305tpi and 1.6 roller rockers
#1
305tpi and 1.6 roller rockers
I have a '91 GTA with a 305tpi and roller rockers(among other mods).
I have noticed that my 1/4 mile times have not improved(even got worse) since I have added the roller rockers.
I have a comp cam - grind #xr258
gross valve lift - int.480 - exh..487
dur @ .006 258 264
dur @ .05 206 212
lobe lift .3200 .3250
lope sep .110
I have also added 981-16 stiffer valve springs.
Is there a chance that I have maxed out the air coming into my motor with the 1.6 roller rockers?
Am I trying to put more air into the motor but it can't use it?
Do I need better heads in order to utilize these roller rockers?
I am considering switching back to the stock arms and will post times and differences.
I have noticed that my 1/4 mile times have not improved(even got worse) since I have added the roller rockers.
I have a comp cam - grind #xr258
gross valve lift - int.480 - exh..487
dur @ .006 258 264
dur @ .05 206 212
lobe lift .3200 .3250
lope sep .110
I have also added 981-16 stiffer valve springs.
Is there a chance that I have maxed out the air coming into my motor with the 1.6 roller rockers?
Am I trying to put more air into the motor but it can't use it?
Do I need better heads in order to utilize these roller rockers?
I am considering switching back to the stock arms and will post times and differences.
Last edited by LB9GTA; 07-23-2005 at 12:52 AM.
#3
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Car: 1989 GTA
Engine: 5.0 TPI
Transmission: T-5 WC
Axle/Gears: Yukon 3.73
I have the exact same cam in my new GM 305 engine. First, I would like to say how satisfied I am with this cam for all around performance for my daily driver. I could have gone for a cam with more lift and duration and a rough idle. However, this was a good choice for my use. Second, I asked my mechanic who installed the engine and cam about up grading to 1.6 ratio roller rockers. He advised it would be too much for my application. It may have something to do with the tight lobe separation angle. Plus it would produce a rough idle which I did not want.
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Car: 2008.5 Mazdaspeed 3 GT
Engine: 2.3 DISI Turbo
Transmission: 6 speed MT
Originally posted by LB9GTA
anybody?
anybody?
You're going to want to search for 081 or 416 port and polishing topics. Basically, the 081 and 416 heads are the same ports, just the 416 is the earlier perimiter valve cover version of the same head.
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#8
i think what there tring to say is that there both too big for ur stock heads, with the 1.6 rockers on the stock heads it can not flow more air in then if u had the stock ones back on.basicly ur maxed out on air flow with the 1.5`s, thats why u never seen a gain, u said u have stock heads with the 1.6 rockers? did u get any work done to them for the added lift of that cam? with the 1.6 i would think that u would run into problems with spring bind on the stock heads,hate to see u break some thing cause ur valves are bottoming out. iam also in sask so not far from u
Last edited by billyhoss; 07-24-2005 at 01:39 AM.
#10
i live in prince albert, north of saskatoon, u may gain, u may not, depends on how much they are out flowing with them 1.6`s on, iam goign to guess u will not see a difference, like someone already said if u take the heads off and port and polish them up u should see a gain with the 1.6`s then
#11
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Car: 1991 Camaro RS, 1993 Camaro Z-28
Engine: what engine, LT1
Transmission: did it come with one, 4l60
Axle/Gears: They spin (most of the time)
hey what is up guys. I have a nice set of already ported, polished, bowl hogged, 305 heads. They have a Manley race flo valves, that are swirl polished, stainless steel, and have undercut stems. they have screw in studs and oh yea they run great. they have apprx. 1k miles, since they were built 250 dollars let me know
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