340 Help. Am I looking in the right spot to fix the issue

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G70464

G70464

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Hi
I have a 340 that is 30 over 10.5 to 1 trw Pistons, 1.5 adjustable rockers x heads and 850 thermoquad, yes the carb is fine. Total timing 34 degrees coming in at 2800 rpm.
Has solid compression on all cylinders 190 to 200.
Plugs are tan.
3.23 gears 3200 stall
I have a Crane 150062 cam, attached the cam card.
Went to MoParty and ran it and dyno it. The car was a Dog. Rear wheel 302 ft lbs torque 3100 rpm 205 hp at 4200 and then it dies off.
No power over 3500 Rpm. Goes straight down at 4200.
I think my builder put the cam in advanced could this cause the cam not to react like it should 3000 to 6000 power band
Can it be the distributor going out of phase?
Engine builds power like it should from 2200 to 2400 then the torque curve bubbles up then has a straight decenending line to 4200 rpm where it dies at 225 ft lbs
Any insight is helpful
There is no Crane tech support to let me know where the cam should be installed.
camcard 150062 (Small).jpg
 
Doubt the dist is out of phase which one is it? Curved right they do wonders. 34 total with Vac? Also where is the initial timing?
 
All I really know is that you have good compression and tan plugs and ran poorly at moparty.

Did this engine run good before moparty?
 
Take your dyno numbers back to your engine builder and ask him why.

I don’t understand why folks have an engine built by someone that doesn’t use a dyno to tune it and verify power levels.
 
ch1ll said:
Take your dyno numbers back to your engine builder and ask him why.

I don’t understand why folks have an engine built by someone that doesn’t use a dyno to tune it and verify power levels.
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There are not many builders left where I am and the one with the dyno is not good with Mopar stuff
 
halifaxhops said:
Doubt the dist is out of phase which one is it? Curved right they do wonders. 34 total with Vac? Also where is the initial timing?
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I have a plate that is set at 16 degrees of advance the Mechanical is 34 all in. Initial is 18.
Vaccum is ported and does not enter into wot equation.
 
Was the cam degreed at the time of installation? If not then who knows where it is. You need to know where it lands with your timing set and keyway locations in order to move it to where you want it to be.

Also, Dyno's are not the be all, end all of how an engine performs overall, most don't start to record until 3k. The operator and/or maintenance (or lack there of) can throw numbers off. What gear was the the run done in?

Any track times?
 
With cast heads, a short timing curve, moderate compression, unknown cam timing, and 190-200 psi of cranking compression with the info you provided I’m gonna say it’s very possible that it’s detonating under load and when that happens the power goes away quick. What fuel do you run?
 
TT5.9mag said:
With cast heads, a short timing curve, moderate compression, unknown cam timing, and 190-200 psi of cranking compression with the info you provided I’m gonna say it’s very possible that it’s detonating under load and when that happens the power goes away quick. What fuel do you run?
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93 non ethonal honestly detonation that bad wouldn't show up in the plugs, metal particles, i believe I would hear it. But I still will back the timing for giggles.
 
dano said:
Was the cam degreed at the time of installation? If not then who knows where it is. You need to know where it lands with your timing set and keyway locations in order to move it to where you want it to be.

Also, Dyno's are not the be all, end all of how an engine performs overall, most don't start to record until 3k. The operator and/or maintenance (or lack there of) can throw numbers off. What gear was the the run done in?

Any track times?
Click to expand...
3rd gear run, which I asked for 2nd,
5 runs 75 degrees out no wind or humidity 400 feet alt
All about 15.4 @87 mph manually shifting at 5500 rpm, the car was dead from launch on to the end in a 72 charger. Yes I know B body but this is the only place that talks small block.
 
G70464 said:
93 non ethonal honestly detonation that bad wouldn't show up in the plugs, metal particles, i believe I would hear it. But I still will back the timing for giggles.
Click to expand...
I wouldn’t back the timing down just yet. Throw some good gas in it and make a pass just to see.
 
