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Old 01-11-2012, 06:07 PM
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Looking for Chevy 186 Cylinder Head Porting Flow Results

I am looking for the flow results for a set of these heads that have the larger 2.02/1.60 valves that have been unshrouded and pocket ported. I want to use this information to figure out some cam options and I am unable to find any complete flow information on these heads. With all the cylinder head info out there the closest I could come was some flow test results out of one of David Vizard's books and it was of limited use. Any help would be greatly appreciated.

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Old 01-12-2012, 01:00 AM
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Untouched the 186s w/1.94"/1.50" valves is said to outflow the 292 Turbo Heads w/2.02"/1.60" valves.
Stan Wiess's site has some 186 w/2.02" flow data.
http://users.erols.com/srweiss/tablehdc.htm#Chevy

Read top part to understand Info in columns.
http://users.erols.com/srweiss/tablehdc.htm

Home: lots of good Links/Info.
http://users.erols.com/srweiss/
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Old 01-12-2012, 11:56 AM
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Thanks for the reply. I found those numbers before but there is no information as to whether the heads were modified or not, and if so, what modifications were made. So I don't know how to interpret them. I was hoping that someone might have some flow #'s as a result of the fairly typical modifications that are made to these heads e.g. bigger valves, unshrouding and pocket porting. There are a lot of magazine and books written on the porting techniques, I just can't find the results so that I can determine what cam would best work with the head modifications.
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Old 01-12-2012, 01:31 PM
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Quote:
Originally Posted by clm69z28
Thanks for the reply. I found those numbers before but there is no information as to whether the heads were modified or not, and if so, what modifications were made. So I don't know how to interpret them. I was hoping that someone might have some flow #'s as a result of the fairly typical modifications that are made to these heads e.g. bigger valves, unshrouding and pocket porting. There are a lot of magazine and books written on the porting techniques, I just can't find the results so that I can determine what cam would best work with the head modifications.
There is no way of making a credible approximation. If you want to know you need to have them flow tested, they could be higher, lower, or the same. Just a simple valve job can change that immensely.
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Old 01-12-2012, 01:59 PM
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I was hoping that someone had actually flowed a similarly modified head and could post the results, so as not to rely on an approximation. I didn't think that I would have this much problem given the amount of written information for these heads but I haven't been able to find it so far.
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Old 01-12-2012, 03:05 PM
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Quote:
Originally Posted by clm69z28
I want to use this information to figure out some cam options
Have you computed your static compression ratio? How many cubic inches? What trans? What gear? What size tire? Street only or street/strip or strip only? How much does the car weigh?

It ain't gonna matter much what the heads flow. They're crap compared to most heads that are available today anyway.
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Old 01-12-2012, 08:34 PM
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Most of that information for the car is included in this post DZ 302 Engine Build Feedback- DCR, Quench, etc. and so I am now trying to focus on the cylinder heads. I would like to make sure my various cam options are in the ball park going into the build.
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Old 01-12-2012, 08:52 PM
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Nowhere in your first thread did you say what the intended use of the car is or will be. Appears that you are keeping it stock. Maybe you're talking 30 HP by pocket porting the heads and unshrouding the valves, maybe 20 HP. As pointed out, you need to have them flowed to be sure. Not a real big difference. Won't feel it unless you're winding it out. You'd gain more HP and torque by putting some good headers on it or making sure your timing and carb are dialed in perfectly than pocket porting the 186's. All of the cam companies offer updated "muscle car" cams. You should be talking to them.
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Old 01-12-2012, 10:55 PM
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Yes, the car is stock and is for street use. All I am doing is upgrading the internals of the original 302 engine to get the better performance out of the stock setup. That's the reason for the stock heads and so forth. I just want to take advantage of the latest techniques that can be applied to the older engines.
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Old 01-13-2012, 07:00 AM
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You're missing the point. there is no such thing as "simmilarly modified". The flow variance between that look the same can be huge. You're trying to take a short cut and save some money by not flow testing, which is understandable, but its not doable. If you don't want to have them flow tested any old guess will be just as accurate as any published flow numbers on "simmilar" heads. If they're well done it'll probably be around 230cfm at .500" lift, probably peak around .600" lift IF the bowl was done correctly and the runners were opened up. Those old runner are a real bottle neck at 160ish cc's.
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Old 01-13-2012, 08:31 AM
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Isn't there a set of vortec style heads with the older valvecover system and intake pattern? Grab some JB weld and make your own casting marks, paint them orange. 99.995% of the populous will have utterly no idea that they're vortecs.

If its for concours resto, by all means, use your 186s.

If you want modern power, a set of old AFR 180s and a modern camshaft profile will get your DZ to really shine; and when you sell the car, bolt on the unmolested heads, intake and carb
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Old 01-13-2012, 09:22 AM
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Ap72:

I am not trying to cut any corners; just the opposite, I am trying to determine what the engine performance will be based on a set of assumptions. If those don't seem to work, then I'll modify the assumptions. This is what I have been able to find on these heads so far from a David Vizard publication (the flow #'s are based on a series of mods to the heads); I was hoping to find a more complete set of numbers for a 186 head that had been similarly modified. The final decisions will be based on the actual flow #'s for sure.





Intake valve Lift (in.)
0.025 0.050 0.097 0.194 0.291 0.388 0.485

Flow (cfm at 25 in. of water)
14.800 29.000 54.400 101.000 148.500 178.000 179.700
14.800 29.300 55.000 102.100 150.100 180.000 196.000
15.600 30.000 57.900 112.900 156.400 186.700 196.000
16.600 30.500 57.400 112.900 159.400 184.100 196.100
17.300 31.500 58.900 113.800 161.400 191.500 194.500
17.000 30.700 54.900 110.800 158.000 189.500 195.000
16.900 31.000 59.000 116.500 164.300 193.200 206.500
16.900 31.000 59.000 116.500 164.300 193.200 206.500

Exhaust valve Lift (in.)
0.025 0.050 0.075 0.150 0.225 0.300 0.375 0.450

Flow (cfm at 25 in. of water)
13.600 24.500 38.200 72.200 101.500 126.800 143.100 155.100
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Old 01-13-2012, 05:48 PM
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1.21 giga-watts???!!!!
 
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You're barking up the wrong tree. Upgrade the internals all you want but you're limiting yourself with those 186's. Unless you want to spend $1500 to have them fully ported, you're much better off just putting a modern version of the Duntov 30-30 cam in it. Pocket porting 186's MIGHT get you 215 cfm at .500. Stock Vortec flows .240 at same lift.

You might be able to get more answers that will suit what you already have made your mind up about at Team Camaro. Go to restoration, engine, and performance forums. Lots of Z/28 resto guys over there.
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Old 01-13-2012, 07:03 PM
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Those flow numbers are NOT your heads, keep that in mind. With choked heads go with the longest rods you can along with a very well tuned exhaust system, it'll help pull the most you can through the intake. Well done the heads can flow as much as stock vortecs but they still don't have a good chamber. Make no mistake though your heads are a restriction, with everything done spot on you still won't be much over 400hp.
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Old 01-17-2012, 12:12 PM
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Thanks to all for the input. As always, there is always good comments and alot of knowledge on this site.
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