I am currently looking to replace the camshaft in my SBC. I have a cam in mind and I want to make sure it perform well in my vehicle. I am concerned about it falling on its face coming off the line or just accelerating normally to pass someone. I am not looking for a high reving motor or high RPM power band, especially given my stats below. I am looking at a custom grind Elgin cam -270/280 advertised duration -225/230 duration at 0.050 -.495 lift -106 lobe separation Here are some stats of what I have -Early 70's 355 - Fresh rebuild -Flat top pistons - 10:1 compression -World product 2.02/1.6 SR heads 67CC chambers -NOS Fenton 3 duece manifold with 3 small base rochesters -open lakes pipes -electronic Pertronics distributor -350 auto trans with a stock converter -2140 pound car - soaking wet - lot heavier with driver -Ford 8" 3.25 gears with truetrac -8.20 x 15 rear tires - 30" diameter I do mostly street driving but it does see a fair amount of freeway driving. I am thinking that the 106 LSA will bring the power down low enough and bleed off cylinder pressure So what do you all think? Will I be happy with this cam?
If you put a converter in the car, somewhere around 2500-3000 stall, then it might work ok. But it'll be a dog if you don't.
Jim, is that due to the talller tire and higher gear ratio? I had a 33 pu fenderless with 30 inch tall hurst slicks, a powerglide, and and an early olds rear end with low 3 hundred gears, it wouldn't even turn the tires over. It had a 307 in it with 3 strombergs. I know it was a 307 but the final gearing killed any chances of that motor to make any low end power.
It's a matter of the cam duration vs. what rpm the engine is loaded at. You want the engine to be able to rev freely to at least the rpm where the cam "comes on", and with a cam that size it's gonna be around 2500 rpm. If you can feel the cam "come on" when you're driving, then you don't have the gearing/stall high enough, or you just need a smaller cam. With a stock converter and highway gearing, you need to cam the engine for low end torque, which is why stock cams have such short duration.
x2, i think you will be happier if you shorten up the duration a bit, stay under 220 @ ,050 and since it is light weight loosen the converter up a bit in the range of 2000 .
I would be happy as the devil with it, but it is a lumpy SOB and it is going to want to run in the upper RPM range. You will want to gear accordingly and like Squirrel already pointed out to you a converter with an altered stall is going to be a must have. Send me the cam shaft and I'll give you my already broken in and indusrtructable L-79 cam shaft we'll both be happy as a duck in mud.
Agreed. I'd pick a cam with a lobe center of at least 110, preferably 112. It would completely change the street manners. Right now, you don't have enough rear gear or converter to work with a lobe center that tight.
With the tire size and gear I have, which I am not willing to change at thi point, my normal operating RPM while driving down the road is around 1500-1800. If I get a stall in the 2500-3000 I will by driving around on the stall al the time and overheat the tranny, right? That would not be good. So if the 225' cam is too large, what would you suggest? I was originally told by Engle cams that a 230 at the 50 and a 108 LSA would come on at 1800, so I was thinking that the 225 and 106 would by slightly lower than that. I am being told that I need a short LSA and a larger duration because of the compression in the motor, despite the stock converter and low RPM need. The tighter LSA moves the torque lower in the in the RPM band and tightens up the power band.
I think that he is wanting to shorten up his lobe center because of his compression. I think that 106 is a little tight myself for most fellas, that cam is going to want to run spun tight. 112 isn't going to give him much overlap as a rule if any at all and overlap seems to be what he is after. 108-110 will have a little bit better manners and still give a little overlap at with that duration. ASnother thing to take into consideration is that with that cam and head combo that engine is going to wamt a lot of air, it won't breath to capacity with the described intake setup.
THis motor was originally in my Dad's truck and he switched cams in it and moved from a 110 to 112 LSA to improve idle. The specs on the 2 cams were pretty similar. With no other changes to the motor or converter the results were horrible. THe truck was a complete dog off the line after the cam swap. The 110 LSA was a monster on the street and the 112 was horrible. I need to keep a tight LSA. porknbeaner, what do you mean by run spun tight?
