Hey guys, I am freshing up of my old 383 short block (nicknamed the "magic" motor"). This time its going into my '86 4x4 K5 Blazer.

Here's the question. I have a stock set of early '90's pre-Vortec 76cc truck heads (1.94/1.5 valves) that just need $200 and they would be good to go.

On the other hand I was considering a set of 76 cc chamber Pro Topline Torker heads. They have 167cc intake runners, 2.02/1.60" SS valves, and LT4 springs. Complete they are alittle more than $500 a pair new.

Vortec heads are not an option for two reasons, first they don't have the exhaust crossover passage for an EGR valve. Second their 64cc chamber's would raise the compression too high for the pistons I already have. Using pump gas is the intended purpose for the motor.

If this motor was going into a non-smog car I would be all over them with a fat solid cam to go with. However, this 383 is going to be used in a 5500lbs truck that will rarely see 5000 max RPM, not only that the cam is mild enough for Cali smog testing.

The Blazer currently has:
-Stock 160HP 350
-Full length "coated" headers
-3" single exhaust w/CarSound High-Flow CAT and Dynomax Race Magnum UltraFlow muffler
-Beefed up 700R-4 tranny w/new "towing" converter
-Beefed up NP280C transfer case
-4.11 gears/posi front and rear
-4" lift, 33" Dunlop A/T tires, and 15x10" M/T Classic II rims.

Do you guys think the Pro Topline heads are worth the money for the purpose of this motor?

Here are the spec's of the short block:
-Early '70's 2 bolt 350, bored 0.030"
-SCAT Cast 9000 383 crankshaft
-Dynogear Hyper flat pistions 9.0:1 w/76cc heads
-Stock X 5.7" rods, resized w/ARP bolts
-Everything Ext balanced
-Clevite 77 P Bearings
-Edelbrock Performer SMOG cam .420/.442", 204/214 dur @.050", 112 LSA

The cam is the only thing I don't have yet. I will be running a Performer EGR intake, stock computer controled Q-jet w/a "G" secondary hanger and secondary "CC" rods. The dist is also computer controlled and will remain stock for the time being.


Any help is thanked in advance.

Thanks guys!!!

If the old heads have the "torque swirl" hump in the intake port, changing them would be a very good idea. The larger ports and valves will help the 383 breath. If the heads do not have the torque swirl feature, I don't think you will gain much, if anything, for your towing use. BTW, your engine will love you if you give it 1.6 rockers. That cam really responds to the higher ratio. You will notice the torque increase.

Originally posted by Pat Kelley:
If the old heads have the "torque swirl" hump in the intake port, changing them would be a very good idea. The larger ports and valves will help the 383 breath. If the heads do not have the torque swirl feature, I don't think you will gain much, if anything, for your towing use. BTW, your engine will love you if you give it 1.6 rockers. That cam really responds to the higher ratio. You will notice the torque increase. The heads do have the "hump" in the intake port. I have some older '70's heads too (w/o the hump), but they need seats and guides. If I went through all that I would just to the aftermarket route.

I haven't bought rockers yet, but I worry the high ratio will raise the lift so much that I might have issues with emissions. Plus, you gotta remember this is a big heavy truck, I am not sure I need more lift.

The Torker heads look to be the way to go. I have World's SR Torquers on my driver and am very pleased with them. I suspect the PT's are pretty much the same head. I also have the same cam with 1.6 rockers and the Performer Plus intake. Everything seems to work very well together. With 3.36 gears and a 200-4r trans, while towing the trailered 67, I'm able to hold 60-65 mph up any hill I've came across, yet (3rd gear, of course). I calculate about 272 hp using mph and weight with PreStage.com's (http://www.prestage.com) calculators (92.93 mph (1/4 mile), 3600 lbs, 20% drivetrain loss). This is with exhaust manifolds. So I suspect you should push 300 hp with headers.

IIRC, Comp's Magnum roller tip 1.6 rockers are smog legal. Increasing lift, while maintaing the same advertised duration, will increase torque. This is how roller cams make more power.

Agreed, I think I will go the Pro Topline Torker route.


I have a slight cam change though. Instead of the Performer grind, I stuck an Erson RV cam I've had for years in it.

Its new and pretty mild (which is why I've used it).

Its a single patern cam, but should do well with the better aftermarket heads. Here's the spec's w/1.5 rocker arms: .429/.429" lift, 288/288 adv dur, 214/214 @0.050", 111 LSA. If I use 1.6 rocker arms, I will have .458" lift.


Another question, what size valves should I go with? They are offered in both 1.94/1.5" or 2.02/1.65" valve sizes. Although I doubt a "truck" motor needs larger valves, I don't think it would hurt anything either with a 383 stroker. Plus, they could be used for something else down the road if required too.

What do you think?

Definitly go with the larger valves. The increased displacement will love it.

TTT

BTW, your engine will love you if you give it 1.6 rockers. That cam really responds to the higher ratio. You will notice the torque increase.I will second this!!! I had the following in an old '70 Nova:

'78 350 short block... 150k miles on bottom end
8.2:1 C.R.
204/214 .420/.442 112 LS cam
76cc heads, pocket ported, 1.94/1.6
Q-jet
1.625 headers - 2.5" dual exh.

Swapping from a stock Q-jet intake to a Performer RPM, and (at the same time) replacing the stock stamped rockers with 1.6 magnums was a night and day difference! The car picked up throughout the entire rev range.

Prior to this swap, my best MPH was ~93. After the rockers and intake, the car ran 97-98 mph in the 1/4 with the same stock converter and 3.08 gears. 98 mph in a full weight '70 Nova is pretty darn good for an "aged" smogger short block in a full weight Nova (even the spare and jack were in tact).

Like Pat said... something about that cheap cam and 1.6's just seems to really work well for a mild application.

I have a friend that just got his 383 back from the dyno and he made 526hp and 550 ft.pds. with AFR alum. heads. They flow great!!!!! Just a thought!!!