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Author Topic:   Compression Vs. Flow
posted November 07, 2001 12:49 AM
I have a set of 52 cc heads off of a 267 sbc that have 1.84/1.5 valves that I have been thinking about using next year. Will the compression I gain get cancelled out by the flow I am losing? I run a 3500 lb sstock on a 3/10th mile track. 5500-6000 max rpm . How much of a hspwr difference would there be with 64cc's and 1.94 or 2.02's. Any thoughts

Wild Bunch Racing
posted November 08, 2001 08:40 PM
Well if you can give me all of your engine specs such as cam shaft. I have a computer program that can dyno you out charts for your changes. Email me and I will let you know what I need to get that for you.

posted November 08, 2001 10:09 PM
You will be kicking a dead horse with the small heads !! If your rule will allow it , angle mill your 64cc heads and use them .

posted November 09, 2001 12:19 AM
Have you ever used small valves on a small track? Or is that just an opinion. My foot hurts from kicking that horse last year time for a change

posted November 09, 2001 12:36 AM
No , it's not just an opinion . I build racing engines for a living , so I can tell you that the flow bench and engine dyno don't lie . If you'd care to give me a call at work , I'd be happy to go over your engine rules with you , and point you in the right direction for next season . Compression is very important , but I would rather lose a point in compression , than sacrifice 50hp worth of air , or more .

You can reach me at 828-286-0780 mon-fri 8:20am-5:30pm (a lot of times later than 5:30)
Steve Hendren
Hendren Racing Engines
Rutherfordton ,NC

posted November 09, 2001 08:14 AM
can heads with smaller valves be machined larger? I have very little funds that I can put towards racing. last year I had 76 cc heads w/ 194 valves I don't know if I can afford to buy camel hump heads. I was some what competitive last year in the features.

[This message has been edited by ryan (edited November 09, 2001).]

Wild Bunch Racing
posted November 09, 2001 08:00 PM
If you have a 76 cc head with 1.94 valves you need to get a set of bigger valves in your engine but torque with a heavy car is the way to go. So you need a set of 64cc chamber 2.02/1.60 angle plug heads that are ported if you can port your heads with your rules you really need to examine your rules and let us know what you can and can't run on your car. Like solid or hyd cam? what limits you have on your heads,intake and exhaust. There are a lot of possibilites to make your car faster.

posted November 09, 2001 11:15 PM
AC156 , to answer your question ... you will still want to use the larger valve head . We have built a lot of 2bbl engines , and the smaller heads will not perform as well as a head with 2.02/1.600 valves . While a lot of people are under the impression that a smaller valve will work better with a smaller carb. , this is simply not the case . Most of the 2bbl engines that we build are using the 215cc Dart Iron Eagle head , ported . The heads have been severely angle milled down to 39cc , and we use the 2.080/1.625 valves in them . The compression ratio is at 16:1 and these engines run on race gas . Air flow is very important , no matter what size carb. your using ! We are producing between 495hp-510hp(depending on the combo) on these engines using a bone stock 500cfm Holley , as per the rules .Give me a call , and I'll be happy to explain the specifics about valve size vs.. carb size vs.. air flow .

ryan ... Your small valve heads can be opened up for larger valves . But , your intake runners will still be much smaller than a stock 1.94/1.50 head or 2.02/1.50 head . Also , as you add the larger valve , you must unshroud your combustion chamber !! If you don't unshroud the chamber for the larger valve , you will be killing yourself on airflow once again ! I understand that your on a budget , but larger heads would be money well spent . I'd look for these casting number heads .....041 , 041x ,292 ,291 , 462 , and 461's . The 041 and 041x heads are about the best stock head that I've flowed (other than 492's or Vortec's) , but they are rare as hen's teeth ! The other casting number heads are very good as well , and maybe a little easier to find , depending on your location .

Hope this helps !

posted November 10, 2001 01:05 AM
Wild Bunch
rules for engine are 11.1 max compression
360 max cubic inch
stock stroke crank and rods for make of motor
any hyd. or solid any lift.
No roller rocker.
Headers allowed( I have Schoenfeld)
Stock intake or torker II edelbrock (I have the torker II)
Q-jet carb (I have modified Qjet)
Holley 2 barrel 500 cfm
Bowtie heads or any cast stock heads No vortec's No porting! Racing fuel allowed no alcohol
There's a couple other little ones that I cant remember

[This message has been edited by ryan (edited November 10, 2001).]

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