPMs, smaller intake ports keep the air/fuel mixture flowing at a higher speed, which means more efficient filling of the cylinders. That in turn = power (torque) at a lower RPM range. That can be good or bad . . . depends on what you want to do with the engine, along with other variables such as final drive gear ratio, converter stall speed (in the case of automatics), etc. If you want to develop your power in a streetable range, I would stick with heads of no more than 180cc intake ports, assuming that you are running a stock torque converer, standard 3.08 or so gearing and such.

Cylinder head manufacturers offer a couple of different combustion chamber sizes for most all of their aftermarket heads. Be very careful in the selection of this variable. You really need to know the deck height . . . or at the very least, the current compression ratio of the engine, along with the combustion chamber size of your current heads. If you know the deck height of your pistons at top dead center, then it is fairly simple to calculate the compression ratio with different combustion chamber sizes. Add to this an optimal quench of .035-.040 if you want to get the most out of a head swap.

Put all of this information together in order to come up with the compression ratio that you would like to run, keeping in mind that pump gas has some very definite limitations which vary depending upon whether you are running cast iron or aluminum heads.

It's a lot to consider. However, a good set of aftermarket heads cost $1000 complete on up . . . you want to make sure that you do it right the first time.

Good luck on your search for power!!
 
R

rpounds

Guest
PS . . . I hope you are running headers . . . the best cylinder heads in the world still need to breathe . . .
 
S

sscam69

Guest
I was actually thinking of putting together a complete engine together.

And in that case a 383 stroker with the dual energy cam and vortech heads performer manifold.

That way I know exactly what I am dealing with. But again there comes that budget right behind it. I would probably not be able to do that until I get a real job.

But what you did mention I have taken into account. The only thing that is really holding me back is the compression ratio of that engine. I would have to pull the heads and CC them. Get a measurement of the compressed gasket and CC them see how much space there is between the top of the deck and top of the piston and go from there. There comes that nasty pre-ignition problem that you always have to worry about.

Hey thats a pretty tight quench area rpounds! Most freak out at .04 let alone .035. The vortechs have a 170cc intake port and 64cc chamber. And are the most affordable for my budget.

You are right about having some good heads. That brings up another option. How about just swapping the heads and see how the car improves? Thats another alternative. The car does feel strong on the low end and is still pullying at the top end so maybe the bottle neck on my current setup is the heads.

Hey rpounds thanks for the insight and the tips. I was hoping to get someone with experience and let me know if I was going in the right direction or not.

sscam69

can you calculate compression ration using a compression tester. I have one and I tested one of the cylinders and got about 120psi
 
R

rpounds

Guest
You can go here to find a corresponding ratio for your compression tester reading.

http://www.smokemup.com/utilities/calc/pressure_ratio2.cfm

However, bear in mind that cam profile has an affect on dynamic compression. Dynamic does not necessarily match static compression. For instance, if you have a cam with an appreciable amount of overlap, you will lose compression at lower RPMs. When doing a compression test, the engine is turning at the speed of the starter motor. If you have some overlap, the readings will be low.

As far as quench distance, most performance builders will tell you to run .038-.040 quench distance, although this number needs to grow with aluminum connecting rods.

For the best of both worlds in a small block, I think it is pretty hard to beat a well built 383 stroker.

As far as heads are concerned, it depends on what you are running right now. If they are stock chevy heads, I can give you some flow numbers that I have collected if you will provide me with the casting number from the heads. The number should be cast in between the valves underneath the valve covers. And yes, it is very possible that your stock heads are robbing some power. There seem to be some real myths floating around out there about the 'efficiency' of some of the stock chevy castings. However, mid to late 70's heads were 'smogger' castings that were a major culprit in lowering engine outputs, so it is possible that there is a huge potential for HP gain by simply swapping out heads (while paying close attention to compression ratio and quench). Edelbrock techs claim 30-50 bolt on HP with Performer heads on a stock 350 SBC. However, they fail to site TQ numbers, which in my opinion, is more important for a daily driven car.

Anyhow, I hope that some of this helps.
 
S

sscam69

Guest
I agree on that low end torque being useful on a street car. I consider that a rule of thumb. I won't be able to get you those numbers til the weekend.

