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Author Topic:   rocker arm question
Scoot
Dirt Freak

Total posts: 330
posted September 28, 2002 09:29 AM
The cam i've been running was ground to pull 16 lbs of vacuum with 1.5 rockers. Its pulling 15 lbs with roller tipped 1.6 rockers. I'm going to drop down to hobby class where i have to pull the vacuum. Do you guys think stock 1.5 rockers will hold up or should i get some long slot 1.5 rockers? The cam is .520 intake .510 exhaust. I have some long slot 1.6 rockers can someone tell me what difference they would make?

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Scoot
Smith Racing Team
870-365-5989

Scoot
Dirt Freak

Total posts: 330
posted September 29, 2002 09:48 PM
Come on guys help me out.

jammin
Dirt Administrator

Total posts: 5556
posted September 30, 2002 05:56 AM UIN: 16262997
Long Slots are needed Scoot. You are gonna break the saddles out of the bottom of stockers.

jammin

Scoot
Dirt Freak

Total posts: 330
posted September 30, 2002 05:57 AM
Thanks Jammin

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Scoot
Smith Racing Team
870-365-5989

tilley88
Dirt Freak

Total posts: 353
posted September 30, 2002 07:10 AM
Go with long slot rockers. 1.6 rockers will increase your lift by roughly 30 thou.

KPLugnut
Dirt Freak

Total posts: 408
posted September 30, 2002 07:31 AM
Above replies are correct. the difference in vacuum, as you asked, between the 1.6 roller tips and the stamped steel 1.6 long slots will be negligible(sp?). The only variation there will be in the sometimes less than good quality of stamped steel rockers and some of the off brands won't actually come out to a 1.6 ratio exactly.
But Jammin is right, you better not try to use plain OEM rockers with that much lift. You're asking for breakage there. Long slot 1.5's will not only drop down your lift #'s but will most definitely change vacuum readings (and performance) too.
Try to see if you can get enough vacuum, tho, by running 1.6's on the intake side and 1.5's on the exhaust....(hot tip of the day).

KPLugnut

outlawstock17
Dirt Forum Champ
Total posts: 620
posted September 30, 2002 07:39 AM
hey scoot, here's another trick used by some of the IMCA guys. they will use 1965 289 ford rocker arms. make sure you ask for the "rail less" rocker. they're 1.6:1, made of cast iron and tough as nails. with the spring pressures that some of the IMCA's run, the stamped chevrolet rocker is prone to failure. have you ever seen a pushrod shoved through one? or it split?

the ford rocker will stand up to a lot of abuse and isn't any heavier. they're cheap and nobody sweats it when they have to let them go in a claim.

another better idea from the blue oval guys. i had to throw that in 'cause i'm a ford guy. LOL

Scoot
Dirt Freak

Total posts: 330
posted September 30, 2002 10:28 AM
Thanks for the replies guys, I bought the cam from Charles at Camcraft, it shows valve lift with 1.5 rockers IN .520 EX .510. Should I try the 1.5's to see if it will pull vacuum? If I can't pull vacuum I'll have to stay in super stock, where I'm just not competative. Any tips on how to gain 1 pd of vacuum?

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Scoot
Smith Racing Team
870-365-5989

rico 08
Dirt Freak

Total posts: 372
posted October 01, 2002 11:41 AM
could you send me a pm on where you got the cam?to gain more vac i'd play with the timing a little and see if it helps also if the cam is a solid try more valve clearance

ryan
Dirt Freak

Total posts: 430
posted October 02, 2002 06:07 PM
I was always told any lift over .500 lift required the long slots. My old neighbor fought constantly with his valve train (550 lift) until I told him about that.

Scoot
Dirt Freak

Total posts: 330
posted October 03, 2002 03:18 AM
Thanks guys for all the replies, I changed to long slot 1.6's and gained the vacuum I needed. WATCH OUT HOBBY CLASS CUZ HERE I COME.

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Scoot
Smith Racing Team
870-365-5989

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