I am starting to think about my next inline build to replace the 250 that grenaded on me last summer. I have heard that BBC v-thing roller rockers can fit on our inline heads. I was wondering if anyone can tell me what has to be done to the head for a 1.7 or 1.8 ratio rocker to fit. I understand that the factory studs will have to be pulled in favour of larger diameter screw in pieces, and probably guide plates(?).
Any info would be great
Thanks
Rob
Hi Rob, i`m gonna follow your question as i have the same need to know as you do. I`m hopiung to here from one of these guys here soon. I Hace read they use the bbc 1:75:1 rockers on 7/16 studs. I have heard some modifications need to be done to the Valve cover for clearance. I hope we hear soon,. I am expecting my Leo Santucci book anyday and hope he covers this as well.
"PACE" sells a stamped steel roller tip rocker if you don`t want the full roller.
Slider
Hi Rob and Slider, BBC rocker's are available in both 3/8 and 7/16 and there are plenty of ratio's to choose from. You can use them with
your stock press in stud's (3/8).
And if you do upgrade to the
screw in studs, keep in mind that both 3/8 and
7/16 studs use the same tap (7/16). So they are
interchangeable. Stacking valve cover gaskets
can help with clearance, and the Mecruiser cover has a little more room than the chevy. Also there are custom valve covers available....but they are not exactly cheap.
Here are some choices of roller rocker arms for the Chevrolet 250:
Crower Enduro Stainless Steel 3/8" stud 1.75 ratio
Crower Enduro Stainless Steel 7/16" stud 1.75 ratio
Crower Enduro Aluminum 3/8" Stud 1.75 ratio
Crower Enduro Aluminum 7/16" Stud 1.75 ratio
Comp Cams Pro Magnum 7/16" Stud 1.7 ratio
Crane Aluminum Gold Race 3/8" Stud 1.7 ratio
Harland Sharp 3/8" Stud 1.75 ratio
Harland Sharp 7/16" Stud 1.75 ratio
348 - 409 V thingys have the same ratio and stud as inline 6's. eBay guy's have inline 6 roller rockers for sale around $165.
i know that Crower, isky, Harland sharp and etc have roller rocker arms specific for the chevy 250, is there any reason to use a big block rocker instead the one build specific for the chevy?
One thing everyone has for gotten. ANY rocker aftermarket OTHER then comps ProMag. rockers NEED to be milled, ground. How ever you wish. BUT the #1 ,#12 Needs to be rounded off to clear ANY Valve COVER,( stock,Marine,Clifford,Offey)I think Mike kirbys cover would clear,And Mine is not finished/Ready Yet But for the way I am Making my cover It should.It will also Be taller then The Marine,clifford & Offey.By at least one inch.
The marine cover is 4inchs tall on the inside.
So by me going a inch taller this should also give more room for a stud gridle & a baffle for the PVC valve.
Going with a lager then 1.75 on the rocker with a HIGH lift cam you have to be sure to double check The Push rod to head cleance. The head may need to sloted more toward the inside of the head (towards the springs) I know someone who tried a 1.8 with a High Lift and that is the issue he seen.
i used alum bbc rockers. also took a hacksaw and cut the corners that interfered with the valve cover. only on the front and rear rockers, that hit. tom
Twisted, please forgive the lack of knowledge as I am fairly new, but what do you mean by "milled,ground. How ever you wish." Is there something that needs to be done to the rockers to make them fit, or is "out of the box" no longer an option?
Rob
try to find rockers specific for chevy 250! it's easy to find, excelent brands avaliable (Crower, isky, Crane)and no need to do nothing!
Hi Rob, unless you use the pro-mag's, then you
liklely will have modify 2 of your 12 rocker's
# 1 (the very front) and number #12(the very rear).
You can use a file, hacksaw,or a grinder ect..
Basically you need to round off the corners of the rocker's #1 and 12.
The reason for this is so they will clear the stock valve cover correct? Because I was planning on building a valve cover out of aluminum for the BBC rockers anyway. And I also went through the archives and found some other info on roller rockers and have now decided I will probably go with a full roller valvetrain from Crower, specific for the 250. Thank you Edy and Winter for your info. The only fuzzy area left is pushrod length.
