maybe my timing is a tooth off?

[EastBay521]

then maybe it was the Z20s? I cant remember off of the top my head I have some of the info bookmarked on my other laptop

[datzenmike]

That would work but I don't know the dish size... they were not flattops..

[KlassicMotion]

I've heard of guys using the ('81-'83) L28e 86mm flat top pistons...

 

 

**Edited after Mike's corrections Below**

 

In my notes, I've got written down that the L18 pistons have a 4.36cc dish to them and that they are 85mm.  That's pretty good for the street if your using a closed chamber head.

Here is a calculator I like to use:

http://www.gtsparkplugs.com/CompRatioCalc.html

 

Some of my figures are estimates, but I think they are close. Here is what I inputed.  Some please correct me if I'm wrong: **(Mike tells me the dish is actually 4.35cc, so I will change that.  At my 4.36cc, it only changes it to 9.79:1)

L18

Bore:                                3.346372    /85mm

Stroke:                             3.070789    /78mm

Chamber vol. (cc):           41        

Head gasket thickness:    0.0472429  /1.2mm

Piston to deck height:      0.017716    /.45mm

Dome Vol (cc): (dished)    4.35

 

= 9.80:1 compression ratio.   I wouldn't want to go too much over that for the street.  9.5:1 is already in premium fuel territory. 

[datzenmike]

Stock L18 85mm 4.35cc dish piston and open 45.2cc head is 8.43

Stock L18 85mm 4.35cc dish piston and closed 41cc head is 9.00

Stock L18 85mm 4.35cc dish piston and 210* 38cc head is 9.38

 

 

L18 with over bore 86mm L28 flattops and 45.2c peanut head is 9.18

L18 with over bore 86mm L28 flattops and 41cc peanut head is 9.85

L18 with over bore 86mm L28 flattops and 38cc  210 L16 head is 10.138

 

 

 

*The 38cc head is the 210 from the L16 and not found on the L18.

[KlassicMotion]

Also, I meant to address this first, but you say your using the 38DGES Weber carb?  The math says that's too big of a carb for that engine.  Don't get me wrong, I love it on my L20B, but the L20B is rated something like 240cfm and I've seen people say the Weber 38 is rated at 330cfm - 390 cfm.  Take that for what it's worth.

 

Back to solving the issue.  Do you have a fuel pressure regulator in line before the Weber?  The Weber is a high volume, low pressure carb.  It uses a 5/16" fuel line (stock 521 is 1/4"), and it's recommended in the instruction to run no more than 3psi.  The stock fuel pump puts out more than 4 psi (at least mine does).  Too much pressure will push fuel past the needle/seat and flood the carb.  It can also change the float level setting.  Check the float level.  Use these diagrams for the correct setting.  Ignore which carb the diagram is for, just pay attention to which shape of float you have.  My 38 uses the float pictured in the 32/36 diagram.

http://www.redlineweber.com/html/Tech/38_dgas_parts_breakdown.htm

http://www.redlineweber.com/html/Tech/32-36_dfev_parts_breakdown.htm

 

I swear by this fuel pressure regulator:

http://www.jameng.com/products/Fuel-pressure-regulator.html?gclid=CPaSo9PgmrwCFYeEfgodC3UAqg

 

Follow these instructions to a "T":  http://www.redlineweber.com/html/Tech/38_dgas_tunning.htm

Take special note to the section titled:  Simple Rules for low speed calibration

It will do wonders for the performance of the Weber.  I did, and I can't express how much of a difference it made.  Once I had a good fuel pressure regulator in place and the float set properly,  I did have to change my jets to get the best performance.

 

There are even better instruction included with the jet kit.  Weber doesn't have these on website, but try tuning the carb first with the vacuum gauge following the instructions, and see what the readings tell you.

[KlassicMotion]

Stock L18 85mm 4.35cc dish piston and open 45.2cc head is 8.43

Stock L18 85mm 4.35cc dish piston and closed 41cc head is 9.00

Stock L18 85mm 4.35cc dish piston and 210* 38cc head is 9.38

 

 

L18 with over bore 86mm L28 flattops and 45.2c peanut head is 9.18

L18 with over bore 86mm L28 flattops and 41cc peanut head is 9.85

L18 with over bore 86mm L28 flattops and 38cc  210 L16 head is 10.138

 

 

 

*The 38cc head is the 210 from the L16 and not found on the L18.

 

Thanks, I thought you might have that info on hand.  I will change my notes, and edit my post ( I don't want to leave any miss-information posted).

 

Hmm....  What about my other figures Mike?  Changing the vol size and dish size, I'm still not getting your figures.  So I can only assume I've got other issue with my figures...

[banzai510(hainz)]

is your carb electric choke and is the flap open all the way when warmed up. I seen people forget to hook it up and no air will pass at higher rpm.

[EastBay521]

yes I do have the choke hooked up. time to start looking for L28 pistons and I agree the carb how it comes is too much for the little motor I was having to change my spark plugs every other week but I didn't didn't bother to change the jets because I knew that motor wasn't going to stay in it forever

[datzenmike]

Thanks, I thought you might have that info on hand.

On hand? hell I worked that out just nowwhen I saw the post. Took me two slurps of coffee to finish. lol.

 

 

Hmm....  What about my other figures Mike?  Changing the vol size and dish size, I'm still not getting your figures.  So I can only assume I've got other issue with my figures...

 

Actually it IS 4.36 but it makes no difference really. You were right and I copied it down wrong.

 

These three are a stock L18 with the three different L head volumes just for comparisons...

