Tuning issues on the Volare

[slant6billy]

So I've been getting a sputter and a slight miss at times at idle. My winter tune was not the greatest, spring tune was completely off.

So I pulled one spark plug at a time. No1 & 3 black carbon. Same 2 & 4. Those are the front 4. The back four: No 5,7, 6,8 were a slight brown with a hint white. Plugs only have a about 1000 miles on them. I cleaned them up and put everything back. I checked the cap and rotor, them too were in very good shape- I've seen worse on my magnum engines. So I started the engine and was bringing some timing into the engine (turning counterclockwise or what is also called advancing the timing) After I shut the engine off she would not start. Way too much timing. I backed it off and got it to start and then back to setting timing. I also put some leaning in the idle mix.

So to give a bit of background: The motor is a 1985 Diplomat AHB 318 with a 30 over bore. Intake and heads are off a 70/71 cuda 340 4BBL. The carb is a Edelbrock performer 750 with the E choke kit. I'm back to running the mopar orange ignition and I don't have lean burn. Distributor is a stock mopar vac advance type.

I took it back out for a blast before the rain last night and she is almost good to perfect. Broke the tires loose and pulled hard through the gears up to about 85....... (oh yeah I mean kmh- HAHAHA) Seriously. She had power, but I noticed the idle was higher after the romp'n. I have suspicion that I might be getting timing chain stretching. The dude who threw the engine together put a summit racing cam 218/228 duration and 441 lift, but I question what chain he used. I would think no-one is that lazy to reuse a timing chain and gears when changing a cam. Chain and gears are a cheap insurance. So I will tear the engine down if and when she fails. Until then I'll keep on with my 360 build.

I get a lot of folks telling me the 750 is too big. The car had a 650 cfm holley and it was not enough. The 750 has never bogged out on me. Even when I thought she was leaning out on me at highway speeds, it was not all too bad.

I've never seen a mopar chain stretch. I've seen them destroy the timing gear and pistons kiss the valves. Do they stretch? Does the idle rising seem like the symptoms off chain / timing movement?

 

[kkritsilas]

I am not certain, but small block Mopars are not interference fit engines, so if the cam chain did break, unless there is some very wild cam and super high compression, the valves should not hit the pistons.

Cam chains on the Chrysler small blocks do stretch. the cam is fairly high in the block, which makes the cam chain fairly long. Each link doesn't stretch that much, but the accumulated stretch form all the links does add up. Without measuring tools and a new chain to compare with, you probably won't notice the chain strethc, but if there is enough mileage on the engine, the cam chain will stretech (and it isn't just small block Chryslers, most cam chains do stretch to some degree, even on more modern engine designs, its just that newer engines have cam chain tensioners to take up the slack).

 

[slant6billy]

I am not certain, but small block Mopars are not interference fit engines, so if the cam chain did break, unless there is some very wild cam and super high compression, the valves should not hit the pistons.

Cam chains on the Chrysler small blocks do stretch. the cam is fairly high in the block, which makes the cam chain fairly long. Each link doesn't stretch that much, but the accumulated stretch form all the links does add up. Without measuring tools and a new chain to compare with, you probably won't notice the chain strethc, but if there is enough mileage on the engine, the cam chain will stretech (and it isn't just small block Chryslers, most cam chains do stretch to some degree, even on more modern engine designs, its just that newer engines have cam chain tensioners to take up the slack).

I never thought about it until you sort of mentioned. I guess there is a way to see by how much the stretch is or how far out the chain has slacked. I also expect the gears to have chain wear.

 

[Aspen500]

A sort of non-scientific way to get a rough idea is, pop the distributor cap off and turn the engine one way until the rotor starts moving and then go the other direction until it starts moving. If it's more than a few degrees, the chain is loose which also means stretched. Most times also, the timing marks will jump all over when looking at them with a timing light at idle. Normally it'll smooth out with a load on the engine.
You can retro-fit a chain tensioner. I put one on my Dakota 3.9L when I changed the stretched chain last summer. It replaces the cam thrust plate.