In an earlier post Mike G. discussed it quite clearly, but I am wondering if anyone happens to have measurements from personal experience with this type of setup. I am still a little wet behind the ears when it comes to valvetrain components, and I don't have the tools required to measure for proper rod length.
Thanks for the help everyone.
I have only use the Crane Gold Aluminum 250 Chevy rockers 1.7 ratio 3/8 stud for 20 years.
Maybe the newer stainless (Like Comp Cams,Crower, etc ) might clear the valve cover.
I had to grind material off the coners of # 1 & 12 rockers to clear my Offy cover & ran two gaskets.
I also,milled flat the sealing surface of my Offy cover because it was not straight.
MBHD
He have a valve cover here in Brazil made for Roller rockers, and no need to modify or grind the 1 & 12 rockers...
http://www.engineracing.com.br/pecasnacionais.html Also, there´re a lot of intake manifolds manufactured by the same brand...
What rocker did you have at the time the cover was checked? Reason I'm asking is When i had those covers here In stock they didn't Look to be any longger then cliffords,Offeys,Or the Marine Cover.a little taller yes But Not any longger. And
that is the Biggest issue.In order to clear The Bigger DIA. springs and a Big BOXie rockers is
These covers Need to have the ends Moved out over The Gasket area.
And out of all the Cast or Die Cast(marine)covers,
The marine cover is pretty much the lightest of them all.
Again this is why i'm making mine is to give it more height,lenght.And to clear the Studs on the
ends.And Not to be boxie looking and at the same time it should also be lighter then the cast?
( won't know this for sure till im done)
Ps. when i ran the marine cover all i had to do was round off #1 & #12 and a single gasket.
(crane golds 1.7)But now Comp Pro mag. 1.73 and Bigger springs So i need the room.Mainly due to
The springs.The marine cover clears the rockers But Not the springs.
Has anyone purchased from the Engine Co in Brazil and had it shipped to the USA..........Thanks
Two possible USA sources for Engine Company of Brazil items:
http://www.t6racing.org/index.html Our own Twisted6 / Larry
http://www.goravenswood.com ebay's Mr. Hotrod6
Items are not alway in stock and may have to be ordered.
Rob
i will be using Crower aluminum rockers, 3/8 stud, i think this is good choice, one thing less to spend time searching on the web!
about the push rod lenght! buy a push rods checker (this was a advice i got in the forum) buying one you will save a lot of head ache and money! measure it, and order it correctly the first time!!! if your application will use more than .650" lift go to 3/8 push rods!
What about using a valve cover for a 235 and getting an adapter from Larrowe & Sons???
I used the Crane Gold on my 292. Previous head rebuilds have always shown what I felt to be excessive guide wear and I wanted to see if the roller rockers would prevent this.
Crane will tell you several things to do and not do in regards to their rockers.
The first is that you should do absolutely no grinding or modifications of any kind. I cut the corners of the cover, spread it open and welded in a filler piece. Quick, easy, one gasket and looks stock.
You must check the rocker geometry, but that is true with even stock rockers.
You must check the clearance between the aluminum rocker and the stud boss.
I had a problem. This engine was built to run under 3000 and so I used the stock studs and new stock valve springs. The previous head rebuild had put the hardened EX seats too low. This time, I used a different shop and had bigger seats put in at the right height and new 1.94 intake valves. The rocker angle was great, but dragging on the stud boss. I made a low speed cutter that rode on a brass sleeve on the stud. It didn't cut against the stud, but took about .030" off the stud shoulder deck.
You might not have the same problem, but with my mild cam and stem height I did.
I cut mine and Ran Them For 17 plus years.With out any Issues.Also one thing you have to keep in mind Is Keep The Heat to a MIN. Go slow/Little at a time.Some rockers also Need to be trimed on the Under side When USEING Large DIA Springs. I have Not ever had to do this Myself But i have seen it.
And Also I have Never seen or heard of any issues with doing do.. BUT like any company who makes ANYTHING if you make any Mods to their product You
Lose what warranty there is.
I also had to radius the corners of the 2 end rockers to clear an Offy alum cover. They are Crane gold race rollers and after 20,000 miles and more than a few silly rpm buzzes they are fine. Like Larry said - Crane is just covering their tail in case of a warranty. "Did you take them out of the box yet? Yes? Sorry, the warranty is expired. "