What is considered a "reasonable" redline for a 1500?

dllubin

dllubin

Don
I've got about 100 miles on my 1500 engine now, and have managed to get it in a pretty good state of tune. It is using the same intake, exhaust, and cam that my 1300 had. The 1300 liked to pull past 8K, and back in the day, the common knowledge was that the 1300s held up just fine with excursions up into that range. This new engine seems rather eager to rev past 7K but I am trying to be a little conservative until I get more information. The bottom end is completely stock to the best of my knowledge. What is considered a reasonably safe upper limit for a 1500?
 
First thing I would do is verify the accuracy of your tach. I had an X where the tach was off by 1,000 rpm near redline...meaning I was trying to spin it to 8,000 rpm instead of 7,000.
 
I'm not a SOHC expert but believe I read somewhere (factory literature) that power peaks at 5,500 on a stock FI engine. I like to rev mine between 4,000 and 5,700 rpm. It seems like anything higher on a stock engine is just peeing in the wind. My tach's redline is 6,500 though. It would be nice to see some power and torque curves for these engines.
 
carl said:
First thing I would do is verify the accuracy of your tach. I had an X where the tach was off by 1,000 rpm near redline...meaning I was trying to spin it to 8,000 rpm instead of 7,000.
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I checked my tach many years ago against a pretty good dwell tach. It was way off below 1K but not too bad at the higher rpms. I've got an oscilloscope here that I could use for a precise calibration - would be interesting to check. The tach is the same one in the dash that the 1300 was connected to. Would be interesting to see if I was winding it past 9K instead of 8K.
 
Cratecruncher said:
I'm not a SOHC expert but believe I read somewhere (factory literature) that power peaks at 5,500 on a stock FI engine. I like to rev mine between 4,000 and 5,700 rpm. It seems like anything higher on a stock engine is just peeing in the wind. My tach's redline is 6,500 though. It would be nice to see some power and torque curves for these engines.
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Yes, if this was a stock engine, there would be no point in going too high. Only the lower end in mine is stock. The cam is much more optimized for the upper rpm range. I used it for a number of years in the 1300 and was pretty happy with it. In the 1500, it revs surprisingly similar to what it did in the 1300 but with a very noticeable increase in torque.
 
So where does everyone running long duration cams decide it's time to hit the next gear? It kind of defeats the purpose of putting one in if you are going to keep it below 6K.
 
8k seems very high for a stock engine. Is the euro spec cam considered long duration? Euro cars are redlined at 6500 I’ve never felt there was any benefit taking it past 6 tbh.
 
You do what feels right.
With a near stock engine, even with a hot cam, I don't think you will break the engine by overrevving it. It will run out of breath before that.
On my quite modified 1600, 7500rpm was a good shift point when really pushing it.
 
Your motor will tell you where the useful shift point is, the power will drop off after a certain point and revving further is useless. Modified motors are a different story as the power keeps moving up the rpm band.

When I roadraced my Yamaha SR-500 (500cc single) it was quite obvious when it was time to shift...to the point I didn't even need the tach.
 
Stock 1500 is good and easily safe up to 8,500 RPM burst even if the power curve has long fallen off before that.
Over the decades of driving an exxe, the tach is mostly useless as the sound of the engine is far more effective than the Tach.

~You're not gonna bust it due to over-revving. It the Lampredi engine does have a mis-hap, it was ready to die anyway. When these Lampredi engines are in GOOD condition, they are mostly unbust-able.

Most power utilized happens when the shift happened slightly past the hp power peak based on a dyno curve. This way, you'll get more area under the power curve. If shift happened before or at the power peak of the dyno curve, available power is not fully utilized.


Bernice
 
OK. Based on the recent inputs, it sounds like I can drive a 1500 similar to the 1300 despite the longer stroke. That is good news as the engine pulls hard right past the redline on my tach (7K).
 
unless modified. the most important difference is revving them both are if you rev high and break a belt in a 1500, you are screwed (probably will never happen) in a 1300 , you do the same thing, you coast to a stop, line things back up, put a new belt on and away you go!!


Odie
 
autox19 said:
unless modified. the most important difference is revving them both are if you rev high and break a belt in a 1500, you are screwed (probably will never happen) in a 1300 , you do the same thing, you coast to a stop, line things back up, put a new belt on and away you go!!


Odie
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The 1300 is the interference engine, not the 1500. i checked mine with the high lift cam and it is still non interference. My 1300 did not break a belt but a disintegrating tensioner did the same thing
 
I would suggest making an appointment with a dyno-equipped shop and have them print some power and torque plots for your drivetrain. You might even get them to help you try different timing, etc. Then you will know where to shift, at least until the next time you change something. I used to have guy in San Leandro but I'm sure he's retired now.
 
