I'm looking to install the stock LT4 cam(203/210 duration, 476/480 lift w/1.6 rockers) into a 305 TBI with vortec heads.

I was told by a rep at a speed shop that the stock LT4 cam can't be used without 1.6 rockers.

I was under the impression the 1.6 rockers would only effect the inches of lift so why can't they work with the 1.5 ratio or is this guy talking thru his *** ?

Thanks for any help.

 

If Im not mistaken, that guy is an idiot.

 

I installed a stock Lt4(not lt4 hot cam) cam in my car in july and have run it with stock 1.5 rockers for the last 3k miles and havnt had a problem.But a guy named Brian at Scoggin Dickey told me that running it with a 1.6 rocker would net a 20 hp gain.The Lt4 cam has a .476 intake .480 exhaust lift with a 1.6 rocker but with a 1.5 it would be .446 and .450.I didnt feel or gain any power with the new cam.I am switching to a set of 1.6 stock stamped rockers made by Federal Mogal for $75 next week and going back to the track to find the diff.I will post the gain they make when i get back friday night.If you are interested in gettin the rockers you can call SDPC at 1-800-456-0211 i am getting them at a local Speed shop i worked at for the last year but recently move to another job so i still get a good deal on all parts.You would probly pay around $80 to $90 for them but would see a diff from the 1.5.

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88 GTA L98 73k miles
Flowmaster catback,Random tech cat,Ported And Gasket matched Plentum,Base and Runners,Hypertech afpr and air foil,Cold air induction,Msd Blaster ss coil,Cap,Rotor and Super Conductor wires.Just installed LT4 cam.

 

Chad i just saw that you were in Garland.Give Speedtek a call at 214-328-9191 and ask for Josh and he will know what rockers you are talking about.He is my brother and would be glad to help you out.If you dont allready have the cam you could also get it from them just ask for a price on it.

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88 GTA L98 73k miles
Flowmaster catback,Random tech cat,Ported And Gasket matched Plentum,Base and Runners,Hypertech afpr and air foil,Cold air induction,Msd Blaster ss coil,Cap,Rotor and Super Conductor wires.Just installed LT4 cam.

 

Yep, he's talking thru his butt. You can run any cam with 1.5 or 1.6 rockers. You just have to make sure the valve springs can handle it.

Also keep in mind the LT4 cam and LT4 HOT cam lifts are given with 1.6 rockers. With 1.5 rockers the lift is lower, like said above.

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1991 Camaro Z28
5.7L 5-Speed (originally 305)
317 RWHP, 418 RWTQ
13.23 @ 107.62 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Member: SoCal F-Bodies
-=ICON Motorsports=-

 

Exactly. That guy is talkin-out-his-****... hehe. On top of checking out the valve springs; you also will want to make sure the slots in the heads where the pushrods go through is big enough to avoid having the pushrod contact the head. Also check out the valve guide bores of the head and make sure the bottom of the retainer doesn't come in contact with the valve guide 'tower'. The higher ratio rockers may also require the use of a longer pushrod to keep the geometry of the valvetrain correct.

All in all, you will likely be fine on the castings of the head (the pushrod slots and the guide towers) with the lift numbers that you are talking about running, but keep these things in mind if you go any bigger in the future..... I would still give the geometry a check as improper rocker geometry will wear the valve guides, valve stems, and the rockers themselves out prematurely....

Good Luck
Laterzzzzzzz

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1987 GTA L98 MD8
355, TFS Heads, LT4 Hot Cam
My GTA

The Minnesota F-body Club

 

I believe a LT4 cam with 1.6 rockers has .525 lift. You quoted the 1.5 rocker lift.
Any good performance Chevy dealer should be able to verify this.
Craig

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84 Z28 305HO, 5spd, 222,000 miles, Edelbrock intake, Hedman headers, low restriction exh(w/cat), K&N air filter, 14.630 at 93.17mph
Del-A-lum front control arm bushings, Moog ball-joints, Energy suspension front sway bar end links, Moog rear sway bar end links, Eibach pro-kit springs, tokico shocks/struts, AU secondary rods
www.indycamaro.com

 

The LT4 HOT Cam has .525" lift with the 1.6 rockers. If you use the stock 1.5s, its only .492", or .498" if you have 1.52s like I do. I agree with what Kevin said, the only restriction you have with rockers is if you run too high a ratio and the valve springs can't handle it. But do yourself a favor and install new springs, retainers and seals with ANY new cam you put in.

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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission
Borg Warner 7.75" 9 Bolt Rear End with 2.77:1 Gears.

Current Mods: LT4 HOT Cam, Comp Cams 1.52:1 Roller Rocker Arms, Accel High Flow TPI Baseplate, Edelbrock TES 1 5/8" Headers, Catco 3" High-Flow Catalytic Converter, Hooker 3" Aerochamber Cat-Back System, Transgo Shift Kit, Performance Resource Chip, Accel Ignition, K&N Filters, Jet TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET: 14.32 @ 97.7mph
(corrected for elevation)

 

Also,if you go over .470 lift on the vortec heads you'll need to trim the valve guides down so the retainers don't hit them. Buy a matching pair of valve springs with the cam you get.
Craig

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84 Z28 305HO, 5spd, 222,000 miles, Edelbrock intake, Hedman headers, low restriction exh(w/cat), K&N air filter, 14.630 at 93.17mph
Del-A-lum front control arm bushings, Moog ball-joints, Energy suspension front sway bar end links, Moog rear sway bar end links, Eibach pro-kit springs, tokico shocks/struts, AU secondary rods
www.indycamaro.com

 

I have the LT4 cam in my LO3 at the present with the stock 1.5 rockers and no problems. The Vortec heads that I had 1.6 Crane gold's on had to have the pushrod slots ground more towards the rocker stud for proper clearance. I also used .050 offset keepers and .050 shims to get the proper clearance for the .480 lift on the Vortec's

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91 RS 5.0 TBI....LT4 cam....Edelbrock headers....3"Dynomax exhaust....5spd.... 3.08.....Ultimate tbi....afpr...ZR 255-50's...Koni's

 

I could get you a stock Lt1 cam that came out of a friends 96T/A for like 30 bucks.I am not sure on the lift of it mabey someone will post it for me.

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88 GTA L98 73k miles
Flowmaster catback,Random tech cat,Ported And Gasket matched Plentum,Base and Runners,Hypertech afpr and air foil,Cold air induction,Msd Blaster ss coil,Cap,Rotor and Super Conductor wires.Just installed LT4 cam.

 

Thanks for your help guys.

SpankuGta, I might get back with you about the LT1 cam.