Cam advice for more torque from 340

-
W

WSUTARD

Well-Known Member
Joined
Jul 13, 2016
Messages
600
Reaction score
69
Location
Seattle, WA
I would love to hear some opinions about a new cam for my 340.

First, the engine is 10.5-1 compression.
Stock X heads with factory rockers.
Currently has a Crowler Cam with 285 dur, 480 lift, 110 deg. (I was told this by the previous owner however I can't find a crowler cam with these specs.)

This is in a 69 B Body and it's only used on the street. I'm looking for more low end torque. I don't race so having my power in the high RPM range does me no good.

I was recommended a Comp XE 268. Not sure if there is something better.

Thanks
 
Crower usually does 112, or 108 lobe centers...maybe a custom grind...? It's gonna be driveable, with tuning..recommendation of a 2400-2800 stall...
 
Have you considered advancing the cam a few degrees to move the band into a lower rpm range? Just check piston to valve clearance before you button er up.
 
Last edited:
I would fill out a form for Mike Jones cams, or Bullet cams, and go with a custom cam. Where the torque starts is the most critical part of your power curve, and they have designed WAY more cams than any of us have ever used. They will cut it for exactly what lsa you need, etc.
 
When you say 10.5:1 compression ratio, is that the factory rating for your year of engine? I seriously doubt it is actually 10:5:1: actual static CR would be in the low 9 range at best with original parts, and you would need domed pistons to actually get 10:5:1 with stock chambered heads.

Run a cranking compression test first and report what psi you get; that will tell part of the story. Do you have any piston and head gasket info to share?

Have you gone through and optimized the ignition timing?

The XE2868 tends to be a good middle ground cam between top end breathing without taking away too much low end torque. The 'XE' series features steeper than average lobe ramps to get better lift versus duration, which is all good for improved low end torque. You an do better for low end torque, but more info is needed on what you really have for static CR. If you really have 10.5:1 static CR, then going to lower duration takes a lot of care. (But I will guess your engine really doesn't have 10.5:1...)

Also, Rhodes lifters will give you lower effective duration at lower RPM's so that is a 'quickie' option to help, assuming you have a hydraulic lifter cam. It supposedly has an effect like shortening the duration by about 10 degrees at low RPM's, so it won't do as much to help low RPM torque as changing to the XE268 cam.
 
69conv said:
Have you considered advancing the cam a few degrees to move the band into a lower rpm range? Just check piston to valve clearance before you butter er up.
Click to expand...

This would be my first move before changing the camshaft. Dyno the car before and after and see what the data yields.
 
One other thing to do- go over your combo from top to bottom, looking for tuning or modifications that will increase torque, like cold air intake, blocked heat riser, etc. Any thread that is asking " how can I make my street strip car faster" may have suggestions on how to improve overall performance. An example is gear ratios. You have a B body and a small block; this needs more gear than a big block would for sure. An example of changes I might make; if i have a 727 trans and 3.23 gears, i would beg borrow or steal to figure out how to go to a 904 with the 2.74 low, and switch to a 3.55 or 3.73, to 3.91 rear gear. Just going from the 727 to 904 low gear deal and a 3.55 would increase low gear overall ratio. By 23 percent. That is the same as a 416 stroker with the old ratios! Add in the better cam, retune, etc. Put all these things to work for you and you will be very surprised just how well that little 340 can move that b body!
 
Last edited:
Thanks for everyone's insight. As you can tell I am a newb when it comes to engine internals.

Yes, I looked on the Crowler site and cant find the specs stated. This causes me pause when trying to change the cam. What if the guy was wrong and I spend time on putting in a cam with very similar numbers? Should there be any markings on the cam that can help me with identifying the specs? I have access to the engine now as I'm doing a suspension upgrade and have it all out of the car.

Do I have 10.5-1 compression? I don't know for sure, I did a compression test once and I think the PSIs were close to what they should be at 10.5-1.
The engine has been built up with KB pistons, titanium valves, and H beam rods and is connected to an 833 4 Speed ending in a 3.55 sure grip. (online calculators tell me its a 4.10 based on my RPM, tire size at 60 mph)

For timing I am at 8 degrees initial. I don't have a timing tape so I am limited to viewing 10 degrees with the timing light. The engine seems to like to be at 8 although im just basing that off idle.

I just watched a video on advancing the cam timing. Seems doable. I might take it into a local engine/dyno shop and give this a go. Although, seems like a dyno would be overkill for seat of the pants driving.

Sometimes this stuff is just frustrating.
 
Don't let it make you crazy, take your time and have fun with it. 1/2 the fun is getting to brag about the obstacles you overcome!!
 
69conv said:
Don't let it make you crazy, take your time and have fun with it. 1/2 the fun is getting to brag about the obstacles you overcome!!
Click to expand...
Well, I have already overcome the obstacle of wanting to drop in a 440! I will keep pecking away at this. Thanks for all the help everyone.
 
