I have hypereutectic .030 over replacement boss 302 pistons (with dome). These are basically the same dimensions as factory boss pistons. The boss 302 head is a cleveland 4bl closed chamber head with large valves. Question, can I run 2bl or 4bl cleveland heads with either closed or open combustion chambers with these pistons? I heard some say the pistons are different for 2bl vs 4bl heads. Obviously the dome would be different but will the boss piston valve reliefs work with 2bl heads?
the valve reliefs should be correct, whether it be a 2V or 4V OC or CC head. The valve spacing and angles are the same, but the domes are totally different, but you already knew that. That's why they make the different pistons for 2V and 4V heads. I do believe that the CC domed pistons may make contact with the chambers on the OC heads, but I am not 100% positive about that.
well, can we determine if the dome problem exists for the chamber as opposed to the valves. I assumed there would be plenty of room in the OC head but maybe not! Help from others???
You must be very carefull what combination you put togather. The 69-70 4v head has the smallest combustion chambers at about 63 cc. The rest of the heads are all larger in cc size because they were used on 351 displacement engines. You can't use open chamber heads because they would result in very low compression, no turbulance and poor performance on top of the large ports that would have low air velocity and be spark knock prone and not run very well at low rpm.. The heads need machine work and plugs to take care of water passage issues to be used on a 289/302 blocks. The 302 Boss heads were made strickly for the 302 block In any event the piston/valve relationships have to be checked as well as for hitting the heads. You need special intake manifold. The original Boss engines used different con rods and some other differences. It's costly to make a Cadilac out of a Volkswagon. Much better to use flat top pistons and good alum heads and get much better performance overall.
You don't quite tell us your objective, but the answer to the question is that the dome is what will cause a problem if you are not using a stock quench head. I would think that the smaller chamber dome would fit into the larger chamber, while pistons for the larger chamber would not fit into the smaller... but everything I have read over the years says that there is a conflict in the large chamber with the small domes. It must have to do with dome height compared to chamber depth in a given spot. The open chambers are wide, yet shallow compared to the quench versions which always seemed deeper to me. You can take pistons to the machine shop and have the dome milled some to gain clearance. I am not sure about hypertectic pistons though, I know this is true for cast and forged. You would also be wise to soften the edges of any remaining dome IMO. Since the remaining dome would not be a close fit with the chamber, you might have detonation issues. Open chamber heads are notorious for detonation problems anyway... just due to the shape of the chamber itself. The rule of thumb for Cleveland guys I know is that 9:1 is the highest compression safe with 93 octane and open chambers. The closed design is known for resistance to detonation. That said, and assuming you are building a street boss... Aussie heads, your pistons (with a slight dome mill), and 289 rods (ARP bolts) would be a good combo IMO. Dave
Bluegrass, I have pistons for 302 length rods (1.602 compression height and 5.090 length rods if I recall correctly), manifold spacers, and the machine work is no big deal. I will also need to drill the block in three places on each side. Using the boss 302 pistons and open chamber heads the compression is a street friendly 9:1 and the smaller 2bl runners would be a better choice! I could also shave the heads to bump compression. I agree, aluminum heads are probably better and easier in the long run but as I've indicated before I'm going for the conversation piece! The one issue I didn't consider, will the boss 302 dome pistons "fit" the open chamber heads? I assumed the valve location is the same in all cleveland style heads but maybe not! Also, I could use a flat top piston with the closed chamber heads but I haven't calculated that compression.
ratio411, didn't see your post before posting my last response. The pistons are designed to be used with standard 302 rods, not 289/boss rods. I agree that the 2bl heads seem to have a shallow chamber while the 4bl heads appear deeper. When I bought the pistons (years ago) they indicated different compression ratios with different size chambers implying the large chamber heads could be used. With that said, they never specifically indicated the pistons were compatible with the large chamber heads! I'm not sure these pistons are manufactured any longer but I'll try to find more on the web. As far as goals go, well, it will not be all that fast but it will look good, sound good and to my knowledge be the only EFI boss powered maverick in existence.
Well, you need to rework the heads for water passage compatability, not just the block. Reference the Ford Motor Sports catalog page 120 to get that info and I would reccomend you get Ford perfornce book by Ganahl and book on 351c/m 400m by Tom Monroe and get some education before you get yourself into a mess. Good luck. You only hear what you want to hear.