Modern engines do have chain tensioners to take up the slack BUT, if the chain stretches the cam timing will still be retarded. On modern engines you'll know, the check engine light will come on with a cam/crank position correlation error fault code P0008. Any 3.6L GM engine with over 60,000 miles will verify that statement, lol! (Job security). They have one primary and two secondary chains and all 3 stretch so cam timing error is multiplied by a factor of 3 over one chain engines and they ARE interference engies.

This is the retro fit tensioner for 3.9L, 5.2L, 5.9L (and any small block Mopar LA and Magnum engine back to 1964).
https://www.summitracing.com/parts/...a-msn-_-shopping-_-srese2-_-mopar-performance

 

[Joe12459]

I've had more than one small block chain stretch, but they were all aftermarket chains. Aspen500's suggestion is the easiest way to quickly verify if the chain is stretched. As he also pointed out, the only thing a tensioner will do for you is quiet the slapping chain. If it's stretched, it will still retard the timing. Seeing that the front four cylinders seem to have an issue, is it possible that those lifters are not getting enough oil to stay pumped up under load, and not fully opening the valves quickly enough?

 

[slant6billy]

Thanks guys. 30 years ago, my Dad went and challenged a few of the neighbors to a burnout contest. My Dad used my brother's 73 Grand Fury Coupe with a 360 and won. A few days later, on one cold frigged night, the engine start throwing gas out the top of the carb. Who knows how my bro was driving at the time. Popped the cap and no movement on the rotor. My brother never knew the precursor to the timing chain letting go. I did a firebird myself and actually shredded the gear. Yep, we got a family propensity to destroying things.

 

[Aspen500]

Main reason I changed the chain (and gears) in my '96 Dakota and added the tensioner is for chain slap. Sounded like a can full of ball bearings at idle. Had the noise when I bought it back in '98 with 48,000 miles and it wasn't all that much noisier at 148,000 when I changed it but,,,,,,the fuel sync was right at the limit without moving the distributor (which houses the cam position sensor) to adjust it. The ignition timing is controlled by the ECM using the crank sensor so that never changes with chain wear. Meant the chain was stretched quite a bit but the truck ran seemingly fine. Actually when I tore it apart, it was getting to a point that it wouldn't have taken much to have the chain jump a tooth it was so loose. After changing the chain and retro fitting the tensioner (all 3.9L had one from '97 on up to eliminate the rattle) I had a noticeable improvement in power and more important for a daily driver,,,,,,,,,my average mileage increased by 2 mpg. Was about 17 in the summer and now it's 19-20 average and you barely know the engine is running at idle anymore.

 

[slant6billy]

Main reason I changed the chain (and gears) in my '96 Dakota and added the tensioner is for chain slap. Sounded like a can full of ball bearings at idle. Had the noise when I bought it back in '98 with 48,000 miles and it wasn't all that much noisier at 148,000 when I changed it but,,,,,,the fuel sync was right at the limit without moving the distributor (which houses the cam position sensor) to adjust it. The ignition timing is controlled by the ECM using the crank sensor so that never changes with chain wear. Meant the chain was stretched quite a bit but the truck ran seemingly fine. Actually when I tore it apart, it was getting to a point that it wouldn't have taken much to have the chain jump a tooth it was so loose. After changing the chain and retro fitting the tensioner (all 3.9L had one from '97 on up to eliminate the rattle) I had a noticeable improvement in power and more important for a daily driver,,,,,,,,,my average mileage increased by 2 mpg. Was about 17 in the summer and now it's 19-20 average and you barely know the engine is running at idle anymore.

HUMMMM? My 95 3.9 in the van had that from the time I bought it in 2008. "Can of ball bearings" is exactly the sound. Parted ways with the Van on Newyears eve, so I'll never truly know. I may jump on the chain to this small block after I pull the motor to drop the 360 in

 

[Aspen500]

That is the exact reason Mopar started putting chain tensioners on the 3.9L (but not the V-8's) in 1997, the idle rattle. I'm pretty sure there was a Chrysler TSB about it that described the complaint and the fix. For whatever reason (firing pulses???) only the 3.9L has the problem, 5.2 and 5.9 do not, even though the V-6 is basically a 5.2L with 2 cylinders chopped off. Nice thing is though, they adapted to the existing design in the simplest way possible so it (the tensioner) can be used back to at least 1964. Unsure if it would fit the poly-318 or not.

