318 with pertronix flamethrower II billet on the dyno

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lomchivok

lomchivok

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My 318 build has me scratching my head. 1800 miles on the new motor.
It's zero decked with 1.81 KB forged pistons, .040 overbore, Indy/Rhs LA X heads with 1.92/1.62 valves, 62 cc closed chambers. .042 quench, a Comp XE268H cam, a holley 4150 650 cfm carb, Eddy air gap intake, a pertronix flame thrower II billet distributor and a timing chain tensioner. It's got 2.94 rear end gears for now (3.23 being assembled now in the garage) and about 9.6:1 compression. Intake centerline is installed at 105.5 on the degree wheel.
At the wheels 281.32 HP @ 5790 rpm and 257.65 torque @ 5690 rpm. pulls done in second gear because of the rear end ratio. 92 octane, 10% ethanol. Oh, and I'm going to up it from a 1700 to a loose 2000 or 2200 stall converter to help with in gear and engaged A/C compressor Idle quality.
air/fuel ratio was good but at higher rpm was leaning out so upped 3 secondary jet sizes and came in good @ 12.76. float bowls are running dry at higher rpm so I do need a better fuel pump.

Here's the thing. This pertronix distributor has the 16* stops in it with 1 light spring (Copper color) and 1 medium spring (Silver color) on the mechanicals. Initial is set at 18* BTDC...that should give me 34* total...vacuum advance disconnected and plugged. I would guess it should be all in by 2800 to 3000 rpm...well, it's not and total advance is not 34*. It's all in at about 3800 and total advance is 40* BTDC, no detonation. We didn't take it any higher than 40*...tech said he thought that might be pushing it.
The Dyno showed that it likes this timing. Moving the distributor for 36* BTDC same springs, same stops dropped 25 hp. 34*BTDC dropped 31 Hp.
The pertronix mechanical stops are cheesy at best. Had them jam up the mechanical advance before and it seems that they also aren't holding timing.
Any one else have problems with the pertronix stuff?? 40* seems like a lot but the dyno proved it to be good so that's where it will stay as long as the distributor will remain constant...I don't trust it anymore.
I just ordered an FBO HEI setup with limiter plate. I guess I should call em and tell em the dyno results so they can set it up accordingly but at 3000 all in.
40* has me scratching my head...any one else have similar timing numbers???

Opinions????
 
First. Remember that 40* at 3800 is not the same at 40* at 3000. You very well could ping at 40* at 3000. A lot of guys that get 32*-36* are all in by 3000. Some even lower. They want to get as much timing in as quick as they can for best performance. That's the difference. Of course you're going to have more advance higher up on the curve. That's just how it works.

As for why you are getting more timing than what you put into it mechanically. It's simple. There's something wrong with the mechanical advance setup on your distributor. I'd pull it apart and check it. Is it new? Did it have problems before? Can you see anything wrong inside? Go through it and see. If you or your tuner have another distributor you can try. Try it and see what happens.
 
Lustle said:
As for why you are getting more timing than what you put into it mechanically. It's simple. There's something wrong with the mechanical advance setup on your distributor. I'd pull it apart and check it. Is it new? Did it have problems before? Can you see anything wrong inside? Go through it and see. If you or your tuner have another distributor you can try. Try it and see what happens.
Click to expand...

But I have the limiters set for 34* total with the springs set for 3000 all in. Shouldn't the mechanical advance stop advancing at the 16* limiters limit. I mean, 18* plus 16* limiters should give me 34* total at 3000 rpm and above and no more mechanical advance above 3000. I thought that was the intent of limiting the mechanical advance so that it would not advance past the set point.
Yes there is something wrong with the mechanical advance...it's the limiters...they aren't limiting...it is a brand new distributor.
 
lomchivok said:
But I have the limiters set for 34* total with the springs set for 3000 all in. Shouldn't the mechanical advance stop advancing at the 16* limiters limit. I mean, 18* plus 16* limiters should give me 34* total at 3000 rpm and above and no more mechanical advance above 3000. I thought that was the intent of limiting the mechanical advance so that it would not advance past the set point.
Yes there is something wrong with the mechanical advance...it's the limiters...they aren't limiting...it is a brand new distributor.
Click to expand...

Talk to pertronix. Tell them their limiter isn't working.
 
Thats a really good rear wheel number, it would beat my 340 by a lot.
 
it's pretty stout, here's the Dyno Sheet
dyno sheet.JPG
 
stixx said:
Peak torque is really high in the curve for that cam...
Click to expand...
Yah, it looks like 5600 is where it started getting lean cause (I think) the float bowls were running out of fuel. Otherwise it looks like the torque peak might have been at about 4800.
Seriously considering going FiTech EFI.
 
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