Bluegrass, I'm certainly interested in the detonation issue and the dome fitment issue. Modifying the block and heads is fairly straight forward. Here is a pretty good link for some info. http://www.jason.fletcher.net/tech/cleveland2v/cleveland2v.htm Of interest, you can run about .470 lift and .220 duration and use standard 302 pistons with inline valve reliefs although one should check clearances. Thanks for the heads up on the source. Also, I was concerned about hooking up the accessories such as alternator because the brackets bolt to the heads!
Okay... You said in your post that the pistons were Boss 302 replacement equivalent. Now to say that they were set up for use with 302 rods means that they are not replacement spec. I suppose I should have guessed by the fact that they were not forged. If the manufacturer gives compression with different chambers, then one would assume that they made the dome 'generic' enough to work with those different chambers. There was a time that street boss engines were a popular craze, just before aftermarket W heads became widespread. Those pistons were probably made to satisfy this fad and are most likely very adaptable to whatever heads you want. Check old magazines and catalogs for the part number and see what it specifies. The manufacturer would know too, even if they have discontinued the part. Doing a search on their site or a general search for the part number online should also help you. One thing is for sure, you don't want to find out later that they don't fit the parts you have already bought, then have to start over, or worse, find out after you start a fresh engine. Good luck Dave
Btw: You are converting it to EFI? If so, there is a Pantera guy that used 2v heads and a 351w truck EFI setup, then hybrid everything together to make his 351c a 2v EFI engine. With the ports and cylinders having the same spacing, so much can be converted to work. Do some searching. I read this guys site and saw his progress pics... I was amazed at how well the W intake lined up with the ports and bolt holes in the 2v C heads. Some things he did: Made the 2v intake ports a little more like the W ports for the first 1/4" into the head. Then he made the W manifold ports a little more like the oval 2v shape of the heads, sorta 'meeting in the middle' between the 2 shapes where the 2 parts meet. I don't know which gaskets worked best. Of course he had to mill some meat off the W lower intake to fit the narrower C engine. Then he modded the vertical bolt holes of the W intake so that the angled intake bolts of the C would work. Some of the stock W bolt holes lined up already though because some of the C bolts are vertical too. If you were doing a 302 block, you should have even less to worry with... Just some port reshaping and the angled bolts. Then you could use whatever 5.0 EFI setup you wanted. How about a nice GT40 intake? Just an idea. Look for that site. I wasn't doing what you are, and I still thought it was very interesting. Dave Edit: The Pantera guy also had to cut the water manifolding off the lower on his application, but that would actually be a plus for you. Just drill the crossover holes in the heads right where you need it and use it.
ratio411, correct! They are canted valve boss 302 pistons but with standard 302 compression height and standard 302 rods. Obviously, this makes it much easier to deal with in the end. I agree that the dome must be designed to work in either case but I want to be sure. Yes, I will have to drill the heads for the crossover and plug the heads on the block face! This is not a huge deal. I also have some forged cleveland pistons that were milled to 302 compression height and therefore have the correct valve reliefs. The only problem is using the closed chamber heads would be required and I really don't want to use 4bl heads. Thus, leaving me no choice but to find Aussie heads which are very expensive! I once ran across a set of Ford SVO 2bl heads that were essentially aussie heads. Should have purchased them! The EFI is already in the car and currently has a stock 91 HO setup. I have the GT40 lower and compcams boxed upper with a 93 cobra computer, injectors, throttle body, cam and MAF sensor. I'll probably go with a larger cam for the thump and I know, the boxed upper kills the bottom end but it is a ton easier to work on and again, it has the "shock and awe" effect. I don't really street race so I thought I would intimidate folks with the EFI boss with the boxed intake! I've seen the Pantera, very cool!
Keep up with Edelbrock here the next couple months... They have a set of 2v aluminum heads that are now, or will be shortly, on the market. They have 2v style ports and valves, with swirl chambers. Unlike stock 2vs, if I recall, they are also set-up to use either 2 or 4v intakes and exhaust manifolds for convienence. They probably cost plenty like any other aluminum head, but they would be light, new, effiecient, have plenty of "awe factor", and be easy to use. Good luck Dave Btw: Edelbrock is also coming out with RPMs and A/Gs for Clevelands too. O/T...
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7945520654&category=33613&sspagename=WDVW found these on ebay.....
