gt500pwr

I've read a bunch about the lt1 cams in an l03 but what about a hi-perf lt1 cam? i've got a guy with a comp 269hr-12 lt1 cam i can get for $50.\
Part Number 07-502-8
Engine 1993-1996 Chevrolet
350ci,
LT1 & LT4,
8cyl.
Grind Number LT1 XR269HR-12
Description
Intake Exhaust
Valve Adjustment 0 0
Gross Valve Lift 0.495 0.503
Duration At 0.006 Tappet Lift 269 276
Valve Timing At 0.006
Open Close
Intake 26 62
Exhaust 74 22
These Specs Are For The Cam Installed At 108 Intake CL
Intake Exhaust
Duration At 0.05 218 224
Lobe Lift 0.33 0.335
Lobe Separation 112

Could i use this with new valve springs?

markymarco

iTrader: (10)

you could use it but you would have to upgrade your heads becuase with a stock lt1 cam it is already stretching the stock heads to the limit

BMmonteSS

You'll also need to retune as the LT1 cam pretty much stretches the stock tune to it's limit as well. In some cases the LT1 cam is too much to be even drivable.

gt500pwr

I've got an EBL going in also, could I not just upgrade the springs in the heads to accomodate the higher lift?

BMmonteSS

Nope, you'll have interferance between the valve seals and the retainers. Only way to go with more than .460 lift is to have the guides cut down.

dimented24x7

iTrader: (2)

Basically with that cam, the whole valvetrain has to go, possibly even the stock roller spider setup would have to be replaced. Youll definatly need new springs, rockers, screw-in studs, have the guides cut, etc. It would be better to just get new heads rather then trying to use the stock ones, which wont be able to breath where that cam makes its power. Potentially you could spend 30-40x the cost of the cam to get it to work properly. On the bright side, youll have a hot motor when your done.

Fast355

iTrader: (2)

The stock roller spider, stock lifters, stock pushrods, and stock style rocker arms will work fine with that cam, after all it is designed for a stockish LT1 with stock roller cam provisions. The hardware above is the same for the LT1 as it is for the L03. On the otherhand, the valvesprings and retainers HAVE to go. They are only marginal on a stock L03 running stock components. The lift will smash the retainers into the valvestem seals. I have found that by using LT4 retainers, I can typically pick up another .040" clearance between the valve seals and the retainers. Using the LT4 style valve stem seal frees up another .05-.10" for a total of approximately .525" total valve lift. The ZZ4 uses these same components on its 463 casting aluminum heads. I had a very similar crane camshaft in my L05 with the stock L05 heads on it with the LT4 retainers, seals, and springs. No problems in 40K miles of driving. The exhaust side of my cam has .509" of lift.

gt500pwr

Fast355, isn't the L05 the 350 motor? The heads would be different that those on the L03 305 right? I talked to my parts guy, he builds hi-perf engines for the track and he figures that with a good spring and the stock 1.5 rockers I should have enough clearance. How can I measure the valve seal clearance?

markymarco

iTrader: (10)

the 350 heads should work on the 305

gt500pwr

I'm not using 350 heads, the stock TBI heads. The springs are K-Motion 750's that I'm looking at:
O.D./I.D; 1.265; App; S ; Max Lift;.610 ; Spring Type; H-11 Single; Seat Pressure; 130/1.700; Open Pressure; 380/1.150; Coil Bind;1.050

My parts guy figures I should be able to, using these springs, be safe with this cam. Any comments?

I also noticed that comp has 2 cams with the same number, one for lt1 and one for 305/350. The specs seem the same, what would be the difference?

The guy also has alum heads for the LT1. How well would they work as replacements on the L03?

markymarco

iTrader: (10)

the 305-350 one might have a fuel pump lobe on it because the lt1 cam has no fuel pump lobe

BronYrAur

iTrader: (1)

He figures wrong. With that cam I would say you definitely need screw-in studs unless you feel like pulling the heads to replace them because after driving for 30 miles after the cam swap you realize the stock studs pulled out almost 1/2" (ask me how I know that) You'll need them cut down or can do what Fast355 said with the LT4 retainers and seals and possibly get away with it, but the for sure safe route is to cut down the guides.

gt500pwr

Yeah BronYrAur, I read about your dillemas... ouch! I guess I'm just trying to get the best bang right now while i'm building the other motor. I really don't want to put any more dough into the 305 than necessary but I figure if I'm changing the timing chain anyways, why not slap a new stick in and give me some more pep without having to do anything to the heads.

BronYrAur

iTrader: (1)

I definitely know what you're thinkin, I was thinking along the same lines but ended up spending way more money than I thought I would. I would have been much better off just buying a new set of heads I think, or even just buying a 350 longblock and throwing that in. My car is much faster now though so I'm not complaining, I just may have gone a different route if I were to do it again.