Converter stall speed observations with new heads, intake and cam.
 

I recently Rebuildt the engine with a topend kit, my limiting factor for cam choiche was converter stallspeed before the topend rebuild, and not knowing what cam was inside the engine.

After completing the rebuild i now know the exact components in the engine:

Old specs on cam, intake and heads:
6x-8 heads untouched, no sign of portwork.
performer intake (non rpm) no portwork.
Cam; Edelbrock ramair 4 clone: 7157 Performer RPM Hydraulic flat tappet (partially wiped lobe(s)
Specs: Duration @ .050 Intake: 231 degrees - Duration @ .050 Exhaust: 240 degrees - Lift @ Valve Intake: .470" - Lift @ Valve Exhaust: .470" - Lobe Separation: 113.5 Degrees - Intake Centerline: 112 Degrees

With this combo my converter flash stalled to 2400 rpm on the tach when rolling at 10-20 mph and going full throttle.

Based on this info i was adviced to not go larger than 230/[email protected] with a 112LSA to have a nice and well functioning combo for cruising and low speed around town driving, as well as doing a few power pulls now&then.

The new combo:
Edelbrock d-port CNC ported 310+ cfm heads
Hurricane singleplane intake portmatced to heads
hydraulic roller BP comp grind: BP8022SP
Specs: HR) 282/288, 230/236, .510/.521, 112 LS (Std Firing Order/ Std Journals)

Doing the same test on flash stall, rolling at 10-20 mph and going full throttle
now flashes to 3000 rpm.

Armed with the power of hindsigth, i guess i could have gone to a step larger cam: 288/294, 236/242, .521/.540, 112 LS ?

But i had no idea the new topend kit would stretch the flash stallspeed by 600 rpm! with the displacement beeing the same, only 1.3 point in CR ratio higher and a lot more airflow

I theory and in practice now if you where looking for maximum acceleration and to maintain the low speed torque ( off idle ) and throttle response you had with the other combo you can go up 25% higher in rear gear ratio, that is if your chassis set up and tires can hook up your new level of power?

Your new heads have at least 28% larger minimum port area then your stock 6X heads did, this in and of itself without the cam change factored in means that the rpm of peak torque and Hp will now be 28% higher then what it was before.

There’s always a trade off with a NA when you make combo changes and it always boils down to what you can make due with less of and what you want more of!

i do about 99% street driving with the car, i dont even have a set of drag radials, in the future i was planning to attend a an annual streetlegal contest during the biggest national car meet that spans a whole weekend "hot august nights"
So going to a bigger cam would be more of a nice to have for the time beeing.
For now my limiting factor would be enough InHg for powerbrakes.

Stuff in a electric vacuum pump then,
Also get a micro switch and a 25 to 30 amp relay.

Mount the micro switch wired back to the relay on the throttle linkage such that when your at close to 1/4 throttle it cuts off the pump since you do not need it anymore.

Most vacuum pump kits come with the needed high current relay, but not with the micro switch to deactivate it by throttle opening.

Increasing your valve lift would raise your power level with no trade offs in street manners. Assuming the valve springs can handle the additional lift.

The old Faithful 1.0 cam would be a good choice i think, as it has more lift but not too much that migth hit valvestem seal to retainer, the paperwork with my heads said max coilbind at 1.130 " but i am concerned about retainer to valve steam seal clerance
Heads have been tested with 1.65 ratio rockers with a lift of .573 @ 384 lbs by butler befor it was shipped to me, so i know it is safe up to that lift.

You've made some pretty drastic changes to the engine so it's not surprising it's affected the torque converter.

It's obviously making more bottom end torque off idle if it's pushed the stall speed up from what you had before.

Actually it all looks fine to me. 3000 isn't all that high and as long as it drives good at light throttle and couples well, I'd leave it be for a while, drive it and enjoy it. Maybe later down the road do a cam change if you feel inclined but at this point, I don't see a reason to unless you're just looking for more power.

As far as power brakes go, I've run as much as a 239/243 @ .050 on a 112 LSA cam in a 455 and it runs the power brakes and AC just fine. If these cams are installed correctly and spread way out on a 112 and have the correct amount of compression, they make plenty of vacuum. That 455 made 13 inches at idle with that cam. A smaller 230 @.050 I could make idle in a 455 with hardly even a hint of lope and would sound pretty stockish.

Yeah that is pretty much my plan, for this season drive and enjoy the car, next year try a larger cam, with no other component changes.
If it does not play out i can reinstall the current cam. hot-rodding hobby :)

:thumbup:

Keep in mind that vacuum is effected to a large degree also by the size of the chamber and overall intake runner volume.

Because of this two motors of the same CID and running the same cam can’t every time be directly compared.

The motor with the higher compression and smaller overall intake runner volume will show higher levels of vacuum.

NOW, you combo can work the Converter for fantastic Street & Strip satisfaction. Then move up to a Q-JET.

I set the idle speed the same (750 rpm) as cam specs duration to duration is similar @0.50 but the roller has a faster opening ramp comparing advertised @"0" Lift
So far pending some idle timing and fuel tuning i have the excat same idle vacuum rigth at 55 KPA that translates to about 13.5 inhg.

No surprise at all the converter is flashing higher. You installed a smaller cam AND raised the compression ratio. This will for sure "hit" the converter a LOT harder.

I was using that cam years before Butler offered it, cam card and dyno sheet below. The build was a 455 with SD heads, just under 9 to 1 compression. It made 16" vacuum at 700rpm's with only 12 degrees initial timing. It was DONE making power just past 5000rpm's.

You wouldn't be taking advantage of the 310cfm heads, it would run as well with 250-260cfm heads....IMHO.....
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