I am trying to pick a cam that will work with the motor and heads I have and work well on the street. It is not a race car, it is a street car. I am hoping ot build about 350 hp with the combination. The motor is a fresh rebuild when I got it so I am not wanting to change pistons or heads, etc. I have fresh 3.25 gears in the rear, so I don't want to change those. I do use the freeway a lot so that is why I used 3.25 in the rear. I am hoping that the lgiht weight of the car will be my saving grace here.
If the majority of your driving is below 1800 Rpms, why would you want a cam that will hurt you in that range and doesn't wake up until 2500 Rpms and up. spun tight means high RPM Squirrel knows his shit. As far as a wider LSA hurting your low end with same specs ? That doesn't make sense , what does it that it was degreed wrong, manufactures mess them up all the time.
Put way too much cam in it, apparently. When I see people who want to "tighten up the LSA" it's usually because they read in a magazine that that's how you get a "nasty idle" The OP is trying to put way too much lift and duration into a drivetrain completely unsuited for it... More people should cam shop only by reading the RPM range....that's really all you need to know in this case, you want a cam that will be in or very near the RPM specs at your cruising RPM's, which with your particular setup, would be a typical RV cam.
To me, I'm not a real fan of going with a tight lobe center cam to bleed compression unless it's a last-ditch effort and you have no other options. Your 10:1 compression is the perfect ratio, especially with the crappy gas nowadays that's loaded with alcohol. You've got a light car, and you're not going to put a ton of load on that motor. If it wants to ping, take a few degrees of timing out of it. Compression makes torque, and if you want power on the the bottom, it makes a huge difference. I still stand behind my earlier post about a 110 or 112 lobe center cam. A well-designed cam like a Lunati Voodoo 60102 or 60103 would wake that car up. I always hesitate posting on threads like this because there are so many variables involved in getting an engine to run at it's optimum. Things like timing, mixture, carburetor tuning, whether the cam was installed with any advance, etc. We can all give advice, but without seeing and hearing the car with my own eyes, it's hard to pinpoint the exact culprit. But in this case, the majority of your issues lie in the cam choice. I just re-read your initial post: Are you considering that Elgin cam, or does your engine currently have that cam installed? If it's just a consideration, what cam is in the engine right now?
Your engine shouldn't start climbing up on the cam until about 3K. maybe higher in the RPM range. You are going to want to keep your revs up with that cam and head configuration. Like say above 3K for just cruising. If you don't you are going to find that you are fouling plugs. With that cam you need to keep your revs up. I have a head and lower end combo that is close to yours, my compression is a little higher and my heads are aluminum. Even with my L-79 cam I normally run in the 3000 RPM range for my engine to be comfortable. With that cam shaft I would expect to run in the 4K plus range the majority of the time. That is why I suggested to gear accordingly, if you gear so that you are at a comfortable cruising speed when you are in your sweet spot you will have a nice ride. If you have to run 100 mph for your engine to be running correctly and you can only go 80 mph you have a problem. Does that make any sense?
It all makes perfect sense. But i am trying to bridge the gap between what is being said here and the suggestions the cam manufacturers are telling me. My request to them is that I want good power and something that gives me good low end power. I want the operating range of the cam to be 1500-5800. I am not stuck on this cam at all. I want the best cam I can find for low end power. A nasty idle would be great, but not the requirement. If this cam is not going to work well, which is exactly what I am hearing, what would be a good cam choice? Should I stick at 220 or be below that? The Voodo 60103 cam that Flat N Low suggested is actually bigger than the one I described in my first post and Lunati says the operating range is 1800-6200. I am trying to figure out why Lunati says 1800-6200 and everyone here is saying the cam won't wake up until almost 3000.
1800-6200 Is that voodoo? must be some kind of magic....they don't work like that in real life. You gotta trade one end for the other, and it sounds to me like you spend 99.9% of your time in the 1500-2000 rpm range, so that's where you want the cam to work well.
There are 2 cams that work good on the street. I have used both and the all "pull" off of idle. The first one is an Isky 280 Mega Hydraulic, a bit lopey but pulls hard. The second one is the Edelbrock Performer RPM Hydraulic less lopey, pulls hard as well. The Isky cam reallisticly needs a converter, however it does work with a stock converter, turn idle up a bit.
