Smallie cam question

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Since it hasn't been done yet, and for discussion purposes.....

View attachment 10595228446_39df37fd60.jpg

My calculations show this cam has a,
112* LSA

With a,
340+.030
11.5 static comp.
Inst. straight up
@ 500' alt.

I show the Dynamic ratio @ 7.69 to 1
And a cranking comp number of 151 lbs.

Advance it 4*, and it's,
Dynamic @ 8.01 to 1
Cranking comp. of 159 lbs.

:D:D:D I like it. Sorry I didn't catch the 81* int close until I saw the box...lol. I verified it and it is correct. Now, will it clean up?
 
OldmanRick said:
Since it hasn't been done yet, and for discussion purposes.....

My calculations show this cam has a,
112* LSA

With a,
340+.030
11.5 static comp.
Inst. straight up
@ 500' alt.

I show the Dynamic ratio @ 7.69 to 1
And a cranking comp number of 151 lbs.

Advance it 4*, and it's,
Dynamic @ 8.01 to 1
Cranking comp. of 159 lbs.

:D:D:D I like it. Sorry I didn't catch the 81* int close until I saw the box...lol. I verified it and it is correct. Now, will it clean up?
Click to expand...

Ahh, the burning question......:D

Not sure how you came up with the numbers, but I like them.
Only math error you made is the .030+ pie-holes. They are STD (4.04)
 
Kirk, it's "Lobe Separation Angle". The wider, bigger number like 112/114, tends to spread the power curve wider in the rpm range. Kinda like a more flat torque curve.

A tight number, say 104/106, tends to narrow the range of torque, but can make the peak a little higher.

Obviously i'm just generalizing. But it is a usable tool, depending on a given combo, to get the most out of the trans/rear gear used.

I guess I didn't answer your question, lol :banghead: . It's the degrees between max intake lobe lift and max exhaust lobe lift on a given cylinder. Changes in the grind here can be where advance is built into some cams, meaning a change in the "lobe centerlines" will effect cam timing. I'm trying to keep this simple...lol.

P.S. I do like that old cam you have. :D
 
OldmanRick said:
Now, will it clean up?
Click to expand...

Well, just unwrapped it and looked at it. It doesn't look that bad. There is no 'rust' on it, only some black-ish spotting mostly on the main journals. I took some photos but won't be able to post until next week as my Firefox browser will not find Flickr (or anything else associated with Yahoo) so I'll have to post them from work next week.
 
If you don't mind me askin, what formula did you use? The United Engine site says use the .050" intake closing figure plus 15 so that would be 58.

OldmanRick said:
Since it hasn't been done yet, and for discussion purposes.....

View attachment 1714669925

My calculations show this cam has a,
112* LSA

With a,
340+.030
11.5 static comp.
Inst. straight up
@ 500' alt.

I show the Dynamic ratio @ 7.69 to 1
And a cranking comp number of 151 lbs.

Advance it 4*, and it's,
Dynamic @ 8.01 to 1
Cranking comp. of 159 lbs.

:D:D:D I like it. Sorry I didn't catch the 81* int close until I saw the box...lol. I verified it and it is correct. Now, will it clean up?
Click to expand...
 
Captainkirk said:
Well, just unwrapped it and looked at it. It doesn't look that bad. There is no 'rust' on it, only some black-ish spotting mostly on the main journals. I took some photos but won't be able to post until next week as my Firefox browser will not find Flickr (or anything else associated with Yahoo) so I'll have to post them from work next week.
Click to expand...

You got time.:D

I haven't seen specs like that one for a while. Makes me want to add another "fantasy" build to my list around that cam. That's the perfect type cam to use in a stock headed muscle car engine with a increased compression ratio. Maybe a Teen with 1.88 "J's", 11+ comp, and some 4.30 gears with a 4spd. Now i'm just fantasizing, lol.
 
