Building a 350...what heads to use?

[instantkevin]

Right now i have a 6 cylinder camaro (shown below). In the next few weeks, I will start building a performance 350 to put into it. I noticed that Edelbrock (on their website) lists all of their cylinder heads and intake manifolds as being compatible with certain year engines. For example, they list the Performer RPM heads only for engines made up to 1986. there are other heads for '87 and later engines. Does this mean that if I were to pull a 350 block out of a 92 Camaro I would have to use the other heads and not the Performer RPM? Or are they interchangable? Are all heads for the fuel injection era, '87-present, centerbolt heads? This may seem like a dumb question, but I'm curious and I don't want to spend money on things I can't use.

Also here is my planned setup.. tell me what you think.
- Edelbrock performer intake manifold #2101, 600cfm carb #1405, perf. plus camshaft #2102. possibly edelbrock performer heads #60909 but not sure. with this setup I should be around 330hp, but its my understanding that if I use different heads I could be around 400hp+. Haven't completed my research yet. What heads do you techs recommend? Or what would you recommend to get me to around 400hp without a blower?

I plan on using a used factory 350 block, probably not bored, stiffer pushrods, and ARP connecting rod bolts. also rebuild 700R4 to handle V8 power with parts from www.transmissionhead.com

[curtis73]

Confirm this with others (or Edelbrock), but late model heads use a different bolt angle on the intake than old heads. They list their heads and intakes as bolt-on pieces and they assume that you would be putting their aluminum heads on with the original iron intake. We know better, but they have to cover their butts.

The old intakes/heads have bolt holes that go straight into the heads (about 45 degrees from straight down) The newer style heads have bolt holes that angle down to improve gasket sealing. It is fine to switch styles, but if you buy late model heads, just buy the intake and valve cover that is designed for them. Otherwise, they all are "interchangable" meaning that they will physically work if you use the right gaskets and components. One call to Edelbrock, FelPro, Summit, Jegs, or PAW will get you on the right track.

As far as your head choice, you have many options. Here are a couple sites for you. they list heads and their factory flow ratings. Here's the best way to describe it:

1) find your desired hp and the rpm you want for the hp peak.

2) have your cam's peak valve lift (lobe lift times rocker ratio)

3) visit the bottom of the first site below to determine the intake flow you need to achieve your goals.

4) visit all of the sites to find the heads that flow what you want at the lift your cam gives.

An example: I was building a 454. I wanted to make 400-450 hp at about 6000 rpms which required about 250 cfms. By visiting those sites I found that stock 049 big block heads flowed 250 cfms as cast. Perfect. Their chambers were of similar size to my current heads so compression was right on the money.

For 300-400 hp, I wouldn't go with $1000 aluminum heads. I would go with the $200 factory heads of your choice. Vortec heads are the absolute perfect street heads. One of the things you want to look for is the most flow you can get with the smallest port volume. Flow makes HP, small ports (and therefore high velocity) make torque. The "best" heads would be ones that provide your peak flow with the smallest port volume. Vortec heads are supreme in this area. They are the late model versions and require the angled bolting, but here's my recipe for you.

Vortec heads, out of the box, bolted on. Edelbrock 2116 Performer vortec manifold. I might suggest a 1406 carb just for the electric choke. Its an extra $20 but you'll thank me for it later. Edelbrock makes a wonderfully easy to tune carb that performs very well. An even slightly better choice is a Q-jet. Trust me on one thing. Pick up the phone, call Jet Performance, order a Q-jet and tell them your cam, intake, and head choice. They will send you the worlds most perfect carb that you can literally bolt on and know that you're getting the best mileage and performance you can get. I've tested this several times. I used a BG street demon on a caddy 500 and got a respectable 390 hp and 13 mpgs. I ordered a Q-jet from Jet and I now get 412 hp and 18 mpgs, and the carb was the ONLY change. The Q-jet is just a better design in all areas. Don't try to set it up yourself. I'm a seasoned tuner and I don't have luck with Q-jets You'll hear terms like Quadra-junk and Quadra Bog, but they are derived from the fact that they are very complicted to tune. There is a reason that Edelbrock makes their Performer intakes with a Q-jet style plenum. I would use a Comp Cams Xtreme Energy cam in an XE-268H grind. The Xtreme Energy line uses the most recent technology to maximize low end cylinder pressures and high end breathing. The bottom line is that they can use less duration to make more top end hp while making less sacrifice to the low end torque. Its a flatter torque curve and it pays off big time.