WSUTARD said:
Thanks for everyone's insight. As you can tell I am a newb when it comes to engine internals.

Yes, I looked on the Crowler site and cant find the specs stated. This causes me pause when trying to change the cam. What if the guy was wrong and I spend time on putting in a cam with very similar numbers? Should there be any markings on the cam that can help me with identifying the specs? I have access to the engine now as I'm doing a suspension upgrade and have it all out of the car.

Do I have 10.5-1 compression? I don't know for sure, I did a compression test once and I think the PSIs were close to what they should be at 10.5-1.
The engine has been built up with KB pistons, titanium valves, and H beam rods and is connected to an 833 4 Speed ending in a 3.55 sure grip. (online calculators tell me its a 4.10 based on my RPM, tire size at 60 mph)

For timing I am at 8 degrees initial. I don't have a timing tape so I am limited to viewing 10 degrees with the timing light. The engine seems to like to be at 8 although im just basing that off idle.

I just watched a video on advancing the cam timing. Seems doable. I might take it into a local engine/dyno shop and give this a go. Although, seems like a dyno would be overkill for seat of the pants driving.

Sometimes this stuff is just frustrating.
Click to expand...



You don't have enough initial timing.

Less than 1% chance you have Ti valves.

Work on your tune up before you change cams.
 
yellow rose said:
You don't have enough initial timing.

Work on your tune up before you change cams.
Click to expand...


I also noticed he didn't list the total timing. OP, remember to ALWAYS check your total timing after setting the base timing. If your idle comes up while setting the timing, as it can when advancing the base timing, reset it and continue.
 
You can go to Harbor frieght and get a cheap dial indicator, buy a degree wheel, make a checking pushrod out of a wooden dowel or what everyou can, and check that cam for timing at .006, .050, .200, and total lobe lift, and where it is degreed. Then you could compare it to Comp Cams master lobe specs, and read the notes on the charactoristics of the lobes. You will learn a lot if you do this. This is a great time to do all this, since the motor is out of the car. Guys here will be glad to walk you through the whole deal!! All this we are throwing at you may make your head spin a little, but take it at your own pace, and you will come up with a great combo. My first build using the help of board members on another site resulted in a car that went 9.30s. The next motor put it into the mid 8s, because of all the help I got. Priceless! Makes me want to pay it forward when l can!!
 
Last edited:
It's going to like 16-20 initial and tailor the mechanical advance to hit a safe total number. Will run like a different car with a bunch more low end grunt.

Stock 318's like more than 8* initial and you have a much bigger camshaft!
 
16-20 initial? Wow. When I was playing with the timing it didn't seem to like going much over 10. I also kept it lower because I don't know how to set the timing curve on the distributor I have. I guess I will put a timing tape on it and check out how to change/alter the timing advance of my distributor.
 
WSUTARD said:
16-20 initial? Wow. When I was playing with the timing it didn't seem to like going much over 10. I also kept it lower because I don't know how to set the timing curve on the distributor I have. I guess I will put a timing tape on it and check out how to change/alter the timing advance of my distributor.
Click to expand...

No need to invest in a timing tape. Just put marks on the balancer with a sharpie or scribe every 10* to 40* (or whereever you choose to stop).
 
Search "hillbilly Timing Tape"

Explains how to do it. You can mark the balancer however you want to. I make two marks, 15 and 30 BTDC,
 
Yes, you don't NEED to dyno it. Use your backside dyno LOL

On the compression: take the cranking compression readings again and post them as well as your elevation. 3 reasons to do this:
1. Good CR is very important for good low RPM torque... like what you want.
2. If you DO have domed pistons and a 10.5 SCR, with a high associated DCR (dynamic compressin ratio), then you are going to have to be a lot more careful with total ignition timing to avoid detonation.
3. If the SCR and DCR are high, then advancing the cam more will lead you even closer to detonation-land.

So you REALLY need a baseline of what you have BEFORE you go too far with cam and ignition advance .

I would also check the TDC mark on you damper to be sure it is at true TDC for the same reasons.

Then I would time the cam with a dial indicator and degree wheel on intake and exhaust, to find where the intake and exhaust peaks are located. Find the angles for .050" or .100" lift on both closing and opening ramps for one each of intake and exhaust valves, and take the mid-point between these angles as the peak points. This will tell you the LSA and the installed intake centerline. If the cam is advanced already (due to installation or a cam ground with advance built-in), you want to know this before you advance it even further. And you are going to need the dial indicator and degree wheel anyway if you adjust cam timing so do it right to start, plus this will get you the actual cam specs.

This is all to get a proper baseline of what you really have before you start the optimizing of timing, so you don't end up with who-knows-what. Yes, it is a PITA but darn, you have some $$ into this, so it needs a solid approach to tuning.
 
the cam will have numbers stamped on the end. Crower has a cam with 280* / 280* duration, .480" / .480" lift and 110*. advance the cam and advance the timing
 
Well, I just got to the timing chain. I needed to get at least thus far because I am replacing the gasket.

