340 Cam Selection

[npfinegan]

I've got it narrowed down to 2 cams for my 340

Howards Roller CL710525-10:
.520./.515
229/233 @.050
110 LSA
106 Centerline

Howards Roller Rattler CL718005-09:
.525/.530
227/235 @.050
109 LSA
103 Centerline

Motor is .030 over, Flat top 10.5:1 pistons, Aluminum RPM heads, 750 double pumper. 1.5 Roller Rockers, 4.30 rear gear, 4 speed manual.

They are pretty similar other than centerline, I want something that sounds aggressive and lopey but makes great power. Mainly going to be a hot street car.

Thoughts?

 

[Newbomb Turk]

Are you SURE the 109 cam goes in at 103? Either way, there is no way I would install that 109 cam at 103. No way.

The 110 cam should be installed at 108 and the 109 cam should be installed at 107.

I’m not sure why Howard’s think moving the overlap triangle that far advanced is a good thing.

 

[Icetech]

Are you SURE the 109 cam goes in at 103? Either way, there is no way I would install that 109 cam at 103. No way.

The 110 cam should be installed at 108 and the 109 cam should be installed at 107.

I’m not sure why Howard’s think moving the overlap triangle that far advanced is a good thing.

I have that 109 cam... and i even called Howards to ask them and they said yes.. install it at 103.. i had to advance it 4* to hit 103.5, i degreed it 3 times from scratch just to double check..

NP, this is what that cam sounds like in a 318 with full exhaust and trick flows... it would be a bit milder in your 340... i may have over-cammed a bit.. cause i'm a 16 year old when i pick cams...

Honestly i would go a bit smaller if i did it again.. but my motor is smaller..

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[Icetech]

Are you SURE the 109 cam goes in at 103? Either way, there is no way I would install that 109 cam at 103. No way.

The 110 cam should be installed at 108 and the 109 cam should be installed at 107.

I’m not sure why Howard’s think moving the overlap triangle that far advanced is a good thing.

NT, why does the 103 bother you? Just trying to learn..i haven't been very happy with my motor and almost consider moving it back to dot to dot (107.5) right now to see what changes, i have it apart at the moment double checking my work trying to track down a weird problem.

 

[Newbomb Turk]

NT, why does the 103 bother you? Just trying to learn..i haven't been very happy with my motor and almost consider moving it back to dot to dot (107.5) right now to see what changes, i have it apart at the moment double checking my work trying to track down a weird problem.

I’ve typed this out in other places so I’ll do a quick highlight of why I think it’s wrong.

If you look at that cam graphically (I go to mgispeedware.com and click on the camshaft calculator and input the cam numbers so I can see it graphically) you will see that at TDC on the graph a “triangle” formed by overlap.

As the exhaust valve is closing and the intake valve is opening they are both open at the same time. That’s what forms the triangle.

When I saw that 109/103 I had to go look it up. And sure enough with a 103 ICL the overlap triangle is shifted to the left of TDC.

It’s my opinion that of you are running headers the overlap triangle should be centered over TDC. To get the overlap triangle centered over TDC with that cam it needs to go in at 107.

Using the camshaft calculator on mgispeedware allows you to quickly see where the overlap triangle is and it lets you change the ICL with just a simple change of advance.

You can go 1 degree at a time and watch the overlap triangle move.

BTW, I never called it the overlap triangle until I read an interview of Billy Godbold when he was at Comp Cams. I understood the concept of getting the cam to straight up which is centering the overlap triangle. And that’s how I’ve been installing cams since high school.

I just never used the term overlap triangle but it is certainly better than saying the cam is installed straight up.

What’s interesting is the math I use to find cam timing for a particular engine always outputs numbers like everyone else does. Like 109/103 or 110/106.

The difference is every single time I put the numbers into the mgispeedware program that 109/103 will have the overlap triangle centered. I’ve never seen it output numbers that has the overlap triangle shifted off TDC to the left, which is advanced.

 

[Icetech]

I’ve typed this out in other places so I’ll do a quick highlight of why I think it’s wrong.

