How would the LT4 "hot" cam perform with a set of 1.6 Crane Gold Race Rockers on a stock bottom end TPI with mildly ported L98 heads, Heddman's, cat-back, etc. What kind of idle does the LT4 have? Would the stock prom function properly with this combo?

 

The LT4 should be installed with 1.6 rockers. Thats what GM recommends. They even sell a whole kit for $520.
This cam has a whole lot more lift that your cam, so a new chip would probably be in order. Are you still running a stock air intakle system (intake, runners, plenum)?
You may not see much in the way of performance improvements until you get some more air into your engine. YOu should also look at some head work too.


From www.paceparts.com
The LT4 hot cam kit includes the following items: one camshaft GM# 24502586, 16 roller rocker arms kit GM# 12370839, 16 valve springs GM# 12551483, 16 valve caps GM# 10212808, 16 valve keys GM#24503856 and 16 valve spring shims GM# 10212809.


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http://www.havemann.com/lee/firebird.html
1989 Firebird Formula, WS6 Package
ZZ4 Crate engine, Accel 24 pound injectors, Accel Superram intake, Accel Large tube runners
SLP 58 mm throttlebody, Edelbrock TES headers, SLP 3" SS exhaust, Random Tech 3" hi flow cat
700R4 trans w/ vette 2/4 shift servo, worked valve body, kevlar band, 2200 rpm stall converter
Borg Warner 9 bolt rear (full poly mounts) Hotchiss panhard rod, Lakewood LCA's, Spohn subframe connectors,
custom chip, Walbro hi-flow fuel pump, Accell HEI billet distributor.

 

The stock EPROM does not particularly like the LT4 HC. It will run, but it likes to stall when it returns to idle after the throttle is opened at all. I am sure that the stock EPROM also will not give you optimized power, but I never ran mine other than in the garage for a few minutes with the stock EPROM.

As for the idle, it sounds pretty kicka$$ to me . It lopes pretty good . It really likes to idle at about 700rpm. Anything lower than that and it will want to die once in a while when shifting into drive/reverse.

There is nothing wrong with running the LT4 HC with 1.5 rockers, you are just leaving power on the table from not running as much lift as you could be. I am running the Crane rockers that you are talking about on mine. They are very nice, especially for the price that I got them for . No big deal, but they can be a little noisey at times, which is to be expected to some extent with roller rockers.

The only thing to consider when running the LT4 HC with the stock setup is the valvespring/head setup. You will need to be sure to get valve springs that won't coil bind and have the valve guides cut down on the stock heads so the retainer doesn't hit it. I think the valve springs that you will want to run will likely be wider than the stock ones so you will also need to have the valve spring seats on the heads cut bigger to accept oversize valve springs.

You will definately not have to worry about valve to piston interference with that low a$$ stock compression ratio and flat top pistons - even with the 1.6 rockers if you choose to use them.

Feel free to email me if you have any other Q's.... I may or may not have the answer...

Laterzzzzz

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1987 GTA L98 MD8 GH3
355 '97 Vortec 4-bolt block, TRW(suck) forged pistons 10:1 CR, TFS 23*, LT4 Hot Cam, Ported plenum and intake, SLP Siam Runners, Edelbrock TES, gutted Cat, Flowmaster, K+N cone, AFPR, TB bypass, AirFoil, !AIR, !A/C, !EVAP, ARAP, 2300 stall, Hotchkis STB.

[This message has been edited by Matt87GTA (edited July 19, 2001).]

 

tpis sells drop in springs for l98 heads no machining required(haven't put mine in yet)running 1.5's on stock or midly portedheads isn't tthat bad considering the heads have a small cross section creating high velocity to much valve lift on a stock runner will kill velocity and will put out less than normal power.go with the 1.5's on stock heads when you switch to larger heads(tfs,afr,etc.)than go to 1.6's

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87 trans am 350,L98 aluminum heads,LT4 hot cam,slp runners,slp 1 5/8 headers,3in.y-pipe,edelbrock base,hi flo cat,air foil,afpr,as&m ported plenum,t-5 tranny w/centerforce clutch and a 3.27 9bolt(11.9in. brakes),ed wright's fastchip,relocated iat sensor,tb bypass,accel supercoil,hollowed maf,slp 3in. catback,a/c delete.

shooting for 13's!!!!!!!

14.10@97mph w/2.01 60'

slp catback is finally on!!!
fastchip prom is in.OH!MAN!
FLOWMASTER S.U.C.K.S