Need help choosing a cam...

A

ArtemisI6

Well-known member
Hello all,

Finally getting back together my girlfriend's '78 200ci to prep it for installation into her base model '67 Mustang.

Just had the block decked to zero at the machine shop, and now comes cam selection.

We're using the stock '78 head, ported and polished, and aiming for somewhere on the lower end of 9.5:1 compression.

We have a 4cyl T5 installed at the moment, and we plan on running an 8.8" rear end with either a 3.55:1 or 3.73:1 ratio, though right now we have the stock 7.25" in there, and I'm unsure of the rear ratio right now - either 3.00:1 or 3.20:1 is likely.

At some point I'd like to put CI's long tube dual outlet header on there with a couple of side exits, but for now the funds only permit usage of a stock log exhaust manifold. For the moment, we're stuck with her crappy, worn out Autolite 1100, and we haven't decided on a new carb yet because the funds aren't allowing for that, and because frankly we're nowhere close to that stage just yet. I was thinking a 2100 series, but that's up in the air. When it comes time to choose what we've already done with the motor will help decide what carburetor we should go with. Right now we want to get the motor itself together. We have a DSII dizzy that came on the '78 motor too, so I just need to pick up a module and do the wiring (once we get a non-SCV carb) and she'll have DuraSpark II also. Right now we're using an Ignitor II that I'm less than impressed with.

It's gonna be a fair weather daily driver for her, and probably won't ever see a track, but we want as much oomph as we can get without making daily driveability a chore and without vastly breaking the bank. To be honest I drive the car much harder than she does, but I'm sure she'll be into the gas some more when it has a motor that runs right in it. It has been an around-town car up until now, but honestly that's just been because we can't trust it on the highway. Once it's more reliable I could see her taking it farther distances. The overdrive transmission will only help that.

I was eyeballing both the CSC 264/274 110* and 112* because I think she'd be very giddy about her car having a somewhat lopey idle, and 1600-5400rpm seems like a good operating range for such a car with such gears - but if I'm making a poor choice here, please correct me. Also, the only difference between the two aforementioned cams is that I can see is the lobe centers. Can someone explain to me in layman's terms what a lobe center difference of 110* vs 112* is? That means the cam timing is a bit farther advanced on the 112*, right? What's that translate to in real world performance terms?


So basically what I'm looking at is:

- base model '67 Mustang, curb weight somewhere around 2500lbs?
- 1978 200ci motor, stock head ported and polished, zero deck height, target compression 9:1-9.5:1
- 4 cylinder T5 swapped.
- 3.55:1-3.73:1 rear ratio planned
- long tube dual outlet header planned
- '78 DSII planned
- Carburetor choice is still wide open
- Probably won't see a track, but we want the most bang for our buck regardless.
- MUST be hydraulic

I'm not against Comp Cams/Isky/Schneider/Clifford either... I really just want what's best for my girlfriend's car and I don't want to make the wrong choice here. I ask that any recommendations anyone makes please keep our future plans in mind, because the concept of gaining more seat-of-the-pants power as we get closer to the cam's ideal components (i.e. adding a header, numerically higher rear gears, etc.). Price is not an issue in cam selection at the moment because I'm getting it for her for Christmas, and I am mostly concerned with her getting the best camshaft she can get.

Thanks in advance for the help, guys!
 
ArtemisI6":vv1026vj said:
We have a 4cyl T5 installed at the moment, and we plan on running an 8.8" rear end with either a 3.55:1 or 3.73:1 ratio, though right now we have the stock 7.25" in there, and I'm unsure of the rear ratio right now - either 3.00:1 or 3.20:1 is likely.
Click to expand...

forget the 8.8 rear end, you dont need the extra strength, and the weight in only detrimental overall. the stock rear end with its 3.20 gear ratio will do you just fine with the trans you have selected, what with its 4.03 first gear ratio. anything more than the 3.20 rear gear is going to make first gear completely useless.

I was eyeballing both the CSC 264/274 110* and 112* because I think she'd be very giddy about her car having a somewhat lopey idle, and 1600-5400rpm seems like a good operating range for such a car with such gears - but if I'm making a poor choice here, please correct me. Also, the only difference between the two aforementioned cams is that I can see is the lobe centers. Can someone explain to me in layman's terms what a lobe center difference of 110* vs 112* is? That means the cam timing is a bit farther advanced on the 112*, right? What's that translate to in real world performance terms?
Click to expand...

your cam choice is an excellent one. the difference between a 110 and 112 lobe separation angle means that the 112 intake lobe is slightly advanced, and the exhaust lobe is slightly retarded. what this does is reduce valve overlap, and tricks the engine into thinking it has more compression than it really does by increasing the dynamic compression ratio of the engine. this is good for low end torque, usually at the expense of a slight loss of top end power. personally i would go with the 112 lobe separation angle in your combination, even though you have the manual transmission. the reason is that with the overdrive, your overall final drive ratio is going to be about 2.01 with a .63 od ratio. that will give you the needed torque to handle that ratio on the freeway.
 