 

[slant6billy]

That is the exact reason Mopar started putting chain tensioners on the 3.9L (but not the V-8's) in 1997, the idle rattle. I'm pretty sure there was a Chrysler TSB about it that described the complaint and the fix. For whatever reason (firing pulses???) only the 3.9L has the problem, 5.2 and 5.9 do not, even though the V-6 is basically a 5.2L with 2 cylinders chopped off. Nice thing is though, they adapted to the existing design in the simplest way possible so it (the tensioner) can be used back to at least 1964. Unsure if it would fit the poly-318 or not.

So my 97 Ram SS/T with the 5.9 magnum would not have it. Got to say it is the quietest engine and smoothest engine I have every had. Swiss clock would be jealous. so Tensioner or not, Ma mopar got it right with that one. Knowing that, folks should be grabbing every SS/T ram wrecked for its power plant. The 3.9 V6 is probably the best V6 out there for putting through the punishment. I proudly admit punishing mine. I had 4.3 chevys spin bearings and Ford V6 die simple death. They are just V6s and don't balance as good as a V8. so all that vibration has to take its toll.

 

[Aspen500]

Nope, the V-8's never got the tensioner but it can be added.
That could be why the 3.9L has the chain rattle without a tensioner. The 5.2 and 5.9 idle smooth like any other V-8 but the 3.9L is a shaky s.o.b. at idle. Makes the radio antenna vibrate. Typical of a 90 degree V-6, even with splayed rod journals to make it even fire. Maybe why the rev limiter comes in at only 4,700 rpm too(?)
Doesn't surprise me the 3.9L is long lasting because all it's really a 318 minus 2 cylinders and we all know how indestructible a 318 (and later a 5.2 and then 5.2 Magnum) are.

A little side info: It just occurred to me that at work, we tear into GM and Ford truck engines all the time for chains, tensioners, guides and cam phasers (Fords), cam and lifters and/or headgaskets, oil pumps (GM), etc...........Very rarely if EVER does a Dodge or RAM engine need to come apart for anything. Most I've ever done to the new Hemi is a water pump. I don't think anyone in the shop has ever had a 5.2 or 5.9 Magnum apart (other than maybe water pump or the infamous intake plenum plate gasket leak). I'm just saying...........

 

[80mirada]

My brother's 03 Hemi Ram broke a valve spring, at over 250,000 miles

 

[BudW]

Hemi’s with broken valve springs and/or dropped valve seats are not that uncommon. I “suspect” it is from over revving – but have no proof of such. I do see one every couple of months or so .

Not exactly an in-expensive repair.


I have a couple of the 3.9L tensioners on the shelf - for anytime I’m going into a small block - one is going in, wither it wants it or not.


I’ve been inside a few 318 poly engines and seen a few Gen I Hemi Parts.

Fairly sure the tensioner will work for the 277/301/318 Polys, and I suspect it may work for the early Hemi’s – but have no way to find out.

There is a lot of performance parts being made for the Poly’s now – whereas 10 years ago, it was ho-hum ever sense the LA 318 came out.

BudW

 

[Aspen500]

It was a looooooooong time ago (like 25 years) but when my dad and I overhauled the 318 poly in his '62 Fury, seems to me I remember the timing set, camshaft thrust plate, etc looking just like the LA engines. As I said though, it's been a while.

 

[80mirada]

The chain tensioner is supposed to fit early A block just like a number of other LA parts.

I had read the valve seats dropped out of early Gen III Hemis from overheating and early spring failure was over revving, but at 250k miles I think is a relatively acceptable failure for one to break. LS motors tend to loose oil pumps at 165-200k.

