hotrodharry

Building a mild 355. Assuming the same compression ratio which head will make more power? I have always heard that the pre smog type head will make 30 to 40 more hp than a smog type head but according to several flow tests I have read the 882 will outflow the 186 by a fair amount. Also desktop dyno shows that the 882 will make more power. Anyone have any opinions or real life dyno numbers that would show this? Thanks

RB83L69

The 186 head came on 325 HP 350s. The 882 came on 185 HP 350s. You do the math.

The 186 has 64cc chambers which give about 10.3:1 on a flat-top 350. The 882 has 76cc which should give about 9.6:1 on the same motor.

I have only been building motors for about 25 years or so, since both of those castings were new, so I have plenty more to learn I'm sure. I can't tell you how many sets of 882s I have thrown in the garbage - literally - and replaced with 186s. I think DD is on crack.

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"So many Mustangs, so little time..."
ICON Motorsports

AlkyIROC

Personally I don't like 882 heads. They're over-rated. Most of them have a dual exhaust passage to the intake crossover. The dual passage heads are thin and prone to cracking. If it only has one passage then it should be good to use. A good heavy casting 76cc head is 993 and 997. They can be opened up to flow just as good.

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Follow my racing progress on Stephen's racing page
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87 IROC-Z Pro ET Bracket Race Car
383 stroker (carbed) with double hump cast iron heads and pump gas
461 Big Block installed and ready for the 2001 racing season

Best results before the 383 blew up
Best ET on a time slip: 11.857 altitude corrected to 11.163
Best MPH on a time slip: 117.87 altitude corrected to 126.10
Altitude corrected rear wheel HP based on power to weight ratio: 476.5
Best 60 foot: 1.662

Racing at 3500 feet elevation but most race days it's over 5000 feet density altitude!
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87 IROC bracket car, 91 454SS daily driver, 95 Homebuilt Harley

Jester

The 882's do have some drawbacks, but on the flowbench they perform very well. Better than most any old GM iron. I'm using them cuz I wanted 76cc chambers..and I'l just praying they don;t crack

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"American made baby. 100% American iron. The muscle among the masses. My hero. Yep, you can take your ergonomically designed, space age, computer controlled, 4 door, cup holding map lighted split double wishbone split fold down retractable cargo covered moon roof piece of transportation and keep it. For I have felt the thunder. And I know the difference!"
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ICON Motorsports

Vader

RB,

I bet my desk is faster than yours! The only problem is that I can't find MT drag tires to replace my chair casters, so I can't really hook up...

Sorry, but I had to laugh at that one. It reminds me of the difference between stret/track horsepower, dyno horsepower, and "internet" or desktop horsepower. It's odd how many guys show up at the track with "450 HP" and go home with barely 250.

There are no liars at the chassis dyno, only excuses.

And if I had all the internet horsepower available for the aftermarket mods and add-ons that I've seen, I could turn my 305 into a 800+ HP screamer without a blower and NM fuel. Add up the 10HP from the airfoil, the 15 HP from the K&N, 30 for the headers, 20 for the rockers, 20 for the free-flow cat converter, another 15 for the AFPR, 15 for the synthetic oil, 15 for the FlowMaster, 25 for the HyperTech (that happens to be sitting on my desktop), 15 for the underdrive sheaves, and 150 for the N² bottle and I should be well over 630 HP already, without touching the heads or cam. Why have I been wasting all my time on porting, valves, and wobblesticks all these years? All I needed to do was bolt on some parts. DU-UH!

I think I understand you completely.

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Later,
Vader
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"I'm'a do Things My Way - It's My way or the Highway."
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Vader

Stephen,

It's amazing how many people overlook the stock castings just because the factory numbers aren't "good". As you indicated, some of those castings are very heavy with light mold core areas, and can be opened substantially to make very good flow. Most of the older ('74-'80) heads are designed for flow velocity, not volume, but are really just heavier walled castings based on the better flowing '60s castings. These can usually be opened a LOT to improve flow without sacrificing strength, and a little work with a welder can open the door to a lot more possibilities. Conversely, some of the aluminum castings are impossible to open nearly as much because of large cores and the necessarily thicker walls. Aluminum needs to be a bit thicker for strength, and is hard to enhance with a welder if you decide to go much farther than the original design.

I can weld some nickel over a 1/4" thick iron casting that is five times stronger than 5/16" thick aluminum, and allow a lot more space for ports. It's really very easy to make huge exhaust ports in a SBC head if you want to spend some time. You just need to think outside the box, or in this case, casting.

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Later,
Vader
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"I'm'a do Things My Way - It's My way or the Highway."
Adobe Acrobat Reader

AlkyIROC

Targetmaster 350 replacement heads are a good example. Grab a set of them from a junkyard engine. Port and polish, larger valves and you'll never know the difference. Now if you "need" small chambers to build up compression ratio then you'll have to look somewhere else but the 76cc heads have unshrouded valves already and installing 2.02/1.6 will still be good.

If you really want to get into the heads and get the spring pockets machined for larger springs, machine off the stud boss for screw in studs etc, then just buy some Dart heads. All the expensive machine work is done, they flow better out of the box than any production heads and it'll be cheaper in the long run.