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the rules are pretty open... any 2bbl, any iron head, all roller OK... gas or alcohol OK. My questions are these... what factors should I consider in selecting cylinder heads for a 2bbl application? Does the 2bbl change recommendations for port sizing? The engine is a 4.030 bore x 3.875 stroke... 395 cu in., street stock car, camaro front, multi-leaf rear, 12" tires
Port design and quality of airflow trump size with a 2bbl. Some guys will try to recommend some big a$$ runner 14 degree stuff but dont waste your time.Quote:
Originally Posted by c.mac.4
best heads i've run are vortec bowties. 2nd best was a set of ported eq 180 runner heads.
If money is not an object, you will leave power on the table if you are not running the 14 degree heads. They do not have to have large runners. About 245 is all that is needed. You must also remember that this is not that large of a cross section, but larger cfm due to the length. If done correctly, will have awesome velocity and all the flow that you will need.
Call mullins and buy the2bbl head they have
Something that I missed in the O.P. is open two barrel rule. There are some big two barrels out there. Go with a larger runner 14* and a very large two barrel.
Just my opinion. :)
Bob
it's amazing to me, the differences of opinion... and to think that a vortec is even comparable, wow... maybe in a flattop, flat tappet, gas, 500cfm deal... MAYBE. Is the RHS/ProAction the only 14* out there? It's been discontinued, correct?
For a 2 barrel application,the carburetor is the restricton,not the head.That being said,the bigger the 2 barrel carburetor that you can run the bigger the head needs to be.If you can get ahold of a big 890cfm C&S,maybe others make one,then the 14* RHS might be a good choice.If you are limited to a 4412(500) then the best head would be a RHS 23* raised runner.Yes the 14* and the 23* are still available from Comp Cam.Only reason you would run a Vortec or a Vortec Bowtie would be when the rules require you to run an OEM head.
Just depends on how big a wallet you have. The vortec bowtie head will be the best bang for the buck. More can be done with the 14 degree or the RR head but it takes large $$$. A 4412 gauge legal needs tons of HG" at WOT under the carb to make it work and to make that happen it takes efficiency. You will not get a 23* head as efficient at moving air as a 14* head. But it takes boatloads of $ to make it work.That's why I always recommend the Vortec bowtie head for a gauge legal 2bbl application.
The original question had nothing in it about keeping costs down.Cost to him is probably
important though or he wouldn't be running that bore and stroke.Probably in a stock block too.You ask general questions you tend to get general answers that may or may not apply.
You're comparing apples and oranges when you compare port volume numbers between 23* and 14* heads... port length is different, so volume is different given the same cross-section. Cross section is the key to velocity. If you were talking about a 235cc 23* head, you'd probably be right.
Cost IS a factor, but decisions are made more on performance gain per dollar than just performance or just price. The questions I asked in the OP were pretty specific, and "ford396" is the only one who really even came close to answering them. Also, it's an SHP block, the bore and stroke combination was chosen by the original builder for good reason, not just a mish-mash of yard-sale parts. I'm looking to replace a set of OLD Sportsman II heads and a flat-tappet cam, because I know that there are better parts available to make this thing perform better. I've seen the C&S 890, but I've heard some folks have had some drivability issues with it. I will also be able to take this engine up a class in the future, by switching to a 4bbl, along with ditching the leafs in favor of a LM-type rear suspension. That allows me a little more leeway toward the bigger side, especially if I'm considering upgrading to a 415 or 430 later. While they might not be optimal now, the 14* stuff would certainly be an asset later. Granted, these points weren't in the OP, but I didn't ask which head would be best now. Thanks to you all for your thoughts and contributions to the conversation.Quote:
Originally Posted by perfconn
and I apologize for the "one huge paragraph"... evidently, there's a glitch when using a Mac
C.mac.4 I have these 14* heads on a big bore short stroke 358 application. Runs very well with gauge legal 4412. Track championship car. We have the opportunity to run a 4 barrel at some shows and the motor loves it. :) This is without any other changes.
I think that the important thing is to keep velocity up in the head for the two barrel. If you are planning to possibly run it as a 4 barrel engine permanently, you may have issues if you port it as an effective 240ish runner, will be down on power compared to larger runner when on the 4 barrel. May have to report at that time.
If this is a flat tappet engine, you will have to cut the heck out of the side of the intake runner for pushrod clearance (even with huge offset rockers). It will leave no room for larger runners down the road. If roller lifter, just go offset on the pushrod seat and you will be able to leave the intake wall intact and have something to work with later, if you so choose.
Bob
great info. thanks Bob
If cost is any sort of factor, remember the 14* get up requires offset shaft rockers, 18* headers, .800 long custom valves, .180 offset lifters, and a special intake.
Id go Bowtie Vortec ( ours made 508hp with a flat tappet 360)
Our 14* 406 full roller with the same gauge 4412 VDL made 536 hp
The 14* heads do not require an offset lifter. I am running them on a flat tappet engine.
My 358 flat top engine with RHS 14* is at 488 at the rear tires with a flat tappet cam and a gauge legal 4412. I know that dynos vary, but I have an almost identical engine, difference being heads, and on the same dyno it is down about 45hp to this one. It has conventional 23* heads.
If you can't breathe it, squeeze it.I'd place importance on a very small chamber with darn near flat-tops, to get you in the 14.5:1 region, and use alky for sure. Don't get stuck having a huge dome to impede flame propogation.14° Rhs are great, if you're sure the rules won't change, or if you will only run one track. If you plan or forsee crossing over to a 23° class, with a 4412 rule, then I'd go raised runner or Dart 215. We've built a 362 4412 gauge legal engine with those heads that made 608hp on an honest dyno. However, it was a high-dollar build with a decent amount of R&D. Just showing it is possible. Also, don't think in terms of runner CC, but CSA, specific velocities, tapers, coefficient of discharge, etc. We don't even look at the CFM #'s on the flow bench, because if you get the other parameters correct, the engine WILL run it's a$s off.
Not to highjack this but I'll assume this is for a aluminum head what would you use if you had all these other rules BUT had to run a Steel Head on a 4412. No CI limit.
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