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Author Topic:   Next step up (Cyl heads)?
Kromulous
Member
posted November 17, 2004 08:32 AM
Were currently running a 360 23* engine, runs well but as racing goes were always looking for more.

So whats the next best step when it comes to cylinder heads? Planning on going to a big bore (4.125) Little M block (380 cubes), same interals as above with new pistons of course. Worried about keeping the torque up, it seems the 18* heads and others have really big runners, 230 cc and up.

I've never delt with any 18* or 14* heads, and dont know whats good or bad with them. Anyone suggest a good next step up concerning heads? for a 380 cubed (4.125 bore and a 3.5625 stroke) engine? I was thinking Brodix 18x so we could use the same rockers etc, are they worth it or should we go for a true 18* head?

Also, were on alky and plan to stay on it, as well the cam is subject to change to compliment the new head. 14 to 1 is our target compression, would like to stay there or lower if that info helps at all.

sdhnc29
Member
posted November 17, 2004 04:11 PM
I would definitely go with an actual 18 degree head from Dart or Brodix. You can also find good used Cup head's still around, but they are very rare to come by these day's. I would not use the 18x, as it is not much better than a good set of 23 degree heads. With the Dart head's you can go with 18,17,16, or 15 degree head's. Each head still uses 18 degree valve train.

As for torque, this is not a worry. 230cc intake runner's are actually quite small by today's standards, especially for alky engines. I would not use anything smaller than a 245cc head for your application. In fact I would want to be closer to the mid to high 250's, and even low 260's on intake runner volume. I would also like to see you closer to 15.5:1 on compression ratio, but I understand if your trying to be conservative at 14:1. Just keep the Chinese part's out of your American made block, and she should last a good long time.

The cam will most definitely need to be changed. Alky engines are very sensitive to cam selection! The most common mistake for engine builder's who do not work with alky much, or guy's who are doing their own stuff, is to cam the engine like a gas motor. Alky is very slow burning, unlike gas. Many people do not take this into account when choosing a cam, or having one custom made. Most cam manufactures are even out of the ballpark on alky cam's. Although many are starting to come around, and are offering book grinds that are close. The main problem with most cam's that are shelf bought, or custom ground is in the exhaust duration. Many people think that you need to run close to, or the same split in duration between intake and exhaust as you do with gas. While you will still pick up a little torque over gas by having a similar cam, you will not be producing the torque that can be made. Since alky is extremely slow burning, you must keep the exhaust valve closed longer. So the split in duration need's to closed up to within 2 degree's in most applications. This keeps the exhaust valve closed longer, and allows the fuel to burn before popping the valve. In comparison if you pop the exhaust valve too early, you have unburned fuel and your torque going out your exhaust pipe. Feel free to call when it comes time for cam selection, and I'll give you a recommendation for your application. You can then have a cam ground by whomever you wish to deal with.

If your looking to save dollars when you switch from your 23's, I would look for some good used heads to start with. If you've got it in your finances to start with new stuff, then that's all the better. If you look for used head's, just be careful. There is a lot of junk out there!

Feel free to call any time, and I'll give you some advice that will help you put your combo together. A 380ci engine with good 18 degree heads should produce around 730-760hp, and around 600-625 foot pounds or more on alky, provided the combo is correct. The HP and torque will vary with cam selection, which will vary with your particular application (track size, track condition, car, cylinder heads, compression ratio, etc.).

Steve

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Hendren Racing Engines
Rutherfordton , NC
(828)286-0780


WPP
Member
posted November 17, 2004 04:39 PM
I know what you are saying about the 18 x brodix recommends the m2 cnc 18 head i think is 256 on the runners what i have notice on these heads is the chamber size were you have to run a large dome to get some compression i talked to bill and i think he gave my the part number 18 sp i think if you don't mind pm back with the specs . My head been screwed up since we started this 18 thing i am lost thanks


Racer111
Member
posted November 17, 2004 06:21 PM
I run a set of Chevy Chapman 18 heads on a 410 real nice.


STICK01
Member
posted November 18, 2004 08:37 AM
so with a 13.9:1 4.165 little M block with a good LW crank and good Crower rods, roller cam, what heads should i try to use? I have been having problems with my DART Pro-1 with a crack around the intake valve seat..

HELP, lost!!!!

Kromulous
Member
posted November 18, 2004 08:52 AM
Thanks for the post / advice Steve. 730 to 760 Hp would be extremely nice. Smaller stroke with the 3.5625 should be plenty smooth, and give us plenty of room to back tune it.

Anyway, you have any issue's with Dart cylinder heads? which brand is better made / quality wise ? Also is it me or does Brodix need to work on there part numbering system? thats a mess !

Also, i wont lie, we are running chinese rods for now. The crank is a callies, that has been worked over, nothing fancy or light weight but still decent. I wont use chinese rods in the M block thou, going to upgrade to some crower's i think, or some nice used ones that i can find.

Anyway thanks for the offer on the advice, when we go to buy what we need i'll give you a call.


[This message has been edited by Kromulous (edited November 18, 2004).]

dgb
Member
posted November 18, 2004 09:46 AM
WPP,

Email with the questions you have Pat, and I'll send the info to you.

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STICK01,

If your going to buy new 18 degree heads, CNC ported, I'd call Mark at Weld Tech and speak with him. Racer111 mentioned Chapman, and they are very good too! Anyway, I would suggest that you have the heads you buy run through the HIP process. This is a High Pressure process that condenses the aluminum, and help's prevent crack's. Any Cup head that you buy would have this done already. Dart and Brodix both make good head's.

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Kromulous,
No problem. The HP range that I mentioned is actually not too hard to achieve with the right combo. I have always liked Dart a little more than Brodix. But Brodix is really being innovative in the circle track department, where Dart has insisted on putting their efforts into the straight line racing. Right now I'd say it's a toss up between the two.

The only issue I ever had with Dart head's was with a set of 23 degree heads that I ran on my own car back in 1990. They had a cracking problem out of the intake side of the combustion chamber, the thinnest part of the chamber. I also had problems with their 14 degree head's that they made back in the early 90's. They cracked around the bottom row of head bolt holes. But I have not seen any problems with their 18 degree heads.

Your not lying about the Brodix numbering system!! LOL!

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dgb,

Thanks man! I was working and racing all summer, so it left little time for typing. If you knew how slow I type, you'd understand my absence ;-) Anyway, it's winter time now, so I might try and learn to use more than two finger's on the keyboard.

Steve

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Hendren Racing Engines
Rutherfordton , NC
(828)286-0780