Yella Terra Roller Rockers Query...

[PanthaVS]

I'm curious about the 1.8 yella terra racing roller rockers, with 5/16" mounting bolts to suit the buick/ecotec. (not street, ultralite or platinum)

1. Being 5/16" bolts, will the heads need modifying on an Ecotec?

2. Why would yella terra machine around the back of them?

3. Do i need a rocker cover spacer to fit them? if so, i can make a "gasket" style spacer out of aluminium and use longer bolts, will that work if i put a paper gasket on the bottom face between the head and my aluminium spacer? (the rubber seal on the covers will seal the top face)

4. Being only 1.8, i remember reading somewhere a while ago... (can't find the article anymore) about limitations of rocker ratio when it comes to installing cams... i believe it was something along the lines of, if you use any higher than 1.8 ratio, it becomes diffecult to install an aftermarket cam and not bash the valves into the piston???? or something???? can anyone elaborate on this please?

thanks!

[cander24]

Not trying to be smart, but for the first three i'd give the guys at yella terra a call. I've always found them really helpful.
For number 4, it really depends on the max lift of the cam you want to run. Off the top of my head, the stock heads will max out at a little over 0.500" of lift (retainer will hit stem seal), so you'd need to do the maths of what your chosen cam will lift at 1.6:1 stock as compared to the 1.8:1 increase (i.e. multiply the lift direct off the cam lobe by 1.8 to give max lift). This sort of lift really demands upgraded springs, and a double row timing chain in my opinion. Best to trim the top of the valve guides also to give a little more clearance if you want to run more than 0.500".

[PanthaVS]

question 4: i found a post on mace engineering's site...

Link: Mace Engineering

"Please note that all rockers which have a ratio of greater then 1.9:1 are not really suitable for use with an aftermarket camshaft, as the many of them will create excessive amounts of lift causing potential damage."

so would i be better getting 1.9 rockers for better lift, and if i wanna cam it, i can still have room for a cam, whereas 1.95/1.97 lift won't give me the allowance for an aftermarket cam?

[glenn l]

question 2 might have some thing to do with clearence, depending on what you call around the back of them might be machined to clear the spring or push rod with the extra lift.

[cander24]

question 4: i found a post on mace engineering's site...

Link: Mace Engineering


so would i be better getting 1.9 rockers for better lift, and if i wanna cam it, i can still have room for a cam, whereas 1.95/1.97 lift won't give me the allowance for an aftermarket cam?

I'd be deciding what cam you want to run before you decide on the rockers. You can buy aftermarket 'performance' cams which are designed for use with high ratio rockers and therefore have less lift direct off the cam lobe, but personally i'd be letting the cam do the bulk of the lifting and therefore probably wouldn't go more than 1.8:1. Just remember that lots of lift created through both the cam and rockers may require additional supporting mods to handle it. Also there's alot more gains to be had in the right choice of cam over high ratio rockers as there's alot more to be had than just lift.
Hope that helps

[GTP 85]

Just spend the $$$ on a decent cam, springs, timing chain kit.

I bought the 1.8 ultra lites years ago for $580. then stuck a grumpy cam in there anyway... Havin RR's in there is good piece of mind, but with what i know now the big cam would work fine with the stock rockers

Oh, and no u dont need rocker cover spacers for 1.8s on an ecotec