That combo should get you easily to the 390-410 range. Your horsepower should peak at about 6000 rpms, and should put you squarely dancing around 400 hp. Your torque will have to peak around 4000 to get that kind of power, so a converter stall increase is definitely in order. The torque curve is relatively flat up to 4000 (it will also dance around 350-400 ft-lbs) so I would suggest a 2800 stall converter. You'll lose a good deal of MPGs, but if you want 400 hp my guess is you don't really care about mpgs Sticking with the 600 cfm carb will help. Your peak requirement would only be about 620 cfms anyway and its always better to go to the next smaller size than your requirement. Vortec heads!!! Just do it.

http://users.erols.com/srweiss/tablehdc.htm

http://www.chevyhiperformance.com/techarticles/41598/

[instantkevin]

Thank you... you have provided me with a whole lot of useful info. It all made sense. But, the part that I'm still trying to demystify is how to match the heads, cam, and intake manifold. I don't want to put together a system that is not optimal for what I am spending. Naturally, like everyone else, I want the most power for my dollar. And I won't get there by randomly choosing parts from catalogs just because the specs look good (although they will give me more power). Basically I am wondering, if I were a molecule of air traveling through the carb, thru the intake, what cam specs would I want for optimal power, what specs on the heads. and if i change the cam, what would I loose and/or gain with a shorter/longer duration or higher/lower lift. You have pretty much answered the question on the heads. But there seems like there should be a set of equations or rules that I can use to find the best outcome for my particular setup. I use to have a program on my (now crashed) computer that would allow me to plug in some numbers (like engine size, tire diameter, rpm, etc) and it would estimate horespower, 1/4 mile times, etc. I'm looking for something similar related to heads, cam, and intake. Do you know of anything like that? How do you choose your combination? Does anyone know of anything like that. I might be making it more complicated than it actually is.

P.S. do you estimate that to be 390-410hp at the flywheel or wheels? If flywheel, what do you think it would be at the wheels?

P.S. 2 No, mileage is not a huge issue. I'm only going to live once, might as well enjoy it. Plus I should be getting a motorcycle in about a year or so. So that will help offset spending on gas.

[curtis73]

You've asked a question that I'm not sure how to answer Choosing parts based on targeted outputs. Its a little complicated to describe but simple in theory.

The first and most important part is a realistic idea of what you want. A 700 hp screaming engine is not smart in a 75 Impala Wagon that weighs 5000 lbs, but you obviously already know that. That part of your quest is already established.

For the most part, things will become clear as you read up on things. Comp Cams website is pretty comprehensive as far as tech is concerned. They'll list targeted RPM ranges based on durations. For instance, if you look under their listings for small block chevy, they'll have descriptions of its performance. Their most mild might say something like, "stock converter, 8-9 compresion, good mileage, stock replacement, 800-4000 rpms." The next one might say, "RV and towing, stock converter with 3 series gears, 1000-5000 rpms." The next might say, "mild stall converter, 3.90 gears, 1800-6000 rpms." After that you'll see things like "street/strip," and "race only," and other things.

The biggest choice is determining what is most important to you. For some its mileage, others its cheap gas and therefore compression, for others its being able to operate emissions/vacuum equipment. Then its possible to decide your target HP and your target RPM. For the most part (and this is a Curtis rule, not a standard) is that one HP per CI is always streetable. Another Curtis idea is that with obvious exceptions, most factory assemblies will spin to 6000 rpms without exploding. Those two rules tend to go hand in hand since most carefully chosen combinations will make 1.1 hp per CI or better at about 6000 rpms. You are starting with a 350, so 400 hp (if done well) can be a daily-driver decent mileage engine without sacrificing much at all. So, lets assume you want to make power in the 1000-6000 rpm range. You can now visit your cam's website and choose a cam based on that range. Then visit your favorite intake's site and choose an intake based on that range. When it comes to intakes there are huge grey areas. Your particular 350/400 target suggests either a Performer or Performer RPM intake. For the street I always choose the less radical intake. It will cost you 5 hp, but it makes up for itself in easy cold starts, low end torque, and hood clearance. Now you can visit those head sites and see how much head flow is required to support those HP numbers. Above all, I suggest buying Desktop Dyno or a similar dyno software program. Read the manual and directions from start to finish since they offer invaluable tips for making the software accurate. I used Desktop Dyno to help my recomendations for you.

