(Login Rages6971) Member from IP address 188.8.131.52
Anyone know if there is a manufacturer out there that makes an 11-12cc dish piston for a stock rod/crank Cleveland? So far all I have seen is for stroker motors and everything else for a 3.5 stroke and 5.778 rod is only -3cc. I am running 4V closed chamber heads (cc @ 64) and factory bottom end. I am trying to get down to around 9ish : 1.
I'm concerned the open chamber heads with a flat top piston will be more prone to detonation then the closed chamber heads with a dished piston. Maybe I am wrong here, I'm not sure. I can get Ross to make some at about $1k for the set. I have both sets of heads ('72cobra jet heads and 71 closed chamber), just not sure the best route with almost 10lbs of boost.
This message has been edited by Rages6971 from IP address 184.108.40.206 on May 7, 2012 10:51 PM
With the extra fuel and air i don't think detonation going to be a problem with the open chambers. However running oc heads with flat tops would be about 8.5.1. I would maybe buy a mild dome piston and run the oc heads to be 9.5.1 and solve some of your detonation fears.I've been battering around how i am going to build a F1r cleveland for years now. Is that a custom bracket in the pic or is that the way it bolts up?
The bracket you see there is the Paxton drivers side mount for a carded 302. The V1 and V2 use the same supercharger bolt pattern as the Paxton on this bracket. I made an rubbing of the bolt pattern on the head then transfered that to the bracket. I ended up drilling one hole (the one directly below the tensioner) then slotting the bolt hole back at the head on the far left.
The big issue was the crank pulley and the fact I wanted to keep my power steering. The pulley for the superchared 5.0 application stuck out way to far and would require all new bolts (8" long or so!)and spacers. I had a spare 5.0 6 rib pulley lying around so thought I would see what it would take to use it. Well the 5.0 pulley and a .625 spacer behind it lined everything up. One thing to note is that you HAVE to use is a 2 belt crank pulley or this won't work.
After all that I had to weld tabs onto the PS pump to lower it so the fill tube wouldn't hit the supercharger spacers and to miss the bottom bolt on the bracket. Also where the PS pump is now is going to require a remote oil fiter to clear the PS line in the back. The PS tensioner bracket is the factory one just cut down. I measured at least 10 times to be sure it would clear the frame rail in this location, but until it is in the car I will never really know.
This message has been edited by Rages6971 from IP address 220.127.116.11 on May 9, 2012 1:06 PM
I think you've done a grand job fitting the supercharger to your Cleveland. Its beautiful. I like centrifugal superchargers, they're my favorite type of forced induction. They spool-up like a turbo, rather than giving the motor gobs of torque at low rpm like a roots type blower. But unlike a turbo they don't have all the exhaust plumbing to contend with.
On the subject of detonation. I've hesitated answering you because its a controversial subject for some people, and I really don't want to get into a discussion on the subject again. Its my experience there is no difference in detonation resistance between the open chamber and quench chamber heads. They are both shallow poly-angle chambers. Neither of them have the characteristics of a classic wedge combustion chamber.
A classic wedge chamber has a large squish area that shields a substantial portion of the chamber from the flame front, creating the opportunity for detonation, making it necessary to keep the clearance between the heads & pistons tight to boost thermal efficiency and avoid detonation. The large valve angles of a classic wedge head create a deep "low turbulence" combustion chamber, which again makes a tight squish area necessary to generate some turbulence within the wedge combustion chamber.
The Cleveland quench chamber has relatively little squish area and the open chamber obviously has none. No part of the combustion chamber is shielded from the flame front with these heads. The Cleveland chambers have more in common with a Chrysler hemi than a classic wedge head in that aspect. But the Cleveland has small valve angles and shallow chambers which give the chambers their turbulence ... and resistance to detonation.
I know this is contrary to what you've been indoctrinated to believe, its a controversial subject for some, others just think I have my head up my arse. But its something for you to consider. It could save you the expense of a set of pistons.
Since you have both types of heads available, and the motor already has flat top pistons, I suggest using the open chamber heads first, since it will cost very little for you to do this. You can adjust the compression ratio via head gasket thickness or milling the heads. If the motor detonates in with the open chamber heads then you'll know you need to spend the bucks on the dished pistons.
Good luck with it.
This message has been edited by gpence from IP address 18.104.22.168 on May 9, 2012 9:01 PM
I actually found a set of forged dished pistons that should get me close to the 9:1 I am looking for. I now know a few people that run superchargers and turbos that are using open chamber heads without any detonation problems, so what you are saying must have some merit. If I hadn't found these pistons then I would have used my OC heads (and still might at a later date). The cost of having custom pistons made is just a little out of my price range with all the other things I need to get done.
