Anyone run 1.7 rockers on a ht383/ramjet cam?

[Awest623]

So the AFR heads I'm getting require non-self aligning rocker arms. Since I already have to replace them, I'm thinking of going with 1.7 ratio scorpions for more lift (I have 1.6 ratio on the stock heads rn). Would raise me from .450/.481 to .488/.511. Just a little worried about how far it could move the peak tq/hp. Thoughts?

Heads: AFR 190cc vortec

Cam: Chevrolet Performance Hydraulic Roller Camshafts 14097395

Duration at 050 inch Lift:196 int./206 exh

Advertised Duration:288 int./308 exh.

Valve Lift with Factory (1.5) Rocker Arm Ratio:0.431 int./0.451 exh.

Lobe Separation (degrees):109

~Alex

 

[Hipster]

Peak tq and hp should stay about the same. There are some arguments that rocker ratios affect duration but it's a miniscule amount. If you want the best performance degree the cam in at the correct centerline as timing chain mark can be off/tolerance stack up.

AFR makes some nice pieces and I have dealt with them in the past. 1.7's are going to move the pushrod closer to the head so call them or check for clearance when you get them. Sometimes you're better off calling and getting exactly what you need (Ie: the correct springs) directly instead of getting a generic AFR head in a box from a catalog. 1.7's increase the rate of lift over a 1.5 so make sure there is enough spring on there. Just because the catalog say good to .550 doesn't mean there is enough spring rate.

I don't care for needle bearing trunnion or aluminum rockers on a street vehicle that's going to see 100k miles.

 

[Madscientist]

You can run 1.7 but what Hipster said is all true and im going to to say that sometimes its every hard to get that sweet spot of the roller tip centered on the valve tip and it can put excess wear on the valve guides. i say upgrade you cam and run the reccomend rocker ratio.

 

[Awest623]

Disregard. I've decided to stick with the oem vortec heads for now.

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[Awest623]

Peak tq and hp should stay about the same. There are some arguments that rocker ratios affect duration but it's a miniscule amount. If you want the best performance degree the cam in at the correct centerline as timing chain mark can be off/tolerance stack up.

AFR makes some nice pieces and I have dealt with them in the past. 1.7's are going to move the pushrod closer to the head so call them or check for clearance when you get them. Sometimes you're better off calling and getting exactly what you need (Ie: the correct springs) directly instead of getting a generic AFR head in a box from a catalog. 1.7's increase the rate of lift over a 1.5 so make sure there is enough spring on there. Just because the catalog say good to .550 doesn't mean there is enough spring rate.

I don't care for needle bearing trunnion or aluminum rockers on a street vehicle that's going to see 100k miles.

I appreciate the info. I've decided to just stick with the 1.6s and oem vortec heads I have. I don't think the power increase justifies the $3000 it'll cost to swap to AFR heads. I'll definitely run them if I ever swap to a 383 but for now I just don't see the reward. My blower should add plenty of power without them.

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[Awest623]

You can run 1.7 but what Hipster said is all true and im going to to say that sometimes its every hard to get that sweet spot of the roller tip centered on the valve tip and it can put excess wear on the valve guides. i say upgrade you cam and run the reccomend rocker ratio.

Decided against the afr heads so won't be running 1.7, see above posts.

I already have the cam running on 1.6 stamped rockers on the factory heads and honestly I like how it runs.

I understand how yall feel about roller rockers. I have stamped 1.6s now, probably not gonna change them out.

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[Madscientist]

Decided against the afr heads so won't be running 1.7, see above posts.

I already have the cam running on 1.6 stamped rockers on the factory heads and honestly I like how it runs.

I understand how yall feel about roller rockers. I have stamped 1.6s now, probably not gonna change them out.

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Ive got nothing against roller rockers. I run them in alot of my engines and builds. You need to have them matched for the cam and the heads and then check for proper pushrod length. a factory 1.5 stamped steel to a 1.6 full roller is good for about 10hp. A bump to 1.7 is only good for another 2-5hp. That ive personally seen on the dyno. The multplided pressure is taking more hp than the added lift and duration.