If you look at that cam graphically (I go to mgispeedware.com and click on the camshaft calculator and input the cam numbers so I can see it graphically) you will see that at TDC on the graph a “triangle” formed by overlap.

As the exhaust valve is closing and the intake valve is opening they are both open at the same time. That’s what forms the triangle.

When I saw that 109/103 I had to go look it up. And sure enough with a 103 ICL the overlap triangle is shifted to the left of TDC.

It’s my opinion that of you are running headers the overlap triangle should be centered over TDC. To get the overlap triangle centered over TDC with that cam it needs to go in at 107.

Using the camshaft calculator on mgispeedware allows you to quickly see where the overlap triangle is and it lets you change the ICL with just a simple change of advance.

You can go 1 degree at a time and watch the overlap triangle move.

BTW, I never called it the overlap triangle until I read an interview of Billy Godbold when he was at Comp Cams. I understood the concept of getting the cam to straight up which is centering the overlap triangle. And that’s how I’ve been installing cams since high school.

I just never used the term overlap triangle but it is certainly better than saying the cam is installed straight up.

What’s interesting is the math I use to find cam timing for a particular engine always outputs numbers like everyone else does. Like 109/103 or 110/106.

The difference is every single time I put the numbers into the mgispeedware program that 109/103 will have the overlap triangle centered. I’ve never seen it output numbers that has the overlap triangle shifted off TDC to the left, which is advanced.

Wow, thanks for explaining that.. i knew it would move the triangle A/R but hadn't really considered it since the "experts" say do it their way (howards in this case) I assume they want it advanced to make torque for a wow factor...

Ok... soo... This might explain something.. my motor wants INSANE timing.. the other day i went and beat on it for a hour with 32* initial and 48* all in without vacuum and zero ping/knock.. this has been making me insane and no one has an idea why it's like this. Could that 103 install cause that do you think?

Hmm.. if the cam events are that advanced.. it would want more timing advance to try to get ignition and cam timing to play together nicely?

I talked to another guy with a howards flat tappet in his motor and he said it wants a lot of timing also but didn't get into specifics, i will have to ask him..

thanks man.

 

[Icetech]

One last thing.. doing research (been trying to figure this out for months) Retarding the install to 107 will drop some cranking pressure in the cyls if i read right? right now i'm at 160 on each cyl.. am curious how much it's going to lose.. not that it matters.. the thing is a dog right now.. chasing my tail on issues..

 

[Newbomb Turk]

One last thing.. doing research (been trying to figure this out for months) Retarding the install to 107 will drop some cranking pressure in the cyls if i read right? right now i'm at 160 on each cyl.. am curious how much it's going to lose.. not that it matters.. the thing is a dog right now.. chasing my tail on issues..

You can go to the Wallace calculator page and input the IVC you have now and the IVC you’ll have of you install it at 107 and it will tell you what the cranking compression will be. Or very close to it.

 

[Icetech]

You can go to the Wallace calculator page and input the IVC you have now and the IVC you’ll have of you install it at 107 and it will tell you what the cranking compression will be. Or very close to it.

damn... hell of a tool, till take a look.. thanks again.

 

[npfinegan]

Are you SURE the 109 cam goes in at 103? Either way, there is no way I would install that 109 cam at 103. No way.

The 110 cam should be installed at 108 and the 109 cam should be installed at 107.

I’m not sure why Howard’s think moving the overlap triangle that far advanced is a good thing.

I think the 103 is to try and achieve a radical sound hence the “Rattler” cam. Will this give me more issues than fun?

 

[Icetech]

I think the 103 is to try and achieve a radical sound hence the “Rattler” cam. Will this give me more issues than fun?

If it's what's causing my issue it's been a massive pain. It runs fine but needing almost 50* of timing is just wrong and eats at me. And honestly the sound is nice but the shaking and all that got old fast.. (solid driver side mount) on the upside the cam cleans up almost instantly off idle and doesn't need much rpm to smooth out. I'm going to reset my timing to 107 tonight but probably won't have the motor back together til this weekend..