The 112° doesn't really have much lope, it's recommended for automatics that need more vacuum. It would be the smoothest choice.
Now a 108°, that would have some lope.
 
I have the 110 and it revs very nicely, I've heard of others having the 112 and not having much bottom but plenty of top (i think because they didn't/couldn't advance it 4*), I think if I redid my engine i would just shoot for the 108 lobe.
from your plans it looks good...
remember the rpm ranges (4* advance is "stock" for these cams)
112-1400-5000 @4* (I've heard stories it's little choppy but mostly smooth @ 800 rpm)
110-1600-5200 @4* (my experience shows that it's smooth @ 950idle rpm +)
108-1800-5400 @4* (I would guess it's smooth with a higher idle too)
advancing the cam 2* will lower that range efectivly 500rpm, so if you had the 108 lobe @ 6* advanced it would efectivly have a range of 1300-4900 and rev faster than the others but making less power overall, correct me if I'm wrong.

I agree with rhobm, the higher rear will help IF you have more HP/TQ but for the 6cyl it's overkill and dentrimental... unless planning for a super :eek:
the 4cyl t5 with a 3.2 rear will have a final drive of 2.76 and a 3.0 rear final drive of 2.37
the 8cyl t5 with a 3.2 rear will have a final drive of 2.17 and a 3.0 rear final drive of 2.04 (with .68 5th gearing)
the 8cyl t5 with a 3.2 rear will have a final drive of 1.98 and a 3.0 rear final drive of 1.86 (with .62 5th gearing)

the 4cyl and first 4.06 is perfect for the 3.2 and 3.0 like rhobm said you wouldn't be able to use it with a different rear ratio.

Maybe the isky 256/256 .450 112-- it is a tad more than stock, you get more lift to help torque. with this cam you'll see the advantage of the 9.5 SCR. where as with the 264 you won't see much of a difference due to the longer duration just a few cents...
 
So it would appear that it's a tossup between the 112* and the 108*. Jack, you said the 112* doesn't have much lope, but the Falcon Six handbook claims it as "B) lopey idle" as opposed to "A) smooth idle" or "C) rough idle". The manual also states it has "adequate" vacuum, which is middle of the road between "good" and "marginal" - to use the book's wording. Would you say the 112* could be considered lopey when compared to a stock late 60's cam, or no? Although the car having a slightly satisfying "performance" idle is somewhat important to me, I have to set my priorities and sound takes a back seat to performance, daily driveability, and reliability.

I typically run this motor around 600rpm for an idle speed if I remember correctly... a little higher than the stated stock speed for a manual (500-550rpm). I'm totally flexible on that, though. I mention this because I figure a lopey cam is going to be more or less noticeable depending upon the idle speed.


rbohm - If the 112* tricks the motor into thinking it has more compression, should I hold off on planing the head to achieve my desired compression ratio of 9.5:1? I want her to be able to run 93 octane (89 ideally) without any problems with pinging. I have heard of cam choices allowing or disallowing higher compression depending on when the valves open... what would you say in this case? I don't want to get the motor together and then find I have to back the timing way off because of a poor cam choice. Basically what I'm asking is, can I run the 264/274 112* with a static compression ratio of 9.5:1 without fearing a large risk of pinging?

Also, the plans for an 8.8" rear end wasn't for strength concerns. Her 7.25" is pretty worn out, and needs either a total rebuild, or a replacement. I can get a Lincoln Mark VII rear disc 8.8" for fairly cheap, and I figured why not? We wanted to go to the 8.8" for more ring & pinion choices and to enjoy the "wheel" benefits of five lug axle shafts. This is quite far down the road, anyway. I didn't realize the 8.8" was substantially heavier than the 7.25". That does concern me because a lighter car = a better accelerating car. What kind of weight difference are we talking about here?

Thanks so much for all the help guys. I'm still struggling with the sheer scientifics of camshaft designs, and I don't want to make a wrong choice for a girl who can't afford to make mistakes. I've read all your posts three or four times over so far... please keep em coming, I love to learn!
 
Howdy Art and all:

The cam references in the Handbook are straight from Mike and CI. Which causes me to suggest that you give Mike a call, or email for his advice. And since MPG has real world experience with his 110 cam, listen closely.

To answer your question- "Would you say the 112* could be considered lopey when compared to a stock late 60's cam, or no?"
Yes, not only is the lobe centers an issue with idle, but so is the loss of vacuum as a result of a longer than stock duration cam. So Yes, you will notice a difference in idle.

Your CR is not going to be much of a concern since the longer duration cam will bleed off cylinder pressure.

Which T5 trans are you using? What is the gear ratio of the 8.8" rear? Is it open or trac-loc type? While it may not be the best choice for your car, it is a piece worth having- even for trade stock. Someone may want it bad enough to trade a 3.2:1 7.5" rear or an 8" 3.25:1, either of which would be just right for you.

PS- be thinking of a 2100 in a 1.14 size for the future.

