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what do i need to know to change from 1.7 to 1.8 rocker arms i got a set of crane gold 1.8 rockers from e-bay and want to put them on my bbc. is there anything that needs to be done differently or can i just put them on and not woory about it.
thanks pat(slotracer) :D
I increases your lift, so you just have to keep that in mind. What engine do you have, with what pistons and cam? If you have domed pistons and a large cam already, you could run into trouble.
You need to know if you have clearance between the piston and the valve at full open at TDC. The "proper" way to do this is with clay on the piston and a micoromiter. The easier way is to remocve the valve springs with the piston in TDC and see how much travel you have between closed and open. Do the math on the travel with the 1.7's (Like old travel is 15mm / 1.7 * 1.8 = 15.9 mm) and make sure you have some room left over.
the engine is a bbc 454 rec. heads kb 203-030 dome pistons, comp cam cb xm 278h-12 hyd. 278 intake 292 exhaust. thanks pat(slotracer) :D
Pat, I'm sorry I didn't get this up for you like you asked.
I got sidetracked when I got mail from da judge :( .
Going from a 1.7 to a 1.8 rocker you will only lose about .015 valve clerance. But the real way to check valve clearance is in the overlap 10 degrees before TDC check Ex. 10 degrees after TDC check Intake and with the valve train loaded all rockers on and lashed.With a dial indicater set up on the retainer and turn the adjuster down until the valve hits the piston.Then you will know what running valve clearance really is.And if just checking with valve train not loaded only #1 cylinder you will lose about .010 loaded.And back off the set screw in the adjuster also.
Badboat1
Left this out if not a solid roller or flat tappet cam make sure you don't check with a Hyd. lifter.
Badboat1
i have a hyd. cam in it. what else is there to know? thanks pat(slotracer) :D
Besides Coil Bind, What Other Types of Mechanical Interference Should You Look Out For?
When you increase the valve lift with a bigger cam or increased rocker arm ratio you must be sure that there is no interference between any of the moving parts. Some of the components that must be inspected for clearance are:
1. The distance from the bottom of the valve spring retainer and the top of the valve stem guide, or the top of the valve stem seal must be equal to the net valve lift of the valve plus at least .060 more for clearance.
2. When using rocker arms mounted on a stud, the length of the slot in the rocker arm body must be inspected to be sure it is long enough to avoid binding on the stud. The ends of the slot must be at least .060 away from the stud when the rocker is at full valve lift and when the valve is closed.
Crane Cams offers steel long slot and extra long slot rocker arms to relieve this interference problem. Aluminum roller rocker arms may be required to provide sufficient travel on larger lift camshafts.
3. The underside of the rocker arm body cannot touch the valve spring retainer. You will need at least .040 clearance to the retainer throughout the full movement of the rocker arm. If necessary, a different shape retainer or rocker arm design will be required. In some cases, installing a lash cap on the tip of the valve stem can provide the clearance required.
4. Valve to piston clearance must be checked to be sure there is sufficient clearance. The intake valve must have at least .100 clearance to the piston and at least .120 clearance on the exhaust valve.
www.cranecams.com/morvtfaq.htm
oh boy what a learning experience this is just a
change from 1.7 to 1.8 and all these things needs
to be checked. called comp cams and they said need to check piston clearance also. looks like one head needs to come off to do that also. hell the engine runs great i do not know if i will gain any h.p. going to the 1.8 so i may just leave as it is. thanks for all the reply's.
pat(slotracer) :D