521 Acts funny when Hot

[culowdragger72]

yeah the intake has the water hook up and its connect to the lower water outlet hook up not the thermostat housing.

 

i don't have speed cable i need to get one ordered.

 

i go thru the gears pretty quick but when i go thru 1st, 2nd, 3rd, 4th it drops about 750-1000 rpm but i get to 5th it drops 1250-1500 rpm.

i just want to know whats a good rpm range to been in with this L20b

[datzenmike]

yeah the intake has the water hook up and its connect to the lower water outlet hook up not the thermostat housing.

 

i go thru the gears pretty quick but when i go thru 1st, 2nd, 3rd, 4th it drops about 750-1000 rpm but i get to 5th it drops 1250-1500 rpm.

i just want to know whats a good rpm range to been in with this L20b

 

There should be a small pipe coming out of the thermostat housing that joins the one from the intake and then go down to the lower rad inlet. Close enough, yours has it and that's good.

 

 

All 4 and 5 speeds rev the same in 4th gear. If the tranny is installed rev it to an even RPM number like 3K and shift into 5th and see how much it drops. From this the overdrive ratio could be worked out and the tranny identified. Knowing what it is out of won't really change much.

 

That doesn't help much. In order to work out the % change you have to have a starting point like 3K in 4th... shift to 5th... RPMs drop to 2250. This would indicate a 25 % change and identify the transmission as an '81-'83 zx.

[ggzilla]

i just want to know whats a good rpm range to been in with this L20b

Keep it above 2000 RPM when acclerating. L20B has a 7000 RPM redline, so don't rev higher than that. Keep it below 6500 in normal use. For maximum fuel economy, let it run in as high a gear as possible. I would keep it above 1500 RPM when steady-state cruising.

[DanielC]

When it gets hot, it it generally better to let the engine rev a little more, rather than pull a higher gear. The higher RPM pulles more air through the radiator. Sometimes, you can actually use less throttle in a lower gear, and maintain speed.

[culowdragger72]

i drove it today and double checked the rpm drop and its at 750 to 1000 rpm going 1st thru 4th and 5th dropped at 1000 rpm.

i drive it in 2250 to 2750 rpm range in the city on the hwy its around 3500 to 3750 rpm and passing everybody speed at 4250 rpm.

[wayno]

Keep it above 2000 RPM when acclerating. L20B has a 7000 RPM redline, so don't rev higher than that. Keep it below 6500 in normal use. For maximum fuel economy, let it run in as high a gear as possible. I would keep it above 1500 RPM when steady-state cruising.

 

 

I just can't see 7000rpms as a redline for a L20b, I have used a stock L20b bottom end with a opened up(BIG valves/ported) W53 head with a stock L20b cam, and the thing falls on it's face at about 4500rpms, the ONLY way that engine will do 7000rpms, is floored in neutral or maybe first, but I doubt it will even do it in first.

I could understand this kind of redline if the cam wasn't stock, but a stock L20b/stock cam, I just can't wrap my brain around that.

[datzenmike]

i drove it today and double checked the rpm drop and its at 750 to 1000 rpm going 1st thru 4th and 5th dropped at 1000 rpm.

i drive it in 2250 to 2750 rpm range in the city on the hwy its around 3500 to 3750 rpm and passing everybody speed at 4250 rpm.

 

Again this doesn't tell you much. Lets say you have a transmission that has a 40% ratio difference between 1st and 2nd gear. Lets say you start in first gear and shift at 1,000 RPMs into second. The tach will drop 400 RPMs. Now you try it again and rev to 6,000 and shift into second. The tach will drop 2,400 RPMs into second. Saying " drove it today and double checked the rpm drop and its at 750 to 1000 rpm going 1st thru 4th and 5th dropped at 1000 rpm." doesn't say what the RPMs were before you shifter into the next gear. If we know that and the drop in RPMs we can work out the % change and the transmission ratios identified and maybe what the transmission is originally out of.

[ggzilla]

Look at your factory 620 tachometer. You'll see the redline is 7000 RPM and the yellowline is 6500. The engine does not make max power there, but it won't hurt the engine to run that high. In every day shifting I would shift around 3000 rpm, or for merging on the freeway rev it to 5000 RPM or wherever it starts to feel a slowdown. No problem merging if you drive it correctly (and aren't carrying a load or have too tall tires).

 

What you don't want to do is lug it, always accelerating from low RPM. For maximum bearing wear, never floor it below 2000 RPM. While the L-engine can handle it, it is not best for the engine.