Its important to recognize that these dyno programs are not entirely accurate as far as predicting nominal output, but they use volumetric theory to determine efficiency. They disregard things like friction and assume things like a proper fuel mix, but they will show you a pretty accurate estimate of your output.

I start with a target output, which is partly from experience. I know that I could build a 900-hp 350, but it will cost me $10,000 and won't make power until 6000 rpms. That's why I stick to my standard rule of 1.1 hp per CI for the mild street engine on basic over-the-counter technology. You'll learn as you go along from experience, but start with a target. If your target is too lofty you'll realize it as you go through the process. You'll get to a point where you see that in order to support that kind of horsepower its going to require $1600 heads and a cam that makes no power below 3000.

There are certain things to remember as you go through this. You know that Quality of airflow is as important as Quantity. It stands to reason therefore that a small block Chevy 350 has more streetable power potential than, say an International Harvester 345. The aftermarket has poured billions into chevy design and they've pushed the limits of the big flow/small port possibilities. The IH engine had three head castings all of which sucked. In order to get them to flow the same as a well designed Edelbrock chevy head, they would have to be massively ported and therefore make the ports big and velocity slow. It is therefore harder to make 1.1 hp/ CI in the IH engine without killing low end torque and therefore streetability.

Once you've visited all of your websites adn determined your targets you can plug the parameters into your dyno simulation software. Sometimes you are pleasantly surprised. Other times you may realize you are below where you want to be. Then you can go back and adjust things. Choose a larger cam and intake and see what it does to your curves. The important thing is that all the components must match or it will hurt drivability and power. The good news is that components like cams and intakes are published with their peak power ranges. Matching them is easy.

[instantkevin]

Thanks for the useful info. You have been very helpful. I think I'll make some good choices on the parts I'll soon be buying. I probably will go with vortec heads. where would you recommend buying them from at reasonable prices? What are some engine combinations that you have built, if any?

[curtis73]

Vortec heads can be bought from GM performance parts, or any parts counter, but I think Ebay is your source. If you want new heads, I suggest calling Dal Slabaugh at 1-877-448-5451. He's at Van DeVere Pontiac Buick in Akron OH, so just ask for Dal in parts. He is the hookup for car parts on the cheap (or at least less than retail) I'm not the expert on them, but do a search for them on the net and you can get casting numbers, etc. They were widely used in trucks for the last several years of the SBC so they should be a very common salvage yard item. I suggest you do more steps of research beyond me since there is rumor of a "bad" vortec head that doesn't flow quite like the others. You can get them as either bare castings or complete assemblies. I would probably buy the bare castings and assemble them since they probably don't have the springs you want anyway. Vortec heads won't take really high lift numbers so you have two choices; limit your lift and supplement flow with duration, or have a machine shop turn down the valve guides so you can have more lift. The latter is more expensive, but not much and it prevents you from wasting time and power on less than ideal cam numbers.

I've built three engines. The first was a rebuilt pontiac 389 with a very mild cam that was one step up from stock. It was pretty awesome and ran forever. The second was a Caddy 500 that I had built with a 204/210 cam that is exceedingly mild in that much displacement. It peaked its torque right around idle (no kidding) and was completely done by 3800 rpms. It acted more like a diesel. The third is still in progress. Its a 454 with a 212/218 cam and some nice head flow. It should make 400+ hp when its done, but I keep hitting little troubles with it.

[instantkevin]

I've compared about six different cams (brock, crane, comp, lunati, etc) and it looks like the comp cams xtreme energy 268h might be the best for me. 224/230 .477/.480 lobe separation:110 1500rpm-5800rpm. According to GM perf. parts, max cam/valve lift should be .475" for the L31 Vortec heads. The XE268h is .477". Should I be concerned, is this difference negligle? I was thinking that maybe a slightly larger gasket would help. OR do you think I should go with the XE262H which is 218/224 .462/.469 110lobe - keepin in mind duration. 268h has rough idle (which doesn't bother me too much) and 262 has 'noticable' idle.

I'm glad you recommended Vortec to me, you just saved me a shitload of money. The flow numbers prove it. I'll be getting some remanufact. L31 Vortec heads from ebay in about 2 days. Around $300-400, what do you think about those? Looks like I'm switching to a Edelbrock Perf. Vortec #2116 intake manifold (idle-5500rpm). Almost done with the major parts and blueprinting phase. Gotta call CompCams to figure out if I can use factory lifters, and just buy new pushrods and valve springs.

