[GRUMPYVETTE]

I was just curious if anyones running the better 18 degree heads and what mods were necessary (lifters, rockers, block mods)and if you felt it was worth the hassels over the comon 23 degree heads, Ive worked on several of them over the years and know most of the info, but I was recently told that its now far easier too do as some design mods have been made to ease the swap process

http://brodix.com/heads/-18c.html

http://www.trickflow.com/product/chevycylinderheads/18degree_raceheads/pr_18degree_race.asp


http://www.dartheads.com/manager/uploads/Tech - 18 deg SBC.pdf

before you start posting.....yeah, IM well aware of the offset roller lifters and shaft rocker assemblies , special pistons, intake manifolds and differant pushrods
ETC. the older system used,


and YES IM aware of these heads BELOW that use standard roller lifters and standard roller rockers, standard headers,and only require the newer intake manifold and heads and pistons, and differant pushrods

http://brodix.com/heads/-18x.html

http://brodix.com/heads/-18x.html

but are they worth the effort VS the 227cc AFR 23 heads below....notice the flow curves very similar between the heads

http://www.airflowresearch.com/227sbc_rh.php

now, I know I didn,t tell you the displacement, compression ratio or application, Im just looking for the basic responce from anyone whose run BOTH heads and its a given that were looking at a 100% race application with the 400 plus displacement and higher 13:1 plus cpr that will involve to get the most from the heads potential

 

[Wolfplace]

There is more to a head than just flow numbers
To answer your question, yes, in my opinion, the 18 & 15° stuff has the capability to make more power hands down than any conventional 23° head & the flow numbers are no where near the same in a real 18° head.

The Brodix X is the hybrid head & not worth the trouble in my opinion.
And to get it correct it will still need shaft rockers regardless of what is stated.
The new AFR "Eliminator" series is arguably the best conventional out of the box 23° head out there but it will not compare to real 18° head.

Just follow the NASCAR traits & power levels as an example.
23 to raised runner (867) to 18 to SB2,,

 

[JOHN WILSON]

Also, the price difference between the 23° stuff and 18° stuff is not as large as it used to be. Now, a full boogie set of 23° CNC'd heads with SS valves and good hardware will run in the $2200 range. A comparable 18° set with full CNC and similar hardware will run ~$3000.

Most of the 18° stuff I see being used are in race applications, but they would do well on the street also, if the port is sized correctly. BMF has several different port sizes available for their 18° head. I think a pump gas 427sbc with the 238cc port and a mild solid roller would make a killer street combo.

 

[383Malibu]

We built a 383" 23° motor with (for the most part) off-the-shelf parts and made 660 hp. Then we spent a lot of money to convert a set of 23° heads to 18° (actually 16.7°) and paid a lot of attention to all of the details and made 847 hp with 381". So, there's a significant amount of power to be had and it's worthwhile if you are starting from scratch. But, if you already have good 23° parts and are looking to switch to 18° stuff, it can be pretty expensive. In that situation, unless you're building to meet a set of class rules, why not go all the way to something like the CFE 10° heads (or even the Little Chief heads)?

 

[joespanova]

I can't touch anything my small block friends haven't already...........the 18 degree stuff ( MEANING THE RIGHT 18 DEGREE STUFF) is hands down a no -brainer..........IF I ever build another motor for myself........it will be an 18 degree 377!

 

[bigjimzlll]

One of the big advantages is the much smaller chamber on the 15 and 18 degree stuff. While on a race engine this is great to get the compression up to where you want it, on a street engine this will cause the opposite problem.
I think the 23 degree AllPro stuff is the way to go for a "street" SBC...for race gas or alky...10-15-18 degree or SB2.2

 

[Doug F.]

We built a 383" 23° motor with (for the most part) off-the-shelf parts and made 660 hp. Then we spent a lot of money to convert a set of 23° heads to 18° (actually 16.7°) and paid a lot of attention to all of the details and made 847 hp with 381". So, there's a significant amount of power to be had and it's worthwhile if you are starting from scratch. But, if you already have good 23° parts and are looking to switch to 18° stuff, it can be pretty expensive. In that situation, unless you're building to meet a set of class rules, why not go all the way to something like the CFE 10° heads (or even the Little Chief heads)?

Roger, how about a few of the high level differences between the engines, compression, cam and what HP peak was at?

 

[383Malibu]

Roger, how about a few of the high level differences between the engines, compression, cam and what HP peak was at?

383” – 23°
Engine - 4.030” x 3.75”
Heads - AFR 220 – 310 / 229 cfm
CR – 14.3
Cam - 274/285 @ .050”, .740”/.709”, 112 ls, 110 icl
Intake - Dart/Wilson w/ 4150 (930 cfm)
Headers - 2" x 32"
Bob weight - 1831 gms
Coatings - piston skirts
Power - 536 ftlbs/6000, 660 hp/7200

381” – 16.7°
Engine - 4.165” x 3.500”
Heads - AllPro 245 RR – 381/267 cfm
CR – 15.35
Cam - 272/298 @ .050”, . 1.009/.824”. 114 ls, 112 icl
Intake - Super Victor w/ 4500 (1250 cfm)
Headers - Stepped, 1 7/8" x 2" x 2 1/8", 27" total
Bob weight - 1398 gms
Coatings - just about everything
Power - 569 ftlbs/7300, 847 hp/8900