Technical > Matt Shaff's Engine Shop

shift rpm

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spookie:
Have 406sbc 12.5-1 comp. 4bolt mains. RHS heads 220cc 2.02/1.60 valves 1.5 rockers.Flat tappet cam:.550in .570ex lift 288/296 advertised duration on 106 lobe separation With 1.43 springs.Crower stack injection on alcohol with 5" tubes. With zoomie headers in 1600# FED what would a good place to start trying shift. PG with 1.76 gear

dusterdave173:
The correct answer is the good ole shift loop
You make a pass shift at 5000, another at 5500, another at 6000 etc and very soon you find out what it likes
My experience as a rookie is that you almost forget to shift those first few runs LOL  it matters much less in our dragsters than any other form of drag racing--shift as soon as you remember ( or get your sight back after launch) and then just let her eat
I run dynos all the time and it is a technical question with technical answer that really does not matter very much in what we are running and doing--but if I had to guess I would say start out around 6500 ish and go from there  Have fun!!!

dusterdave173:
1.43 springs are borderline unless you have high dollar units that are just right--a haul ass drag engine needs the biggest best springs you can get at least a 1.500 or 1.550  Bigger better springs are a GIANT plus in any high RPM engine--I would rather have stock rods and the best spring titanium retainer combo available than the other way around

It really matters more than anything else--build her loose and have a killer spring / titanium retainer package and you will be WAY ahead of the game

wideopen231:
what is stall ? Normally shift around 800 to 1000 above stall. Much earlier and its almost like leaving in high gear,which can be helpful on bad track. Do you shift or is it shifted by solenoid?

dreracecar:
You fail to mention (as do most people posting on here) as to the type of racing are you running , weather its all out, or on a index.
 I was fortunet to have a car that ran below the index and never had a tach on the car (cant see it because of vibration). Driver shifts just at the point of feeling peak before going over the nose. I told him "I dont care where you shift at, but shift it at the same point of feel every time and I will adjust the car to the number" I trust the seat of the pants feel of the driver more than a hard to see needle and a shift light bulb that can fail.

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