7t2vette

Or are they more suited for a 350? What kind of Hp could I expect from those heads, 5.7 rods, 1.5 roller tip rockers, 383 crank, holley 750, 1-5/8" hedders, 2.5" exhaust, 2500 stall converter, Performer Rpm air gap intake, full MSD ignition, and a Comp Cams Extreme Energy 274 (230/236* @ 0.50"; 487/490 lift; 110*LSA??????


[Modified by 7t2vette, 7:35 PM 6/6/2002]

HeaderDesign.com

This should be an excellent street setup. You'll get about 380HP at 5250RPM. Use a 3.55 gear to keep in the torque at cruise speeds, and for good 1/4mile times as well.

7t2vette

What would I have to change to get 450Hp/450FTLBS TRQ???

gtsyellow

i'd expect more than 380hp>? edelbrocks crate RPM 350 is 410hp and quite similar to his 383 build up. i was guessing more around 430hp

gcrouse

Aren't those things only 170-180cc intake ports? If so, a little small for a 383. You'd have great low-end torque but be rpm-challenged. I'd look for something in the 190 range from AFR, Dart, Brodix, etc.

HeaderDesign.com

I did a few more calcs with the Performer RPM heads. I'm not sure the flow data that Edelbrock provides was done with a header pipe on the exhaust. The weak midlift exhaust flow tends to send the engine into premature overrev. I couldn't get the off-the-shelf comp cams to work. But I used the head flow data as given. Here's what I got:

Engine: 383chevy, assumed 10:1comp, 750cfm carb, 1.5rockers
Cam: intake lobe: XE278 (278/234, 0.498" lift) with ILCA 110degrees, exhaust lobe: (286/236, .459" lift) with ELCA 118degrees.
Headers: 1 3/4"x34" with 2 3 /4"x15" collector the crossover
419HP at 5500RPM
454Ft-Lbs Torque at 4200RPM. I could get this more accurately if I had the exact intake runner geometry.

ylose

Here is the data for the heads....but I think you allready had this....

Cylinder head specifications
Edelbrock RPM
* 170cc Intake runner volume
* 60cc Exhaust runner volume
* 70cc Combustion chamber volume
* 2.02 in. intake valve diameter
* 1.60 in. exhaust valve diameter
* 1.45 in. valve spring diameter
* 3/8 in. diameter rocker arm studs
* 5/16 in. hardened pushrods are required.

Flow numbers
.100" Intake/Exhaust 72/61
.200" Intake/Exhaust 134/105
.300" Intake/Exhaust 188/140
.400" Intake/Exhaust 224/160
.500" Intake/Exhaust 233/172
.600" Intake/Exhaust 233/179

this is the engine I am running them on:

Type: Chevrolet ohv V-8
Bore x stroke, inches: 4.00 X 3.48
Displacement, inches: 350
Compression ratio: 10:1
Carburation: Edel 750
flat top pistons
Edelbrock RPM (hyd.) #6073
Adv. Duration: 308°/318°
Duration @ .050'': 234°/244°
Gross Lift: .325''/.340''
Lobe Seps. 112°
Duration at .006 Lift: Intake 308° Exhaust 318° Centerlines
Duration at .050 Lift: Intake 234° Exhaust 244° Lobe Separation: 112°
Lift at cam: Intake .325 Exhaust .340 Intake Centerline: 107°
Lift at valve: Intake .488 Exhaust .510
Timing at .050 lift: Open Close
Intake 10° BTDC 44° ABDC
Exhaust 59° BBDC 5° ATDC
Crane Blazer roller rockers 1.5
Dynomax headers

not sure if I helped....
:smash:



[Modified by ylose, 2:58 PM 6/10/2002]

Ganey

170 is for a street 350. 180+ rec. for 383.

JAKE

This type question comes up a lot and it's not really that easily answered.

There are a lot of factors that go into determining the "right" cylinder heads for your combination.

Bottom line though is to decide on how the engine will be used. A daily driver meant to operate in traffic and where low speed, sharp throttle response is important calls for one thing and a car that always leaves on the trans brake for a quarter mile blast calls for another.

My take on this is that cylinder head companies are in serious competition with each other for the buyer's $$. It seems that the situation has begun to boil down to selling CFM flow numbers, with higher numbers presumably being better than lower numbers; which ain't always so.

I don't believe that's completely true; bigger (more) "ain't" always better. Take Brodix, for example, they go through great pains to post their flow numbers and say that the numbers are accurate, not fudged.

Other companies, like World Products (I believe), don't post any flow numbers because, they say, that flow numbers are so misleading.

