To much cam??

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WARLOCKII said:
The engine is bored .030, 9.5 flat top pistons (cast), stock 906 heads (new valves, seats, 3 angle valve job) no port work. Edelbrock dual plane intake w/ 750 carb. The cam is a Comp 284H (484 lift, 104.0 intake centerline, duration @.050 lift 239int, 246 exh, lobe seperation 108.0). 2400 stall conv. and Schumaker headers with dual exhaust. The cam and crank gear marks were aligned when installed and the balancer is 1-2 degrees from being dead nuts on.

The issue is the engine only develops 5-6 in. vacuum at idle (15 deg.initial timing) and 10-12 in. at 3500 (34 1/2 deg. total timing). If I give it more initial timing the vacuum will increase but I end up around 50 deg. total timing. The PB hardly work, it wants to die when put into gear (unless I turn the idle speed up).
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Why are you running vacum advance. Dissconnect it adn set your timing at 19 initial and 38 total. See if things improve. If they do it wants more initial. Get the dist re-curved.

What does it idle at?

Were your pistons for the open chamber 88+cc heads?

I've never had great luck with the eddy carbs. Have you tried anything else?

the cam isn'ty too big but the specs are not going to yield pleasant street manners and it isn't cut for a mopar. small centerline, moderate duration and tiny lift = not good.

Another thing you have to consider is that you really don't have a big block. You have a physically large block with small block cubic inch. Anycam you put in it will seem a little biger than say somthing 100 cubic inches bigger.


MTmopars said:
Seems light on the stall converter for that cam.
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3500 would seem more appropriate and if it's a quality converter (I use an Art Carr) you won't even notice it.
 
txstang84 said:
Exactly, Rob-that's where I was driving. He installed it straight up, so advancing it would likely help out. What I've seen is timing sets (what kind, did he use?) that actually retard timing a few degrees-as much as 6* with stock type timing sets or low budget double rollers.

I'm actually kinda waiting for younggun to come on here and say we're all overreatcing. :) since he's running a COMP 294S Magnum grind in his 383 with 84cc Edelbrock heads. But I think he's running more stall and more gear...pretty sure those Eddy heads are about a good 6cc smaller than the 906s too.
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here i am! lol. you are correct. I do have an even bigger cam in my otherwise stock bottom end 383. the math puts my engine in the 8.8-9.2:1 copression range. my cam is .254 @.050. it is a huge duration for the short block. I know that if i were to tear it down and put a new cam in i could prob get a little bit more power out of it but i just dont wanna tear it back down. I am running the 84cc eddy heads with a single plane m1 intake. all that being said. i know my combo is all wrong. i built the engine when i was 19 and was just buying go fast parts from a catalog. live and learn. they are correct about the timing. my cam is installed at 106*. it was degree'd. when i first fired the engine i had about 10* initial timing and 35* total. the thing was a dog. it had a huge overly rich idle that would burn your eyes outta your head. i got the dizzy reset with the help of cracked back. i now have 22* initial and 36 total. the thing starts up with the flick of the key and sounds nasty as hell. could it make more power? sure! but it runs pretty damn hard and does well enough that i enjoy it. keep in mind though that i am running a 4500 rpm stall converter and 4.10 rear gears with 28" tall tires. my opinion is that your cam is in retarded, your have too little initial timing, not enough stall converter and not enough gear. it all comes down to what you want from the car and what you can live with.

[ame]http://youtu.be/aLTuGFWyDuw[/ame]
 
I'm not sure of the exact comp ratio, just stating the advertised ratio. The heads were not cc'd. I really don't want to buy another converter or rear gears, the car has about 20 miles on it since it was put together. If a milder cam would make it more drivable I would rather do that.
 
