I was just curious as to whether or not installing different ratio rocker arms would be okay for a 305 TPI engine and if it will actually provide an HP increase or not. A buddy of mine mentioned installing 1.6 rocker arms to open the valves a little more to increase power. Is this possible and/or worth it??

 

Is it possible? OF COURSE! Thats the whole point.

Take a camshaft w/ .480I, .510E lift w/ stock 1.5 ratio rockers.

Now replace the 1.5s with 1.6s and now you are running .512I, .544E at the valves.

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Webmaster:SETHIRDGEN
GM Tech
ASE Master Auto Technician + L1
1987 Trans Am: 357ci
Ported TFS heads, ZZ4 cam, headers & exhuast and other go fast goodies
13.53 @ 103.77

 

Yes it's possible!

I used Crane Gold Race Roller Rocker arms n the 1.6 ratio. Make sure you buy the "Self aligning" units made for 3/8" studs because that is what your TPI engine needs. They should run close to $300 out of a Jeg's catalg if I remember correctly. Goodluck!

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Denny Villemure
1989 Camaro IROC-Z Convertible, 305 TPI, 2.73 Gear, Flowmaster 2 chamber. 15.60 on motor, 14.20 on a 75 shot from NX. Woo hoo!
www.denny.cz28.com

 

Denny, was there a noticable difference when you went to the 1.6's? Track times would do fine. I've been thinking about getting a set myself.

Bob

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'88 IROC stock 350 TPI, auto, stock 3.27 gears, headers, Flowmaster exhaust, all the free stuff---best et 13.88 @101.18 mph

 

What exactly will going to 1.6 roller rocker arms do for my car and what kind of performance gains should I expect? Is this safe just to change those? Sorry guys, I'm kinda new with engine components

 

When using extended ratio rocker arms you must still be aware of the rest of the valvetrain. Extended ratio rockers are just a poor mans cam swap. They will increase lift and very slightly increase duration. Depending on what cam is in the engine the extra lift gained must be observed. Valve springs must be changed if the extra lift excedes the original springs lift limits. The bottom of the valve keeper must not hit the top of the valve stem also.

Going from a stamped steel rocker to any kind of roller rocker will see a performance improvement. Going from a 1.5 roller rocker to 1.6 roller rockers you should only see about a 5hp increase.

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Depending on what year your TPI car is determines wether you need self aligns or not, I have done the swap on 86 and 87 TPI cars and they were fine with non-self aligns, my freinds 91 T/A neede the self aligns. Your springs and such will be fine with the stock cam and 1.6s unless they are already tired. The stock lift is just under 400 on the intake and a little over 400 on the exhaust on the early TPI cars. I gained a solid 2 tenths with my 86 and my 87 with onle roller tip rockers of 1.6 persuation.
Perry

 

I should of posted this in my original post. My car is an '87 IROC-Z with the LB9 TPI motor

 

I've heard (from TPIS book - test was on stock '85 vette motor) that 1.6 intake and 1.5 exhst is best...1.6 on exhaust didn't help power and hurt idle quality. Few companies sell a 1.5/1.6 mixed set and they're ususally $250+. has anyone done 8 1.5's and 8 1.6's?? Also, on my '88 305, would 1.6 roller rockers clear the valve covers? How about 1.6 roller tip rockers? I'm thinking of doing this mod and I see that Summit sells a set of 1.6 roller tip steel rockers for $99. Has anyone used the Summit brand? '88 needs the self-aligning rockers, right? Thanks for any help guys.

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Go Lil' Camaro Go
OoOoOoOoOohh!

Ramones-Halfway to Sanity @1987

 

OK, I found that the '88 has self-aligning rockers. Anyone else have any imput?

 

Rocker arm ratios.....Was somebody reading camaro performers this month

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Remember to free up your time around June 22 2003 and bring your Camaros to the Peach City Beach Cruise.(Plenty of classic and muscle will be there lets bring the Camaro contingent). For more information see www.peachcitybeachcruise.com .

1989 Iroc Z28 305 TBI
100% Stock (For Now)