I know the basic "nut shell" of what roller rockers do, what they cost, how they work, etc.
That said- if i were to throw roller rockers in, say a 3.3L v6, would I have to use ones marketed for Mopar engines or are all "1.5 ratio roller rockers" the same?
In doing a roller rockers conversion, are the roller rockers & attaching hardware all thats needed?
This is assuming this hypotheroletical engine build used roller rockers of the same or barely bigger ratio- I'd imagine throwing 1.7's or 1.8's in a 318/etc Mopar that was designed for 1.5's could lead to clearance issues, needing to remachine some varrious parts, etc.
I also noticed that for the newer magnum engines, Mopar has switched from the traditional mopar 1.5 ratio (used in the 318/360/440/etc) to 1.6 OEM... they're still not rollers- just a larger ratio.
How would roller rocker 1.5s compare to traditional nonroller 1.6's in the same engine? Would the difference in ratio be the same or better than using the same ratio with just rollers? I ask because with the newer OEM magnum engines running 1.6, it might be cheaper and easier to get a set of OEM nonroller 1.6's than it would be to get a set of rollers in either 1.5 or 1.6 ratios.
So what do you all think?
RAM MAN
10-08-2005, 10:39 AM
Interesting project ... I dont know the exact answer so I would hope some one else would chime in here
I would think it would add about 10HP ... is that what you were shooting for ?
shelbydodgeimp
10-08-2005, 03:49 PM
Well the thing is- the companies that make roller rockers, like compcams- say it will give 20-30 hp while using roller rockers of the same ratio in place of the OEM traditional rocker arms.
I'd imagine you'd be more up around 30hp by running a larger ratio like going from 1.5 to 1.6.
If you take a 1st generation 3.3- throw a 58mm TB, '94 style cam, '99 style upper intake manifold, cone airfilter & highflow 3" exhaust it should put the 3.3 around 160/180 hp (very roughly speaking), even if these only gave 20-30 hp, that would put the 3.3 to around 200 hp without even getting into playing with the bottom end (pistons, crank, stroking stuff out, changing compression ratio, etc). It would be fairly easy to take a 200hp built up 3.3 to over the 250hp mark with just a few minor bottom end changes, and thats without going into boost.
The other question is- is it worth paying $100-300 for a roller rockers conversion (assuming I can find ones that will work in the 3.3) if it will only be giving me 10-30 hp?
RAM MAN
10-08-2005, 07:43 PM
well, IMO I think thats a cheaper way to pay for HP than swapping in a different cam
which again I would guess would net about the same results, and probably a thousand dollars cheaper
shelbydodgeimp
10-08-2005, 08:11 PM
True, it would be cheaper than a custom cam. Best I can do in the way of a cam is the 1994 revission (used threw 1997... dunno if they kept it after 1997 or changed it again after 1997) gave the 3.3 abt 2-3% better acceleration, I could easily grab a "loaded" top end off of a 1998-2000 3.3/3.8 and use the better+newer cam with a higher rocker ratio (not sure if I'd go with rollers due to price but...).
I've heard that grabing the gearing out of some A604s used in smaller engines give a decent improvement in acceleraton- even if its an other 2% it will make it easier to get to that 200 hp w/ OEM bottom end mark. If I can meet or exceed 200hp with the stock bottom end, it would be fairly easy to get to Shelby's 250hp mark or even a 300 hp mark if I can get the bottom end to survive 10psi of boost in the long-term.
Anyway I am getting ahead of myself here.
First:
1) How do the 3.3 rocker arms mount- shaft or stud? Chronologically the 3.3 is between the 318 (which was shaft mount) and the magnum engines (stud mount) so I suppose it could be either.
2) The 3.3 ratio. Is it 1.5 OEM? In all likelyness it is, but I cant seem to find an FSM set nor 3rd party manual which gives rocker arm specs on the 3.3! Assuming its 1.5, 1.6 would prolly work w/out clearance/machining problems. But would I need a rocker arm spacer like the 318/360/440 guys need when going from the OEM 1.5 to 1.7/1.8? I know the 318 (that the 3.3 is losely based off of) can take a 1.6 w/out spacers or machinging, but I do not know for sure if the 3.3 is the same way in this reguard.
'course if someone could find a way to use "stud mount" in "shaft mount" engines and vice-versa, the mounting style question would be moot and make life a hell of a lot easier.
RAM MAN
10-09-2005, 03:30 PM
sounds like a great project
keep us posted on your progress
shelbydodgeimp
10-11-2005, 04:59 PM
Well, it ends up that the 3.3 uses rockers with an offset of .53125"
This appears to be an unsual offset spec, hopefully the LA 318s use the same offset- if not, the closest I can find are the .550" offset rocker arms used on the exhaust rockers in some GM engines.
The question now becomes- in worset case, will .550 offset rocker arms work in a .53125" offset application? I know that if its too far off, it will adversely wear down on the valvetrain....
faterotong
10-11-2005, 08:15 PM
Just a little thought on boosting a 3.3. Chrysler did do some testing on boosted 3.3/3.8's. They all blew up with "moderate boost" so I doubt you'd be able to get it to last for a long time. I remember there was one guy that threw a rod cuz of that in a 3.3l minivan.
shelbydodgeimp
10-11-2005, 08:49 PM
Actually thats true of the 3.8, not the 3.3.
The 3.8 has such thin cylinder walls that you can't rebuild a 3.8- you might as well throw out the block and machine a 3.3 to 3.8 specs if you want a fresh 3.8 build. Boost on a 3.8 with such thin cylinder walls will crack the block.
The 3.3 on the other hand is a totaly different animal from a boost application perspective. In all reality- whatever tests Chrysler did on the 3.x's with boost were prolly with the 3.8. This was also suspected to be the case considering that thoughts to use the Dynasty in a special police package would have included the 3.8- not the 3.3 (and no, the 3.8 was not ever offered OEM in the Dynasty). If I were to guess, they were thinking of a police package Dynasty consisting of a turbocharged 3.8- however between the 3.8's rebuild & boost problems, the A604's reliability problems and the start of the LHS/Intrepid series in 1993.... any thoughts of making a police package dynasty was very short lived. Why spend all the R&D when the next generation of cars (LHS/intrepid) was just a year or two away? 3.8 saw its first use in 1991, with only 2 years before the very first LHS/Intrepids rolled into car dealerships.
The 3.3 has been proven to work under boost applications- there is a turbocharged 3.3 intrepid, a turbocharged 3.3 dynasty (running up to 15lbs of boost), a turbocharged 3.3 minivan, and lastly APC's concept minivan was a supercharged 3.8 (just running lower boost figures), both engines would certainly be reliable with 0-5psi of boost, the 3.3 with stock internals can withstand 0-10psi of boost. With a forged crank, I would not be surprised if the 3.3 could withstand up to 20psi of boost reliabily- hence the interest in machining the 3.5's forged OEM crank to work in the 3.3 (doable but pricey- abt $300-1000 USD in machining costs).
At any rate, roller rockers have nothing to do with boost. They're an old pushrod modification going back to the old 318/360/440 N/A buildups of the muscle car era- and are great mods to do in either a n/a or boost application.
You could theroletically build a N/A 3.3 (if you're affraid of boost) and get some 250-300+ hp out of it with reliable results. Again- matter of how far you want to go, what octanes you want to limit yourself to, and what kind of cost you'd be willing to spend.
