Hey i recently installed a hotcam and lt4 springs in my bolt on Lt1 and i was wondering if the 1.6 rr were worth the extra hp? If so NSA or SA? Would i need a different sized pushrod? I have stock hardened. Thanks in advance

 

Any insight please

 

They are a fairly easy upgrade... SA takes less parts to install but aren't typically ran as high rpms as NSA.

 

I have a hotcam and have used 1.5 and 1.6 stamped rockers on it. At the track there was no difference in times between the two ratios. I will say with the 1.6s the engine sounded better and seemed to run stronger but the track doesn't lie. I'm sure sometime down the road I'll switch to 1.6rr from my current 1.5 stock rockers.

 

Thanks for the replies guys..guppymech was this with the lt4 springs also? are you running hardended pushrods?

 

I was using the LT4 springs but with the 1.6 rockers I felt the engine was getting some valve float at 6K. I switched to some PAC 1212X springs that work with the stock retainers and the engine revs much cleaner. IMO the LT4 springs don't work at higher revs with the hotcam.
I have the stock pushrods, you only need hardened PR if you're going to use guideplates with NSA rocker arms.

 

I would upgrade the valve springs also. Youll probly have valve float in higher rpma with the 1.6 rr. Also id buy 7/16 nsa rockers. It cost litte extra for the 7/16 studs and guidplates but youll have room to grow.

 

two things contribute to more HP with "roller rockers" which are ligher lift than stock.

1. less friction vs stamped rockers 'release" more HP because there is less parasidic drag on the valvetrain
2. Higher lift ratio of 1:6 would yield more HP..

so going from stamped 1:5 rockers to 1:6 'roller" rockers generally yeilds about 10 hp gain..which to the wheels is closer to 7...

...and at the track on a diffrent day than you ran before you may not see any ET/MPH gain or you may but that would be more due to track conditions and DA diffrences between the 2 days vs 7 more RWHP

the LT4 springs were spec to use with LT4 valves which are lighter (sodium filed) than solid valves used on stock iron or AL heads or even aftermarket heads. LT4 springs are regarded as being barely good in a stock LT4 motor with 1:5 rockers....using heavier valves, higher lift with 1:6 RR and spinning the motor above 5500 rpm really take them past spec especially in the long run.

There are many spring manufacturers for alternate spring choices that will work better at higher RPM's and last longer. The "bee hive" spring for example is what many use. COMP, PAC, Howards all make them. "Most" aftermarket springs are spec to install at 1.8" and stock is 1.75" so when using a 1.8" spring installed at a lower height increases open and seat pressure...in itself sometimes OK but at the same time decrease the "max lift" ability of the spring so coil bind would happen sooner than that spring is spec at if installing at a lower height. Now add 1:6 RR and you make that coil bind window even tighter. This is why most aftermarket heads using springs installed at 1.8" have the spring pockets machined down to allow for the extra height. Also if using a "dual" spring the valve stem guide casting is machined down to allow a smaller valve stem seal to clear the springs.

With that said you are most likely "OK" in running something like a 915 or even a 918 spring with 1:6 RR and the Hot cam before getting into coil bind but without doing the math on lift and knowing the max lift of a spring I can't answer that 100%

hardened PR...they are used when running NSA rockers as you need guide plates which they rub against. With stock SA type rockers or SA Roller Rockers you don't need hardened PR. What many do though is get thicker wall (.080) PR which are hardened but more important are thicker so they don't flex like stock PR do at high RPM's. Many make thicker wall PR. Trick Flo is what I use.

 

This is the best description of the issues involved with valvesprings on stock heads I have read. In keeping the stock rockers (a self imposed limitation) I was looking for springs with less than 340-350lbs open press. I was liking the seat and open numbers I was seeing with some springs run at the LT1 installed height until I got to the reduced coil bind height and saw they wouldn't work.

As alot of people have said it's best to plan mods with future goals in mind.