 

Wayno, large ports sometimes make less usable power than stock. For example, big ports and an RV cam will fall flat on its face by definition. The stock L20B engine with stock cam & gears will rev right up and doesn't even reach max HP until 5600 RPM. After that yes, the rate of acceleration will slow. Actually it will start slowing after about 5400 RPM where the peak torque is. That's with a stock L20B, you now better what your modified L20B will do. And perhaps different years of 620s are different.

[culowdragger72]

i drove it shifting it at 3000 rpm thru all the gears and it drop 750 rpm to 1000rpm when shifted.

 

i drove yesterday and it started to studder or cutting out thinking it was vaperlock it is not, i believe its an ignition problem for sure now because i can here the gas getting sprayed in the carb when i'm pumping it while my truck is dying.

 

for the pertronics ignitor, i'm running two resistors at 1.8 a piece and coil is external resistor type and 970 is the # on it.

i hope that helps because its doing alot more when hot and its 110 degrees out side when driving.

[banzai510(hainz)]

Pertonix

use the 1.8 and just the coil. What I understand the external resisitor type is already a higher ohms. say like 1.6 like the stock coil.

I use the stock coil and ballst and never had a proplem.stock is 3.2 ohms

 

You make have added to much resistsance thus making it current limited on the higherr rpm.

 

I had a pertronix on my 521 and notcie at wide open it would cut out. I thought crap. I cked my dizzy ans found that the shaft was loose thus cause it to cut out. Usually to is MORE noticlible when having points as it cause the coil to fire when you dont want to. Cutting out poping blowing up mufflers ect.....

[culowdragger72]

i'll try that, i will remove the extra resistor.

[ggzilla]

shifting it at 3000 rpm thru all the gears and it drop 750 rpm to 1000rpm when shifted

Excellent gearing, which will keep it in the powerband should you ever rev it high enough to be in the powerband. But also works well when short-shifting at 3k. 1000 drop keeps it above 2k.

[culowdragger72]

i felt like i was going thru the gears to fast but the truck runs like it has a V-tech when you mash the gas. its real responsive.

[ggzilla]

felt like i was going thru the gears to fast

That's good. Who want a vehicle that goes through the gears slowly? Only guys who don't like to shift.

[culowdragger72]

Will I took it out for another drive after I removed one of the resistors and it cut out a lot fast. So I reconnected the old one and add another resistor on top of that and problem solved and a added bonus it stopped dieseling. An I ran it hard truck runs like a champ once again.

 

 

Thanx everyone for the help.

 

 

 

[banzai510(hainz)]

So this means YOU installed the wrong coil

 

a stock 1.6 ohm ballast and a 1.6 ohm coil is stock. should have worked perfectly with Points or the Pertronix.

 

 

Key to COILS is readin the fine print on input resisitance.(what type ignition its used for)

Most kids see a BLING coil and think its going to make their car faster in theroy. but in reality if makes them break down sooner.

 

 

My cars I run a Accel SuperCoils. Butin the instructions it says use the stock ballast and the one that come in the kit a .85 ohm(that most people dont use). No ballast resisitors the car with points wont make it down the street!!!!!!!Or pertonix over 4 aps could break the module or if running a Unilite break those also.

 

Well glad it works.

Just ffel the coil if its HOT to make sure its OK.

[ggzilla]

Glad to hear it's working now.

[banzai510(hainz)]

heres the Toyota part corolla 1976 , all in one

BECK/ARNLEY Part # 1788025

Contains External Resistor

 

http://www.rockauto.com/catalog/raframecatalog.php

[culowdragger72]

that's a cool looking coil, it looks like a newer nissan style coil. as soon as i get some dough too buy another one.

 

thanx again Hainz

[culowdragger72]

i'm back again and installed the new coil and resistor and rebuilt the weber dgv 32/36 and my truck starting to be jerk again.

 

i don't know what to do i'm guessing its the pertronics ignitor, i went to the junk yard and yanked out a dizzy from a 73 620 with single points and its a one wire set up.

 

how do i wire it?

[ggzilla]

Why do you keep buying parts instead of finding out what is wrong?

 

Didn't it work fine with the TWO resistors?

[culowdragger72]

turns out the they where bad and replaced with a new ones and run it with one it ran fine and then it started the jerking and i installed the second and it still does it.

 

it might be the ignitor not sure though.

[ggzilla]

I don't follow you. Did it run fine with two resistors or not?

 

Well anyways, you can wire up the points distributor, the ONE wire goes to the coil- terminal. But keep in mind that used points are not reliable and cannot be set reliably without a dwell meter.

[culowdragger72]

with one or two resisters it does the same after a 15 to 20 minute drive.

 

so the one wire hooks up to the negative side of the coil?

[Outlaw720]

hey culowfragger72 can you take a picture at a different angle of how your throttle return spring is set up??