I am having a hard time deciding something for the car I plan to put one of these very nice tachometer that fits in lieu of the clock (that I don't have anyway). I love it because it looks original, fits perfectly and will be great now that I have the T5 (and I am reving a little )
Question is, should I go for the 6000 rpm or the 8000 rpm.
-> On one hand, I think that my rebuilt 289 can go higher than 6000 rpm -> On the other hand, if I put the 6k it would somehow be a nice psychological limit and will be awesome to "rev it to the max"
Hope you got the point, let me know what you think
< Message edited by _Remi -- 4/30/2008 11:24:54 AM >
whoooo ... revving higher than 6000 has to be a proper rebuilt I believe if it is revving higher than 6000, then def go for a 8000rpm tach. But if it's rather 5000max, get the 6000rpm put it this way: if you have a 6k tach and can rev 6500, how would you know where to stop?! (i thought that was the whole point of a tach ;-)
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1964 1/2 289 2bbl (autolite 2100) with holley headers and flowmaster 40s new: Quick Performance Racing 9" rear, Moser axles, 3.5:1 trac loc from FRPP and T5. CSRP disc brakes front and FRPP discs back. New wheels and tyres
It depends on what engine and components you have. A 302 could easily rev higher than 6k. I big block probably would not.
The stock redlines on the ford engines per piston speed are: 289 7300 302 7000 351 6000 390 5500 428 5200
With a stoke motor, you want to stay below 3500fpm piston speed. With heavy duty components, you want to stay below 4000fpm. With race components, you want to stay below 5000fpm. Now yes, valve float comes into play as well.
Given that, you should get the 8000 rpm if you are running a 289 or 302.
Not only that, the valve springs wouldn't hold the valve train, the valves would float. Anyway, get a 8,000rpm tach in case you ever do a rebuild that's performance oriented, since most likely it will do 6,000rpm or more.
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Who cares how much horsepower it has, all that matters is how fast it goes!
Best run 13.23 at 106.97mph with a 2.183 60' Times from before tune and driver mod.
If it has good rod bolts and a balance job, the block will usually crack first.If valve float isn't an issue with that. Seen guys take em to 7500 on a regular bassis, and then loose oil psi because of a broken block. But staryfury hit it, 5500 is pretty much it with the stock rods bolts.
I bought the 8000 RPM for my '67 coupe. I wish I had the 6000. At idle, the the thing is worthless. The gauge is too small for 8000 to be very accurate.
IIRC, the original 6K tach was for the 6 cylinder model. A V8 model had an 8K tach. So if it were me, I'd prefer the 8K tach.
i was convinced on the 65 models the tachs in the rally pac were all 6k. Only the Hipo was 8k tach. And +1 to the redlines. I might be able to turn my stock 289 7000+, but I'm quite convinced not more than once
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1964 1/2 289 2bbl (autolite 2100) with holley headers and flowmaster 40s new: Quick Performance Racing 9" rear, Moser axles, 3.5:1 trac loc from FRPP and T5. CSRP disc brakes front and FRPP discs back. New wheels and tyres
Please do not miss understand my numbers. Piston speed dictates how much load is put on the crank, pistons, rods, and rod bolts. Most stock motors are good upto 3500fpm if everything is not worn out. As I said above, the valve train is not taken into account on these numbers. The delimiting factor on the valve train is going to be rpms. Also not taken into account is can the motor pull enough air to get it to these levels. That is going to depend on your cam, intake, and heads. All I wanted to show is what a good condition low end will handle.
If you have a good lower end, with good valve springs, and your engine design will allow it, the 289 will turn 7000k without needing crazy nice parts. Maybe your tired engine will not do that safely, but there is no magic number or calculation to determine that. It may be good to 2000 or it may be good to 5000. That is going to depend on how worn out and stressed it is!
Regardless, the stock rod bolts are a severe weak point. There's a reason the K code motors got special rods/rod bolts; they needed to be able to spin up to 7k safely (and they do). The point is, a stock non-hipo 289 bottom end is NOT good to 7k, even when it was brand new. Now, slap some ARP rod bolts in and I might feel safe taking it to 6500 with a solid top end setup.
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Joined: 11/9/2006 From: South Shores, CA Status: offline
quote:
ORIGINAL: nassaubayman
I bought the 8000 RPM for my '67 coupe. I wish I had the 6000. At idle, the the thing is worthless. The gauge is too small for 8000 to be very accurate.
I was going to recommend the 6000 for the same reason. On the '65 Rally Pac, the 6k tach is easier to read than the 8k.
Printable Version
New tachometer: 6000 or 8000 rpm? - 
I plan to put one of these very nice tachometer that fits in lieu of the clock (that I don't have anyway). I love it because it looks original, fits perfectly and will be great now that I have the T5 (and I am reving a little 
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RE: New tachometer: 6000 or 8000 rpm? - 
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