what solid cam is equivalent to a hyd 268 ?

-
yellow rose said:
Instead of guessing and trying to hobble the thing and make it better, why not call and buy the correct cam for what you have?
Click to expand...
That 273 just does not have any compression at 8.8 . trying to see what combos will raise the compression for the big erson. it will make some big power with the right combo I think .
 
You need Hopi pistons. Big $$$$. That is why I'm going 340. More hp for $$ spent. Plus I have x heads and ld340 in the shelf. I have closed chamber 302's as well I was thinking for 318 short blocks I have. Ultimately if you stick with 273 it will be pricey.
 
stroker402 said:
That 273 just does not have any compression at 8.8 . trying to see what combos will raise the compression for the big erson. it will make some big power with the right combo I think .
Click to expand...
Stock? only the 68 to 72/73,340s; but you can't put closed chamber heads on those cuz the pistons come above the deck. Well I guess you could if you wanted to.
I once put 318 heads and cam on one, Called it my big-bore teener. In a 65 V100 wagon, man did that thing have snap! That was my third car, and second Mopar.The year was about 1974/75, best I can figure out.
Lessee what a 360 would look like with closed chamber teener heads on it and that 286 cam. Here ya go
Static compression ratio of 9:1.
Your dynamic compression ratio is 7.28:1 .
Your dynamic cranking pressure is 141.35 PSI.
V/P (Volume to Pressure Index) is 120, and 120/82= plus 46%, over base

How'd I get 9.0 Scr
Well the stock-bore 360 has a swept of 737.2CC
I used 60cc heads,an .028 gasket at 6.5cc
and pistons down .125 for 26cc. I guessed at this
For a total chamber volume of 92.5, and so
(737.2+92.5)/92.5~9/1
No worries about P/V or P/H, or Q.
Now if you have the 57cc heads, the Scr rises to `9.25, and
Static compression ratio of 9.25:1.
Your dynamic compression ratio is 7.48:1 .
Your dynamic cranking pressure is 146.46 PSI.
V/P (Volume to Pressure Index) is 124, and 124/82~ plus 51%

Oh wait that's roller-cam engine compression. Now you can just stick that 286 into a magnum 5.9. ......at ISA of 105, and those Magnum heads will pump up the top-end pretty good

But if you shaved the Magnum heads to 60cc
Static compression ratio of 9.4:1.
Your dynamic compression ratio is 7.59:1 .
Your dynamic cranking pressure is 149.29 PSI.
V/P (Volume to Pressure Index) is 127, and 127/82~ plus 55%
But before you get too excited about 127
Here's a stock LA360 with the 252/112 cam@8.0True Scr.
Static compression ratio of 8.0:1.
Your dynamic compression ratio is 6.94:1 .
Your dynamic cranking pressure is 132.71 PSI.
V/P (Volume to Pressure Index) is 122 .....and 122/82~plus49%. over base
Again VP is only a measure of low-rpm performance
 
Last edited:
stroker402 said:
I'm going to check and see what heads are on that 1968 318 I got my eyes on.
Click to expand...

68 and up 318's and 273's should be 675 open chambers. 8.8:1 is not bad with available gas today. If you want to go 318 I'd build it like a 340. Pistons and 360 heads, copy everything a 340 had, then you will have something. Only you won't have enough tire under an early A. Get the right cam and set it up right, degree it, in the 273. Then have at the 318 whatever you want. Forget the Erson, Call and get a custom cam for what you want to build. Then you will be happy and done.
 
Sooooooooooo , if I use the stock 1968 318 which I think came with the open chamber 675 heads ,..... can I switch to my 920 closed chamber heads with my erson ?
 
It would be a lot simpler, and cheaper, to buy a junkyard magnum 5.2 or 5.9. A stock 5.9 Longblock with a carb and intake will be VASTLY superior to any 273 on the street.
 
Even if it had 12.5 to 1 compression , a 273 with that big Erson is gonna want 4.56+ gears. If you want strong performance and want to keep your 3.55s, get a bigger engine and a smaller cam.
 
stroker402 said:
Sooooooooooo , if I use the stock 1968 318 which I think came with the open chamber 675 heads ,..... can I switch to my 920 closed chamber heads with my erson ?
Click to expand...