 

[AJ/FormS]

You say the 750 is not too big...
That cam will power peak around 5200. With a 904, it will want to be shifted around 6500, to drop in at 3900, for a powerband of 2600, centered at 5200. So your carb size would need to be ;
318 x 6500/3456 =598 cfm at 100% VE. With manifolds and full exhaust you'd be lucky to hit 85 % so, 598 x .85 = 508cfm, so really a 500 would be good for you. You can of course run a bigger carb. But generally at 3000 and under,the 750 will be too much, suffering driveability issues, especially with low-compression engines. A vacuum secondary type carb may not even open the secondaries early enough. A smaller carb will be much sharper and easier to tune, at those lower rpms, and you should be able to open the secondaries earlier and faster, for more midrange. The smaller venturies will do a better job of atomization, and increase torque and decrease fuel consumption under all circumstances. Most teeners quit reving long before 6000, so Ima thinking that a well-tuned 500 would be plenty.
It would take a heck of a tune to get tirespin out of a Stock teener with those big chambered 2.02s, and a 750.
I can't imagine a situation where the front 4 plugs are rich, and the back 4 are normal. Ima guessing the back 4 are sucking air,(possibly from the PCV or brake booster) and the carb has been enriched to compensate. The intermittent high idle is probably the secondaries sticking slightly open, or a poor T-port synchronization.That cam should idle with the secondaries completely closed, and idle-timing of 14* or a little less, and power timing of 34*@ 3000rpm or a little higher depending on true compression ratio.
I can't believe you get tirespin with that combo! What gears are you running and are you spinning both tires? How high a TC are you running? Dual exhaust and/or headers?

 

[slant6billy]

You say the 750 is not too big...
That cam will power peak around 5200. With a 904, it will want to be shifted around 6500, to drop in at 3900, for a powerband of 2600, centered at 5200. So your carb size would need to be ;
318 x 6500/3456 =598 cfm at 100% VE. With manifolds and full exhaust you'd be lucky to hit 85/90 % so, 598 x .875 = 523cfm, so really a 500 would be good to 6200, for you. You can of course run a bigger carb. But generally at 3000 and under,the 750 will be too much, suffering driveability issues, especially with low-compression engines. A vacuum secondary type carb may not even open the secondaries early enough. A smaller carb will be much sharper and easier to tune, at those lower rpms, and you should be able to open the secondaries earlier and faster, for more midrange. The smaller venturies will do a better job of atomization, and increase torque and decrease fuel consumption under all circumstances. Most teeners quit reving long before 6000, so Ima thinking that a well-tuned 500 would be plenty.
It would take a heck of a tune to get tirespin out of a Stock teener with those big chambered 2.02s, and a 750.
I can't imagine a situation where the front 4 plugs are rich, and the back 4 are normal. Ima guessing the back 4 are sucking air,(possibly from the PCV or brake booster) and the carb has been enriched to compensate. The intermittent high idle is probably the secondaries sticking slightly open, or a poor T-port synchronization.That cam should idle with the secondaries completely closed, and idle-timing of 14* or a little less, and power timing of 34*@ 3000rpm or a little higher depending on true compression ratio.
I can't believe you get tirespin with that combo! What gears are you running and are you spinning both tires? How high a TC are you running? Dual exhaust and/or headers?

430 rear gears, converter is a bit more than stock. Not ferociously spinning the tires, but I have enough rubber and asphalt stuck to the 1/4 panel. Shes running better now with additional tuning. I hit her with the timing light and the timing is not jumping all over, so it doesn't look like the chain is all that bad. I may just put a smaller 600 cfm on it for kicks and see results.

 

[AJ/FormS]

Oh, 4.30s and a bit of a TC. That explains it!
That K6901 is a very slow cam, and unless you have bumped your compression up near 10.5, is gonna have take-off issues. Which I imagine is why the 4.30s?
The specs are 276/288/114, lift of .441/.441, and 050 of 218/228. This cam has a 276 less 218 =58* of clearance ramps. A high intensity cam could have 44* ramps,(some are less) so yours is sleeping for (58 - 44)/2 =14 degrees.Half of these are at each end of the intake cycle, So during 7* of these, the engine is not making any compression, and another 7* is kindof wasted at the other end during overlap.
At 8/1 Static c/r, this baby will give you just 6.18Dcr and 113 psi cylinder pressure.
At 9.5Scr the Dcr comes up to 7.29/140psi.
At 10.5Scr, things are finally looking good at 8.0/160psi
If you are not pushing 10/1,or better, I would launch this cam into outer-space. Well I would anyway.
If your pistons are down in the hole like stock, and those X-heads are stock/uncut, you need the fastest most intense cam you can lay your hands on. Then you can go back to a smaller more street-friendly gear, and have a better performing combo.