G70464 said:
There are not many builders left where I am and the one with the dyno is not good with Mopar stuff
Click to expand...
Unfortunate as that is, it saves time, money and aggravation even if you have to travel to find one. Lucky for me, my local builder does it all. 1929 Cord, 302 GMC all the way to race engines for local short track and drag racers.
 
Did anybody check to see if the TQ was getting to WOT? Secondaries not opening?
Sec main jets? Some had small 0.125" jets; some came with 0.143" jets. Carb getting enough fuel? Air valve linkage operating freely?
Agree with RRR, could be soft valve springs.
Crane ground 5* of advance into most of their cams, & this cam has that. Doubt that this is a cam adv/ret issue.
 
what about the fuel system?? lack of fuel will cause those problems. in the tank is a sock on inlet, those get plugged up, and don't let engine get correct amount of fuel, also how about the fuel pump? on which side of fuel pump is the filter?
 
Ok answer a bunch of questions
I appreciate the thoughts.
The motor is very Lazy it accelerates like a diesel above 3000 grand.

Thermoquad has full WOT I have been building them for 15 years. 2 different carbs 800 with 98 143 1997 rods 850 100 143 1996 rods same results.
Fuel filter, Mopar metal, is before an edelbrock high flow pump 110 gpm 6 psi

Entire fuel system was new 14 years ago, all stainless new sock. Everything is tan and I read down into the plug and it is dark so it looks less likely since it has not gone dead lean.

I had a previous 340, that a cylinder cracked, set up the same and it pulled much harder. The springs are the correct ones for the cam, they where reused.

Another bit of info car gets horrible fuel economy cruising on the highway, which also relates to power dropping off, cruise at 3000 rpm right where the power drops off on the dyno graph. Previous 340 got 17 on highway cruising this struggles for 15. Almost identical builds.

I know there is 5° of advance built in but if it is put in 8° advance wouldn't it peak really early and just have nothing over 4000 rpm.

So I am pulling the distributor checking the timing plate reset timing and run it
Next I guess larger 2ndary jets 151
Next disassemble engine check degree the cam to spec of 107.
 
ch1ll said:
Unfortunate as that is, it saves time, money and aggravation even if you have to travel to find one. Lucky for me, my local builder does it all. 1929 Cord, 302 GMC all the way to race engines for local short track and drag racers.
Click to expand...
That is a GM motor yes my one shop does those, Mopar not so much.
 
What are you using to control the distributor / ignition?
Electronic distributor I assume so, are any ignition wires coming in contact with control wires for the distributor?
I remember back when there were warnings about certain ECU's that were to be avoided when wanting performance. So, if you are running the orange box or any good MSD ignition you should be good
 
You can check cam timing with the balancer to see if it's close. Fire the motor to get the lifter pumped up, pull the valve cover and hand rotate until #1 intake pushrod just starts to open. You should be near 31* BTDC on the harmonic balancer.
If cam timing is is in the ballpark I would be looking at the ignition. I gave up on orange boxes and run old analog msd 6ALs on both of my cars with a ford style e core coil.
190 to 200 cranking compression is good, and looks like you have a handle on the carb. You could hook a fuel pressure gauge and tape it to the windshield to see if fuel pressure drops when your foot is into it.
 
With that cylinder pressure and cam, that thing should pull hard to at least 5,500. What balancer are you using. Sounds like your timing is way off from the gitgo. If it's a stocker it may have slipped enough that your getting bogus readings all the way around.
 
OldmanRick said:
With that cylinder pressure and cam, that thing should pull hard to at least 5,500. What balancer are you using. Sounds like your timing is way off from the gitgo. If it's a stocker it may have slipped enough that your getting bogus readings all the way around.
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340sFastback said:
Have you taken a piston stop and verified top dead center on the balancer?
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I replaced it whe I rebuilt the engine, I also verified TDC when it was done.
TDC is still correct.
 
I pulled the distributor and the reluctor wheel was hitting the magnet, the plate was at 18 not 16 and the springs where too heavy.
Set gap to 0.008 plate set to 14 and removed a spring
Total is now 32
Guess my younger self didn’t double check my work.
Took it for a drive can spin the tires from a roll.
Pulls a bit harder
Will go to Mexico to see how it runs.
 
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