Posted by Keith in Washington [108.162.245.62] on Friday, March 28, 2025 at 12:18:13 :
In Reply to: Muffler Armor posted by Vaughn [162.158.175.22] on Friday, March 28, 2025 at 10:38:59 :
That engine loves RPMs. With 4.89 with 36” tires and no overdrive you will turn 3000 RPMs at 60MPH. I had mine balanced and etc and it will do over 5000RPM without blinking. I have an Edelbrach 4 barrel carb. I put it on a dyno in Reno which is at 5000 feet and I was getting 200 hp to the rear wheels with and old worn out Carter 300 cfm carb, an original distributor along with regular unleaded gas. With a new carb, electronic distributor and aMSD box I am well north of 200 now.
The only thing I might add is an overdrive. It doesn’t take long to get before you have to shift again. The SM420 is a 4 speed with a real low granny first gear so effectively its a 3 speed trans. 4.30 would help but that is only a 12% reduction in RPMs. The 4.89 gears makes it really short legged but the high rpm’s help out.
When I first had it on the road I had glass pack mufflers until I decided what the final solution would be. With those glass packs I could drive through the parking garage at Microsoft and set off a bunch of car alarms on some pretty high end cars. That would bring guys running to check out why their car alarms were going off. I would walk out of the garage with a smile on my face. One day I circled through all levels of the garage and set off 50+ alarms. Something about the vibrations those glass packs had just off idle was great fun. The current mufflers aren’t as much fun.
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