WOW! Fantastic information, my friend. I've copied this and saved it to my "Demon" file.
A little background... Though my car is a 1972, It now has 10.5 to 1 pistons and has older 2.02 heads with 30 thousandths shaved off of them, so probably 11 to 1? The came was also changed years ago with a mild upgrade... I'm thinking somewhere in the neighborhood of 484 lift, 268 duration. Does that sound right? Anyway, it was pretty much the same dimensions as a 1968 4 spd cam which was supposed to have been the biggest FACTORY cam. It's and automatic with a shift kit and has an aftermarket convertor which I believe is a 3500 stall (HUGE mistake). I was under the impression that the factory convertor was 2800. I also, for top end, had the plenum cut out of the factory intake which is still that way but I have another factory manifold on had if I want to change it. Keep in mind that these changes were done almost 50 years ago, before we had this information highway we have today. I could spin my N50 Goodyears til the cows came home but when I wound it up and shifted it into 3rd gear the car would completely fall on it's face. I have a theory now that the convertor was the issue. I do have a stock one that will go back in sometime soon. The gear which was originally a 3.55 posi was change to a 3.91. These days, I'd probably prefer maybe 3.23 but I do have a 28" time on the rear now which my calculations bring it pretty much back to 3.55. I confess, I made all these changes in my early 20's and didn't really have a total understanding of what I was doing. Bigger mistake was pretty much doing it all at once so when I had to iron issues out, I had no idea where to start.
You have me thinking about that living with headers stuff. I do have a couple of good dents, primarily from the install that I guess I could try to patch up (I wonder if a good Dent puller could do a decent job and then just seal the hole?) On my old Hookers, the center link has to pass through one of the tubes. Does your set get around that? Like I mentioned before in a reply, these DO NOT come out without lifting the motor so it's not something I can routinely do.
Thanks again for the opinions and especially all the Knowledgeable information. Great Stuff!
Blessings...
Brother
Yur on the right path and notta chance would I force a 268 cam to breath thru logs. My headers are TTI under-chassis, so not under the steering.
IMO, the real problem with the under-steering headers is/are chassis related. The factory T-bars are just too soft, and the shocks are junk too. and, IMO, guys just run their street cars too low. Now that I have more money, or did before I retired, I wouldn't be afraid of that type of Header, cuz I discovered 1.03 bars are just fine, a higher ride height is just fine, and adjustable shocks are just fine too! lol.
I am very familiar with 340s laying over in Third gear with 3.55s and tall tires.
Top of third was always where my stockers got smacked by the guy in the other lane. and you know why?
lemme tell you.
that 340 cam was an emissions cam. it had great specs but that whole engine was a mess. Nobody that I know, would build a clone today, to do anything but be a sort of Tribute car.
The First problem with a factory 340, was that it was never a 10.5 engine.
To be a 10.5 engine, the TOTAL combustion chamber size would have to have been 73.3cc's. Well criminy the heads alone were nearly that big.
Doing the math on any one of my 4, I can't get past about 9.4Scr.
The second point is that stinking 114* LSA cam, drops the DCR down to in the basement at 7.4 at an elevation of 900ft. That is stinking low.
The third point is that, with an LSA of 114* the Overlap is down to 44* off the advertised. Same cam on a 107, would have been a half-way decent 58*.. Which would have worked VERY well with headers. As it was with the logs, that cam fell on it's face when the going got tough.
The fourth point is the slow-azz intensity of that cam. It was designed to last about half a million miles, it seems, lol.
The fifth point is valve springs that barely made 5500 rpm on a good day.
In factory-stock form, that engine was a mess, and it showed, the car couldn't break 100 in the quarter, and trap-times were mid 14s.
That engine, IDK how, got a reputation, which IMO, was only because Ford and Chevy couldn't seem to bring anything better, at a similar displacement.
When I realized that I shouldda bought a 69 Chevelle with an aluminum headed 427, I went straight to the junkyard and got me a 4.10. and I got me a sweet new clutch, and big stinking tires, and some stinking valve-springs.. That solved my Third-gear lay-over, problem, while simultaneously eliminating any hiway travel. But at least I could now keep up with all my buddies with bigblocks, I was so dumb to have bought a 340, and think I could hang with the big boys. lol.
That 340, already distressed for a while, was less than two years old when I blew it up . The warranty engine that they gave me was a bigger dog. I idled it around for another two years then sold it to pay backrent.
Those were my first two 340s.
Next, a buddy scored a junkyard 340 which had sat with water in it , and because I was the guy with a torquewrench, I got to put the 340 heads/topend/and cam onto/into his Hi-compression 318/69 Satellite, and for this great privilege, I got the left-over parts. I was ~21 years old.
So, I had this old beater 65 V100 wagon that burned nearly as much oil as gas.
And I had a friend with a recently pulled, good-running 273/automatic combo, and
I had this reasonably fresh Satellite topend.
You know it; I bolted that all together (minus the 273 core) and stuffed it into the little wagon, 2bbl and all. Well, the only exhaust worthy of this monster would be fenderwell headers, and 2" straight pipes. I was in business; push-button auto, and the little yank-it lever, for Park.
now, here's the deal, with the early 318 heads, and the early-closing intake valve event of the 318 cam, this thing had Dcr up the wazoo. and it ran like a raped ape . To this day I remember that very high compression big-bore 318; and to this day, I still have the core, cuz a couple of years later, I got married and gave the car to my up and coming baby-brother, minus the engine/trans, but with a good 225, not the old oil-burner.
What did I learn?
Compression makes heat, which makes torque, which makes power. and
On the street, 6500rpm is not what you want.
Here I had had,
a 4500/5000rpm engine, that was crazy big fun, and with 3.23s still made great fuel-economy on the hiway. and it came out of a pile of junkyard and leftover parts, and those glorious fenderwell headers. I was forever sold on headers. that was about 1976 and that was 340 number 3.
By 1980, I was again driving a 340, this one with a lotta miles on it, and back to a 4-speed again. and it had headers. Daymn if that engine didn't surprise me. But, it was all bark/no bite, even with headers. I drove it until she threw a rod bearing, then parked it, and pulled the engine. Then I had kids, and there she sits out behind the garage.
The handwriting was on the wall; I was done with 340s. What I didn't yet know, was that I was actually done with that stinking 340 cam. But I wouldn't find that out until the last kid was graduating.
I started a new project in ~1997, but that will have to be another post. This one would be a super-hi-pressure 367LA, with a 292/292/108 cam.