Honestly, going any farther is daunting. Seems like I could really mess things up by removing the timing chain and gears.

Question, how would I advance the cam timing from here? Just move the teeth over a few?
I posted this on my other thread about the heads and pistons but here is TDC with my piston. It looks to protrude out the block by the amount of dome in the middle.
IMG_1377.JPG
IMG_1375.JPG
 
good to see the pistons above deck for compression-clean them and look for numbers. you can not move the cam even 1 tooth, that would be too much, give us a picture of the timing set, and if you are lucky the bottom sprocket will have more than 1 keyway
 
OP, those pistons look like Keith Black KB243's. The step of the KB's is going to be around .020" to .040" high. You can check by sighting across a feeler gauge and the piston top, with the gauge placed on the outer step to get an idea of how tall this step is. Also, look at the pistons from underneath to see if you can see any markings around the pin bosses.

With that PT8553 head gasket and unmolested head chambers, your static CR (SCR) computes to be around:
9.2 for the KB's

With your present cam, and assuming it is installed with no advance (as it looks from your pix with no extra crank keyways), then your DCR (dynamic compression ratio) will be:
6.8 for the KB's

The KB's and the stock head chambers have low enough DCR to totally explain your lack of low end grunt. With the cam like you have, you would have to advance it a crazy number of degrees, like 13 degrees, to get the KB's DCR up to the mid 7 range. And for really good torque, you need to get it up even more.

IMHO, with this info, I think it is a 100% complete waste of time to advance this particular cam for what you want to do with the car. I would recommend a new cam like you originally proposed doing. You need IMHO to find one with an intake
closing angle of 60 degrees. This can be found on the cam timing numbers published in the specs. You can see that kind of intake closing angle here for the XE268:
20-223-3 - Xtreme Energy™ Hydraulic Flat Tappet Camshafts

Also, since in another thread, you indeed seem to have coolant leakage. This would be a good time to not only have the heads checked for warpage, but also have them milled maybe .010". That, with a Felpro 1008 gasket, is going to get the
SCR with the KB pistons (IF that is what you have) up to around a true 10.1, and the DCR with the XE268 cam will be around 8.1. That is all gonna make a HUGE difference in low end torque. And that is as far as you probably want to push
up the DCR to keep the tuning reasonably easily to run on pump fuel.

There are other combinations of head milling and head gaskets and cams that will get your DCR up to this range, but that is where you need to be heading for straight low RPM street use.

Again, check those pistons to see how high that step is to be sure what you have there. From those pix, that is my best guess of what you have.
 
nm9stheham said:
OP, those pistons look like Keith Black KB243's. The step of the KB's is going to be around .020" to .040" high. You can check by sighting across a feeler gauge and the piston top, with the gauge placed on the outer step to get an idea of how tall this step is. Also, look at the pistons from underneath to see if you can see any markings around the pin bosses.

With that PT8553 head gasket and unmolested head chambers, your static CR (SCR) computes to be around:
9.2 for the KB's

With your present cam, and assuming it is installed with no advance (as it looks from your pix with no extra crank keyways), then your DCR (dynamic compression ratio) will be:
6.8 for the KB's

The KB's and the stock head chambers have low enough DCR to totally explain your lack of low end grunt. With the cam like you have, you would have to advance it a crazy number of degrees, like 13 degrees, to get the KB's DCR up to the mid 7 range. And for really good torque, you need to get it up even more.

IMHO, with this info, I think it is a 100% complete waste of time to advance this particular cam for what you want to do with the car. I would recommend a new cam like you originally proposed doing. You need IMHO to find one with an intake
closing angle of 60 degrees. This can be found on the cam timing numbers published in the specs. You can see that kind of intake closing angle here for the XE268:
20-223-3 - Xtreme Energy™ Hydraulic Flat Tappet Camshafts

Also, since in another thread, you indeed seem to have coolant leakage. This would be a good time to not only have the heads checked for warpage, but also have them milled maybe .010". That, with a Felpro 1008 gasket, is going to get the
SCR with the KB pistons (IF that is what you have) up to around a true 10.1, and the DCR with the XE268 cam will be around 8.1. That is all gonna make a HUGE difference in low end torque. And that is as far as you probably want to push
up the DCR to keep the tuning reasonably easily to run on pump fuel.

There are other combinations of head milling and head gaskets and cams that will get your DCR up to this range, but that is where you need to be heading for straight low RPM street use.

Again, check those pistons to see how high that step is to be sure what you have there. From those pix, that is my best guess of what you have.
Click to expand...
Looks to be .03" but it's hard to tell. I will ask the machine shop to measure the heads. Maybe that will tell me if they have been milled before.
 
You must log in or register to reply here.
-

Back
Top