[instantkevin]

Also.. if you have Dyno software, what does it come up with for 268 cam, vortec heads (220cfm/150 - in/out) on a 350ci?

For anyone else this thread has helped, I found some very useful info about cams at theses sites:
chosing the right cam
http://www.chevyhiperformance.com/te...8_0405_choose/

matching heads and intakes
http://www.babcox.com/editorial/us/us110128.htm

[curtis73]

I love that you've got the bug. You are just like me. You have to know the best plan for you, not just cough up numbers that fifty thousand others have done.

I like the fact that you're leaning toward the comp XE line. I'm not an expert by any means, but that line seems to have the leading edge in lobe ramp technology. I finally got a chance to use the XE line in my latest 454. I used the 262 (212/218 with .504/.510 lift) and I love it. I don't have it tuned in just right yet, but its so strong in my 4600-lb wagon.

350 with 9.5:1 and the 268 cam spits out about 372 hp at about 5600 and 395 tq at 4000. My original 390-410 was a little lofty... sorry to mislead you, but those 400-hp numbers would be very attainable with a little light pocket porting... or maybe even stock castings. I've never built one (except in theory) like this, so maybe a better SBC person here can help you more with their individual experience. We're to the point where theory ends and individual experience will help you fine tune. The other thing that Desktop dyno can't decide is chamber efficiency and flame front dynamics. The chamber shape and quench has a large effect on power.

There is a little discrepancy here since the 220+ cfm flow of the vortecs is capable of supporting more hp, the desktop dyno is coughing up lower numbers; probably for the reasons above. The cam seems matched well since the MAP pressures are all nicely paired, but my guess is that if you put 9-9.5:1 compression, the 268 cam, and vortech heads, you'll be pushing 390. Spend a little extra cash on roller rockers and you'll be around 400.

They say that the power is really in the heads and its true. I bought some stock remanufactured heads and they preformed just like stock. If you spend a little extra cash before they're bolted on it will show up as power. Some things are really just picking nits, but it depends on what you want to pay. In my case, I wanted to bolt on flow with minimal cash, so I took the stock reman heads. If I wanted to lay out an additional $500-600 I could have made another streetable 40 or more hp. Since my project was very limited by my cash flow I opted not to go with the extras.

As far as the lift, Comp will tell you the straight answer. I think you'll be fine since the .475 numbers are conservative. I can't imagine that .002" will kill the whole works. Altering your gasket thickness won't change things since you adjust the valves based on preload. Proper adjustment is the same regardless of the distance to the lifter. As far as lifters, any new lifter ("new" is the key here) will work, but Comp does sell some fine lifters. I went with less expensive factory spec lifters, but comps are great. Pushrods and rockers are cheap compared to the whole budget so don't skimp. Valvetrain is a sensitive thing, so just start new with all of it. Comp will steer you right on all of these things, so just take it from them. They also don't mind if you call them for tech info, but buy parts from Summit or Jegs or PAW. They charge retail price, but I said, "you don't mind if I shop Summit for your parts, do you?" and he interrupted me to say that their vendors are the best place to get their parts.

[01rigidsporty]

I have a similar set up but I was wondering if anyone could tell me about how much HP/Torque I might be putting out. I just bought the car so I havent had time to do anything with it yet. Its a 1980 Camaro with a 1969 235HP 327. As far as I know its all stock (fresh rebuild) except with an Edelbrock 2101 intake and an Edelbrock 1406 carb (600). Would thse 2 items add much HP? I was also thinking of putting in an Edelbrock 2102 cam to match the carb and intake. How much HP does anyone think I might get with all that? Thanks.

[NOVA71]

How's the build going? I've got a similar set up. 350, flat tops, 9.5 compression, RPM airgap intake, chevy bowtie heads, TH350 tranny, 3.42 posi. Anyhow, I am looking into getting a new cam for my engine. I was thinking going with the XE 268H or possibly the 262. I don't want anything too radical, just a cam that makes good power and have good street characteristics. I contacted Comp Cams, gave em my specs and they recommended the Magnum 270H. So, I guess I'll probably go with that. Just figured I'd pass on the info to ya. You might want to consider that cam if you didn't get yours yet. Or if you went with the 268 let me know how it worked out for ya. I still think that the XE268 would be great anyhow.