 

Stock L18 85mm 4.36cc dish piston and open 45.2cc head is 8.43

Stock L18 85mm 4.36cc dish piston and closed 41cc head is 9.00

Stock L18 85mm 4.36cc dish piston and 210* 38cc head is 9.38

 

 

These three are stock L18 with 1mm oversize (86mm) pistons and 4.36cc dish

 

45.3cc open head..... 8.584

41cc closed head...... 9.15

38cc 210 head...........9.62

 

This is the same motor with 1mm overbore and L28 flattops and same three heads....

 

L18 with over bore 86mm L28 flattops and 45.2c peanut head is 9.18

L18 with over bore 86mm L28 flattops and 41cc peanut head is 9.85

L18 with over bore 86mm L28 flattops and 38cc 210 L16 head is 10.138

 

 

Any reduction in the piston dish volume increase the compression, lowering it will increase it.

 

Increasing cylinder volume (bore or stroke) will lower compression, reducing volume will raise it

 

 

[ggzilla]

38/38 is not too big for a 1.8-liter engine. It won't cause low vacuum.

 

It may not be optimum for a low rpm 1.8 engine but is great for a 7000 rpm L18 - when jetted correctly.

[KlassicMotion]

38/38 is not too big for a 1.8-liter engine. It won't cause low vacuum.

 

It may not be optimum for a low rpm 1.8 engine but is great for a 7000 rpm L18 - when jetted correctly.

 

I totally concur. Choosing a carb setup seems to be a give and take at best. Using math to match the cfm of the carb to the cfm of the engine seems to give better throttle response and low end torque. But putting an oversized carb on tends to give more power on the upper end. I tend to run 50-100cfm more than what the engine pulls, and tune the carb accordingly.

[datzenmike]

The engine doesn't have to pull the air as hard through the larger carb so there is some small increase there. But it's not all just that or we would be running 1180 Holly dual pumpers.. and we don't. The stock carb is a compromise between mileage performance and what I call drive-ability. Any other carb, especially a 'larger' one will gain some performance at the expense of the other two. The weber carb is as simple as they get. It's a pipe that mixes gas with air.

[EastBay521]

So today I solved my top speed issues I went and got a timing light the timing was way advanced so im guessing the L16 and L18 crank pulleys are different? I got it up to 90mph but it didn't seem to want to go anymore. ther is still room for improvement so im not worried about that but its still running warm

[datzenmike]

Probably reading the scale wrong.

[ggzilla]

Top speed is below 90. You will find the speedometer is not accurate.

[KlassicMotion]

.... so im guessing the L16 and L18 crank pulleys are different?

 

There is an early pulley and a later pulley, and corresponding pointers, but I'm not sure when the change over was, or which side of the line the L18 fell on.

 

Early pulleys have 6 timing marks, and a single pointer on the passenger side (L16 for sure).  Later pulleys had one mark, and a pointer with multiple marks, on the driver side.

 

I expect Mike or ggzilla will be able to rectify/ratify my statements.

[EastBay521]

I thought the speedometer was going to be  way off but I was going thru my friend neighborhood and the police had put up one of those little trailer things that tells you your speed while my speedometer was reading 40mph the trailer was saying I was doing 37mph. I know its not 100% accurate but good enough for me

[ggzilla]

That is 8% off. So when it said 90 MPH you were really doing 82 MPH.

[EastBay521]

it was actually reading 95 I just said 90 because I knew it was off

[datson4life]

my l16 would get to 100 mph on a 36 weber B)

and then i rebuild and messed with it, and made it look pretty and couldnt go over 70mph :sleep:

so i sold it and bought a ka :devil:

went over 110mph and i think i messed up diff :sleep:

and dirty gas tank killed my new fuel pump :sleep:

and i got more rattles than ever :sleep:

[banzai510(hainz)]

So today I solved my top speed issues I went and got a timing light the timing was way advanced so im guessing the L16 and L18 crank pulleys are different?

 

You should be able to figure/know this out by using the correct timming plate or or pointer before or after the crak pulley swap. yes soem are different and some use the swat ooth timming plate. or use the ones that cam ewith the motor. is also helps you know TDC and the timming issue you claim. Ever L motor guy should have a timming light in the fist place

 

90 95 is the limit on a 521 with the geasr ratio. I woundt do over 75mph for a extended period of time anyways on a 521. Why? then buy a faster truck or car.

[EastBay521]

id be flying in a dime if I could afford one. but with that out of the question ill be looking for a clean 720 diff in pik n pull

[banzai510(hainz)]

I think there is spline count issues for different ratios on those so might have to change out the spider gears of soemthing if I remember right but Datzenmike will know for sure

[EastBay521]

so now ive got a new problem. the other night I went to the store and noticed my headlights were very dim until I stepped on the gas then they would get bright, so I thought maybe it could be the charging system. then the next morning on my way sto school I came to a light and the idle just dropped I thought it was gona die so I took it straight home. after school I started it up, it would fire rite up then the idle would drop until it was about todie then it would surge back up and drop again so I thought maybe it could be the charging system.

 

so I changed the voltage regulator and took my alternator into the parts store to be tested and it tested good and still did the same thing with the new regulator. so next I thought maybe it could be the ignition I checked all wires they were properly connected so I swapped dizzys and it still does the same thing I checked for vaccum leaks, changed fuel filter, oil doesn't smell like gas.

 

and when I step on the gas it will kinda hesitate then rev but the rpms don't drop like normal it will rev and then slowly drop the rpms. so I drove it hoping it would go away it was still doing the same thing where the idle would drop until it was about to die and some times it would but this time when the rpm drop really low the ignition light would flash and at the same time the light would flash the voltage regulator would make a clicking sound. what could this be  I don't know what else todo

[EastBay521]

..