So lets say you traded that 276Turd away for a theoretical high intensity 262/270/112 cam with the same .050 of 218/228 . This would lower your ICA from 69* to 61*, and your engine will be capturing more compression.
At 8/1Scr,your Dcr will now be 6.56/123psi. That's a half point gain. And comes with an increase in low speed performance.
At 9.5 Scr, the Dcr is now up to 7.75/153psi(up from 7.29)
At 10.0, the Dcr is 8.15/163 just on the border for pumpgas.
At 10.5, the Dcr is up to 8.55/173psi, which is now probably too high for pumpgas.Up from 8.0/160
Are you starting to see the picture?... yeah it took me awhile too. Although the pressure number gains look small, relatively speaking, at 9.5Scr, the increase is 6.3%. This does not mean a torque increase of 6.3 %. It means kick-azz tirespin vs say a prayer and hope it gets going. I'm talking with street-friendly gears, here; not 4.30s and 2400 stall.
The thing is, What is Dcr? Dcr is a snapshot of engine performance, and gives us a way of comparing the primary engine parameters of compression and cam.
In this case you can see exactly how a lazy cam compares to a high intensity cam. Hi-intensity simply refers to how fast the cam is able to go from one lift of note to another lift of note. In this case from advertised (probably .006inch) to .050 inch lift. I call this a lazy cam, but that is probably a misnomer. This lazy cam could be used in an engine that had a little too much Scr, to help it escape detonation. It very definitely has a purpose, just not in a low compression engine.
So to recap; If you are looking for more performance, in a low compression engine, you need a really fast cam. That 218/228 is a really good size for a teener. The fast rate 218 will also return better fuel economy, cuz the engine will be more efficient.
'Course you may not care about mpgs with 4.30s lol...
And to cap it off, X-heads in your application are probably not bringing anything to the party, but the 4.30s are masking it.Since they are already installed,and you are building a 360, I see no point in shelving them, although I would, if I had a nice set of closed chamber LAs, or Magnums.

 

[slant6billy]

Oh, 4.30s and a bit of a TC. That explains it!
That K6901 is a very slow cam, and unless you have bumped your compression up near 10.5, is gonna have take-off issues. Which I imagine is why the 4.30s?
The specs are 276/288/114, lift of .441/.441, and 050 of 218/228. This cam has a 276 less 218 =58* of clearance ramps. A high intensity cam could have 44* ramps,(some are less) so yours is sleeping for (58 - 44)/2 =14 degrees.Half of these are at each end of the intake cycle, So during 7* of these, the engine is not making any compression, and another 7* is kindof wasted at the other end during overlap.
At 8/1 Static c/r, this baby will give you just 6.18Dcr and 113 psi cylinder pressure.
At 9.5Scr the Dcr comes up to 7.29/140psi.
At 10.5Scr, things are finally looking good at 8.0/160psi
If you are not pushing 10/1,or better, I would launch this cam into outer-space. Well I would anyway.
If your pistons are down in the hole like stock, and those X-heads are stock/uncut, you need the fastest most intense cam you can lay your hands on. Then you can go back to a smaller more street-friendly gear, and have a better performing combo.

