The combination is very important. It has to all work together but the bottom line, the power is in the heads and "bigger is better" is not always the trick.
65 Barracuda 318 Rebuild, Cam, timing, lifters maybe a kit?
- Thread starter JeffreyLee
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We're not the only ones with issues. I laughed at this one.
Tuning a 1406 Edelbrock Carb with Bog
Tuning a 1406 Edelbrock Carb with Bog
302 heads were around since 1985. I will stick to my guns (or my opinion 
), open chamber heads will outflow closed chamber heads any day, if given the same compression it will be the winner. Flow and compression are both winners, but if I have to chose between the two, I'll take flow in the 1/4 mile any day. But that's me, and I know i'm kicking a dead horse... LOL
), open chamber heads will outflow closed chamber heads any day, if given the same compression it will be the winner. Flow and compression are both winners, but if I have to chose between the two, I'll take flow in the 1/4 mile any day. But that's me, and I know i'm kicking a dead horse... LOL
The ports flow not necessarily the chambers. Yes I would agree that a 9.5/1 318 will make more higher rpm power with 340/360 heads. (Open chamber)
They have larger valves and ports. I bet a closed chamber 302 head will out power a open chamber 318 head if both are built with the same compression.
They have larger valves and ports. I bet a closed chamber 302 head will out power a open chamber 318 head if both are built with the same compression.
I disagree with the quote I highlighted. .....
We may never know!
Bighead440
Well-Known Member
I *prefer* the "302" heads on a stockish 318 shortblock (as per Chrysler's results confirming), with the high port velocity and small chamber. I add 360 valves with associated bowl blending and deshrouding of the chamber walls (milling to reduce the chamber volume back to stock) and port match the intake ports to 360 size (except for economy, mpg oriented builds where a small port intake is used) so any 340/360 intake can be used without port mismatch.
Wyrmrider
Well-Known Member
from the 318 build article
- 331 HP at 5750 RPM:
- Swapped the 360 heads for ported and polished 302 heads modified with 1.88" intake/1.60" exhaust valves
- Mopar Performance P4120249 valve springs
- This combo produced a 41 HP increase over the previous combination, netting 1.12 HP per cubic inch!
- This combo also produced more power than all of the other combinations from the lowest RPM on up"
- my comments
- I agree that 915 X J heads may make more top end power above say 3500-4000 so what for a street car with stock gears and converter
- the X J combo would take a longer duration cam to do it which would kill the bottom end
- Velocity wins here IDK about the Edelbrocks LAX EQ or other heads- where they fit in
- they would obviously be winners in the 3500 up area but around town?
- Anyone have an inexpensive CNC program for the 302 I still have access to my old SERDI so I can DIY-otherwise take your time and do it by hand
- OPEN CHAMBER HEADS are losers (without high octane gas and high revs)
- toolman A semi ported 302 may well outpower a semi ported X or J or 915 even looking at the graph anyone check Stan Weiss site yet?
dartfreak75
Restore it, Dont part it!
I how much was gained from the 1.88 valves vs the 1.78 valves in the 302 heads. Id like to the the same test done with each step. Instead of going straight from 360 to "best effort" 302s go from 360 to stock 302s then work up the heads just to see what does what and where. I dont think I'm gonna fool with the 1.88 valves in my heads. ( unless I can find a way to cut new seats myself) but I am gonna port them. And depending on how much money I have when it comes time to start putting it back together I am gonna try to have them milled .02-.03.
dartfreak75
Restore it, Dont part it!
I'm not following you on this one? What's funny?
Not speaking to the port design, X, J, swirl port, or throwing in the "x" factor of compression, or whatever. Speaking solely to the design and flow of the cylinder head in the chamber, the closed chamber design will not flow as well as an open chamber head.
Bighead440
Well-Known Member
Without bowl cutting and deshrouding the gains would be minimal, but WITH these mods, great gains can be had. There is a thread somewhere that posted the steps and gains, but I disremember-lol-where I saw it. (MoParts?)
We here on FABO aren't the only ones with that problem. The fix is bumbling along.
Yes valve shrouding is an issue. Some days I wish I had a dyno. LOL It would be fun to test some things out.
The only dyno I have is the Desktop Dyno. I built a basiclly stock 318 with 10/1 compression and then changed the chamber shape from "wedge open" to "wedge closed". The closed chamber head made 3 more HP and 3 more lb/ft at the same rpm. Who really knows unless you would build a engine both ways with the same compression. I'm sure the closed chamber heads do shroud the valves and don't flow as much but the combustion efficiency of the closed chambers may be as or more important. Pure speculation on my part.
Wyrmrider
Well-Known Member
maybe desktop is using BBC closed vs open where there is a loss
on a Mopar the open is all on the side away from the port flow
the combustion chamber on the spark plug side on a BBM is basically the same open or closed
on the SBM that is true of the really early head vs the open but the late heads have a much better chamber
you can tell because it does not require so much timing
you can always open up around the valves out to the bore-
the late closed chamber heads flow pretty good IMHO in the half inch lift area- more so than the about 450 for the older heads but IDK at high lifts
that's a place for W heads or high buck or experienced porting on the 360 heads but evidently porting works on the 302's also
what about the late 360 heads?
remember a little hand work on the heads pays a lot of dividends
on a Mopar the open is all on the side away from the port flow
the combustion chamber on the spark plug side on a BBM is basically the same open or closed
on the SBM that is true of the really early head vs the open but the late heads have a much better chamber
you can tell because it does not require so much timing
you can always open up around the valves out to the bore-
the late closed chamber heads flow pretty good IMHO in the half inch lift area- more so than the about 450 for the older heads but IDK at high lifts
that's a place for W heads or high buck or experienced porting on the 360 heads but evidently porting works on the 302's also
what about the late 360 heads?
remember a little hand work on the heads pays a lot of dividends
nm9stheham
Well-Known Member
Hold the phone....! I'm gonna side with you this time willrun.... LOL! It's because of that very important qualifying phrase that you inserted: "...in the 1/4 mile...". Application, application, application.....where do you need the torque band, and how wide and high do you need it. Drag racing and tractor-pulling are off in their own special corner of the performance map, and pumping fuel-air into the engine as fast as possible is most of the battle there.302 heads were around since 1985. I will stick to my guns (or my opinion
volunteer
Well-Known Member
The factory (5/16") bolts are only a 'Grade-5' rating, which would indeed accept a torque value of no more than 20, but IF you replace with Grade-8, this would up the max. torque to 25 - - and in no way would be too excessive as to distort the rocker shaft. I have been doing this 'upgrade' for over 40 years - and sleep better to boot.
Most of you should know that the B/RB engines had same rocker setup but used larger 3/8" fasteners that easily torqued to 35.
Tip no.2 would be to use either a factory 340/360HP hydraulic cam (and new lifters) OR the equally good Summit Racing version which has .441" lift on both intakes and exhausts. I think this one also has slightly more 'overlap' than (OEM) Mopar. Very nice 'driveable' cam.
I also noticed that, since your car is mentioned as a '65 model, it would NOT have come from factory with an LA-318, but instead a 273. Better check casting number on left side of block (behind starter).
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