what hole you keeping that pump cam on? 1, 2 or 3?

any sign of stumble?

i've got a small hiccup part ways on the throttle.. initial take off is smooth

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70 Plymouth Valiant 4dr

What is this stumble you talk about?

Can't have that when drag racing or daily driving...

Holley 390 is typically the pink cam in #1, have also done some work with the Orange cam in #2...but the duration of the shot wasn't as long when going from part throttle to truck passing WOT and it would lean out until the economizer kicked in....

Holley 600 with annular boosters is typically pink in #2

I will have to check the Holley 450 I have that I had modified with downleg boosters to see what I had finally set it to before going back to the 600....

hey fellas just an update here.. i've been playing around with different ideas and am getting very close to eliminating that high rpm ping (almost nonexistent now)

- try a colder plug. i dropped 2 ranges down from the stock recommendation and it was a big help.
i skimmed through the thread but didn't see if you are running the HEI ignition.. if so... i'd start looking at the turn ratio and ohm rating of the coil you're running..... might not be a huge difference but definitely worth investigation..

as for the stumble i had? i dropped to a #53 jet on the primary side (from 55's) and went up drastically on the accel pump cam....
damn thing runs like a new car...

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70 Plymouth Valiant 4dr

Thanks for posting this info - very useful, as i will be upgrading to a long runner manifold and Holley 4 barrel carb (390 or 465).

I have a very similar setup and have had pinging issues too. The SL6 Forum was very helpful (http://www.slantsix.org/forum/viewtopic ... c&start=15).

Recurving the dizzy was the biggest help in my case. I have dropped down one plug range, but will try 2. I still get some minor pinging from around 100 kmh if I'm not careful.

Will definitely install a WB02 sensor and vacuum gauge next.

My specs are as follows...

0.06" bore (232.7ci)
0.1" removed of block
0.06" removed of head
9.87:1 comp
comp cams 264s solid cam
pocket port cylinder heads with 1.7"in & 1.44" ex stainless valves and V8 springs
hi-tec extractors (headers) into 2.25" single exhaust system
stock two barrel intake and carter 2bbl carby
HEI Electronic ignition conversion & re-curved distributor
runs on 98 octane


Cyl Bore Diameter 3.46 in.
Eng Stroke 4.125 in.
Number of Cyl 6.
Combustion Chamber Volume 52 cc.
Piston Crown to Block Deck Face 0.080 in.
Piston Valve Relef Volumes 0 cc.
Compressed Gasket Thickness 0.040 in.
Gasket Average Bore Diameter 3.525 in.
Piston Dome Volume 0 cc.
Piston Dish Volume 0 cc.
Outside Diameter of the Piston at Top Land 3.428 in.
Dimension Piston Crown to Top Ring Groove 0.326 in.

Engine Capacity 3813.462 cc. or 232.712 ci.
Compression Ratio 9.8716:1

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Love cruising in a bare metal Val!

That equates to about 93 on the US/Canada octane scale.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Yeah, I would not use a comp cam 264 on anything higher that 9.5:1 scr

Do you know what you centerlined the cam intake to?

I plugged all the data into the DCR calculator I use and you are above 8 which is fine, but because the cam has a short overlap and low advertised duration, advancing the cam will cause some issues.... this build would have been best served by using something more akin to the Erson 270 or Erson 280/270...

The next question is what is your mechanical and vacuum advance set up for?... with this combo init+mech+vacc... should not exceed 47....

What spark plugs are you using?

Is there a specific reason you decided to choke the build with a 2 barrel over a 4 barrel? (Literally, if using headers, that SCR, OS valves proper porting, going to a 270 duration cam with .470 lift, and even a 500 cfm 4 barrel Edelbrock the engine would go from being a 150-160 hp engine to 190-200 pretty easily and still get reasonable mileage if the drivetrain was setup right...., just curious.)

Thanks DI.

My aim was for a 9.2:1 CR, but my engine builder got a little carried away.

The two barrel carter is there purely as I was pressed to get the car back up and running - so time was the biggest factor. Despite not being ideal, the engine has been super reliable and nice to drive since the rebuild. Looking forward to doing the next set of upgrades - hopefully soon!

can't argue with your cam/carby advice. Should go well with the long runner aussiespeed 4bbl manifold.

Don't have specifics on the mech and vac adv settings for you at this time. Will see if i can source that from my tuner.

Spark plugs are NGK BP6ES.

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Love cruising in a bare metal Val!

If this is a BBD... and without a vacc gauge while driving and an O2 sensor to watch I suspect 2 possible issues:

1) Because the engine isn't "stock", the metering rods/jets will need to be changed or the mix richened as you may have some areas that the carb can't supply a hotter build like that under load.... (i.e may go lean at partial throttle).

2) The carb is undersized for the build leaving the vacc. high under almost all conditions leaving you with most of your vacuum advance when you don't want it/need it.

Time to get the vacc gauge at a minimum, and then work toward the WB O2 sensor...

DI,

Timing settings I dug up the other day (following the initial tune) that answers one of your questions.

Adv - Start RPM 950
Adv - Total RPM 3000
Total Adv Mech 28 degrees
Vacuum Adv 10 degrees
Total of 38 degrees

_________________
Love cruising in a bare metal Val!

DI,

Vacuum gauge installed (finally!). What specific info would you require to confirm your point 2) above?

_________________
Love cruising in a bare metal Val!

What is your vacc reading at the following:

low idle after warm up in P
Low idle after warm up in D with brakes applied
Typical cruise vacc reading on highway
Typical passing vacc reading on highway
Vacc Reading at WOT

DI,

Apologies for the delay. Haven't had a chance to get out on the highway til today. Here are the vacuum readings in INS/Hg. Let me know what you think.

Low idle after warm up in P - 17/18
Low idle after warm up in D with brakes applied - 15
Typical cruise vacc reading on highway - 13/15
Typical passing vacc reading on highway - 5/7
Vacc Reading at WOT - close to zero

Have got the O2 sensor bung welded in, but will be a while before I wire it all up.

Let me know what you think.

_________________
Love cruising in a bare metal Val!

Readings look normal for an automatic car with a good street tune...

The O2 sensor will help pin it down to see if you are dipping lean when the pinging occurs, if there is no lean dip then you will either have to switch to a cam that will better support the compression, invest in spiking every tank with some high octane fuel, or detune the distributor curve (which unfortunately will lose some performance....).... there is one other way to go but it's not a good choice, you can richen your mix (up jet, raise/change the rods, etc...)... that will add extra fuel to help supress knock, but the disadvantage to this will be that the extra fuel can wash the cylinder wall down causing premature wear on the cylinders....

DI,

Thanks for the quick response - appreciate your thoughts.

Will be interesting to see what results come up with the o2 sensor.

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Love cruising in a bare metal Val!