318 and 360 mounts, and cfm/hp ratio?

-
S

svitaks

Member
Joined
Dec 27, 2005
Messages
13
Reaction score
0
Location
Norfolk NE
i have a 71 318 would a 80's 360 have the same motor mounts or whould i have to swap something. and does anyone know what the cfm to horsepower ratio is for a certain cylinder head, it was in a mopar muscle mag. tech article but i can't find it anywhere. any help is appriciated. thanks everyone.
 
There is no cfm/hp ratio I'm aware of. Unless it was for a certain engine they were testing. hp is too dependant on other parts besides highest flow rating. Even flow ratings by different flow benches are barely comparing apples to apples.
 
svitkas,
The HP/CFM ratio is air flow cfm's divided by 1.67 which is the standard from super flow for 10" of water pressure drop X 3.44 which is the factor from superflow for HP conversion. This is consistent with all superflow benches regardless of size or type, 110,400,600,1200 benches. When flow work is done and accurately we have only seen a 3-4 cfm difference between 5 different benches, the more work that is done in the heads and done right the more HP the engine is capable of making. Now in race engines these # can increase by as much as 30% due to how well the engine is machined and assembled. For instance we have a experimental engines that we try different things on this one just happens to be a 360 .030 over. The heads are 318/302 castings with minor work done, the heads flow 218 cfms with a 125 cc intake port runner with 1.88/1.60 valves. The valves are the WRONG SIZE for these heads but we did these 10+ years ago and decided to use what we had knowing that with the right heads and valve sizes the engine will make more power and torque. The engine is a dished piston engine 10.8 cc's TRW forged, but they are heavy and will be replaced with lighter ones when the engine gets rebored, the cam is a old 70's Prostock grind from Isky that Bob Glidden used to run in the Plymouth Arrow with the small block. The block has been decked .070 so the pistons are .035 in the hole, we used fel pro .044 gaskets and M-1 intake with a modified 850 DP carb, the exhaust is Dyno max 1 5/8 hedders with dyno max race mufflers. The car is factory stock with working head and tail lights and wipers, the car hits the scales @ 3100lbs it has a 5.29 gear with 9 X 30 tires and a PTC 8" converter. The gear helps to off set the tire size, this equals out to the same as a 28" tire and a 4.56 gear at the traps or a 4.10 and 26" tires, but greasy tracks need a tall tire and we had them so we used them. The rockers are iron adjustable with chrome moly pushrods and dual springs with 130 on the seat and 320 open pressure, the rest of the parts are factory stock and unmodified. The car this weekend ran 7.37 @ 94 MPH 1/8 mile at a corrected altitude of 3254 ft above on 93 octane pump gas with a 1.57 60 ft. time.
The heads that flowed 218 that are on the engine made 373 hp to the ground and 455 hp out of the engine. Now to use the formula 218 cfm's divided by 1.67 = 130.53 X 3.44 = 449 HP is what the heads are capable of making with stock parts. With more attention to machining we made a additional 6 HP more than the heads were suppose to produce for the airflow that they made.
I hope this helps answer your question. Sorry for being so winded but it was the shortest and easiest way to explain it.
 
The 360's do take a different engine mount on the driverside if I'm not mistaken and the passenger side uses the same mount.
 
Hey Bobby! Nice read. Ya gotta do me parragraphs. My eyes get lost on the computer easy for some reason.

The 318 mounts can be used. Just use some washers to take up the extra space due to the mount being wider.
 
that is exactly what i needed to know. you guys know your stuff let me tell ya, thanks alot. thats not the exact formula mopar mag. had but it will work.
 
The nice thing about this formula is that it will work on any automotive engine, it's not just for mopars. If you have the airflow data from any head, you can figure out the output of the engine in which it will be installed. Providing that the rest of the engine has the correct parts to make the engine respond to the #'s.
But this will give you the potential of the heads, it sure is fun to see how airflow effects a engine.
 
I stand corrected..I got this link from a friend after asking about this...Thanks BJR!

http://www.bgsoflex.com/flowcalc1.html



using your numbers, it comes to 449hp@6300rpm.
I would add tho, this assumes a lot about all the other parts of the engine. The real intake port starts at the throttle plate of the carb, and includes the plenum and intake runner. It also verifies how good BJR is at figuring total packages.
 
Thanks! Moper for the nice comments!
Not too bad for running thru the mufflers, and useing all stock componets in the short block for rotating assembly and on 93 pump. We figured that we could pull another 100-150 Hp out with the different parts and still remain 365 ci. with factory iron heads.
The last race 365 made 681 hp @ 6800 rpm's with aluminum heads and a roller cam that wasn't really large.
 
One of my mentors is an ex Stock Eliminator racer (in the 90s). His record setting (E, F, G, and M stock records in NHRA and IHRA) Ford couldnt be more basic. 351 Cleveland, hydraulic cam. Stock carb, intake heads, rods, crank, block, and factory design and weight pistons. In a 71 steel Mustang, with 5.17 gears, 9" slicks, and a Jerico. The car was a rock steady 11'teens. leaving the line at 6800, shifting at 8000. That engine made 485 hp thru the Autolite 4bbl carb. No doubt with the right science, stock parts can work.
 
The thing is that the engine in the stock eliminator is a highly precision piece, and a price tag to go with it. The engine and heads in this combo could be built for alot less and have power thats very close, still useing factory parts and pump gas, without the high price tag.
Most people don't understand that a engine for stock eliminator run's in the $10,000.00 to $20.000.00 range and 80% of this is in machining and isn't done over night. They go thru countless sets of rods just to get a good set, and blocks also, then the same with heads as they are all just castings and the flow varys from head to head and port to port.
The engine that we did could be built for $4500.00 anywhere in the country, which isn't much for the power return and streetability. So there's not much special about this engine, just the right combination of parts, and this one could be alot better if the heads were changed with the right valve sizes. The head change would be 40 HP and 30 Ft.lbs better, so there is still some left. This would put it in the low 11's with ease.
 
You must log in or register to reply here.
-

Back
Top