WARLOCKII said:
I'm not sure of the exact comp ratio, just stating the advertised ratio. The heads were not cc'd. I really don't want to buy another converter or rear gears, the car has about 20 miles on it since it was put together. If a milder cam would make it more drivable I would rather do that.
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you need to speak with a few cam manufacture's. be completely honest with them and tell them what you are looking for. they make cams that are designed to optimize cylinder pressure in low comp. engines. the whiplash line from hughes for instance is one of them. I would get some opinions on here about that. you can leave your rear gears and converter. you need to address the timing first thing. that ALL STARTS with the cam install. if you just line up the dots and put it in you have no idea at all where your cam is at. degree'ing a cam isn't that hard and a kit only cost about $75-150 bucks. go on youtube and have a look. thats how i learned how to do it. there are dozens of videos that show you how to do it. If you dont want to do any of that then i would bump your timing forward 2* at a time. start the car. if it starts nice and easy then keep going forward 2* until you get a slow cranking or it kicks back on the starter. then go back 2*. i bet you will be in the 19*-22* range. then you have to figure out how to limit the mech. advance in the dizzy. you want to limit it to about 35-37* total advance. all of that with the vacuum advance un hooked and plugged. this is the starting point for every thing.
 
Power brakes need vacuum around 10" at idle to work dependably. They are the limiting factor by far. In terms of idle quality - If you want brakes, ignore the idle quality. If you want the raspy idle, replace the brakes with non-power assist or hydroboost. The cheapest/best overall way out IMO is to replace the camshaft and be happy you can stop rather than shake the ground.
But - that being said - if you do the pressure testing it might be that the cam or timing set is screwy and the cam is in retarded regardless of the dots. A very lazy 383 will wake right up with optimized cam timing events - even using the factory 383HP camshaft. I've had to move them as much as 8° (not a Comp...) to get the ICL in the right place according to the piston - not the dots.
 
the cam isn'ty too big but the specs are not going to yield pleasant street manners and it isn't cut for a mopar. small centerline, moderate duration and tiny lift = not good.

Another thing you have to consider is that you really don't have a big block. You have a physically large block with small block cubic inch. Anycam you put in it will seem a little biger than say somthing 100 cubic inches bigger.
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Perhaps I'm being a little judgemental here, but these two statement implicitly contradict each other. First you say the cam is not too big, but that you have a short stroke engine so it'll act like a bigger cam than it really is. So, by that rationale, no cam is too big for anything but just be aware it may run like poo...also, when you compound the short stroke with a high duration/overlap cam with unknown but believed low compression, it only compounds the issues.

OP: Pretty sure you already knew that though.

How about this:

1) Cylinder pressure test
2) adjust your timing/curve

report back...
 
younggun2.0 said:
you need to speak with a few cam manufacture's. be completely honest with them and tell them what you are looking for. they make cams that are designed to optimize cylinder pressure in low comp. engines. the whiplash line from hughes for instance is one of them. I would get some opinions on here about that. you can leave your rear gears and converter. you need to address the timing first thing. that ALL STARTS with the cam install. if you just line up the dots and put it in you have no idea at all where your cam is at. degree'ing a cam isn't that hard and a kit only cost about $75-150 bucks. go on youtube and have a look. thats how i learned how to do it. there are dozens of videos that show you how to do it. If you dont want to do any of that then i would bump your timing forward 2* at a time. start the car. if it starts nice and easy then keep going forward 2* until you get a slow cranking or it kicks back on the starter. then go back 2*. i bet you will be in the 19*-22* range. then you have to figure out how to limit the mech. advance in the dizzy. you want to limit it to about 35-37* total advance. all of that with the vacuum advance un hooked and plugged. this is the starting point for every thing.
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I like this ^^^

Dude, your Dart just keeps getting nicer every time you post up a picture. Nice to see you got some glass in it-looks and sounds so damn good.

