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Author Topic:   vortecs and dome pistons
JohnG
Member
posted August 21, 2004 07:33 AM
why put domes in a vortec head?
The vortecs are like 59cc. So why even try to stuff a dome piston in it.

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Jason Boivin
http://www.rcracing-team.com


engineman
Member
posted August 22, 2004 03:45 AM
Horse puckY! I do it all the time, you have to grind the square pad down around the spark plug hole (mainly round the corners off) or notch the dome to clear it. If you are running a very big dome, you may have to notch the top of the dome for the spark plug to clear...as the vortec head has the plug moved inward more toward the center of the cylinder.

I use a lot of speed pro H617 hyp. dome pistons with vortec heads with good results, but you have to do the mods above to make them work.

Ok....I guess when you get done...you have a custom piston

Mark T.

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Mark's Racing Engines

(903)883-0196

www.northtexasracing.com

engineman@northtexasracing.com


hobby10k
Member
posted August 22, 2004 03:36 PM
now I hear alot about vortecs, are they a pretty good head?? I use just camel humps now. I am looking at getting some good heads next year and if I can get the same results from vortecs as world heads then might go that rout, just wondering

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GO FAST, EAT DIRT, LIVE RACING


engineman
Member
posted August 23, 2004 04:28 AM
vortecs kick double humps in the **** in stock form.


hobby10k
Member
posted August 23, 2004 05:23 AM
alright, but what about compaired to like world heads??

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GO FAST, EAT DIRT, LIVE RACING


UFnARacing
Member
posted August 23, 2004 05:55 PM
Hey Mark, I'm not in any way knocking what your doing with the Vortecs, but I have some questions. I run Vortecs on my 383 motor, with a lot of mods in order to run the .650" lift roller! I have "custom" pistons like you talked about, with the cutout for the plugs. Oh, by the way Jay, you run domes so you can get up to 14:1 like mine! Anyway, my builder says that if you smooth out that pad, it really messes with the swirl characteristics, which is the main advantage to these heads. Do you have any dyno or flow numbers with and without? Just trying to see if theres something better out there.

Thanks.

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http://www.ufnaracing.com


jay116
Member
posted August 23, 2004 06:34 PM
please note...NO WHERE did I say it couldnt be done. I just simply stated why do it.
Shave the vortec and run flat tops you'll get every bit of the 14 to 1 that you think you need. I stated it before my but my boss has a 350 making well over 500 horses using flat tops and vortec heads. I just think there are better ways to make horse power other than increasing compression.

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Jason Boivin
http://www.rcracing-team.com

[This message has been edited by jay116 (edited August 23, 2004).]

engineman
Member
posted August 24, 2004 03:48 AM
quote:
Originally posted by UFnARacing:
Anyway, my builder says that if you smooth out that pad, it really messes with the swirl characteristics, which is the main advantage to these heads. Do you have any dyno or flow numbers with and without? Just trying to see if theres something better out there.

Thanks.


well without getting into a huge debate over swirl, I can tell you that on my flow bench with my swirl meter it does not affect swirl unless you really cut that pad down a bunch.....the chamber wall on the intake side is what dictates swirl....for the most part. Port bias,valve shape,seat shape,intake manifold, ect.. has a lot to do with swirl, heck I've even been playing around with cam overlap and found that tight LCA cams can... in some cases disrupt swirl at low intake valve lifts due to scavaging. And yes....I have a folder full of flow sheets & swirl patterns for vortecs and other heads.

we can go on and on about swirl....BUT to get back on track here, we are talking about "claimer engines" and to clear most "cheap" domes you just need to knock the corners off that pad, and like I said cut the dome a little. doing this is not going to hurt the swirl enough for the power to fall off.

Heck "MR FLATTOP" above in the second post is really correct....cuz if you are really worried about swirl....the domes hurt the swirl pattern (and disrupt the flame travel) worse than cutting that pad when the piston is anywhere close to the top,it's a trade off. And to get the compression you want with a flattop and a vortec, you have to angle mill them, and thats a pain in the a$$ with a vortec head cuz you have to fill the water passages on the outside edge of the chambers and that gets you right back out of "claimer" price range.

Besides that, by the time you do all that you can buy a better head....Dart,Pro topline,or World. you cant beat the price! and they all work great right out of the box. My personal favorites are the Pro Topline heads, they seem to not have as much core shift as the others, and they seem to flow a little better. you can get real impressive flow numbers out of em' if you know what your doing! The downside is they are a lot hevier than a vortec. HMMMMMMMMM....antoher trade off!
BTW there are a lot of good engine builders on this board, and I value all of their opinon's. I do this for a living, and I learn new stuff everyday.....thats why Im on this board...to learn. so I hope I didnt offend anyone with my opinon on this thread.
Ok...I'm done writing this book...

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Mark's Racing Engines

(903)883-0196

www.northtexasracing.com

engineman@northtexasracing.com


engineman
Member
posted August 24, 2004 04:24 AM
quote:
Originally posted by jay116:
please note...NO WHERE did I say it couldnt be done. I just simply stated why do it.
Shave the vortec and run flat tops you'll get every bit of the 14 to 1 that you think you need. I stated it before my but my boss has a 350 making well over 500 horses using flat tops and vortec heads. I just think there are better ways to make horse power other than increasing compression.


Jason, yur right, most engines dont need 14:1 compression....and there are better ways to make HP. I agree. But some engines need that compression...Alky engines for example work well with that kind of compression, in fact thats about right for it. Some camshafts that bleed off a lot of cylinder pressure at lower rpm respond well to a higher compression ratio.

Then again you can get pumping losses with the wrong camshaft and too much comp., and a whole bunch of other "bad" things can happen from too much compression that can cause you to lose HP or cause engine failure.
so you are correct, but we dont know what combo he is running, he just might need that much comp. I'm a flattop fan myself, in fact I try to use them whenever I can, but sometimes a dome is the only answer when cost is involved....speicaly if it's an imca mod claimer engine on alcohol that needs the compression.

beleive me,no one is against you...youre on track.

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Mark's Racing Engines

(903)883-0196

www.northtexasracing.com

engineman@northtexasracing.com


UFnARacing
Member
posted August 24, 2004 10:24 AM

Both of those are the kind of posts I like! Just to clear some points up, though.

I don't have a claimer engine and I can't run anything but GM cast heads. I would have absolutely loved to put Proline or Dart heads on and be done with it!

I debated and debated about using domes or flat tops. I knew, as did my engine builder, that the domes would affect swirl and flame travel. But, in the end it seemed that raising compression was the best and most cost effective way to get the HP. I also didn't want to angle mill them, too much PITA and $$$$. Let me state for the record, I would have rather used flat tops. My heads are already flat milled as far as I want to go (.040"), so with that and flat tops, it would have only been about 12:1. I think I spent my money effectively to get that extra 2 points or so. These heads aren't ported, ran out of time and didn't want to spend the $$ for the machine shop to do it. Looking back, maybe not the right decision but I thought $$ spent on compression would be better than money spent on flow.

Thanks for the info on the flow and swirl numbers, that's why I originally posted. I've never really asked my builder if he had any data to back up his theory. Hopefully the head rules will change for next year, but if they don't I have some direction of what to try.

Like I said, these are the kind of posts that I think most readers like. We put out some good info for people who go with Vortecs. If I had this info before I made my decisions, I might have more HP for the same money!

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http://www.ufnaracing.com


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