I read in Hotrod magazine a few years ago, that a "272" Crane cam in a 350 smallblock with a 2400-2800 stall conv. was the (Performance wise) most cam & converter combo to run on the street. I followed their advice and I like it. However, on a stock or near stock 350 build (modest daily driver), a 260 Crane was best with a stock or slightly higher converter. I took their advice on my other cars and was also satisfied! Also: For a "305" smallblock (Mostly stock build) I run a 252 Competition cam. I've built about 12 engines (3 cams mentioned) for friends and they were all happy with these combinations....just my two cents!
Exactly. That is why I posted to make sure I did not screw myself, since I was a little worried the cam was too big for my application. With all that sorted out, what would you suggest as a good cam for what I need. I appreciate all the help guys.
I would suggest calling some cam companies (I suggest Comp and Lunati) and see what they recommend. By the way, I'm very familiar with the 60103. It'll pull to 6000 with good springs, 6200 with beehive springs. It's good, snappy cam that pulls hard from 2200 on. Those current fast-ramp street designs that were the brainchild of Harold Brookshire work very, very well. I prefer roller cams, but if you're on a flat-tappet budget, they are a great choice.
You got a light vehicle and good compression. I am a real fan of the GM L-79 cam for a streeter. A lot of companies, I like the crane that I am running. Someone said that you can't buy a crane cam any more I haven't tried for several years. It has a mold lope and good manners. I run mine retarded a litle bit, not what most people will tell you to do. I am not suggesting that you run your cam retarded if you chose this particular cam shaft. Run it straight up or advanced a little bit, and it will perform better for you on the lower end. That is what I would do if I were in your situation. Something that we all should remember is that cam shaft selection is going to very on whomever tells you what they run. I have a tendency to do what has always worked for me, but other fellas will have as good success with something else.
Suggestion: Crane "Blueprint Series" 300 hp 327, or Comp Cams 260 series, very good driver cams, if you want a thumper you need gears, etc. that allow cruise in the cams RPM range.
I've always wondered about the advice to choose a street cam to run in the 1500-2000 rpm range, because that is the range you spend the most time in on the street. Ok, isn't that what the stock cam does? So, when you want to beat on it, it runs out a 2k?
A Comp 268H is a good all around grind for just about any reasonable SBC combo,,,reasonable means compression(heads,pistons),intake system,& gear ratio.
I have. In fact all the cams I have looked at have been what the cam companies have suggested. They all have been in the mid to high 220s duration at the 50. I think Comp cams is the only one that suggested a 220. I think my best bet may be the Voodoo cam at 219.
The XE 268H is only 1 degree smaller than the cam I described in my original post. So I would assume it would also be too big for my application. According to their dyno chart ( I know i can't assume my motor will mimic that chart) says i would be running around 125-150 HP or less at my cruising speed. The other thing to think about is when I do get on it (when I really need the power) it will shift down and I will be running it through the total RPM range. I think I need to lay out the total RPM range of where the motor runs when I am on it to see where exactly I need the most power. I know I am making a bigger deal of this than I need to but I don't want to be unhappy with this motor. So I am trying to make sure I make an educated informed decision on the cam choice.
The thing to remember on the first cam mentiioned is the lobe separation. it was the tight lobe separation that was going to be the killer. You take the same cam numbers and a 110-112 lobe separation and it tames it down a ton. With the tight lobe separation (this is not actually proper terminology but it works for this discussion) you get a lot of overlap one valve opening before the other is completely closed. That is good in a high rev situation but not for low end torque. In a perfect world you would be running all the time with your engine operating in the torque not above it or below it. That is where your engine is most efficient. I try to tune my street engines so that I am right near the bottom of my power band at cruising speed. The down side to that is that I suffer around town a bit, I am alway running in a lower gear. It doesn't bother me because that is the way I drive anyway. You may find that the cam that you like just needs a gear change for you to be comfortable with it. You have alrready chosen a gear so you will want to pattern your cam shaft to go with your gears, if you had already built the engine then you would just be patterning your gears to go with your engine. I know this for a fact before all is said and done you will make a decision and you will be able to make it all work together one way or another.
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