Upgrading my heads

[awd92gsx]

Grumpy,

 

Seeing as how I have the old '77 emissions heads, wouldn't it be in my best interest to move to something like a 64cc head to raise compression (with everything else being equal)? Is it worth the extra $$ for the lighter weight aluminum heads.

[grumpyvette]

while I prefer aluminum heads, just making a head from aluminum does little but lower weight, and allow the head to transfer heat to the coolant faster,its the design of the head that matters more to potential hp.

 

on a MILD PERFORMANCE build the orriginal design VORTECs can be an excellent choice.BE AWARE THERES SEVERAL VORTEC HEADs AND THEY DIFFER A GREAT DEAL, first Ill discuss the original vortecs, but below find the new big port vortecs a TOTALLY differant head design

 

lets look at a few things, heres some old info posts

 

now I need to point out something many guys overlook,...

VORTEC HEADS are SMALL PORT TRUCK heads DESIGNED for LOW RPM TQ NOT PEAK POWER each vortec head test in that article showed the tq peak at close too 4000-4100 rpm, after that the heads/cam used were not able to fill the cylinders to full voluumetric efficincy so tq started to fall off , as the rpms increased and by about 5500rpm it became a loosing cause

remember the formula for

 

HP=tq X rpm/5252

so if you make 400 ft lbs at 4000rpm thats 304 hp

make that same 400 ft lbs at 6000rpm and its now 456 hp

 

if your looking for peak power numbers youll need a cylinder head with a significantly larger cross sectional area to allow good higher RPM power

 

below youll find some things to read/play with

 

http://www.n2performance.com/lectures/airflow.pdf

 

http://www.rbracing-rsr.com/runnertorquecalc.html

 

heres a chart FROM THE BOOK,HOW TO BUILD BIG-INCH CHEVY SMALL BLOCKS with some comon cross sectional port sizes

(measured at the smallest part of the ports)

...........................sq inches........port cc

edelbrock performer rpm ....1.43.............170

vortec......................1.66.............170

tfs195......................1.93.............195

afr 180.....................1.93.............180

afr 195.....................1.98.............195

afr 210.....................2.05.............210

dart pro 200................2.06.............200

dart pro 215................2.14.............215

brodix track 1 .............2.30.............221

dart pro 1 230..............2.40.............230

edelbrock 23 high port .....2.53.............238

edelbrock 18 deg............2.71.............266

tfs 18 deg..................2.80.............250

 

Potential HP based on Airflow (Hot Rod, Jun '99, p74):

Airflow at 28" of water x 0.257 x number of cylinders = potential HP

or required airflow based on HP:

HP / 0.257 / cylinders = required airflow

NO! ITS NOT FOOLPROOF! BUT ITS A VERY GOOD TOOL!

 

what tends to make me crazy is guys that insist on running vortec or similar small port heads and a dual plane intake for max low rpm torque, when I or someone elsae builds thier engine,who then come back and want thier 383-421 sbc to run the big hp/tq numbers and pull hard at 6000rpm and above where those small ports are far past there effective air flow limits

Ive built some KILLER engines useing the 215cc and 230cc IRON EAGLE heads and SIMILAR larger port heads that made great torque in the low and mid ranges, a dual plane intake,with long runners and a 600cfm-750cfm carb helps, as does a cam thats designed for the midrange torque, and full length headers , with 1 5/8" primairies,its NOT the port size in the cylinder heads ALONE that determines the results! its the COMPLETE MATCHED COMBO and the thought that was put into makeing the components match the intended power curve, and matching the cars rear gear and stall speed to that power curve, sure you might be running slightly higher average rpms, to get the best power ,but youll be making a whole lot more power at the rear wheels too!

if you want to get good mileage and decent torque and limit yourself to 1500rpm-3500rpm the small port vortec type heads work great on a 350,thats what G.M. spent the money researching the design to do! ,they are after all TRUCK HEADS!

but increase the displacement to 383 or more and spin the engine to 6500rpm and they become a huge restriction!

while a larger head can give up very little if anything down low in the rpm range but pull far bigger numbers on the hp/tq up higher in the rpm range simply because its still able to flow the necessary voluum of air the engine needs, G.M. knows that! but they also know that 90% plus of the time EMISSIONS and GAS MILEAGE and smooth just off idle low rpm torque is where most engines are used, so they build to fit MOST users expectations

 

http://www.rbracing-rsr.com/runnertorquecalc.html

 

 

play with the calculator,, notice the vortec heads 1.66 are would peak the torque at about 3100rpm on a 383, while a dart 215 cc with its 2.14 port only moves it up to about 3950 rpm AND THATS ASSUMING the larger port head has a matching larger intake runner the whole way to the carb venturies, if you stuck the same intake and other mathing components on BOTH cylinder heads the differance in rpm ranges would be more likely to be in the 300rpm range

 

http://www.chevytalk.org/threads/showfla...rue#Post1196687

 

VORTEC HEADS are an excellent value,if I was building a 283-327-even some 350 sbc combos, Id be looking at them seriously

I think vortec heads are really a nice cylinderhead,

its just that I constantly have guys looking at the $500-$600 price range and forgetting about the other NECESSARY MATCHING COMPONENTS/ ACCESSORIES which raise the price that must be used to get them to work correctly , like rockers,intakes,valve covers) and both expecting them to be EQUAL or better than true high performance aftermarket heads at 1/2 the cost and expecting those vortecs to preform like the better aftermarket performance heads.

