88'camaro305TBI

iTrader: (2)

I will be running this cam with L31 vortec heads upgraded for better springs and machined for higher lift by SDPC. Is this cam rated with 1.5 rockers or 1.6? Which rockers should I go with?
btw this is for a 305 w/ 670 holley carb.

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Pat Hirsz
www.iit.edu/~hirspat/MyPage2.htm
88 305TBI
Mods:Hooker Aerochamber 3" exhaust, no cat,SLP 1 5/8" headers and y-pipe March pullies, no smog, 180 thermo,
14x4 K&N, 3.42 gears(open), Ultimate TBI Mods,AFPR,MSD(ignition,coil&wires),Edelbrock TBI Manifold, 190ltr/hr fuel pump,
Eibach springs with KYB's all around,
Harwood cowl hood, Z-28 wing, fresh paint(black)
120,000 miles, 5spd, T-tops
0-60mph-7.2s-Gteched

92 RS, 305TBI, auto, 3.08 gears, 180 thermo, glasspack (no muffler)

jcb999

i would stick with the 1.5s on a 305. especially with stock gears. you will probably need some self aligning one.


I miss the 3.42 gears in the 89sig. I thought we were talking the 92 with 308s. 1.6s probably would not be bad for a 3.42, its just that 305s arn't really rpm motors.

[This message has been edited by jcb999 (edited July 31, 2001).]

RB83L69

Cam specs are for 1.5 rockers.

I see no reason not to use 1.6 rockers, as long as the springs and the heads can support the added lift. They will give increased breathing at higher RPM, which will move the peak torque to a higher value at a higher RPM without sacrificing any low RPM performance. This is especially true if you use good valves, with undercut stems, which provide a significant flow improvement. I don't think the ones SDPC puts in those heads at the bargain-basement price are that kind though.

I just put the L69 back in my 83 so that I could get it through CA emissions. I used a set of 186 "double-hump" heads with port and other work including 1.45" diameter springs, Comp 1.6 roller-tip rockers, and a XM264HR cam, the marine version. So far I'm pretty happy with it; it only has about 200 miles on it though. It did make it through smog at about 8 miles (one trip around the block, then off to the smog *****!)

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"So many Mustangs, so little time..."
ICON Motorsports

Guest

RB, why didnt you tell me? You didnt need to go and replace the engine to pass smog around here. I sure hope you had another good reason for pulling it.

RB83L69

Yup, that was about the only reason... although I must say, the gas mileage from this motor so far is fantastic, it gets almost the same around town as my 400 did on the highway (17-18), and it's still not broken in yet. I know of no particular tricks to fool the CA smog **** wehrmacht so i just did the easiest & most obvious thing. It only took a weekend to do the swap, since it's not exactly a major ordeal or anything to change the motor in one of these cars. The toughest part was finding all the pieces of the L69 after it not having been in the car for 10 years, and then moving across the country.

What else did you have in mind?

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"So many Mustangs, so little time..."
ICON Motorsports

88'camaro305TBI

iTrader: (2)

Thanks Guys, i will get the 1.5 non-self aligning rockers then (will have guide plates) so that i can still be able to use the stock valve covers.

RB83L69

Stock valve covers do not necessarily interfere with 1.6 rockers any more than they interfere with 1.5s. That depends on the design of the rockers, not their ratio. 1.6 rockers are actually smaller (shorter) than 1.5s.

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"So many Mustangs, so little time..."
ICON Motorsports

88'camaro305TBI

iTrader: (2)

The cam has pretty high lift numbers already with the 1.5rockers (.487,.495). Will going to 1.6 rockers decrease gas milage?(not much of a concern, but i think this will be my final decision factor). And i don't know if i should be concerned about valve to piston clearance with the 1.6's or any other clearance problems? Thanks.

RB83L69

They don't affect gas mileage. There are no piston-to-valve clearance issues. The only real issue is the heads: the valve guide to retainer interference possibility, and the valve springs. As long as both of those are in order, then there's no reason not to go with the higher ratio.

I have them on the XM264HR in my "new" 305 with some significantly ported 186 heads on it, seems to wind up just fine... it takes about half as much time to get from 4000 to 6000 RPM as it does to get from 2500 to 4000; if I stand on it in 3rd, it pushes me farther and farther back in the seat the whole time. Being a new short block and all, I'm not really beating on it, but so far, I can assure you it's nothing like a stock 305. I suspect yours will be much the same: with all that flow, it will benefit from all the valve opening you can give it.

Think of it this way — does it make sense to put heads that flow like a fire hose, and then at the end of that nice huge open port, just barely crack the valve? Of course not. Open it as far as you can. It makes no more sense to design a motor like that than it would to take drinking-straw-sized ports and put fire-hose valves and valve action together with them.

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"So many Mustangs, so little time..."
ICON Motorsports

88'camaro305TBI

iTrader: (2)

I appreciate all your help RB83L69, I would like to go with 1.6 non self-aligning rockers. After looking into the archives, I found that i would have to change my pushrods to hardened pushrods because i would be running them with guideplates. Is this correct?

RB83L69

That is correct, the regular stock ones would not be wise to use... the ones that Comp specs to go with that cam, part # 7809 IIRC, should be fine... they're about $35 or $40 from Summit... in fact, I have a set of them laying around that I didn't use, if you want them, e-mail me

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"So many Mustangs, so little time..."
ICON Motorsports