Vacuum for this 228/236 duration cam? 455

Well again, I don't know about the engine, as I didn't build it. But....

It's got what I believe to be 76 heads with big valves, and I know the builder upgraded the pistons to up the compression. So what does that add up to. H392nc is the only part number I can find in the documents for the pistons. I do think the heads were milled.

Duration specs as listed in the thread title. At 050, 228 236. .489 lift
112 Lsa
Advanced 4 deg, actual advance 2 deg (this is a note on the cam specs printout)

 

Sorry don't have em, that's all I got.

 

It's a new ta balancer,

no it doesn't ping with no vac adv.

Yes it looks like hi compression now

 

If you must run vacuum adv stick a ball bearing in the line before you plug it in and problem solved :grin: I could find that piston part # on a google search.

 

I think so too.

any thoughts on ideal stall speed for a converter on this camshaft?

 

It's a custom comp cams grind.

 

In relation to camshafts, it's important to identify why your putting in a converter.

If it's to soak up the pulses of a larger cam, you need to make your converter vendor aware of that.

I have had a couple folks get back to me with a concern with my 9.5" converter, that it's "too tight" so they have idle problem issues. These are converters that flash stall as high as 3500 rpm.

I can help them out, by increasing the unit end play, but don't like to do that, because while it makes the converter "looser" at idle, what is really happening is your compromising efficiency. So while it will idle better, it won't lock up as well at speed.

I try first to help them to get the engine to run better.. before we resort to a band-aid.

The idea that "you need a converter for that cam, has two origins.. one was to help the idle out, the more prominent reason was to get a modified engine to it's power curve faster.

15-20 years ago, there was no need to consider this, the 11 and 12" 2200-3000 rpm converters were big sloppy messes compared to the 9.5's we have now.. and you would get that mush at idle, whether you needed it or not.

What converter does the car have in it now Ken?

Your compression numbers look like the valvetrain/cylinder sealing are in the ballpark, but the vacuum is pretty low on that size cam.

JW

 

TCI Street fighter is in there now (EDIT: that's not correct, see my next post). Feels loose. Then again I haven't really been hammering it yet. Tuning little by little.

I ought to get another vacuum reading now that I've driven it and tuned a little.

 

Um...that would be good advice Mr. Wizzard! Ken, don't forget that you are MORE then welcome to (other than the hassle and I offer help) to try the Saturday Night Special out to make sure you have the right stall. I think the Saturday Night Special is around 1800-2000 stall. It is sitting in the basement still on the TH400. If you like, you keep.

 

I ran a Coan 11" 2200 RPM stall "tight" converter with a 3.91 rear end.

The cam was very similar to yours.

I found that 36 degrees of total timing (16 initial and 20 in the distributor) gave great throttle response and 15" of idle vacuum.

Limited the vacuum advance to 10 degrees.

 

I was incorrect. Its not a TCI streetfighter rated 3000-3500

The T/C is a TCI Breakaway, stall advertised at 1000rpm over stock.

I need to get a tach on the car.

Its coming alive as I tune the carb and timing.

 

Through PM's I suggested Ken check his valve springs and he found they were waaaaay under spec with 45lbs closed, 225 open.He installed new springs and problem is solved.

 

Thanks for relaying the solution! 45lbs closed! That's the stuff go-karts use!

 

Nailhead! :grin:
Lofting strategy?