Horsepower for 69Z 302 w/#140 cam

[Lynn]

I guess everyone has an opinion on this. I helped a buddy install a 140 cam in his 68 Z in 1970. I also ran a 140 cam in a Z engine with headers for a while in the 80's, so of course, now I am an expert, right? Maybe not. In the 1970 install, we didn't know squat about recurving (and I mean me and my buddy; obviously there were a lot of guys that could do that, but we were oblivious). That 68 didn't idle very well, and didn't run that well until 3600 rpm. With headers and no resonators, it ran like stink after that. Watched him take it to 8,000 rpm repeatedly without a failure. All we did was put one weak advance spring in, leave the other one, and put her back together, then play with timing until it would scream. Stock vac advance can, all hooked up like the factory had it. in my 80's build, the distributor was correctly recurved, but I was unaware of a low vac option for the vac advance, but did know enough to hook it to manifold instead of "ported spark" like the factory did.

Anyway, here is my take based on those experiences, AND some additional facts I have learned since.

1. 1980's build, idling at 1,000 rpm, I never had idle issues using 4053 carb. Power brakes were never starved for vac.
2. Much as I like Mike, and hope this engine is everything he wants, I don't see this being much of an improvement over the 30 30 cam if using manifolds instead of headers.
3. Several knowledgeable guys have insisted the chambered exhaust actually flows WORSE than the stock exhaust. It just makes more noise. I have no hard data to back it up, as I am only an "internet expert" on this. If it is true, then chambered after manifolds just makes things worse. If it can't breath, the cam isn't going to work.
4. Scott asked about 4053 carb and 480 distributor. Both can be used, but the distributor must be recurved and a different vac can (B26) used. Timing all in by 3000, limited to 24 to 26 degrees (at the crank) of centrifugal and about 8 to 10 more vac. Hook vac advance to MANIFOLD vacuum. Start out with initial timing at 8 to 10 <span style="font-weight: bold">without</span> the vac advanced hooked up, again at the crank. With the distributor set up like that you may not even need to re-jet the carb, but then again, you may. You won't know until you get it set up.

[ban617]

Another point that will effect the timing is what fuel are you going to use ?

[miket1]

Using the original 4053 carb.,rejetted, and the point type dist. w/ a Pertronix module in place of points, 37 degree total timing all in at 3000 rpm.
93 octane gas and 5 gal. of 100 octane aviation gas added to the tank.
Quench on the chambers is .035
Vacuum at 1000 rpm is 5 in.
Not loading up at idle, but I only have 1 hour break in time so far, mostly at fast idle 1200-1700 rpm using Brad Penn break in oil with zinc.
So far it is running good and smoothes out nicely as rpm's come up a little.
I am going to fine tune the dist. a little more this week.
My 69Z is an early build factory chambered exh. car so I don't want to change that, keeping my exh. manifolds and smog equip. on also.
If I don't like the way it performs on the street I will change it back to my .030/.030 cam.

[Salvatore]

I would NOT change it back Mike, I would do what Lynn says about the exhaust and so forth. The 30-30 runs well and if you do not put a steeper gear in it and make that engine breath a little the 140 cam will be a deterrent I believe.
Forget about the smog and all that stuff at this point. Make it run good with a few more changes.

[Lynn]

Mike: I &quot;get&quot; the vintage build thing, but when you sit down and think about it, I believe it is easier to put on headers, exhaust and gears than to change the cam once it is in the car. I have original exhaust for my car as well as manifolds and smog. I can put them on any time I want to look completely stock.

I am surprised you only have 5 inches of vac at idle. I had a good 10-12 at 1,000 rpm with a 140 cam.

[miket1]

I checked the vacuum thru the carb. port, I will check it directly thru the intake to see if its different.

[ZLP955]

Good advice from Lynn. Only thing I noted is that John Hinckley recommends the B28 vacuum can rather than the B26. No idea if there's much (any?) difference though.

[L78steve]

With vacuum at 5&quot; at idle neither can will pull in that low. You will most likely have to use a ported source to prevent driveability problems at low speeds.
The timing will be all over the place at idle.

[Lynn]

Don't know the spec of those vac cans. It may be the B28 I was thinking of. I had an MSD on the distributor machine last week with a B26, so that is what made me think of that number. Seems it worked at 8 or 9 inches.

You need the one that will engage with the least vac.

[Salvatore]

I would unhook the vacuum advance from the distributor and run it like that. Had mine done years ago and plugged the hose up. No issues at all.