One of the things you seldom, if ever, see are velocity numbers and from all I've read and from the dyno results I've seen, velocity is as, or maybe even more, important as CFM, max or otherwise.

Many just look at max flow numbers and judge the head based on that, but low and mid lift flow is critical to overall power production, throttle response and driveability.

So whether Performer RPMs are "right" for your combination depends on how you plan to use the engine. Too big a head can be a real PIA to operate on the street, even though they my have outstanding flow numbers.

I remember installing a 468 BB in an 86 Trans Ams years and years ago with big port, open chamber aluminum heads. Car was a dog around town, but on the interstate with the Rs up, it ran away from anything that challenged it. Perfect example of a set of heads not "right" for the job.

Last year one of the mags published the only flow bench head tests I've seen that factored in velocity. The tests were run at a university and extreme measures were taken to make sure there was a level playing field for all the heads tested. I believe the results are posted on the web, but I lost the URL. Maybe some has it and can post it.

I'm running Performer RPMs with 70 cc chambers and 170 cc ports. I chose these because of the way I intended to use the engine, low and midrange torque and seldom (make that rarely) as high as 5500 RPMS. Now, if you plan to rev higher, then you may want to step up to Victor Jr's which have larger ports and outstanding flow. Edelbrock's got their act together in their heads, with all that new, expensive CNC equipment they installed.

Remember, though, that it's the combination that counts. You've got to have the cam, intake setup and exhaust to take full advantage of those high RPMs.

AFRs are great too, but pricey. They are generally the standard against which all the others are measured, but that might not remain so. You have to be sure to specify that certain holes are drilled and tapped for sensors if you order AFRs. Unless they've changed the way they're shipped.

Canfields usually come in right behind AFR in flow and velocity.

But as far as value, Edelbrocks are hard to beat and their intake/exhaust flow ratio is excellent; Better than Vortecs, Bow Tie and many other heads. I saw some flow comparisons involving the much proclaimed Vortec and Bow Tie. The Vortec and Edelbrock 6073s flow about the same on the intake side but the 6073s flow much better on the exhaust and have a much better ratio: intake to exhaust. The 6073s are high velocity heads too.

When you look at flow, another point too is that some heads stall and even lose flow past a certain valve lift, so be sure to check that out. And don't forget a head that is soft in the low and mid range but flows like crazy at .600+ lift won't be a good choice if you cam only lifts the valve .520 or so.

Like I said, this question isn't easily answered.

Just my thoughts.

Jake

robzr

They may not be an ideal head, but I wouldn't worry about them being too small. I know a guy who runs low 11's with a hyd cammed 406 with off the shelf Performer RPM heads in a '67 vette, high 9s on a 200 shot. Granted he hooks very well (running a full Tom's setup, upper controls, heims everywhere, 12 bolt IRS).

Rob

HighHopes85

http://www.chevyhiperformance.com might have been the head flow data you were thinking about. You have to scroll down in the main frams to the head article, just up from the bottom of the page.

ylose

found it...actual url is http://www.chevyhiperformance.com/ed...&viewtype=text




[Modified by ylose, 9:26 PM 6/12/2002]

Dryseals

By all means listen to Jake, flow numbers do not mean what you really want and need to hear. The same cam on a 350 will not work as well on a 383, your piston travels further.

7t2vette

Okay, so now I am officially confused! Are the heads suitable or not? The car will be mainly a street car, with the occasional trip to the strip. If I didn't already buy the heads, I probably would buy a set of AFR's, but I have them, and now I am so unsure. Maybe I will just stick with a 355! :confused:

JAKE

I apologize if I added to the confusion; that certainly wasn't my intent.

In a nutshell, YES, you chose an excellent set of cylinder heads and you'll be happy with their performance. Be sure to check the position of the guide plates when you install them; the installation sheet shows you what to check for.

Also verify correct pushrod length too. If memory serves (which it does less and less now since I've gotten old), a longer pushrod is called for if certain rockers are used.

I've had mine installed for over two years now without a single problem! I did opt for the larger diameter springs (which is a no cost option) to allow me to run a higher lift cam. I'm currently running 1.6s on the intake giving me .605 valve lift with the hydraulic roller I installed a month or so ago.

Hope this helps.

Jake


[Modified by JAKE, 5:20 PM 6/13/2002]

robzr

Thought you might be interested in this link:
http://www.nuibe.com/elco/engine.html

Rob

7t2vette

Rob, could you email me the address of the guy you thought I should talk to again please? I accidently close the IM with the address you sent me! Thank you for all your help, this is why I am addicted to this forum! :cheers: