Need advise for taming car down alittle.

[deputycrawford]

     Hello all. I'm back. I finally brought the car home. I have figured out several issues on the car and will fix them. My question is what cam do I put in this thing? I'll start with a few specs. The cam is way too big for the supposed 9.35 to 1 compression ratio.

75cc 906 heads.
flat tops, .040 over, with 6cc reliefs. .023 deck
.040 head gaskets.
Performer RPM intake with Race Demon 750
High volume oil pump and 7 qt pan
9 1/2" converter 3500 stall
410 gear and 28" tall drag radials
Engle custom cam KV2 intake lobe/ KV3 exhaust lobe  108 center degreed at 104

     With the current cam, my cylinder crank pressure is 125 psi. That is stupid low. I am going back to a hydraulic cam but need to keep the converter and gear for money reasons. I am thinking a Comp Cams High Lift .525. I already have the High Lift .545 and liked it.  Maybe the old standby Engle K56 would be a good choice. Anybody have any ideas?

Jerry

[firefighter3931]

Jerry,

Welcome back !  Are you looking for hydraulic or solid cam recommendations ? Improved vacuum idle ? No more racing ? Cruiser type build ?

The K56 would definately mellow it out and build low speed cylinder pressure. 



Ron

[Challenger340]

Hi Jerry
I'm a little confused with the specs you posted ?

Those dimensions(75cc Head) yield a static C.R. of around 10.5:1, not the "supposed" 9.35 you mentioned ?

Are you sure they aren't 85 cc 906 Heads, or did you Mill them to the 75cc ?

The reason I ask, is because if it is the "10.5" C.R., it's gonna be prone to detonation, and a "smaller" Cam is just going to make it worse ?

Even with the low cranking pressure, it should be starting to gain good Volumetric Efficiency @ the 3500 when the convertor hits, with the 245 @ .050 Intake Pattern at 104 ?

Nonetheless, what does it DO, or NOT DO very well, that needs "taming down" ?

[firefighter3931]

Hi Jerry
I'm a little confused with the specs you posted ?

Those dimensions(75cc Head) yield a static C.R. of around 10.5:1, not the "supposed" 9.35 you mentioned ?

Are you sure they aren't 85 cc 906 Heads, or did you Mill them to the 75cc ?

The reason I ask, is because if it is the "10.5" C.R., it's gonna be prone to detonation, and a "smaller" Cam is just going to make it worse ?

Even with the low cranking pressure, it should be starting to gain good Volumetric Efficiency @ the 3500 when the convertor hits, with the 245 @ .050 Intake Pattern at 104 ?

Nonetheless, what does it DO, or NOT DO very well, that needs "taming down" ?

Bob, The engine in question is a 383 so that's why the static numbers are low. I can't remember the piston to deck measurements off hand....it's been a few years since this engine was built.

I agree with you on the cylinder pressure  Too short of a cam will cause detonation issues with a non-quench iron head build....so we need to be careful when picking the "right" cam profile.

It sounds like Jerry is looking for a smoother idle and more bottom end power...... but i'll let him fill in the blanks.



Ron

[b5blue]

Hey guys the first cam that came to mind for me was P4452783 (for taming it down) Or am I too "old school"  ?

[deputycrawford]

     Sorry guys. I have to remember its been awhile. It is a 383 just bored .040 over. I hacked the heads .050 for the 75 cc chambers. The heads have also been ported quite a bit. The pistons are .023 in the hole. The valves are stock size. The springs are comp 913. The intake has been hacked .060 to match the ports and ported for some flow. I really like the nasty idle and coming up on the stall. The 28 in drag radials hold the launch ok.
     I have a complete 3.23 pig on the floor for next years road trip but will keep the 4.10 in for around town. I don't even have the money to spend on the car right now but I have an addiction again. I thought I beat it but I am sick again. I must cackle at stops lights and scream down the road at just 60 mph. It is just too addicting. I just need better cylinder pressure and want to go back to a hydraulic cam.
     I used to shift around 6800 rpms but will probably never see a drag strip again with this car. Shifting by 6000 rpms will be fine. Cruising is for me now. I have a 2009 holden Commodore for the drag strip if I want. Thats why no money.     Thanks for all the advise guys.

[b5blue]

I think we all hope you stay "sick"!!!   

[deputycrawford]

     I guess I have to add a few things. I started thinking about Wes and Geri. Wes is demanding I bring the Charger to the next Charger meet.  
    I am thinking I will only use the 3.23 for the trips but might get lazy and keep it in the car.  I really like the 3500 stall and really want to keep it but am afraid I will create a mismatch set up. I guess I need some suggestions and will live with the realistic build. I guess I am looking for the fewest parts to put this thing back on the road.

Jerry

[b5blue]

I'm running 3.23 and like it, I'm changing to a 145K TC mostly for streetablity and mileage soon. Ron will be a better guide on this stuff than I could ever know....sounds like you got a neat beastie under the hood!!

[deputycrawford]

     Thanks for the reply B5. I understand you do not want me to get well anytime soon.    Challenger340, you asked what it does or does not do well. Not really anything bad. It just seems a little lazy at part throttle from a dig. You have to get into it about 1/3 throttle to get it to leave a light with some decent pull in the driver seat. I know some of it could be converter but I have to idle it around 1100 rpms and it needs some throttle pressure at some lights when in gear. That tells me it needs a smaller cam. I am hoping to keep the gear and converter and get better response at part throttle. The 3500 stall does make it sound serious to people when I am entering or leaving a car show or meet of some kind. I love that.


Jerry

[Challenger340]

Ah Geez ?
That makes sense, it's a "383" hence the 9.35 ?

Yeah, that Cam seems too big for a 383, unless ur just Bracket Bashing.

[firefighter3931]

    I guess I have to add a few things. I started thinking about Wes and Geri. Wes is demanding I bring the Charger to the next Charger meet.  
    I am thinking I will only use the 3.23 for the trips but might get lazy and keep it in the car.  I really like the 3500 stall and really want to keep it but am afraid I will create a mismatch set up. I guess I need some suggestions and will live with the realistic build. I guess I am looking for the fewest parts to put this thing back on the road.

Jerry

Jerry, if you're planning to use 3.23's....the 3500 stall will be a mismatch. The converter will be slipping a lot (generating heat) and won't lock up.... so rethink that gear choice. 

If you want to run the 3.23's then plan on a converter swap and go with the K56. If you keep the gear and stall i would look at the Comp XE275HL.Whatever cam you use should have a 110 lsa to tone down the idle and improve drivability. 

* both the K56 & 275HL cams are 110 lsa "off the shelf"



Ron

[deputycrawford]

Thanks for the reply Firefighter. So my combo would be one of these two choices.

      1.   4.10 gear    3500 stall    Comp Cam XE275HL

      2.   3.23 gear    2800 stall?   Engle  K56



   I will probably go with the Comp to keep the cost down on the change over. I have a large trans cooler and guage hooked up. Can I get away with putting the 3.23 in for a long trip? I would watch the temp guage and give it a rest if it got hot. If I can get away with that, I will just keep an extra gasket and fluids for the switch every year.

[firefighter3931]

Yoou could try the 3.23's and monitor the trans temps closely. On the hwy at cruise speed it will probably be OK but in traffic (stop & go) it will heat up.



Ron