not a 396 just a 323:(

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396PLYMOUTH

396PLYMOUTH

My Little Mopar
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I having cam issues I think! I have a 318 .040 over kb167 302 heads mild port work wieand stealth intake holley 670sa mopar 292/.508 cam 727 w/11 inch 3000stall converter (NEW). I have no bottom end at all.... The car has a 2.94sg 26.5 inch tall tirei know I need a gear what else could be wrong?
 
The factory didn't ship cars with 3.55, 3.90 and 4.10 gears just to limit the top speeds, ha ha.

I run a 26 inch tire and 3.90 gears with my old 318 and at times wished it had 4.10's
 
Well, from everything I've heard about the Purple Shaft cam, it seems like your root problem lies only in your rear gear and cam selection. My understanding is that cam offers so much duration that it really only offers a strong powerband above 3000-3500 rpms. That, combined with your high 2.94 gears, seem to me to be the only problems. The 292 purple shaft seems like a lot of cam for a 318, so I wouldn't be too surprised to hear that the thing doesn't really rip until higher RPMs. Maybe the .484 lift Purple Cam and/or lower gears would be a better choice for your combo?
 
Im definatly going to change gears but I installed the cam like a chevy 12o'clock crank 6o'clock cam. Does anyone think this will effect performance?
 
MN1968Valiant said:
Well, from everything I've heard about the Purple Shaft cam, it seems like your root problem lies only in your rear gear and cam selection. My understanding is that cam offers so much duration that it really only offers a strong powerband above 3000-3500 rpms. That, combined with your high 2.94 gears, seem to me to be the only problems. The 292 purple shaft seems like a lot of cam for a 318, so I wouldn't be too surprised to hear that the thing doesn't really rip until higher RPMs. Maybe the .484 lift Purple Cam and/or lower gears would be a better choice for your combo?
Click to expand...

Advance the cam 4* if you have valve to piston clearance,

3500 stall would work much better.

But them Gears,............ THEY HAVE TO GO!(2.94:1, WOW!:-D)
3.55 at the least.
JMHO
 
When you say aadvance the cam, do you mean physicaly remove the timing cover and do it that way?...... I have about 26* intial and 6*mech advance
 
396PLYMOUTH said:
When you say aadvance the cam, do you mean physicaly remove the timing cover and do it that way?......
Click to expand...

Yeah, if you have never done it, have a friend that has, help you.
It's a long process if you degree it, instead of just throwing in a 4* and calling it good.

Advancing will give more bottom end torque
Retarding it, will give more top end power

I would focus on your gears first. they will be the biggest improvement!
 
396PLYMOUTH said:
Im definatly going to change gears but I installed the cam like a chevy 12o'clock crank 6o'clock cam. Does anyone think this will effect performance?
Click to expand...

It's a good possibility. Not because you installed it like a Chevy, cause it's the same procedure on all American V8's. The problem is you didn't degree in the cam like Cudafever said. The issue comes in where the timing chain set may have been built retarded and/or the cam may have not been ground properly. I don't even rebuild a stock engine anymore without checking the cam timing.

It is entirely possible that it is degree'd correctly but you just never know. If it's 4 degrees retarded that will cost you quite a bit of bottom end torque. top that off with the airplane gears and you've got a dog out of the hole.

IMO you need at least 3.73 gears for your combo.

Also more timing might help. Have you experimented with the timing to see where it runs the best?
 
I have it as far as it will go I have been thinking about pulling the cam and re-installing it 12-12 and see where that gets me or just going with a different cam all together like a comp 280h or lunati 268.
 
more gear\\\\ 4.30 \4.56 \4.88
If you want more power, then go with a higher stall speed.
3800 to 4000 stall converter would work good.
Sounds like your trying to go fast.
This is like a race set up ,but that's the kind of cam your running.
Your cam will make peak torque after 4000rpm's.
Try a 9 1/2 dynamic converter down the road, but first change the gear.8)
 
I just bought a new converter so im stuck with it! I think I will just go with a 4.10 set up and go from there. Keep you guys posted thanx for the info...
 
396PLYMOUTH said:
I have it as far as it will go I have been thinking about pulling the cam and re-installing it 12-12 and see where that gets me or just going with a different cam all together like a comp 280h or lunati 268.
Click to expand...

Installing the timing gears at 12 and 6 is no different than 12 and 12. You notice how the top (cam) sprocket is twice as big as the crank gear? That's cause the cam turns at half speed of the crank. If you install the timing gears at 6 and 12 O'clock and rotate the crankshaft exactly one turn the timing gears will now be at 12 and 12. The only thing that's affected by installing the timing gears at 6 and 12 vs. 12 and 12 is when they are at 12 and 12 #1 cylinder is on the compression stroke and at 6 and 12 #1 is on exhaust stroke. Therefore when you install timing gears at 12 and 12 that's when your rotor should be pointing at #1 cylinder.