Do you suggest a particular gasket to get that quench area assuming a zero deck height?

After running that calculation I got approx. a 9.5 compression ratio which is not to bad. The problem is I don't know the head chamber volume. That brought up another question.

I ran the test by just turning the engine not actually running it. Is this the correct procedure? Like you mentioned of you have a lot of overlap you are not going to get a good reading. Actually you are getting a good reading of the compression but for that rpm BUT what about the top end? That will affect the compression as a result of that same overlap. So do I turn the engine on and rev it to see what reading I get? You mentioned static and dynamic compression. I am assuming static would be the compression you get from just turning the crank by hand and dynamic would be with the thing running. I would figure dynamic is more for obvious reasons.

I still have time to figure this out. Right now I am debating wether to start grad school or work. I figure which ever comes first but the end is coming near. I graduate on May 13. If I stay for grad school I am going to swap the heads first and buy a dual plane manifold and see how it works out. Of course I am going to dyno it before to get a baseline. I am sure it will improve but we weill see how much. If it is still not to my satisfaction I will swap out that cam for that dual energy. I really like the low end torque curve.

If I go work I am going to put that stroker together with a blower. OH YEAH!!!!

sscam69
 
R

rpounds

Guest
By static compression, I'm talking about what the compression shows by simply doing the math. Static compression will always vary from dynamic compression, if for nothing else, the math does not take into account any leakage that may occur past the rings, cam overlap, etc.

Compression testing is normally done with a warm engine, the coil disconnected and spinning the engine with the starter. Let the cylinder pump up on the compression stroke 4 or 5 times (you can hear and feel when that particular cylinder comes up on it's compression stroke if you have the other spark plugs out). This will give you your dynamic compression. Then you can calculate from this actual pressure (PSI) what your dynamic compression ratio is.

For a good look at quench, go here:

http://www.kb-silvolite.com/page05.htm

This is an often overlooked area for backyard mechanics like us. I guess I'm as guilty as the next guy for running down to the auto parts store, asking for a head gasket set and ignoring these rules. Last engine I put together (a 4.3L V-6 a few years ago), my ol' man happened to ask me about quench. I must have given him a dumb look, cuz he took it upon himself to explain the whole thing. Then he proceeded to ask me why I hadn't listened to him better when I was a kid working in his shop. :)

Anyway, take a look at the article. It is pretty helpful. Oh, I might mention here also that if you are wanting to run a fairly high compression ratio, the quench becomes more important in fighting pre-ignition (detonation).

Ron
 
S

sscam69

Guest
I just caught on!

I just barely learned about quench a while back.

I have learned about most of the mechanics through Chevy Hi-Perofmance, Super Chevy and Car Craft. CHP just had a really good article on quench and I have read in other articles that .04 is getting close to risky because of play in the piston when it reaches TDC. You know how pesky inertia works sometimes.

I have read in situations like these you want to go with Hypereutectic pistons because of the low expansion rate. This allows you to use tighter clearances with the piston and close in on a tighter quench area. Someone at one time mentioned that forged was the way to go. What do you think?

So assuming zero deck the quench is dependent on thickness of the compressed gasket?

I will have those casting numbers on those heads for you tommorow. I am really curious as to what they are.

We never listen to our pops the first time LOL.

Frank

p.s. that link did not want to work
 
R

rpounds

Guest
Yep, Frank. You are exactly right. The pistons that you use have a definite impact on where you should set quench. Connecting rods also. I think I mentioned in a previous post that the optimum quench has to change based on a number of factors, pistons, connecting rod construction, etc. It's best to follow a piston manufacturer's recommendations for a variety of reasons.

As far as the engine that you are currently running, I doubt that you have a zero deck hieght right now. More than likely, you are down in the hole a bit. Unless you have specific specs on the parts that are in the engine right now, you'll need to check the deck hieght with a depth micrometer. Usually with a stock engine, you're not going to be able to get anywhere close to .040, unless the block has been decked.

There are numerous articles on the internet concerning this. And a lot of it comes from guys a lot more knowedgeable than me. I guess I kind of started out with the idea that you really should pay some attention to quench in order to get the most out of a new set of heads (or your old ones for that matter). However, I wouldn't get too concerned if you end up at .060 or so.

Ron
 

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