OK, You can go to 920 heads bump the compression up a bit. It is not compression that makes power. Compression is an adder. Flow is a multiplier. You can play the game of high compression then a big cam to bleed off pressure. I am not up for it. I am a strong street runner, not a racer, and I am cheap. I have a friend who raced Super Stock Class, back when you could not port heads. His friend raced Stock Class. Their cars were very fast. It gave you an idea of what stock parts in engines were capable of, if you had good machining and the right combination of parts. A 273 is a great engine with good compression for todays gas, if you put the right combination together. As you know they are quick revving and very efficient. The heads flow plenty for 273 cu in. Untouched 273/318 heads give you about 170 cfm intake and about 120 cfm exhaust. Untouched 360 heads give you about 190 cfm intake and 140 exhaust cfm, Untouched 340 heads give you between 200-220 cfm intake 145 cfm exhaust. Untouched Magnum heads flow about what 340 heads do with + 20 cfm on the exhaust, if I remember correctly. Magnum EQ heads are even better. The point is, you should decide what you are up for and how much money you are willing to spend. It is the combination, and I mean all of it, that gives you the quick revving monster you had for a while. You are talking about getting a second engine and swapping parts between the 2. I don't think you will be happy going that rout. It is cheaper to get the right cam for the 273 and use the Erson cam in the 318. But I'd go with at least 360 heads on the 318. Then new pistons. Deck the block. Then bore and hone with torque plates. Mill the heads .040 on the block side and .038 in the intake side. Add Stainless steel valves and beehive springs. Balance everything. Sell the 650 and get a 750 carb. Change out the bellhousing and flywheel so you will have a chance to hold the power you are making now, in a 66 Cuda? You see where I'm going. Oh, and I have done all this and more. The 64 was so fast you had to drive around town in 2nd gear or the next thing you knew you would be flying. And that was a 273. But it was truly great watching my mother drive it...
 

RustyRatRod said:
No. All the small blocks have 6.123 connecting rods.
Click to expand...
I meant to say that my 273 in question has thicker Rods in it ,, maybe that is why it's such a dog and can't rev up fast. here is a pic of the larger rods that previous owner built engine with.

my 273 rods II.jpg


my 273 rods.jpg
 
Last edited:
stroker402 said:
I understand , yes previous owner/ machine shop looks like he mix matched everything in this engine.
Click to expand...
Well, when I try, and I mean try to sift through AG's formulas, I end up going out the back door thinking front door. I open my trunk to check the oil. Then, what others added, i'm at least 2 days away from getting my zip code back :D
 
It's so interesting (and frustrating) how these threads go so far sideways.
 
Bigger rods may have been used to offset piston weight or pin weight differences. In essence to balance engine.
Good luck.
Sneaking out the back door now...lol
 
stroker402 said:
I understand , yes previous owner/ machine shop looks like he mix matched everything in this engine.
Click to expand...

Well my fabo followers ............ My 273 blew up , it cam up with a rod know the other day and I have it all ripped apart already. noise was coming for #5 rod 'spun bearing ", but once I tore into the engine, every bearing was scored and more bearings were spun so bad they looked like tin foil. probally revved too high at rpm 6400 or oiling issues , oil light never came on and it does work , so it had oil , could be alot of things . It's all water under the bridge at this point in time. I have another good 273 crank, rods 10/10 and pistons read to go to the machine shop for clean up and start assembly.
 
stroker402 said:
Well my fabo followers ............ My 273 blew up , it cam up with a rod know the other day and I have it all ripped apart already. noise was coming for #5 rod 'spun bearing ", but once I tore into the engine, every bearing was scored and more bearings were spun so bad they looked like tin foil. probally revved too high at rpm 6400 or oiling issues , oil light never came on and it does work , so it had oil , could be alot of things . It's all water under the bridge at this point in time. I have another good 273 crank, rods 10/10 and pistons read to go to the machine shop for clean up and start assembly.
Click to expand...
Do it right and **** can that cam. That's what started your unscheduled engine disassembly issue!
 
I installed an XE262 in a '65 273 2bbl. Cylinder pressures were 95-110 cold. Runs great but not in the car yet.
You guys are really overthinking things lately. Minimal static compression, pump fuel, mild gearing and convertor = smallish cam.
Not buy another engine.
Not mill heads.
Not advance the **** out of the wrong cam.
Put a cam in that will work with it and go have fun.
 
You must log in or register to reply here.
-

Similar threads

J
[FOR SALE] Ultradyne solid lifter street cam fits LA or magnum small block engines
Replies
0
Views
311
jwise
J
Saltcityslant
Hydraulic Cam // Solid Lifters
Replies
18
Views
569
Killer6
K
1
  • Locked
[SOLD] Erson solid cam/lifters/rockers/pushrods
Replies
4
Views
345
Desoto291hemi
Desoto291hemi
greyghost340
  • Locked
[SOLD] Solid Cam for Small Block
Replies
3
Views
538
540Valiant
540Valiant
B
  • Locked
[SOLD] Small block solid cam
Replies
2
Views
502
B3422w5
B
Back
Top Bottom