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Does anyone know that max RPMs for a Spryte

Z

zspryte

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My tach went out and I need to replace it on my 1202 Spryte (Ford 1967 6 cyl. 170 cid). The current tach goes to 10,000 RPMs which I am pretty sure is over kill. That said, does anyone know at what RPM this engine "red lines" at. I can find the max. horsepower for this engine (105 HP at 4400 RPMs), but not max RPMs.

Thanks
 
zspryte said:
My tach went out and I need to replace it on my 1202 Spryte (Ford 1967 6 cyl. 170 cid). The current tach goes to 10,000 RPMs which I am pretty sure is over kill. That said, does anyone know at what RPM this engine "red lines" at. I can find the max. horsepower for this engine (105 HP at 4400 RPMs), but not max RPMs.

Thanks
Click to expand...

In "most" cases, when a engine manufacture rates a engines peak HP, it is at the highest RMP that the engine will make HP before the Horse Power quits rising OR starts to fall off. They do this with with a "load" being applied to the flywheel. However, that same engine can AND will spin faster if it is allowed to free rev (no load put on the engine) BUT it should never be allowed to do so, because the engine (in this case is not making anymore HP beyond 105 at 4400 rpm ) AND also, it is not designed to spin much faster than "peak Horse Power RPM" which in this case is 4400 rpm because the internal components are "usually" not balanced well enough and valve springs not stiff enough, so what will begin to happen is, valve float, and damaging vibration that can AND will damage the engine IF the engine is allowed to spin much faster long enough than peak HP RPM. So having said all this, it would be safe to say in this case the engines "red line" would be about 4500 rpm. Just because a tach in a vehicle goes much higher than peak HP RPM dose NOT mean the engine can OR should ever Rev that high in factory stock condition :thumb:
 
i just put about 300 miles on our spryte and ran it at 2100 rpm.seemed to be in it's "happy spot".don't know how high it will go.....didn't even want to hurt anything.ran perfect every day.bill w
 
Thanks for the info. I assumed it was 5000 RPMs or less based upon the year.

I tend to drive between 2000 and 3000 RPMs and only unintentionally venture above that. I have an OC4 rear end with high-ratio drop boxes. In 4-th at 3000 RPMs I hit about 8 mph. For most of my commute I am on a pretty flat surface and would like to go at as reasonable a pace as possible. If I don't pay attention to the tach, I sometimes find my RPMs drifting a little too high.
 
At 3000 RPM's I travel 151 ft in 13 seconds (11.5 ft/sec) which is 7.87 MPH. At 2000 RPM's it takes 20 seconds to cover the same distance between my marking poles - 5.15 MPH. I clocked it many times since I could not believe it.

I got a copy of my original "Vehicle - History and Sales Record" from Petersons. It says my final gear ratio is 2.33-1. My effective sprocket circumference is 4.25 ft so that at 11.5 ft/sec my rear axial is spinning at 162 RPMs. I cannot correlate my engine RPMs with my axial RPMs since I don't really know what the "final gear ratio" refers to so and how the gearing plays into it. Is the ratio for 1st or 4th gear? Does it include the reduction in my drop boxes or not? Maybe my tach is incorrectly set up (or not). It would be nice if this was true so that I could go a little faster without worrying about my engine.
 
With my new tach installed and set up correctly, my idle RPM's dropped by a third. It appears that my old tach was apparently set up for 4 not 6 cylinders by the mechanic that I bought the unit from. I cannot wait to reclock my speed and once in a while go a tad quicker while still keeping my RPM's at a reasonable level. It is amazing what you can gain by actually reading the instructions.
 
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