So lets say you traded that 276Turd away for a theoretical high intensity 262/270/112 cam with the same .050 of 218/228 . This would lower your ICA from 69* to 61*, and your engine will be capturing more compression.
At 8/1Scr,your Dcr will now be 6.56/123psi. That's a half point gain. And comes with an increase in low speed performance.
At 9.5 Scr, the Dcr is now up to 7.75/153psi(up from 7.29)
At 10.0, the Dcr is 8.15/163 just on the border for pumpgas.
At 10.5, the Dcr is up to 8.55/173psi, which is now probably too high for pumpgas.Up from 8.0/160
Are you starting to see the picture?... yeah it took me awhile too. Although the pressure number gains look small, relatively speaking, at 9.5Scr, the increase is 6.3%. This does not mean a torque increase of 6.3 %. It means kick-azz tirespin vs say a prayer and hope it gets going. I'm talking with street-friendly gears, here; not 4.30s and 2400 stall.
The thing is, What is Dcr? Dcr is a snapshot of engine performance, and gives us a way of comparing the primary engine parameters of compression and cam.
In this case you can see exactly how a lazy cam compares to a high intensity cam. Hi-intensity simply refers to how fast the cam is able to go from one lift of note to another lift of note. In this case from advertised (probably .006inch) to .050 inch lift. I call this a lazy cam, but that is probably a misnomer. This lazy cam could be used in an engine that had a little too much Scr, to help it escape detonation. It very definitely has a purpose, just not in a low compression engine.
So to recap; If you are looking for more performance, in a low compression engine, you need a really fast cam. That 218/228 is a really good size for a teener. The fast rate 218 will also return better fuel economy, cuz the engine will be more efficient.
'Course you may not care about mpgs with 4.30s lol...
And to cap it off, X-heads in your application are probably not bringing anything to the party, but the 4.30s are masking it.Since they are already installed,and you are building a 360, I see no point in shelving them, although I would, if I had a nice set of closed chamber LAs, or Magnums.

thanks man. Good info. So the current motor might not be set up for the best output, but there are some unkowns- I 'll tear it down and put the other motor in see here-----. In the garage, I have the 1992 LA 360 from a 3/4 ton Ram (low miler) I know the spec on it. 8 to 1 comp, factory roller cam 178/ 180, hi flow heads, heavy duty crank. So I put a MP 6 qt car pan and p/u tube, Edlebrock Performer 360, just acquired Keithblack gear drive, MP waterpump, MP distributor. Still need a cam and looking at the Comp cams thumpr retro roller 283/303 duration & lift 513 /498. For rolling around, I'm sticking with the Edelbrock, but with 8 to 1 I'm going for the FI tech injection and a Powerdyne Supercharger with 10 psi. Something will break from the 904 to the driveshaft- I fully expect.

 

[AJ/FormS]

Again, with just 8/1 Scr, Camming is critical. Just one cam size too big can break a street combo, and then you are stuck with street band-aids like big gears and TCs.
I hope you are not expecting miracles with that LC 360. It is just 13% bigger than the 318. While the 360 will really perk up the low rpm torque,(allowing about 13% less gear than those 4.30s) a stout teener can totally annihilate an LC 360. That 13% might be just 25 or 30 horsepower. The real power comes by getting the compression up,and getting the heads to flow.Then matching the cam to that.And then helping it breath with intake,headers,and a freeflowing exhaust.
IMO the thumper type cam is not a good choice for a LC engine. It will just make a bad situation worse.
For instance; that 283 cam, in at 106*, will drop the 8/1SCr to a Dcr of 6.3/116psi. Can you say disappointing?It will be a slug off the line with anything but a way-to-high-for-street,converter. Even with the 4.30s.The power won't really start until way up the rpms, Ima thinking 4000/31mph(2.45low). Off the line, the neighbor's kids will, will pull you on bicycles.OK maybe that's extreme, but you get the picture.That cam needs 10.5 Scr, to make 8.2/165; about the limit for pumpgas.There is no such thing as a performance cam, that will wake up an 8/1 LC 360.Not even a teener cam will make decent Dcr/pressure.
What that means is start saving money, cuz you are gonna have to do something about that 8/1 compression.

Oh crap, I missed the supercharger sentence, Sorry. IDK how that happened. But still same story on that 283cam. I wouldn't use it, unless somebody gave it to me. Even then, probably not.............
But you know what? That super will fit on the teener, and it already has a pretty good supercharger cam in it, and great heads for the application. Ima thinking that would be an easy 300/350 hp, just as it sits.Another 2psi might get you 400. And that will be way to much for the chassis,I bet...........