Effect on Stroker - New Cam?

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fishy68 said:
I'm really surprised to hear it lugs so much with your current cam. I have a 408 with a cam of very similar size and it's ground on a 108 center, although it is a solid flat tappet and I am running an automatic but it's smooth as silk from 900 up.
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Mine did not lug at all with the 727-4200stall convertor I had installed previously. But when I went with a TKO600 5 speed, everything changed. I love rowing the gears, but it lugs now whereas it never did with the auto. That torque convertor smooths everything out, which a kevlar clutch can't.
 
i may be off base but my 360 pulls like a bear from idle and i have a bigger solid cam,. do you have a buddy with a good running 750 or there abouts holley you could try?
 
jimmyray said:
I am sure the proposed cam swap will lose top end power, but I wonder if the flatter curve will offset it, for a more driveable but similar overall performance.

I've read a lot of threads,and many go for very large cams, sometimes into the 260 @ 0.050 range for a street engine. Having never ridden in one with that size of cam, can't help but wonder at it's manners on the street. Maybe mine just needs more tuning, but that engine sure moves around a lot, although the car has a nice rhythm to it at idle...

Switching to a manual transmission really revealed the lugging nature of the cam. And, it barely pulls below 2500 rpm. going uphill in 5th at 60 mph requires a downshift when it dips below 2000, as it just loses mph.

Love the sound at idle, tired of the drive-ability, and inability to break into the 11's for the tradeoff.
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Its a trade off, I'd try more int. timing 1st. as suggested, this will clean things up & make it easier to tune, you really don't want less then 1000 rpms on a stick car anyways, even with a mild cam, 11-1200 rpms wouldn't be out of the norm.
 
I think with you needing to have smooth power at 1800 the cam is on the edge of too much. Have you taken any cylinder pressure readings? It might be a better approach to degree that cam and advance it by 2-4° if the pressures allow it. I don't think it's too big but it should work fine. Also - how tunable is that carb? Have you tuned with the 6 speed? You may have air bleed or emulsion tube issues trying to make it pull that low down.
 
RAMM said:
JimmyRay obviously finds the current cam a little too hairy. I can see that. The duration is a little too much for a real tame engine. I see this all the time where a customer thinks they want that bad *** sound and idle but find out that it really makes the car a pain in the *** to live with when you are driving it a lot. The cam you are considering on a 114 CL will knock the crappy manners right out of a 400+ cube mill. Just make sure your dynamic compression doesn't get out of hand. Otherwise you will love the new personality of your engine. J.Rob
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Exactly. Thank you.

RAMM to you find customers that later come back for smaller cams, not wanting to admit it to others. They keep it on the down low.

A lot of people say their cam is tame. But they only drive their cars a few times a month. Or only at the track. Or even to the track.

I wonder how many actual miles Jimmy Ray puts on his car. In the southern climate he lives, he could almost drive his car every day of the year.
 
autoxcuda said:
I wonder how many actual miles Jimmy Ray puts on his car. In the southern climate he lives, he could almost drive his car every day of the year.
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About 2500 last year, 1200 of which was the Hot Rod Power Tour, Little Rock to B'ham.
 
jimmyray said:
Mine did not lug at all with the 727-4200stall convertor I had installed previously. But when I went with a TKO600 5 speed, everything changed. I love rowing the gears, but it lugs now whereas it never did with the auto. That torque convertor smooths everything out, which a kevlar clutch can't.
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I can definitely see that converter smoothing things out a lot and the clutch making things rougher down low. The converter in my car was spec'd for my old 360 and stalled 3000 with it. The 408 has so much more torque it'll easily stall 3500. Nevertheless it's very tight and pulls real good at even real light throttle. I said that to only say this (again), I think some good tuning could go a long way on your combo your running now because it just seems to me by the experience I've had riding in cars with strokers none had any issues whatsoever pulling below 2500 rpm with a cam the size of yours. I know David set up your TQ and I have the utmost respect for him but I wonder if Moper is onto something with his comments on the air bleeds or emulsion tubes needing some work. If you were close I'd let you throw my extra Holley 750 4 corner idle carb on it and see how it does down low. If you have a buddy with one you might give it a quick try. That and put more initial timing in it too. Just my .02
 
Idle quality will definitely come from the cam & tune. With the issue of bucking in O/D, I have to believe your 5th gear has a ratio in the .60's. I still think even that can be tuned around with the 3.73 gear. But, maybe not??? "Fishy" & some others brought up the carb.......Any chance it's lean under the load at low rpm's in 4th/5th gear?


Good luck however things turn out. I hope you get the most out of it, and have the drivability your looking for. :thumbrig:
 
If the heads flow that much cfm....? then the smaller cam is not going to help much.
By advancing the cam, it make it act like a smaller cam(more bottom end)

If you didn't degree the cam, could be retarded from the intended center line causing even more "low rpm problems.

Adding more timing could help as well. if it has the stock mechanical adv spring in it (one big spring and one heavy spring in it). Your probably not getting full adv. until 3000 or so. this could be some of you lugging at 1800 rpm as well.

So what rpm do you shift at, at the track, with the current cam?
 
...maybe I'm just looking at this the wrong way, but with that much cam, and that transmission, I'd run more gear...probably 3.9x or 4.10. TKO has a decent OD gear...might as well use it.

...and like a few others have said, there are likely some tuning nuances to work.
 
