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#1
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318 beef up
Hey guys !! If I was going to beef up a 318(1972) with 1968 340 heads(202) valves and dual plane intake mounted with a Thermoquad (big one) off a 400, also running hooker headers with 2 1/4 exhaust. What would be the best Bump stick to use for streetability????????? It had be mentioned to me that I should use something out of 360 !!!
Any thoughts !!!!!! Oh Ya Happy Holidays |
#2
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A bit vauge on the discription, but I'll take it from where it stands. Assuming it's a 360 T-Q intake, "Not" a performer, I would,
1. Mill the heads to get the allready dead compresion out of the basement to a 9.0-1 ratio. 2. Depending on rear end ratio, (Read, intended use) I would do the MoPar 260-268 duration cam for mild use around town with good mpg's. Ratio - up to 3.23's or, The stock/updated version of the 4bbl cam used in HP 340's. Ratio up to 3.73's Light port work in the head helpful. or, The 280 duration cam with good head work to comploment the cam and a rear ratio of 4.10. This cam would benifit from a better intake. RPM/Stealth. |
#3
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You forgot the Three most important peices of information; The application, The RPM power range (tire size and gearing) and the engines compression ratio.
A stock 360 cam is very mild at 252/256 duration, 0.410"/0.412" lift. For general performance the 340 cam is decent, but there are better cams avaliable that might match your application/engine configuration better. |
#4
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Just run with the .441 cam and go to 2 1/2" exhaust instead.Enjoy!
Happy Holidays and a Faster New Year! |
#5
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You better check your valve to cylinder wall clearance. The 2.02 valve in that cut head may want to tag the cylinder wall, a dye grinder will work to put a samll notch in the bore for clearance.
Here's couple of hot tips: If your replacing the guides have the machine shop intall the smaller 11/32 Chebby style guides..think about it....smaller, less restriction, lighter easier to lift and less velocity on the seat. Get in there with a dye grinder and get rid of that big valve boss in the runner. Be sure and gasket match that intake. Have the valve bowls bull hogged. Check and double check the valve geometry. After you run it for awhile pull the rocker arms and look at your valve tips, the wear line should be dead center on the stem and if you have a star pattern on the tip your floating the valves. Mystery of valve float? It occurs at too high of RPM or....maybe at about 3500-4500 rpm, this float is harmonics building up in the spring and vibrating through the valve train causing the valve to bouce, you won't hear it or notice it but eventually it'll cost you big bucks. That inner flat spring is a vibration dampner and when they get tired they allow the harmonics to build just like in a crank shaft. |
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