RustyRatRod said:
If you don't mind me askin, what formula did you use? The United Engine site says use the .050" intake closing figure plus 15 so that would be 58.
Click to expand...

Hi Rob. I hate the +15 calc's. I've found that using the advertised (.004/.006) number gives a truer outcome, considering how the newer aggressive lobe can distort things in the .050" range.

I use this formula, I have it written on paper...lol.

As a Example...using his cam...

Half the Advertised intake duration....................298* = 149*
Plus the LSA...which I converted from a Wallace calc... + 112*
Minus the advance, difference between LSA and ICL.... - 0*
Total......................................................................=261*
Minus.......................................................................180*
Equals......................................................................81* Int close.

I have no idea if you get what I wrote, lol. I had this formula for years. I think it's good and takes out a lot of variables with the different cam companies measuring in different places.
 
Glad you got good info. I figured that amount of overlap on the old cam,would bleed off some compression. I I'm a budget guy,hopefully you can use that existing grind.
 
I know we've been mainly looking at dynamic compression here, but that's really just a small piece of the puzzle. Piston design, chamber design, head composition, and timing curves, play a big role in what we can get away with on pump fuel. Some of the guy's running big compression numbers, have just hit their combo's dead on vs their available fuel and the altitude where they mainly operate their engines.
 
OldmanRick said:
I know we've been mainly looking at dynamic compression here, but that's really just a small piece of the puzzle. Piston design, chamber design, head composition, and timing curves, play a big role in what we can get away with on pump fuel. Some of the guy's running big compression numbers, have just hit their combo's dead on vs their available fuel and the altitude where they mainly operate their engines.
Click to expand...
Well, guys, to be fair, this motor hasn't seen the street since the early '80s, before ethanol. But detonation was never an issue with the TRW slugs and pump gas. Maybe the ignition timing played a role? Full advance (32* by 1500) and no initial timing setting...just dialed in to 32* full advance. The piston domes and heads showed no signs of detonation either. Or maybe I just got lucky? IDK...
The figures Rick is showing look pretty reasonable to me even at 11.5:1. I would sure like to build the ghost of the old motor if it will run on pump gas.
 
Kirk, after going over the numbers, i really think the setup you're looking at is a good one. Maybe some more input from others could change my mind, maybe...lol.
 
OldmanRick said:
Kirk, after going over the numbers, i really think the setup you're looking at is a good one. Maybe some more input from others could change my mind, maybe...lol.
Click to expand...

Well, Rob doesn't seem to think much of it. I'm sort of in uncharted waters here because we're dealing with premium gas that's 93 octane with ethanol added as opposed to the 97 octane leaded fuel that was available back in the '70's. I plan to blend my fuel when I can 15:1 unleaded premium with 100 octane avgas (which has 4X the tetraethyl lead found in the old 97 octane leaded premium) and/or use octane boost when I can. But we all know there will be times & places where that won't be possible, so I hope the compression bleed-off we discussed previously will keep me in the 'safe zone'. I still have time to change my mind...in fact, I could build the spare '69 340 using the stock pistons and X-heads if I wanted. So if anyone else wants to throw their 2 cents in, go for it!
 
I'm glad you have some time to weigh your options. I think the reason i'm attracted to your build is i just get tired of seeing lower compression, bigger cam, street builds that seem to need 20+ degrees of initial to be streetable and idle halfway clean. Just seems like some guys building "hot rods" are leaving a lot on the table to me. I have to admit i've been out of this game a long time, and the main reason i'm here is to just keep up with the current trends, just incase I ever get the chance to play this game again before it's too late. I'd never try and advise someone to step over the line. After all, it's you guys time and money, not mine. I might just need to observe more and talk less. I do really hope your combo comes together with big power, and not too much more expense. I'm still subscribed. :D
 