Just a quick question.
Your advance isn't tipping in at an idle, is it?
Just asking, I've done a few manual transmission swaps and had one or two that would be doggy driving off in first gear due to the advance. The reason for those examples was the mechanical was adding a few degrees at the set idle and when the idle came down with the initial engine load, the extra timing dropped out and the engine dogged. It wasn't an issue with the automatics before because the base idle tune on the hotter engines was being set in gear and this anomaly didn't get noticed.
 
Revhendo said:
Just a quick question.
Your advance isn't tipping in at an idle, is it?
Just asking, I've done a few manual transmission swaps and had one or two that would be doggy driving off in first gear due to the advance. The reason for those examples was the mechanical was adding a few degrees at the set idle and when the idle came down with the initial engine load, the extra timing dropped out and the engine dogged. It wasn't an issue with the automatics before because the base idle tune on the hotter engines was being set in gear and this anomaly didn't get noticed.
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Interesting thought. Below is attached the Distributor tuning card from FBO when they set it up. It has a Vacuum advance, and may have something to do with the lugging as well. I am going to get it out tomorrow, and I will pay attention to the vacuum and A/F ratio in the low end ranges, and particularly when it is lugging. I also have the Vacuum hooked to manifold vacuum, as it adds in the extra advance at idle.
 

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Could vacuum advance, vacuum signal from that decent sized cam, distributor curve, and cruising under 2500 rpm altogether in combination be creating a problem??

I'm not much of a tuning guy.
 
I would disconnect that vacuum advance and run minimum 21 degrees initial timing. I run 25 initial with mine and 32 total. Works great. Pulls hard right off idle...
 
340sFastback said:
I would disconnect that vacuum advance and run minimum 21 degrees initial timing. I run 25 initial with mine and 32 total. Works great. Pulls hard right off idle...
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So you have 7 degree mechanical advance.

Jimmy Ray has 18 degrees mechanical advance in the distributor. If he ran 21 initial, he'd have 39 total.
 
autoxcuda said:
What way would you go with the curve?

I wonder if that FBO curve was setup for the motor before he added the 5 spd. ???
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IMO, not enough initial. 16 is good for a stockish 340-360, not a cammed up engine.
 
autoxcuda said:
What way would you go with the curve?

I wonder if that FBO curve was setup for the motor before he added the 5 spd. ???
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You are correct, it was set for a 727 with a 3000 stall converter, which I later changed out to a 4200 stall 9.5" Dynamic convertor. I also had a 8.25 with a 4.10 gear at the time, it's now a Dana 3.73.

I gave Don at FBO all of my engine/tranny/rear details, and this was the distributor he suggested and set up.

I'm going to test it with the vacuum disconnected, and the timing set to 22 or more. If it likes it, I will modify the advance plate to narrower slots. and then experiment with leaving the vacuum on or off.

Incidentally, whats the max initial timing before it starts getting hard to start?
 
Vacuum advance should not be hooked to manifold vacuum. I don't doubt it makes the idle better but that should be approached via more initial timing. Vacuum advance hooked directly to manifold vacuum generally does very little for the mid range where it's designed to help because anything above part throttle you don't have enough manifold vacuum to pull the vac adv in. Strokers with moderate cams generally like a lot of initial timing and the timing curve to be all in pretty early. The FBO curve isn't a whole lot better than some stock distributors had. IMO you need to advance the timing until it just starts kicking back when you try to start it (engine fully warmed up) then back it off 2-3 degrees and use that for your initial timing setting. Then modify the dist. so you get approx. 32-33 degrees total timing all in by 2400-2500.
 
jimmyray said:
You are correct, it was set for a 727 with a 3000 stall converter, which I later changed out to a 4200 stall 9.5" Dynamic convertor.

I'm going to test it with the vacuum disconnected, and the timing set to 22 or more. If it likes it, I will modify the advance plate to narrower slots. and then experiment with leaving the vacuum on or off.

Incidentally, whats the max initial timing before it starts getting hard to start?
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If you go to 22 now, with your mech adv curve, you will have 38 total. That should ping driving when it hits full advance. But you could do that to check how it idles.
 
jimmyray said:
You are correct, it was set for a 727 with a 3000 stall converter, which I later changed out to a 4200 stall 9.5" Dynamic convertor.

I'm going to test it with the vacuum disconnected, and the timing set to 22 or more. If it likes it, I will modify the advance plate to narrower slots. and then experiment with leaving the vacuum on or off.

Incidentally, whats the max initial timing before it starts getting hard to start?
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Sorry Jim. I was typing my last reply when you were typing. Max timing when it gets hard to start varies from combo to combo. Mine starts kicking back at 24-25 degrees but I've seen other combo's not kick back till 28 degrees

BTW: a properly setup vacuum advance can be a help on a street driven vehicle. Helps in fuel mileage and helps keep the plugs burning cleaner.
 
fishy68 said:
Sorry Jim. I was typing my last reply when you were typing. Max timing when it gets hard to start varies from combo to combo. Mine starts kicking back at 24-25 degrees but I've seen other combo's not kick back till 28 degrees

BTW: a properly setup vacuum advance can be a help on a street driven vehicle. Helps in fuel mileage and helps keep the plugs burning cleaner.
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x2.

The FBO curve is flat out wrong for what you have now. The vacuum advance can be adjusted - not the number of degrees but the inches of vacuum required to move the arm. You need to use an allen wrench down into the vacuum nipple to do this. It might just be two turns counterclockwise and you're good to go. Tune the carb and I'd drive around with a vacuum gage on the window to see where things are at in real time.
 
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