LOOK

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

 

the basic conversasion usually includes statements like

 

"why pay $1300 for canfields,AFR,BRODIX,DARTS,ETC when you can buy VORTECS for 1/2 the price and get the same results"

 

thats comparing apples and oranges,vortecs are a good choice on the 350 and smaller sbc engines or when max low and mid range power concerns are much more important (read that daily driver and street performance) than high mid to upper rpm power used in a high performance(read that serious street/strip and track engines)

 

read that GOODWRENCH QUEST ARTICLE carefully

 

http://www.chevyasylum.com/chp/goodwrench4-1.html

 

notice the vortec heads WERE a MAJOR improvement, over the aluminum corvette heads and stock iron heads,but were already having the flow into the cylinders drop off after 3800rpm on that 350 test engine, outstanding performance over stock heads but hardly up to a the flow standards of a good aftermarket heads potential

IM NOT AGAINST VORTECS,FAR FROM IT! I JUST NEED TO POINT OUT THEY ARE NOT AN EQUAL TO THE BETTER PERFORMANCE HEADS, ON A SERIOUS COMBO, AND THERE ARE THOSE THAT WOULD HAVE YOU BELEIVE THEY ARE!

 

 

unless you already have the vortec heads and already have the other necessary parts to make them work ID advise useing the standard 23 deg aftermarket performance heads in MOST applications ,

simply because the BETTER heads AFTERMARKET HEADS available flow significantly more air,AND COST LESS " TOTAL" IF YOUR LOOKING FOR MAX PERFORMANCE, rather than a mild boost in torque over stock heads and vortec heads will cost more,in many cases, "TOTAL " by the time your thru with the WHOLE installation process

IM NOT saying vortec heads don,t work well! in the CORRECT APPLICATION they work EXTREMELY WELL

but they do have limited lift and flow potential, unless reworked and that gets expensive fast!

but by the time you get the matching ,intake,valve covers,rockers,ETC. the costs add up substantially

 

 

the SR heads would NOT be my first choice thou!!

 

if you want vortec style small port heads ID get the EDLBROCK Etec simply because they have advantages like they are ALUMINUM

 

BUT ID SPEND THE EXTRA MONEY AND GET THE AFR 180cc or 195cc heads PERSONALLY, sure your looking at a few hundred more in cost(not NEARLY as much as you MIGHT think, once you add in the extras the vortec heads REQUIRE) but your also looking at much better heads

chevy has just announced NEW versions of the vortec heads which are designed for increased flow and are similar to the FASTBURN heads but the new vortec 206cc heads are CAST IRON with a 64cc chamber

PART # 25534371 bare# 25534431 assembled

theres also a slightly improved 175cc version part# 25534351

 

read this

 

http://chevyhiperformance.com/techarticles/148_0506_thunder/

 

these new heads are drilled and tapped for both old and new valve cover and both old and vortec style intakes, they have 2.00 intake and 1.55 exhaust valves and 65cc chambers

GM has also released a new 383 425hp crate engine part # `12498772

 

 

25534431 Vortec Bow-Tie Large Port Cylinder Head, Complete

GM Performance Parts' latest and most powerful iron cylinder head with "Large Port" for Street or Racing. This Vortec design Special Performance cast iron cylinder head features revised intake and exhaust ports and includes 2.00" hollow stem intake valve P/N 12555331 and 1.55" sodium filled exhaust valves P/N 12551313. The deck surface is .450" with 65 cc combustion chambers, 206 cc intake and 77 cc exhaust ports. All Vortec intake ports are taller and narrower than early model Chevrolet heads. The valve cover mounting holes are for both early model flange and late model center. This head also includes intake manifold mounting holes for both early model 6 bolt main and late model 4 bolt Vortec design. The head has screw in rocker studs P/N 12552126, large valve spring pocket machining, and will accept up to .530" lift camshafts without modifications. Heads are identified with the Bow-Tie logo on the exterior of the head below exhaust flange and Vortec logo on top of intake port area. They also feature GM logo cast into bottom of intake ports. Includes valve spring P/N 12551483, valve seal P/N 10212810, and spring cap P/N 10212808.

Technical Note: You must use a raised runner design intake mainifold P/N 10051103 (6 bolt mounting), or Vortec design 12366573, 12496820, 12496821, 12496822, and 12499371 (4 bolt mounting) with this head. You can use production Vortec intake gaskets P/N 12529094 (torque spec. 11 ft-lb/ 15Nm) for mounting Vortec design heads or use P/N 12497760 (torque spec. 30 ft-lb) with conventional material when using on early model raised runner or Vortec design intake manifolds, this gasket has both 6 bolt and 4 bolt Vortec attaching holes. Head casting P/N 25534371C.

look at the flow chart on the link

 

http://chevyhiperformance.com/techarticles/148_0506_thunder/index1.html

[awd92gsx]

Thanks Grumpy. More than likely this will be the ONLY chance I get to really spend some decent money on my engine for a very long time.

 

So, basically, I'd like to get a set of heads that I know I'll never have to upgrade. It seems like the Vortec's, while OK, fall somewhere in the middle when it comes to performance.

 

Based on everything you just pointed out, I think I'll ante up and pick up some aluminum heads.

 

Any dealings with the quality of Edelbrock vs. Trickflow?

[grumpyvette]

well after building a bunch of engines and seeing the results I have a set of ported TRICKFLOW heads on my 383 if thats any help.

but I bought them knowing there were better heads available, but also knowing that for the money they are one of the better values in a less expensive aluminum head.

and I was looking for a street/strip type combo NOT a all out performance cylinderhead, to maximize the torque in the 3000-5500 rpm range for the street/strip application that corvettes 383 was built for

[awd92gsx]

Well, it is (and probably always will be) a street driven car. So...no need to go too "all out" on a set of crazy performance heads.

 

From what I've been researching, the Trickflows are going to be my choice.