OldmanRick said:
I'm glad you have some time to weigh your options. I think the reason i'm attracted to your build is i just get tired of seeing lower compression, bigger cam, street builds that seem to need 20+ degrees of initial to be streetable and idle halfway clean. Just seems like some guys building "hot rods" are leaving a lot on the table to me. I have to admit i've been out of this game a long time, and the main reason i'm here is to just keep up with the current trends, just incase I ever get the chance to play this game again before it's too late. I'd never try and advise someone to step over the line. After all, it's you guys time and money, not mine. I might just need to observe more and talk less. I do really hope your combo comes together with big power, and not too much more expense. I'm still subscribed. :D
Click to expand...
Rick, I'll be the first to admit that, yes.....I wanna build a clone of that kick-*** little screaming ankle-biter of a motor I used to run and if I can, I will. Other options are there, but not really where I wanna go with this. I don't want to end up building a motor that will detonate itself to death, but if the numbers work and I can sneak in under the wire, then dammit, I will. When experienced guys like yourself and Jerry at Crower Cams tells me it could work, I get excited......:blob:
 
sorry - for crashing your thread, but i just wanna show some pics, how pistons would look like if the fuel you bought does not have enough octane (shell v-power advertised in Germany with 100 roz) - 318 teenie screamer 11,8 CR with stock 318 heads ... it lasts for nearly 9000 miles before it was killed by worse gasoline

pistons are KB-Hypereutics with dome



4ihlmpm9.jpg

76ocb2ko.jpg

f8xgivox.jpg

swyymgns.jpg

sttphv2k.jpg
 
That damage looks more like incorrect ring gap to me.

lilredridinghoo said:
sorry - for crashing your thread, but i just wanna show some pics, how pistons would look like if the fuel you bought does not have enough octane (shell v-power advertised in Germany with 100 roz) - 318 teenie screamer 11,8 CR with stock 318 heads ... it lasts for nearly 9000 miles before it was killed by worse gasoline

pistons are KB-Hypereutics with dome




4ihlmpm9.jpg

76ocb2ko.jpg

f8xgivox.jpg

swyymgns.jpg

sttphv2k.jpg
Click to expand...
 
RustyRatRod said:
That damage looks more like incorrect ring gap to me.
Click to expand...

I would tend to agree; saw this before in a 351...same story, rings got too toasty and popped a chunk of the crown right off.

That being said, we're also comparing a hypereutectic piston to a forged one.
 
the ring gap was set to the specs given by KB (but i don´t have the numbers right now by hand) - the curios thing is/was: absolutly no splitters, splints or any small piece of the pistons to find somewhere, also the edges are not sharp (likewise on brocken parts) all smooth, looks more like the hypereutectics were vaporised.
interesting thing is also: the "vaporised" area on all 8 pistons is directly located below the intake valve (which is opposite from where the spark plug points toward)


also talked with 3 different engine builders here in Germany one have had a similar looking damage on a supercharged engine, and the other two, have nearly the same damage on high compression Volkswagen Race-engine (circle track) and they stated it was a typical damage from "high-rpm-detonation" ,which you cant hear while driving. they also stated, that if i would have used this engine only for drag-racing etc. the pistons would have last longer, but the heavy amount of miles with about 3200-3500 rpm on the German Autobahn in combination with to less octane have caused the problem - maybe with aluminium heads (better heat transfer) every thing would have been fine
 

I still go for incorrect ring gap. I don't care who set what. Somebody got it wrong, IMO. Broken ring lands and piston crowns like that are a dead giveaway. You can even see where the rings scored the cylinders when they tightened up.
 
One thing I do KNOW. Old TRW Power forged pistons,take a lot more than that one did. I like this build. The compression,makes it work. We ran a actual 11:7 to 1 340 in a 72 Dart,on Cali 91 pump gas. Small roller cam,Manning Brady heads. 4:88's ,huge stall. The gear multiplication and stall ,reduces the "load" on the engine lugging. When he raced,we dumped in some Av gas,low lead.(like 102-104 octane). Hope this helps.
 
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