Merry Christmas

Adios, David
 
rbohm was right on, however..... the lobe center depends somewhat on the primary usage. Highway 110 - City 112. (editted)

rbohm":2oftcddq said:
ArtemisI6":2oftcddq said:
We have a 4cyl T5 installed at the moment, and we plan on running an 8.8" rear end with either a 3.55:1 or 3.73:1 ratio, though right now we have the stock 7.25" in there, and I'm unsure of the rear ratio right now - either 3.00:1 or 3.20:1 is likely.
Click to expand...

forget the 8.8 rear end, you dont need the extra strength, and the weight in only detrimental overall. the stock rear end with its 3.20 gear ratio will do you just fine with the trans you have selected, what with its 4.03 first gear ratio. anything more than the 3.20 rear gear is going to make first gear completely useless.

I was eyeballing both the CSC 264/274 110* and 112* because I think she'd be very giddy about her car having a somewhat lopey idle, and 1600-5400rpm seems like a good operating range for such a car with such gears - but if I'm making a poor choice here, please correct me. Also, the only difference between the two aforementioned cams is that I can see is the lobe centers. Can someone explain to me in layman's terms what a lobe center difference of 110* vs 112* is? That means the cam timing is a bit farther advanced on the 112*, right? What's that translate to in real world performance terms?
Click to expand...

your cam choice is an excellent one. the difference between a 110 and 112 lobe separation angle means that the 112 intake lobe is slightly advanced, and the exhaust lobe is slightly retarded. what this does is reduce valve overlap, and tricks the engine into thinking it has more compression than it really does by increasing the dynamic compression ratio of the engine. this is good for low end torque, usually at the expense of a slight loss of top end power. personally i would go with the 112 lobe separation angle in your combination, even though you have the manual transmission. the reason is that with the overdrive, your overall final drive ratio is going to be about 2.01 with a .63 od ratio. that will give you the needed torque to handle that ratio on the freeway.
Click to expand...
 
8) i might suggest the other way around as the wider lobe centers increase low end torque, but the difference is small. as for running 9.5:1 compression with the 112 lobe center cam, go for it, as it wont run your cylinder pressures too high. in fact this engine may be able to run nicely on 87 octane while running 14 degrees initial timing.
 
rbohm":3obmgf33 said:
8) i might suggest the other way around as the wider lobe centers increase low end torque, but the difference is small. as for running 9.5:1 compression with the 112 lobe center cam, go for it, as it wont run your cylinder pressures too high. in fact this engine may be able to run nicely on 87 octane while running 14 degrees initial timing.
Click to expand...
Rich you are correct, I got them backwards (fixed now). I wasn't thinking clearly that early in the morning. :oops:
 
AzCoupe":1sflfxgx said:
rbohm":1sflfxgx said:
8) i might suggest the other way around as the wider lobe centers increase low end torque, but the difference is small. as for running 9.5:1 compression with the 112 lobe center cam, go for it, as it wont run your cylinder pressures too high. in fact this engine may be able to run nicely on 87 octane while running 14 degrees initial timing.
Click to expand...
Rich you are correct, I got them backwards (fixed now). I wasn't thinking clearly that early in the morning. :oops:
Click to expand...

8) dont feel bad, i get that way sometimes too. now, who am i again? :LOL: :LOL:
 
Hey thanks a lot for the help, guys! I really appreciate it. On what seems to be a majority recommendation, I ordered a 264/274 112* camshaft from Classic Inlines yesterday along with a new set of lifters. I can't wait to see how it performs!

While we're on the subject of cams, how do things such as lift and duration affect horsepower, torque, and the power band? I know lift is (in inches) how far the valve opens, and duration is (in degrees) how long it stays open for, but as I stated previously I'm trying to comprehend the science of the camshaft and how it helps to dictate engine performance.
 
ArtemisI6":5l0rk7jo said:
Hey thanks a lot for the help, guys! I really appreciate it. On what seems to be a majority recommendation, I ordered a 264/274 112* camshaft from Classic Inlines yesterday along with a new set of lifters. I can't wait to see how it performs!

While we're on the subject of cams, how do things such as lift and duration affect horsepower, torque, and the power band? I know lift is (in inches) how far the valve opens, and duration is (in degrees) how long it stays open for, but as I stated previously I'm trying to comprehend the science of the camshaft and how it helps to dictate engine performance.
Click to expand...

8) in general, more lift usually helps low end torque.

more duration helps top end power, as does more valve overlap. narrower lobe centers also help top end power.

advancing the cam helps low end, generally, while hurting top end.

these are all rules of thumb, and like any rule of thumb there are exceptions. for instance i have tuned race engines where we found that more exhaust lift hurt power, and other times more exhaust lift helped power. i have also tuned engines were advancing the cam hurt the low end while improving the top end, and other engines where advancing the cam helped both ends. same with retarding the cam.

as jlopes said, david vizard is an excellent source of good information on building power. he was one of my college instructors.
 
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