Cam size and performance feedback

[MantisX620]

Hoping any of you guys with cammed L series can share your stories of how they perform. I'm looking to get either the isky 280/480 or the 290/490. I know either of these will make my l20b a dog down low, but how do you guys like midrange and top end? My engine is pretty much stock except R1 carbs, electronic ignition and 2 1/4" exhaust. I'm hoping a cam might wake it up a bit and let me use some more of the revs instead of shifting at 5k or so when it's running out of steam. I realize these engines don't make an assload of power to start with, I'm just wanting a little more to play with.

 

Also if you think there might be an alternative to isky, I'd like to hear those stories too.

 

Thanks guys

MantisX

[Dolomite]

Have you tuned the carbs well? I wouldn't think it would run out of steam at 5 grand. I have a stock l20b with sss carbs, shit starts getting fun around 5k and redlines at 6-6.5k rpm.

[Jesse C.]

What cylinder head are you running? Dished or flat top pistons? Is your ignition points or electronic?  Maybe you do not need a cam. Sometimes just getting the base parts right will help out quite a bit. 

[TENDRIL]

I have been driving a 280/480 in my l20 since I've owned it it's nice but I have nothing to compare to, that being said I can definitely keep up with some of the swapped cars on fun runs and a bit faster than stock l20s but it's fed with dual webers an matchbox dizzy on a a87 penut head, not great for putting around and in traffic

[Doctor510]

Check the "total advance" when tuning.  Should be at 34-36 degrees BTDC at 2,800 using mechanical adv only  Also, re-time the cam to the #3 hole.  Check the valve lash.

[scooter]

well my motors a 2.3, but even with the high duration z-196, its still a stump puller out of the hole.

 

im also unsure if you need to re spring those smaller isky cams, but I would anyway, the l20b in my truck seems to float around 6200-6500..

not to mention your valve springs are most likely 30 years old.

 

if you tow, I wouldn't go too crazy... but if you barely haul anything, put a bigger one in and work on your tune.

[john510]

Ive got a Web camshafts grind 155,488 lift,252 duration.Dual mikuni 44,s a ported A87 closed chamber head.Its got a smooth idle and good low end manners.It keeps pulling past 6500 rpm,s.Its an L-20b

[datzenmike]

What cylinder head are you running? Dished or flat top pistons? Is your ignition points or electronic?  Maybe you do not need a cam. Sometimes just getting the base parts right will help out quite a bit. 

 

'77 should have U67 and all L2-0Bs ran deep dished pistons and that's not likely been changed. Which begs the question... how did you manage to use the stock exhaust manifold that bolts to the bottom of the intake?

 

 Advancing the cam to the #3 position actually aids low RPM cylinder filling, not high. Retarding to #1 can benefit high RPM cylinder filling at the expense of low speed power. The amount isn't spectacular. I would mess with the tune first before moving onto a radical cam change that will rob your low and present mid range and pack everything into the above 4K range..

 

Agree the R-1s shouldn't run out of breath at 5K although the cam might be. http://community.ratsun.net/topic/7862-r1-carbs-lots-of-pics/ is a lot of reading but pretty sure the jets need to be re-sized for a larger displacement 2 liter engine.  You are likely running lean at top end. Some thought should also go into intake runner length, or 'ram'  tuning. Tune for mid RPM gain.

[Dolomite]

Do you have an afr gauge? I thought my shit was perfect, then found out my top end issues were from running sloppy rich up top. After leaning it out a bit, it idled better and pulls way harder up top.

[MantisX620]

A wideband is actually on the way. I am getting an Innovate. It does make sense that it could be running rich or lean up top, but the last time I checked the plugs, they had the brownish hue to the tips. Once the wideband is in, ill start there and see what I get.

 

I can rev it past 5k or so but my butt dyno says theres absolutely no more gains being had. Sometimes im in 4th or 5th and without downshifting ill ease down on the pedal and it actually pulls its strongest and longest during these times.

 

Timing is set at 12 degrees @ idle. the manifold I got does have a port for distributor vacuum so that is also hooked up. The carbs also pop pretty bad out their intakes until the truck is warmed up, then theyre smooth.

 

Thanks guys

MantisX

[datzenmike]

You would have to run WOT for some time and then get the clutch in and the key off, roll to a stop and pull the plugs. Driving home to check would muddy the reading

[HRH]

If they're popping out the intakes that's likely timing.  And/or lean fuel mixture.  Or excessively rich.  If nothing's been changed, I'd probably say lean due to the fact they're bike carbs.

