Timing a "unknown camed" engine....

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brasil

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Hello ...

I am trying to set my timing.... but it seems to be a long way to get good results..

My set up..... 1973 340 cui block with x heads 1971 Cast iron Intake HP Manifolds 800 cfm
TQ with 97 pri and 139 sec 1966 rods... accel Distributor ( the OEM Mopar look-a like )
Unfortunatly the cam is unknown.... also the cr ratio..
Compression is very good 180 psi ( cold engine) +/- 5 psi....
Only the vacuum is low... 11-12 " HG @ idle... ( 900 rpm )

so when I set the timing around 16-20 deg BTDC the engine runs o.k. I limited the advance so all in is 35 deg. ( vacuum on top )
My Problem ist..a light pinging while accelerating...while cruising.... I think it is the CURVE
seems to be too fast ..too soon.. too what ever...
What is a good curve.... to use.. a very fast one.. all in @ 2000 rpm or is there an advantage of using a slow curve.. all in @ 3000 + rpm....

Normaly a High CR engine needs less timing @ idle.... but a big cam loves more timing...as far as I read... so do I have a change to come to an end.. with this issue...? without pulling the heads - to check the CR ??

Thank you for your help

Greetings Juergen
 
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Thanks abodyjoe! I have a similar situation. I have a 73 340 with a bit lower compression the OP'S AND I have also have an unknown and somewhat wild solid lift cam in it. I also having trouble getting consistent timing. Hopefully these articles will help.
 
thanks abodyjoe !!
I will read the article...and try to solve the problem... will keep you all informed...
the only question ...still in the room : THE CURVE.... I have a tuning set from Mopar...with a lot of Springs.. als those shims that go into the slots in the distributor...to change /set the total advance...
With the STOCK brown and silver springs the car is a little "lazy..and with the purple orange combo ...it pings a litte under load....

Greetings Juergen
 
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brasil said:
thanks abodyjoe !!
I will read the article...and try to solve the problem... will keep you all informed...
the only question ...still in the room : THE CURVE.... I have a tuning set from Mopar...with a lot of Springs.. als those shims that go into the slots in the distributor...to change /set the total advance...
With the STOCK brown and silver springs the car is a little "lazy..and with the purple orange combo ...it pings a litte under load....

Greetings Juergen
Click to expand...

Spring kit curve chart for mopar/mallory distributor:
 

Attachments

  • mallory advance dizzy.pdf
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Stiffer advance Springs will slow the curve.
Open chambers, flat tops with a cranking of 180 might like 2800-3000rpm full advance. The initial at 20 is ok, you could get higher but that would shorten the advance divide between intial and full, anything less than about 8 degrees advance and you may as well lock it out at 32 degrees and call it a day. If you get light pinging with 35 degrees total. ..you need to back it down or get better gas. If you meant it pings with vac advance hooked up, then scrap the vac advance because if you can't run much more than again about 8 degrees vac advance...its not worth it.
 
the mallory instruction sheet is the same like the accel one..only the accel one uses a Silver and Brown spring as stock set up.... the curve purple orange would be fine....but all the curves start very fast within 500-800 rpm and my idle is 900 rpm...so I think I have to bent the perches...to raise the begin of the curve
I will try to set my idle @ 16-18 deg.... and then 16-18 deg. advance on top.... I think I have a old Ford dizzy layin around..perhaps I can use those springs also...

Greetings Juergen
 
If it were me. I'd do as the article says. Find what it likes initial. Then find what it likes for total. And go from there.

Instead of messing around with welding the slots and all I'd buy the plate from FBO I think it is to make tuning the curve fast and easy.

Most of my cars I set the dist up with one light mp spring and the lighter stock spring. Brings total in about 2100rpm and has worked well for in the past.

You sure the pinging isn't a lean condition?



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abodyjoe said:
If it were me. I'd do as the article says. Find what it likes initial. Then find what it likes for total. And go from there.

Instead of messing around with welding the slots and all I'd buy the plate from FBO I think it is to make tuning the curve fast and easy.

Most of my cars I set the dist up with one light mp spring and the lighter stock spring. Brings total in about 2100rpm and has worked well for in the past.

You sure the pinging isn't a lean condition?



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Click to expand...
When its too lean it surges at full advance cruise speeds.
 