 

****** has great advice on this.

Also run the 1.6 because that's what the cam calls for. I didn't get valve float up to 6400 on mine but after 30k miles on it and I tested the springs, they were pretty weak. So I suggest using a better spring as well.

I will highly advise running SA rockers. If you're not planning on breaking 6500rpm, stay SA, you'll be fine. 3/8 studs and 5/16 PR will be fine. You can still run hardened PR's for added strength though.

 

You guys are great..thanks for all the info

 

OP

look at the specs on your cam card for open & seat min pressure required. This link for a Crane spring kit for the AL heads is plug & play with a 1.750" installed height

http://www.summitracing.com/parts/crn-10308-1/overview/

there are other options. IIRC Howard makes some for 1.75"...would have to check though

I have the 10309-1 springs on a iron head 355 motor I am building. Not saying these are the best springs but are good and I have had no issues running the 10309 versions with 1:6 RR with a 227 cam. I did have the pressed in studs pulled and machined for screw in ARP ones though.


AL heads have screw in studs

 

I used the 10308 kit and was happy with it.

My only complaint was that they come with shims instead of proper locators, but that's not a big deal when talking about the rpm and spring pressures being used with that sort of spring.

Peaked at 6300 with a 227int cam, no valve float. Used SA 1.6rrs(crane golds) with Comp hardened PRs.

 

amen to that

there were posts a few years ago about COMP "bee hive" springs being bad. a refrence to a particular batch # was made and it very well could have been "bad" springs. Something about COMP switching manufacturer.

In any event I suspect some failure was due to people installing them shorter than spec, having a high lift cam and running 1:6 RR AND reving the **** out of the motor which **** a spring.

I am no expert but have listened to people who know WTF they are talking about regarding engine builds and specifically valvetrain geometry,,,,it is the "geometry" part many ignore.

yeah you can slap in springs at a shorter height which will increase open and seat pressure...maybe to much with a high lift cam.... then have a lash to tight....then wipe a cam lobe. It may take 200 miles to have issues or 2000 miles...but incorrect combination of parts and improper install will cause major issues sooner or absolutely later.

The OP got a cam designed for "LT4" which in itself is compatable with the "LT platform" aka LT1. Then got "LT4" springs assumeing they "match" the cam. They do in a LT4 head motor but not heads with heaver than LT4 valves...and he has issues now at higher RPM's that will progressively get worse as the springs weaken in terms of spring pressure. Not a fatal mistake with the combo of parts but one that causes attention to swap in a correct spring for the application.

 

yeah I agree locators would be prefered, the kind that has a raised skirt on the valve stem side. absolutely need steel shim under them on AL heads which the 308 kit has.

I would think those "shims" were sized so they just clear the valve stem casting essentially making them a 'locator" as they could not move around if they were sized that way.

I have shims of various thickness on my AL headed 383 with COMP 918s but they have proper locators on top of the shims.

 

I've heard sbc valve springs and lt1 valve springs are basically interchangeable, is this true? If so I can get sbc comp springs good up to 600 lift for a little bit of nothing? Or should I suck it up and go Howard springs?

 

One thing to keep in mind while selecting valve springs and retainers is that not all retainers sit low enough on the valve stem for self aligning rocker arms to work. If the retainer is too high the SA tabs will rub on the retainer. Now something as simple as valve springs for a hotcam just got alot more complicated. In the long run going 7/16 stud and NSA RRs will handle anything you can throw at it.

 

My motors out right now getting the hot cam kit with impala gasket. cant wait to get it back together

 

A locator to keep the springs themselves in place, not the shims. The shims fit fine around the valves and wont go anywhere .

I bet the springs slide around on those shims quite a bit when running. I didn't have any problems with them of course, but for piece of mind I would have loved a proper locator...but then would need to play with the keepers/retainers or get longer valves to keep the same spring height. Not something you want to do on a simple H/C stock shortblock street car.

Again though, I'd recommend the kit to anyone with a mild-medium cam on LT1 heads.

 

Try these if your on a budget. Heard good and bad things about them.
http://www.alexsparts.com/lt1-valve-...rs-locks-cups/