[banzai510(hainz)]

a Cam will help a bit its just the cost and finding parts that will be avail like the lash pads. Lash pads are a best guess from isky if you get those. If a regrind then youll need at lost 180 or above. key is getting retainers also. stuff is getting harder. New rockers would be needed and most are like 26$ a pc which is too much in my opinion.

be honest if you have R1 carbs already I bet you go pretty good with a L20.

also one can up to sprocket number #3 to get a little more lower end start.

 

 

webcams only does regrinds now if you send yours in.

I think isky is still new and have a good parts supply I think.

Schneider is only regrinds now also.

[Nuclear Water Boy]

A wideband is actually on the way. I am getting an Innovate. It does make sense that it could be running rich or lean up top, but the last time I checked the plugs, they had the brownish hue to the tips. Once the wideband is in, ill start there and see what I get.

 

I can rev it past 5k or so but my butt dyno says theres absolutely no more gains being had. Sometimes im in 4th or 5th and without downshifting ill ease down on the pedal and it actually pulls its strongest and longest during these times.

 

Timing is set at 12 degrees @ idle. the manifold I got does have a port for distributor vacuum so that is also hooked up. The carbs also pop pretty bad out their intakes until the truck is warmed up, then theyre smooth.

 

Thanks guys

MantisX

12 degs????? Yikes. Get you're dizzy recurved so you can run more static advance and have all timing in at about 3200/3500rpm. This is how you wake up a mildly built engine and is what I did with my LZ2.2 with all the usual mods and 10:1 compression and it worked great,when I had one.

[MantisX620]

My wideband should be here Wednesday. Hopefully I can get my brother to weld in the bung and ill post my results here and/or in the R1 thread. Im actually excited about seeing where its running so I can make changes. Does anyone know if its possible to rent a carb sync? Ive heard of doing a bench sync but of course a dynamic sync is more accurate.

 

As for the cam, I think ive decided on the 280/480 from Isky. Since i have an extra stock cam, ill send it off for a regrind. Ill just need to find a source for the varying size lash caps so I can get the geometry right.

 

Nuclear Water Boy, where does one get a dizzy recurved? How does the person know what they are curving it to? I like the sound of having all the timing early.

[banzai510(hainz)]

order from isky and the cams might be new and maybe dont need a a core (save it first) see what they say.

 

if new cam they send I think size 160 lash pads.

 

key is how much of the head and valve seats get milled and the tops of the valve stems to make it even across the board on top. one can be off a little long as it dont go off the end of the rocker

save this

http://www.spannerfodder.com/the_works_escorts-generic-image.php?imageName=images/the_works_escorts/pinto/pinto-rocker-ratios.gif

[scooter]

you can also get lash pads from schnieder if you cant get the ones your need from isky.  also you can put manley 8 mm lash caps made for other things under it. they wrap around the tip of the valve, but aren't deep enough to hit the keepers. they will raise you .080 if you cant get a tall enough lash pad.

 

these only work if someone didn't cut a shitload off your valve tips.

[datzenmike]

12 degrees is the correct timing for a stock L20B at 750 idle. As compression goes up the timing timing can be retarded.

[Doctor510]

What is your total timing @ 2,800 RPM?  Should be about 36 BTDC

[MantisX620]

So I have some sorta good news/bad news for guys running 1.8mm mains and are about 3.5 turns out on the screws. I got my wideband installed and heres what I observed so far. This is without me touching a thing yet.

 

Idle:  14.7 - 15.2 AFR

Part throttle under load : 15.1 - 16 AFR

Part throttle cruise: 14.9 - 15.4

Full throttle: 13.7 initially but the closer to redline I get it starts to lean out to 15.8 -16 AFR territory.

 

Based on the reading ive done, ill need bigger mains possibly to get that full throttle AFR down. I also heard that the needles can also cause this increasingly lean effect as they arent letting in enough fuel fast enough. Before I drill my mains, I think ill try raising the needles to see if that richens it some.

 

To reiterate, my engine is virtually stock. I have 2 and quarter exhaust and elec ignition. Stock cam. 

[datzenmike]

 

Idle:  14.7 - 15.2 AFR This is fine.

 

 

Part throttle under load : 15.1 - 16 AFR  This is not fine and should be below 14 slightly.

 

Part throttle cruise: 14.9 - 15.4 This is fine

 

Full throttle: 13.7 initially but the closer to redline I get it starts to lean out to 15.8 -16 AFR territory. This is not fine. Should be lower 13s or even 12s to start but should stay near there and not lean out as you rev up

 

 

 

Info on R-1 tuning... http://community.ratsun.net/topic/7862-r1-carbs-lots-of-pics/