I can almost tell how big a cam is, in an sbm, when I do the T-port sync.
A stocker will require no additional bypass air over the pcv.
A 292 cam will want about .04 to .05 sq inch, which is the equivalent of about a quarter inch round hole,or two 1/8th to 3/16 holes. This is in addition to the pcv.
My 230* likes the equivalent of two holes about 2/32to3/32.I used to drill these holes through the primary butterflies, cuz in my opinion, the idle is smoother, than if the engine gets dry air by secondary cracking.When I used to do that I put the holes up near the low-speed discharge ports. But no closer than 5/16 from the edge of the blades..
To figure out the amount of bypass air I had a pcv hose drilled with different sized holes. I would just uncover/cover the orifices until the engine liked what it liked.It's easy to get carried away with lots of idle timing. But then it can make trouble under load, and then guys might unhook the Vcan. That works for racecars just fine, but for cars that spend huge amounts of time in the idle to 3500 zone, the Vcan is very important;at least to me. Far more important that a few footpounds at WOT, or a smoooooth idle. I'll sacrifice a little power-timing in that zone anytime to be able to run 20* of Vcan. These days, 80% or more of my engine's run time is spent in that zone, so engine efficiency trumps power.If I need more power I downshift and let 'r rip.With 3.55s, 33mph is 2800 in 2nd, and 4500 in first.See what I mean? at 2800 I run about 28* of power timing plus another 20 in the can so that's 48* for fuel efficient cruising. But at go-time the twenty degrees drops out, and at 4500rpm she runs full power-timing, and is sitting right close to peak torque.I run 87E10 with 10.7Scr. The Dcr comes in at about 8.7, and cylinder pressure is 175ish. I run a two-stage curve in an old teener dizzy. 2800 is the knee-point; then it slows down to 32 at 3400.
See, I don't much care what my power-timing is at idle to 2800 cuz theres only one time I'm ever there; namely at WOT, and I'm on my way to somewhere else. How often does this situation appear? Oh, I dunno, once in a blue moon.
From 20 mph on, in first gear, the engine is over 2800, so has all the power-timing it can take, (namely 28*@2800 to 32*@3400).But I am a hammer-down kindof guy at after 20mph, and let the drama begin. Besides with a starter gear of 10.97(manual trans), it blows the 295s away almost right off idle.
If you have an automatic with a 2800TC, same thing.Set the power-timing and advance rate to be correct at 2800 and beyond. Then get the T-port sync set right, and go have fun. Never mind what the power-timing is at 1200, 1600,2000 or 2799.The only time you will be there is when cruising.Then give her as much Vcan timing as, and bring it in as fast as,she will take it.Then you will cruise smooth,and efficient, and save gas.Your rings and oil will thank you for it.
Anyway, that's my opinion, and it works for me.This is not to minimize anything that has already been said or quoted.
 
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sounds like a plan... but I will never drill the trottleplates from my 6319 Thermoquad...they are hard to find...

about the lean condition... the plugs are nice brownish..
and the Carb ist also running a little richer than stock...095 vs 097 primarys.. 1940 vs 1966 rods...

Greetings Juergen
 
@AJ/FormS

yes I understood this in the same way... I have a old EDE 1405 laying around...that has drilled primarys...
so I will give "HIM" a try.... perhaps it works....


Greetings Juergen
 
..so what I did yesterday.... I set the timing@ idle to 10 deg... BTDC... then 24 deg. of advance.... so 34 deg. all in
now the engine was idling like crap.... ( of course )
so I hooked up the vac. canister to manifold Vacuum...that brings the timing up to 20 deg BTDC... and the engine runs very smooth now... when I accelerate I have no pinging.... perhaps this is the way to go... ( even if the construct looks a little strange....)

Greetings Juergen
 
abodyjoe said:
If it were me. I'd do as the article says. Find what it likes initial. Then find what it likes for total. And go from there.

Instead of messing around with welding the slots and all I'd buy the plate from FBO I think it is to make tuning the curve fast and easy.

Most of my cars I set the dist up with one light mp spring and the lighter stock spring. Brings total in about 2100rpm and has worked well for in the past.

You sure the pinging isn't a lean condition?



.
Click to expand...

have you tried one spring from the Mr. Gasket 929b ford kit?
so the original mopar small spring and 1 Mr.Gasket mopar 925d spring is all in@2100rpm?
I'm all in now @ 2000 and would like to slow it down to around 2400...
 
I used the OEM Ford springs..( 68 Mustang 302 Distributor )The car runs good...but I have to verify the numbers ( advance aso ) the next days... will keep you informed
The timing @ idle is now 17 deg. BTDC 18 deg. advance
and around 15 deg from the vacuum canister... so far so nice.... but when I drive steady 50 mph .. ( more or less)
I think I have some "noise " comin from the engine...If I go off the accelerator the sound is gone...also if I accelerate ..
Perhaps I need to reduce the Vacuum advance a little more...??