I was going to have to replace the pistons regardless of what head I used because it has hyper pistons in it now. I didn't originally intend to use any power adders when I built this engine. This is what happens when you have a fox body Mustang with 150 shot of nitrous on it. I am tired of filling the bottles and thought this would be cheaper and more fun in the long run on this project.
Not sure how many folks tend to favor closed heads
May 11 2012, 11:01 AM
over open when specifically talking about naturally aspirated higher compresssion builds over say 10.00 to 1. I'm thinking it's probably a majority
but some like to write them off as just not properly informed. To me, if you just consider the two chamber designs, they are of radically different geometry, not? All else equal, simply due to differing geometry, one of these heads will have less tendency to detonate than the other, however small. Consider two billiard balls randomly chosen from a set of billiard balls. One will be heavier than the other if weighed accurately enough. One will be larger in diameter than the other if measured accurately enough. This difference exists in two balls of the same general geometry (round ball). Although not so easy to measure as with the billiard balls, of the two different heads, all else equal, one is going to be more detonation prone than the other. I don't think this can be refuted but I also can't offer a definitive, reasonable, easy way to quantify or measure it. Several things about the closed head give me more confidence at higher compression than the open head. The quench area peaks the curiosity of my brain cell in several ways to help reduce detonation tendency. It adds additional turbulence at a critical point (near or at TDC) that the open head cannot. Most all literature on detonation talks to turbulence as a good thing to help avoid detonation. The word itself, QUENCH means to cool rapidly. This quench area squeezes the volatile end gas into close proximity with the cooler surfaces of the head and piston. If you subscribe to theory that hot end gas is where the spontaneous explosion (detonation) may start (some distance away from the flame front) then there seems to be some advantage here for the quench head as it cools the end gas. If the end gas is cooler it is less likely to detonate. Along the same lines, if you can burn the charge faster, burn the end gas before it takes on excessive heat, ie; in a smaller chamber with shorter distance to burn (and less time to heat the end gas,) you have probably reduced detonation tendency. If you don't subscribe to the theory that the closed head offers a shorter distance to burn (i choose to ignoring the quench area as a detonation prone area) you should at least recognize that the quench area reduces the volume of the end gas significantly by squeazing much of it out into the chamber proper. If the detonation explosion occurs in the quench space it has much less volume of gas to burn and cause harm. Of course this all assumes the flame has not reached the quench area before TDC. All of this I admit is a very loose discussion of detonation. I'm not saying you cannot build a successful engine combo with either head. There are many factors that figure in to detonation. Detonation is not a universally well understood phenomenon. Folks have been working on it since the advent of internal combustion engines and continue to do so. My point is only that when looking at the heads by themselves, the closed head seems to have some features one might explot to help reduce detonation tendency. I tend to give tthe benefit of doubt to the closed head as the better head with regard to detonation tendency.
Well I have most everything routed now, just need to tear down and redo the bottom end and decide what route to go with the head options. I also need to come up with a color scheme so I can send everything out for powder coating. This should look pretty good when finished up.
JE pistons are $100 a hole. When I built my 4.125 bore 302 I had them do 10 so I had a couple spares. Maybe a bit pricey but the end result is usually worth the effort.
Open & closed chambered, The one experience I had in "79", my Cobra Jet in the Ranchero needed a rebuild. I had an open chamber 2v engine with a stock 4 barrel setup to run in the down time. Even with the timming way retared it would nock like hell unless you got into all 4 barrels. But that is an n/a aplacation.
The old TRW's had some. The 2416 (for 351c) had a .080 deep dish for -8.5cc and the 2414 (for the 400) had a .135 deep dish for a -14cc. These are the same forgings as the 2379's. I have a set of 2416's or you could get 2379's and have a dish cut in them. Wouldn't cost much.
I now have a set of the 2416 pistons that I am planning to run with the quench heads. I need to do some calulations to see what the overall and static compressoin is going to look like and if it can survive on pump gas. If I can't drive this on the street without special fuel then it is pointless.
Thanks for pointing out the piston #'s that they used to cut down, I know once apon a time someone used to do that. I might see if anyone still has blanks like that that can be cut down.
With the 0.030 over 2416 pistons down in the hole .020 and a 0.041 head gasket and 74cc head (OC 4V) is 8.6 to 1. With a 70cc head it's 9.0 to 1. With a 64cc head it's 9.5 to 1. I like to looks of the OC heads with the dished pistons.