This is what I have, Crane rollercam 270/276 adv.duration 452"/.465 gross lift, new springs that were ordered with the cam, 1.6 Comp Cams roller tip rockers. Going on a L98 with stock heads. I thought this was a pretty mild cam, by using the 1.6's am I pushing the stock valvetrain too far? I just got the 1.6's so I could send them back for 1.5's but I dont really want to because I already wish I could have got a bigger cam but I didnt want to have to do any machine work on the heads. (Sittingbull, if you read this, I started this other post because it was getting off topic of that other thread)

 

Yup, you're going to have coil bind at the least.

Without machining the heads you will HAVE to stick to 1.5 rockers.

Don't feel bad, though. Typically a street engine only gains somewhere around 5 hp from a rocker ratio change. If the heads can cope with it, and you need new rockers anyway, then 1.6s are the way to go. Otherwise, just stick with the 1.5s

 

I was going with the roller tip rockers since I had the top end apart and heard that the stock rockers were not that great. But as I said, I dont want to have any machine work done at this point. So should I send them back and get the 1.5's , or just use the stock ones and send them back and get something else for the money? I already have AFPR, headers, and new timing chain.

 

If it is an L98, TPI, they don't rev high enough to really make any use of roller tip rockers anyway. They tend to max out at around 5000 rpm. Some companies make rockers that are very consistent in their ratios, while GM is not noted for that. Still, you are only looking at a 5 hp gain, or somewhere in that neighbourhood.

If you really feel that the stock rockers are done for, then get new 1.5 ratio rockers. But don't feel bound to roller tips for an engine only able to turn 5000 rpm.

 

he won't coil bind so long as the installed height of the springs are 1.800.

his new lift is .482/.496

using 1.150 as coil bind then
.100 safety margin

1.150 + .100 + .482 = 1.732 intake
1.150 + .100 + .496 = 1.746 exhaust

i'm at .490 right now on mine and no coil bind. but my springs are at 1.800 and my pushrod holes were not machined. but, put a set on one cylinder and turn the motor over by hand just to make sure the pushrods do not hit the head on the stud side. and check the valve springs for bind. at full lift, you should be able to get a sheet of paper between the coils. that's about .016" thick.

 

Backing up a step or two...

Do you already have the Crane-supplied springs installed? If not, what is the outside diameter of the springs? You may find that you need head machining anyway, just to accomodate the replacement springs.

If the new springs are installed, you should be able to mock up on set of valves with the original rockers and measure coil clearance. From that, you can determine if the added lift from the 1.6:1 rockers will be an issue. Make sure you watch the valve guide and seal clearance as well.

On paper, it looks like it could work, but it all depends on the valve stem length and installed height.

Backing up another step, your clearance issues won't matter with "stock" L98 heads with pull-out rocker studs, since the studs will raise out of the heads and provide the extra clearance anyway. If you don't want the studs floating around in the oil pan, you'd better plan on screwed studs before running the engine. That may change the geometry a little, too, so you'll have to mock up a set of valves and check clearances at the stud/fulcrum, push rod hole, retainer, and valve guide. A pair of checking springs is very useful for this purpose.

 

The springs are not installed but I dont have them here with me to measure them, they are with the car at my brother's. But I know they are stock diameter because when I ordered them I told them I was using my stock retainers and not doing any headwork. I'm not really trying to push my valve lift to the limit by using 1.6's, I didnt realize they would make that much of a difference in the cam lift as to be borderline too much for the stock valves. Would I be better off to just exchange them for the 1.5's? With my mildly modded engine it wont make a difference between the 1.5 or the 1.6 anyway will it? I just wasnt looking at the big picture when I ordered the 1.6's. Will I still need to change the studs even with the 1.5?

 

wonder why my studs haven't pulled out yet? (smart comment supplied).

using stock retainers - meaning you are still going to keep the rotators on the exhaust side? you might as well wait to put them on after you do the head work. yes make sure to check the retainer to guide clearance. my suggestion is to hold on to all your new parts and do it right the 1st time.

here's a thought. if you don't want the car down to have the heads done. get a set off someone. get them done. then turn around and sell yours.

 

The springs are only 1.700"- max. recommended lift and rpm .510" - 6,500 .

 

Now you have to decide whether you want the hassle of doing some machining to the heads in order to accomodate the cam or simply choose a smaller cam.

 

I think I will just send the 1.6's back and get 1.5's, not sure yet if I will get the roller tips or just the stock style. I know I dont want to go with a smaller cam and I dont want to mess with the heads just to be able to use 1.6's. Maybe down the road I will be able to get some machine work done on the heads or get some good heads that will allow me to run a bigger lift but right now I have to stick with what I have got.

 

Yes, that cam will work well with a 350. Let us know how it works out. Should put you into the 13s