Cam swap

[noah_t]

Have a sbc 350 with a Holley contender 300-36 intake, Holley 650 carb, 1-5/8 hedman headers, dart 2 heads, 1.6 rocker arms, and was wondering what’s the best/biggest cam I can put in to make the most power? It’s in a 1986 k20 so I need big power to get it moving. Thanks

 

[paulrowe]

More specifically you need big torque to get it moving. A big lumpy high lift cam isn't going to help you. Check out the Comp Xtreme 4x4 or smaller Xtreme energy cams. What transmission are you running. Alot of guys seem to like the Comp 268H cams.

 

[idahovette]

Good call Paul. More torque would be better for that rig!!

 

[Rusty Nail]

Saw-weet!

+ 1,000 kickass cool points for running such an extremely awesome intake manifold.
Ku-dos. That is the best intake manifold ever made!

The long runners will naturally make torque in the low range.
The single pattern 268H will ALSO make good torque but is really out of breath near 4300 rpm and is FORTY YEARS OLD where your intake is aged the exact same but will readily support 7200 rpm in stock form.

Unfortunately I do not have a suggestion for a magical bump stick to generate the power of your dreams, I only forward the motion that if you use a 268H , you leave some 3,000 rpm on the table that will be looking for a camshaft to make a good home.

I own both a 268H AND a 300-36, but they perform with different engines, in different vehicles, used for different purposes because they do not compliment each other.
.

My ¢ 0.02 - keep the change. Camshaft technology has advanced a great deal since the 268H and those heads want better.

You must be registered for see images attach

 

[75gmck25]

The 268H is a good choice for a truck, but with your Dart heads you do have some other options. For good low end torque I would stay with similar duration to the 268H, but maybe you can find a more modern grind. That duration should feel strong when you need it, but will flatten out at higher rpm. However, how often do you drive at a higher RPM?

If you want to go for higher horsespower you could use more duration, but I would still go no more than about 225-230 @ .050 so that you keep the low end torque. If you look at the torque curve for this type of cam you may find that it has a flat torque curve that works just as well as the 268H at lower RPM, since you have decent flowing heads.

Do you know your compression? Something around 9.5 is usually a good compromise between good power and still being able to use regular gas. Something in the 10.0 range would allow you even more cam choices, but cost you more for premium fuel.

Bruce

 

[noah_t]

What do you guys think of a Howard’s cam 110245-10? The duration at 050 inch is 225/231. The duration is 278/284. The lift is .500/.510 and the operating range is 1600-5400.

 

[75gmck25]

I like the specs on that cam, but Howard's recommends a 2500 stall to get the rpm up quicker. What gear ratio do you have and what size tires? It shows a power band starting at 1600 rpm, but it might still be soft on the low end power if you have high ratio gears and/or big tires.

Also check the specs on your heads and springs to make sure they can handle that lift. .500 is the about point where some heads have limitations.

The Howards cam number you gave is also a retrofit roller cam. Is that what you plan to do? I just went through that drill with my SBC 350, and it adds quite a bit to your parts cost to use a retrofit roller cam.

Bruce

 

[noah_t]

What do you have to do with a retro fit cam? I’m a newbie to this stuff so I don’t know a whole lot. Also I have 4.10 gears with 35’s but was possibly planning to go 4.56’s and put a stall in

 

[75gmck25]

A retrofit roller cam requires retrofit roller lifters (more expensive than the lifters that came in factory roller blocks), and a cam button to prevent the cam from moving back and forth in the block. Most of the Howard's retrofit roller cam and lifter kits are about $670-680, vs. a standard hydraulic cam for about $150.

Unless you have the money budgeted for a roller cam conversion, I would stick with a standard hydraulic lifter cam. You could any of several Howards hydraulic cams.

4.10s and 35's should work fine, but 4.56's would be a little better. I'd probably stick with the 4.10 gears, but use a 2500 rpm stall converter.

Bruce

 

[bft305]

I am not super knowledgeable about cams and as others have said every setup is different. I will say I am running a small Lunati Voodoo cam. My 350 is mostly stock and I like this cam a lot! Very smooth running and good torque! I would probably say call the cam maker and ask for their suggestion

 

[75gmck25]

Since you seem to be early in the process of building up your engine, I have a few suggestions/comments.

I usually group cams something like this, based on the duration at .050.
About 195-200 - stock cams; runs smooth, good low end torque, runs out of steam about 4500 rpm. You can still improve it by using a dual plane intake and headers with duals.
About 210-214 - often called an RV cam; still decent low end torque and good idle, but more horsepower than stock. Works much better if you improve the intake and exhaust at the same time you swap cams. An RV cam, combined with a good intake and headers, is a very common upgrade.
About 220-225 - May work okay with stock low compression heads, but it really needs better heads to get the benefit. You should also have a high stall converter or low gears to get RPM up quickly, or it will have a very soft low end.
About 230+ - Don't even bother with these unless you have great flowing cylinder heads and higher compression. They will have a good rump-rump sound with a stock engine, but its all noise and no power increase.

For heads
Stock SBC iron heads are about 8.0-8.2 compression, and they don't flow that well. If you go beyond a simple "RV cam" upgrade, its best to plan for new heads. The price leader for good flowing new heads is the iron SBC Vortec. The 64cc chambers bring compression up about 1 point, and they flow much better than any of the older heads. However, they do have limits for total lift unless they are modified, and its also common to find junkyard heads that have cracks from overheating. There are also now several budget aluminum heads that come close to the price of the iron Vortec, especially if you pay to have the Vortec heads modified for higher lift.