I'm not sure of the exact comp ratio, just stating the advertised ratio. The heads were not cc'd. I really don't want to buy another converter or rear gears, the car has about 20 miles on it since it was put together. If a milder cam would make it more drivable I would rather do that.
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This is why we're kinda curious on the piston part numbers/type. In any case, I still like suggestions from Rusty, moper, younggun, and bomber...but if you don't mind swapping cams, you may want to look into something about 268-270* total duration and properly degreed with correct timing, etc
 
Dude, your Dart just keeps getting nicer every time you post up a picture. Nice to see you got some glass in it-looks and sounds so damn good.

thanks man! it has been apart since the fall of 2003 until this spring. this summer was the first time i got to drive it again. needless to say i didnt take it easy. i railed on the thing. 2 block long burn outs, tach'd it out in drive (7200 rpm in drive = 146 mph according to my speedo) 7k shifts till the cows come home. best summer of my life. only bad part is that its done for the year now. lol

 
Doh! stupid expensive tires! I did watch the movie you posted up a few months ago-like 8min long where you're driving around your locale burnin' it up. Too bad for me I won't be back on the mainland for another 4 years to put my car together. In all reality, if it ever do finish it enough to drive and enjoy it, it'll probably be 10 years from now...in the interim I'll have to live vicariously through others.
 
Oh and on the vacuum advance thing. If it's a street car, it needs a vacuum advance. No ifs, ands or buts about it.
 
RustyRatRod said:
Oh and on the vacuum advance thing. If it's a street car, it needs a vacuum advance. No ifs, ands or buts about it.
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Why does it need vacuum advance if it's a street car?

My car must not be running right if that is the case...
 
This isn't a thread about vacuum advance. If you want to discuss it, please make a thread about it. I don't want to get completely off track here.
 
OK, I ran a compression test today and I know the engine has roughly 20 miles on it and time breaking it in on the test stand. Maybe the rings are not completely seated but the numbers bother me:
1-130
2-120
3-130
4-155
5-120
6-135
7-140
8-145
If the cam was installed a couple of degrees retarded would the valve timing be off far enough to cause these numbers? I didn't have time before work to shoot oil in the cylinders to see if that would increase the numbers, maybe tomorrow. I don't realy have any blow by coming out of the valve covers but I think I'll run a leakdown test this weekend anyway.
 
WARLOCKII said:
OK, I ran a compression test today and I know the engine has roughly 20 miles on it and time breaking it in on the test stand. Maybe the rings are not completely seated but the numbers bother me:
1-130
2-120
3-130
4-155
5-120
6-135
7-140
8-145
If the cam was installed a couple of degrees retarded would the valve timing be off far enough to cause these numbers? I didn't have time before work to shoot oil in the cylinders to see if that would increase the numbers, maybe tomorrow. I don't realy have any blow by coming out of the valve covers but I think I'll run a leakdown test this weekend anyway.
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That is a pretty good deal of variance-35psi extreme spread. If the cam were retarded, it would lower cranking pressure compared directly to advanced, but the numbers should all be consistent. I don't want to sound rude but did you get the same number of strokes in all cylinders to arrive at those numbers?

Good idea on the leakdown test, and maybe try farting around with the timing and drive it around some more to help the rings seat, if that's indeed an issue.
 
Am I the only one pondering the possibility that the valve job didn't go so well considering those numbers?
 
The results are what I expected - but low to very low IMO. They should be about 35-40psi higher if the engine was fully broken in, truly 9.5:1, and the camshaft was in where it should be. The varience is probably due to the rings seating and valve job. Not a huge deal - they'll improve a little with some time. But I don't think it will be what it needs to be. I would either replace the cam, or pull the timing cover and degree it to see where it is now. Regardless of replacing or resetting - a degree wheel needs to be part of the solution.
 
Hey warlock, have you had a chance to mess with your timing yet? I'm actually interested to hear if things have changed or improved
 
I had some time to think about what I wanted to do while on vacation and decided to go with a new cam and lifters. I'm thinking Comp cams XE268H and this time I'll degree the cam. I will post the results when completed. Thanks everyone for all of the great help.
 
if you have any questions about degreeing the cam let us know. if you want to know what advancing and retarding the cam does to the engine and power band speak up. this is critical knowledge to have when it comes to building a great engine combination. trust me. im learning it all late. when you have to go back and change parts or just live with what you have built it takes some of the fun out.
 
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