Cratecruncher said:
I would suggest making an appointment with a dyno-equipped shop and have them print some power and torque plots for your drivetrain. You might even get them to help you try different timing, etc. Then you will know where to shift, at least until the next time you change something. I used to have guy in San Leandro but I'm sure he's retired now.
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That would be a nice thing to do now that I've got some confirmation on a safe rpm range for the engine. I know the advance curve is not quite where I want it. I was going to recurve the original 74 distributor again (I think it may have lost a spring), but I've got a Bosch distributor that came with the 1500 that I may as well do instead and get rid of the points. I just need to build a box with one of those GM ignition modules to interface it to the coil.
 
dllubin said:
That would be a nice thing to do now that I've got some confirmation on a safe rpm range for the engine. I know the advance curve is not quite where I want it. I was going to recurve the original 74 distributor again (I think it may have lost a spring), but I've got a Bosch distributor that came with the 1500 that I may as well do instead and get rid of the points. I just need to build a box with one of those GM ignition modules to interface it to the coil.
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You can just use a late 124 Spider coil, heat sink and ignition module rather than build the box up, it will all be in one place and get it out of the side that can fill up with water. You might add a vinyl flap over the top to ensure rain water doesn’t run onto it all the time. Just a thought.
 
dllubin said:
The 1300 is the interference engine, not the 1500. i checked mine with the high lift cam and it is still non interference. My 1300 did not break a belt but a disintegrating tensioner did the same thing
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oops. I had a 50% chance. guess I shouldnt bet on the horses today!!!

Odie
 
Longer strokes of the 1500ccc has been accounted for by increase in connecting rod length. A healthy 1500cc Lampredi motor will survive endurance racing with a 8,500 RPM red-line easily. We proved this in LeMons racing. IMO, there is too much concern over busting the Lampredi engine by over-revving. Honestly, you're not going to bust it with 8,500 RPM burst of a few seconds or more. Running constant between 5,000 to 8,500 RPM full power on a race prepped Lampredi engine hour after hour is an entirely different service condition.

If you ever sit with me in an exxe, you'll be surprised at how the Lampredi engine is driven with zero regard to the tach and red-line. Been doing this for decades with no ill effects. Stock USA motors run out of gasp about 6,000 RPM, but motor will sort of continue to rev up.

As for getting rid of points, use the stock Bosch distributor with a MSD. The GM module is the same used in the Marelli unit found on later 124 and similar Lampredi twin cam. It is a sort of OK unit no better or worst than the stock Bosch unit.


Bernice
 
Better to fix the drains properly if that location is used for EI. That is a proven rust spot in the exxe due to clogged drains.
Best location for any EI unit is in the spare tire well.

Bernice


kmead said:
it will all be in one place and get it out of the side that can fill up with water. You might add a vinyl flap over the top to ensure rain water doesn’t run onto it all the time. Just a thought.
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Rupunzell said:
Longer strokes of the 1500ccc has been accounted for by increase in connecting rod length. A healthy 1500cc Lampredi motor will survive endurance racing with a 8,500 RPM red-line easily. We proved this in LeMons racing. IMO, there is too much concern over busting the Lampredi engine by over-revving. Honestly, you're not going to bust it with 8,500 RPM burst of a few seconds or more. Running constant between 5,000 to 8,500 RPM full power on a race prepped Lampredi engine hour after hour is an entirely different service condition.

If you ever sit with me in an exxe, you'll be surprised at how the Lampredi engine is driven with zero regard to the tach and red-line. Been doing this for decades with no ill effects. Stock USA motors run out of gasp about 6,000 RPM, but motor will sort of continue to rev up.

As for getting rid of points, use the stock Bosch distributor with a MSD. The GM module is the same used in the Marelli unit found on later 124 and similar Lampredi twin cam. It is a sort of OK unit no better or worst than the stock Bosch unit.


Bernice
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Sounds like I can pretty much drive it the way I drove the 1300 with an occasional pegging of the needle. I normally shift based on sound and feel. I'm only keeping an eye on the tach because of zero experience with this engine.

As far as the distributor goes, I've got the Bosch unit that came with the 79 engine but no box. I figure I would be better off building up a GM module than looking for the original Bisch box. My other option is to build an interface between the distributor output and one of the CD units I was using in the 70s and 80s. Or I could go with an MSD as you suggested. They make a nice product. I've installed one of their CD units in another car. The reality is that even at 8,000 rpm, the demands on the ignition system are relatively modest for a 4 cylinder engine. A V8 at 4,000 rpm would have the same ignition requirements. Based on that, I was thinking that the best solution may be the one with the fewest things to go wrong. From what I've read, the GM module is pretty bulletproof.
 
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