For intake
Its hard to beat the value of common aluminum intake manifolds like the Edelbrock Performer or Performer RPM. You can move up the chain and get better flowing intake manifolds, but unless you have a really high performance engine you probably don't need it. Stay away from single plane manifolds that are designed for high RPM, and if you drive in cold weather you don't want an air gap manifold.

Headers
Long tube headers are best, and you can buy them at several price points. Picking one with thicker flanges and thicker header tubes will make it last longer and be less prone to leaks. Also take a look at the collector design because some have improved it beyond stock and they are easier to install and seal to your exhaust.

Exhaust
You always want dual exhausts, even if you don't use headers. The optimum size for most SBCs is probably 2.5", but most aftermarket systems use 2.25" pipe. Even 2" pipe will work for a stock engine.
A balance tube or H-pipe makes a small improvement in performance, and the tone is usually more like a traditional muscle car. X-pipes may sometimes flow a little better than H, but they are a PIA to fit, and the tone gets raspier. An H-pipe may also be effective at lowering the noise level if you have loud mufflers.
Straight through mufflers usually flow the best, but you have to buy good ones if you don't want it to be loud. Turbo mufflers are a common budget choice, since you can buy relatively cheap ones and still get a good sound that is not too obnoxious. Chambered mufflers like Flowmaster also work well, but may drone at constant speeds.

Bruce

 

[MikeB]

You said that you want a cam that will get the truck moving. Does that mean you would like more power right off idle?

What are the specs of the cam you have now?

What is the engine's compression ratio? And how big are the intake runners on the Dart heads? Anything more than around 185cc is not conducive to low RPM power in a 350.

 

[Rusty Nail]

Those are both knowledgable guys that made good comments.
I have been biting my tongue because I heard once that it is better to remain silent and let others WONDER if you are stupid, rather than open your mouth and remove all doubt.
Somebody has to be the devil's advocate, right?

xc_hide_links_from_guests_guests_error_hide_media

There simply MUST BE more information given about the cylinder heads. Details are required dude..any "advice" taken regarding camshaft selection simply cannot be given much weight, in part, because compression ratio is so very,very critical.
I feel it only responsible to assume a stock, OE cast, dished piston.
See? We NEED more details. Look in the or a, cylinder and TRY to determine if a stock piston is present...I think that will help.

Look, I LIKE single pattern camshafts because I believe and trust them. They make sense to me and I understand that. There is no guess work - it's math.
If I offer a suggestion it WILL be single pattern or damn near.
The intake manifold is limitless, but is it a daily driver that will see stop and go traffic in between hanging out at stoplights?
Intended RPM operating range + vacuum friendliness are WAY TOO important to guess at without knowing the Compression Ratio. You will most-assuredly have to put in some work in order to ask a bunch of faceless strangers on the internet such a question before you can ever get an answer worth a damn IN REAL LIFE.

4.10s
35s
Limitless intake
1.5/8 Headers
Dual exhaust
Holley 650 is a limiting factor and kind of rare, are you SUURRREE it's not a 600 or a 670? This caps your potential because you didn't say 750.
Unknown intention - oh yeah!
1.6 rockers -are you CERTAIN?
1986 K20 with unknown stall speed. MUST assume stock 1800? I don't know.

No emissions concern?

Roman Emperor Marcus Aurelius said, “The impediment to action advances action. What stands in the way becomes the way.”

 

[MikeB]

Rusty Nail -- Good advice. Glad you came out of your shell!

However, don't dis the 650. Holley's old school #80783C is one of my all time favorite carbs, and certainly not a limiting factor on all but the hottest of hot 350s.

And since you like single pattern cams, what are your thoughts in general about the Comp 268H? I've always heard it was a great street cam, good up to 5500 RPM or so with an otherwise stock engine. And I think it is (or was) one of their biggest sellers.

 

[Rusty Nail]

Thank you Mr.B.

There is a 268H in the Blazer's 408 and very truthfully sir, I do not have enough experience running it to post a thorough review. I can easily recall being disappointed in how quickly I thought it ran out of breath simply riding down the highway across town. I think 5500 is far too generous of a number given the 3.73s on 33s with crap compression and a crap Performer intake on crap 882 heads WITH a bad Quadrajet. Power fell like a rock off a cliff at whatever RPM it was...I didn't even have a tack but it was a significant action. Like hitting a wall but that could have been any number of possibilities then.
Saying much more about how a 268H ran in my 408 would NOT be fair to anyone as my truck was not in a running condition to meet my standard at that time in general it seems like a bad choice for me because it doesn't appear to match the way that EYE drive... I didn't pick it.

It'll be back though - that engine - it'll find home in my C20 before you know it AND I have since began to build that engine around THAT camshaft. Ask me later. It's gonna get a fair shot and WILL see it's day in court.

I have two single pattern cams in three engines. The 362 in my SS has a ERSON AH-8 in it.
Yes I said ERSON. Sig. Erson.

I'm not knocking a Holley 650, I simply am not convinced dude has one - because they are rather uncommon.
Mike you even agreed with my statement about it being a limiting factor. Because it is but yeah, chances are better that it will not limit the OP's engine, yet that fact remains and the statement stands as-is.
It's even MORE limiting should we come to find out dude really has a 600.

That only brings us back to not having enough information to offer a responsible opinion, but he asked us anyway.

Post count +1.

One day I WILL install the 350c.i./350hp - L46 cam of my dreams into something. I think it's .450/.460 ?
Look , I get that I almost contradict myself with the whole technology bit , but I WANT TO use an L46 cam. I didn't ask for anyone's opinion lol...welcome to the internet, kid. L46 cam + 300-36 = sbc heaven. So what they got it right forty years ago? You can't improve perfection or make a rounder wheel.



It's REALLY NOT the cam selection what is so important, OP.

Listen up! This part is critical..

Matching the parts TO EACH OTHER is far more imperative.