Greetings Juergen
 
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ir3333 said:
have you tried one spring from the Mr. Gasket 929b ford kit?
so the original mopar small spring and 1 Mr.Gasket mopar 925d spring is all in@2100rpm?
I'm all in now @ 2000 and would like to slow it down to around 2400...
Click to expand...


i've always used the mp kit.
 
O.K. i think i got it backwards...the Mr. Gasket Ford kit is 925D and the Mopar is 925B...whatever
anybody got a total with one Mr.Gasket Ford spring and the original light stock mopar spring?
 
well then putin the next bigger weight or turn the vaccum advance down just a smidgen , mine love being all in at 2400 rpms , launches like a rocket , but your after gas milage my stall is 3000 yours sounds like 22- 2400 raed under msd spring combo"s and it will give you the basic Idea , but there are a lot of veriables here so check off 1 by 1 . you will get it . Gl your brother winstoninwisc
HAGR812 always
 
I changed the jets...went up to 98 and used 1966 rods... now I can dial in the idle mixture much better..screws are 2 1/2 turns out now... before I had to turn them ou 3.5 to 4 turns ..
Also the rods are easier to tune.. before I had to "ilft " the TREE about 4-5 turns...now I am in the 1 turn range..

Looks like the carb was runing too lean ...right ?
Then I changed the springs in the Distributor.... Idle 18 deg...and 16 deg
of advance..all in @ 3600 rpm...
runs o.k. the AFR is 13.8 @ idle 14.4
while cruisin and 11.5 -11.8 when I accelerate hard... but there is still a slight ping...when I reach about 3500 rpm... ( I think I need to reduce the advance... )
The Vacuum canister .....that is the biggest problem... when I drive steady 55 mph the foot more or less off the gaspedal... I hear some strage sounds
comming from the engine...like pinging
If I go off the pedal the sound goes away... same if I step in harder...

Greetings Juergen
 
brasil said:
I changed the jets...went up to 98 and used 1966 rods... now I can dial in the idle mixture much better..screws are 2 1/2 turns out now... before I had to turn them ou 3.5 to 4 turns ..
Also the rods are easier to tune.. before I had to "ilft " the TREE about 4-5 turns...now I am in the 1 turn range..

Looks like the carb was runing too lean ...right ?
Then I changed the springs in the Distributor.... Idle 18 deg...and 16 deg
of advance..all in @ 3600 rpm...
runs o.k. the AFR is 13.8 @ idle 14.4
while cruisin and 11.5 -11.8 when I accelerate hard... but there is still a slight ping...when I reach about 3500 rpm... ( I think I need to reduce the advance... )
The Vacuum canister .....that is the biggest problem... when I drive steady 55 mph the foot more or less off the gaspedal... I hear some strage sounds
comming from the engine...like pinging
If I go off the pedal the sound goes away... same if I step in harder...

Greetings Juergen
Click to expand...
Try adjusting the vac canister to decrease the advance, "off the top of my head "11/32 allen head in the canister nipple clockwise seems right. Basically...if it doesn't ping with the the vac advance unhooked ....then its just a matter of adjusting the canister to limit the vac advance...it definitely sounds to be the problem and carries the symptoms.
 
Disconnect the Can to see whats what, and what to do. The Can can be mechanically limited in the backside by spacering the stop. I have used washers, slotted just wide enough to drop over the arm, and then pinching them closed. Just use your imagination.
While it's true that a big cam needs timing, it also needs idle-air.If you are throwing idle-timing at it, in an effort to gain smoothness, you may be sacrificing driveability, as you are discovering. I wonder if you are trying too many things at once. Firstly your A/F is pretty close right now, so leave it alone for a while. Then disconnect the Vcan for a couple of tankfuls, and concentrate on getting rid of the pinging. This will take aggressive driving from idle to 4000 rpm, no more. And not so much in first gear. The engine needs to be working hard.
I like that you have slowed the rate of advance down, very significantly. Perhaps pulling out 2 more degrees is all you need. I'm also glad that you are listening to your ears and other senses, and ignoring your head which is probably desperate to crank it up.
 
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post a photo of your two front spark plugs . do not rely 100% om afr readings . richer is better than leaner for a performance app.

also, if your engine runs over 190 degrees and/or you have around 10.0 compression or more, you can try 1 step colder spark plug.
 
barnett468 said:
post a photo of your two front spark plugs . do not rely 100% om afr readings . richer is better than leaner for a performance app.

also, if your engine runs over 190 degrees and/or you have around 10.0 compression or more, you can try 1 step colder spark plug.
Click to expand...

1 step colder from stock that is.
 
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