 

[Icetech]

You can go to the Wallace calculator page and input the IVC you have now and the IVC you’ll have of you install it at 107 and it will tell you what the cranking compression will be. Or very close to it.

K.. so 107 centers that cam over TDC it looks like.. but why 107? or is it different with every cam depending on how it's ground? it looks like on this one going 109 install would retard it slightly

 

[Newbomb Turk]

K.. so 107 centers that cam over TDC it looks like.. but why 107? or is it different with every cam depending on how it's ground? it looks like on this one going 109 install would retard it slightly

I can’t remember why it comes out that way. And 109 would be slightly retarded.

Maybe @PRH can explain it. I know I’ve read how that happens but I don’t have the book with me to look it up lol.

 

[PRH]

Winner of the “camshaft challenge” talks about his selection thoughts.

In the final minute he talks about his “process”.
He uses the same formula I use.

 

[Icetech]

Winner of the “camshaft challenge” talks about his selection thoughts.

In the final minute he talks about his “process”.
He uses the same formula I use.

Nice, i hadn't seen the vid.. did watch the challenge stream though...

PRH, you agree with changing this from 103 to 107? trying to figure why my motor wants way too much timing..

Howards Roller Rattler CL718005-09:
.525/.530
227/235 @.050
109 LSA
103 Centerline

 

[Icetech]

Just looked at NK's webpage.. that LS stuff is sooo cheap...

 

[PRH]

PRH, you agree with changing this from 103 to 107?

I do not(but that doesn’t mean I’m right).
You’ll either have to try it and see what happens, or have someone with decent engine modeling software run it thru the program and see what it spits out.

On paper your combo seems fairly straight forward, so it’s a mystery as to why it’s a slug.

I like data…….. so my answer is to “test”.
I’d get in on a chassis dyno for a few pulls……. If for no other reason than to establish a baseline.

 

[Icetech]

I do not(but that doesn’t mean I’m right).
You’ll either have to try it and see what happens, or have someone with decent engine modeling software run it thru the program an ls see what it spits out.

On paper your combo seems fairly straight forward, so it’s a mystery as to why it’s a slug.

I like data…….. so my answer is to “test”.
I’d get in on a chassis dyno for a few pulls……. If for no other reason than to establish a baseline.

The slug part doesn't bother me as much as the wanting 48* of timing... i know they want what they want but it seems nuts... and going from 103 to 107 i don't mind trying just afraid of losing bottom end i already could use more of

 

[PRH]

At the chassis dyno you’d get to quantify the results of moving the timing around.

If it indeed makes more power at 48* than say 34-35*, to me something is just plain “wrong”.
And not 4* of cam c/l wrong.

Don’t take this the wrong way, but how confident are you in your cam degreeing skills?

 

[496 polara]

You guys are far above my pay grade but has the balancer been verified at tdc? Inaccurate reading at the balancer?

 

[PRH]

I’m pretty sure that’s all been hashed out on other threads.

 

[Icetech]

At the chassis dyno you’d get to quantify the results of moving the timing around.

If it indeed makes more power at 48* than say 34-35*, to me something is just plain “wrong”.
And not 4* of cam c/l wrong.

Don’t take this the wrong way, but how confident are you in your cam degreeing skills?

It was my first time... i did it 3 times from scratch just to double check it. I ended up at +4.. that's why i was thinking just go dot to dot and at least it should act normal there. I have had like 30 old cars and never saw something like this. I talked to one other Howards user and he said he runs a lot of timing.. waiting on a reply about how much.

This is where the timing chain is setup now.. even if i degree'd it wrong being +4 i wouldn't think would do this.. i know it's a bad combo.. but come on

(key is in the a4 slot)

BTW... really hate asking for help on this stuff... just kinda stuck right now. thanks for taking the time to even read it.

 

[Icetech]

You guys are far above my pay grade but has the balancer been verified at tdc? Inaccurate reading at the balancer?

4 times..