If you do tear it down the only thing you can do with your current setup is make sure it's degree'd in. Degree'ing the cam means your checking and adjusting the intake lobe centerline and setting it to the cam manufacturers specification which generally provides maximum perf. For instance if the cam card calls for an installed intake lobe center of 108 that's what you shoot for. When you check it you may find it's not at 108 but at 110 or 112 which means the cam is retarded and that'll cost you low end torque. Could also be at 106 or 104 which can help low end torque.

Also you seem to be confusing cam timing with spark timing. I say that cause I said to try more timing. When I said that I meant more spark advance cause you said you have it at 26 initial with 6 degrees of centrifugal advance. That only equals 32 degrees total. Try advancing the dist. a couple degrees at a time until you find the point of maximum perf. without it spark knocking.

But again your biggest problem is the gears.
 
Well another reason for me to swap out the cam was compression, according to what I have in my set up -kb167 .040 over, zero deck height, 302's milled .025, gasket compressed thickness is .028, gasket bore diamater 4.060 stock stroke and stock rods= 10.50:1 compression but with that particular cam its more like 8.5:1. I have actually put 87 octane in it and it ran fine no spark knock or nothing! But when you take off from say a 25 or 30 roll the thing really pulls good from 2500 to about 5800-6000 rpm so I am hoping that the gear will fix the majority of the problem.
 
You have no low end because the parts are mismatched. Was the blocked decked heavilly? Did you use the MP thin head gaskets? Were the heads simply milled to clean up the gasket surface or milled to lower the chamber size? Because otherwise the pistons are not at zero deck, the stock type gaskets are thick, and the head's chambers are around 62ccs. That means your true static compression is close to 8.9:1, or low. Add to that the cam which is too large for the gearing you have, probably need to be degreed to be even close to where MP wanted it, never mind what you might want to run it at, the intake with 340/360 sized ports, the carb that is the dry-flow equivolent of a 750cfm Holley, the heavier and harder to spin 727 with a huge convertor, and no gear. If it were me, I'd take a couple cylinder pressures and see where you're at. If it's lower than 140psi you have issues requiring more changes. For a quick fix, swap the carb for a 570 or the oldschool 600 Holley and advance the initial timing and curve as far as you can. For a longer term fix, if you want to keep the gearing, I would plan to swap in a 904 (has a lower 1st gear, weighs 40lbs less, and takes 20 less hp to drive) with a tight 10" convertor with a stall no higher than 2400, replace the intake with a Performer 318/360, replace the carb with the 570, and recam with something more modern that will work in the power band the gears put you in. I'd imagine it's currently like driving a wet sponge until it hits like 4K rpm.
 
Your compression should be fine.
In fact,since the motors zero decked and a closed chamber head is installed,your compression is perfect for the purple shaft cam.
The motor is right on the money:-D
The only thing that would improve your performance with your combination, the way it is, are the following:
1)TOTAL TIMING SET AT 30 DEGREES OR MORE
2)CARB TUNING-PUMP SHOT INCREASE
With a tight converter the engine will like a rich pump shot.
3)4 hole -CARB SPACER-HELPS VELOCITY
4)GEARS-:toothy10:
Since your stuck with your converter,the way you adjust the carb, will be very important, little changes ***will make a big difference.
 
One thing you might investigate is Rhoades hydraulic lifters. They bleed down at low speed so that a large cam has less lift and duration for better idle and low-end torque. There are 2 versions - street and race. I put the original street ones in my 273 (mild 422/444 cam) for better mileage, but haven't run the engine yet. List ~$110, but got mine on ebay cheaper.
 
You have no low end because the parts are mismatched. Was the blocked decked heavilly? Did you use the MP thin head gaskets? Were the heads simply milled to clean up the gasket surface or milled to lower the chamber size? Because otherwise the pistons are not at zero deck, the stock type gaskets are thick, and the head's chambers are around 62ccs.



Well infact MOPER it is zero deck because the piston (kb-167) comes right to the top flush with deck of the block and yes the heads were milled to achieve a smaller chamber size. As for the gasket its a mopar performance gasket .028 thousands compressed thickness ( tourqed to spec ). So its not a mishmash of parts thrown together I tried to replicate a few other builds out there using what I had and like I said its starts pulling nicley around 2800-3000 or so. As for the the trans im stuck with it my bank account wont let me change it so I have to make do with what I have..... And thank you for your insight it has helped me with my decisions on what to do. :)
 
Ok, sounds like the homework was done rather than tossing parts together... I apologize for assuming it wasn't. However, the cam, gearing, convertor, and carb sizing are still off. I think it's great that it pulls after 2800. But a street car with that gearing, at least in my area, isn't spending much time there around town. the mismatch really only matters if you feel there's something "off". But you've posted that you're noticing just that.
 
I guess my intial question was Is a cam change nessacary for my combo? Im gathering thats its no , I did some timing adjustments now im 37* total and it seems to run better so im going to have a gear installed probably a 4.10 or something close to that I will keep everyone posted and thank you all for the input of info :)
 
Gears is where I'd go first... Everything else will fall into place with that change. AS far as the cam..So long as it was degreed I'd leave it alone for now.
 
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