1991 RS 305

The 85 TPI 305's had a fairly good cam from GM. 86 and later, the dreaded "peanut cam" entered the picture, with the result of a 25 hp drop. Anyone know the specs of the 85 TPI cam? I've been told that its literally the same cam as the "L69", which I believe is from the 305 H.O. of the previous year. Anyone know how this cam compares to the "L98" cam used in the later 80's into the 90's on both the 305/350 TPI's. I do know that the "L98" cam IS a roller cam, and the 85 TPI was NOT a roller cam engine. But i'm curious if the lift/duration/etc are similar. Comments?

As a side note, G.M. seemed to go out of their way using many different cam grinds for their small blocks, especially in this period(peanut cam, L69, L98, TBI cams,etc). Seems for both TBI, and TPI engines, one or two of the hotter cam grinds would have worked well across the board, made them ALL perform a bit better against the 'Stangs, and been cheaper to manufacture, needing less part##, inventories, etc, to manufacture. Its usually cheaper and more efficient to commonize parts for mass production. Just a thought.

Drew

iTrader: (58)

From what I have read, the L69, 85 LB9, 87 L98 cams all are the same, the only difference is the 87 is a roller cam.

85transam1

I have a 305 TPI so I would also like to know how good this cam is as compared to the other years.

The Anvil

Drew hit it bang on the money.

All 1986 TPI engines got the peanut cam regardless of manual or auto trans. 1986 was truly a dreadful year for the cam situation, as that was when federal emmissions changes took effect and near as I understand it, GM went conservative with the cam that year so they would have no problems with passing the EPA requirements with the Tuned Port 305 engines. Thankfully, it was a 1 year only deal, and subsequent years saw the cams for the 5-speed TPI and L98 engines get better, with the best cams coming in 1988-89. The auto trans TPI 305's however, were saddled with peanut roller cam for the rest of their days beginning in 1987 and ending in 1992.

Back to 1985, and as Drew pointed out, the L69 cam went into the new for '85 TPI 305 also. Those are pretty good engines in stock form, making good power for back in the day.

Dave

palric

iTrader: (1)

I'll have to double check... but I think the '85 TPI cam was 202/206 @ .050 and .403/415 lift.

The flat tappet L69 HO cam was 203/209 @ .050 and .410/.423 lift.

RP.

1991 RS 305

O.K., so the 85 305 fortunately got a decent cam stock. Now, I, like many people no doubt, am wondering if 1.6 ratio rockers would work well with this cam? Would it require new springs, pushrods, etc? Do they need to be "self-aligning"? Full roller or roller-tip? How 'bout clearing the valve covers? New valve seals? I am not too familiar with this aspect of things, so any comments or input would be appreciated. Thanks in advance.

Guest

The L69 and 85 TPI cams are exactly the same, the specs are not different. The GM PN is the same.

86 L69's dont have a peanut cam.

palric

iTrader: (1)

Well the TPI and the L69 did. Everything else did much poorer. 1.6s will work with any stock 3rd gen cam that I know of. I think '87 and up needed self aligning units. Push rods and springs are cheap I'd go with a new set of either.

my .02 cents worth,
RP.

Jim85IROC

iTrader: (2)

1985 (L69 & LB9)
Duration @ 50: 202/206
Lift (1.5): 403/415
LSA: 114.5
GM Part #14088843

1986 (LB9)
Duration @ 50: 178/194
Lift (1.5): 350/385
LSA: 109.0
GM Part #14094097

1987 (LB9 5-Speed, L98)
Duration @ 50: 202/207
Lift (1.5): 404/415
LSA: 114.5
GM Part #10088155

1988 & 89 (LB9 5 speed, L98)
Duration @ 50: 207/213
Lift (1.5): 415/430
LSA: 117.0
GM Part #10066049

1990 (305 5-speed w/G92 & 350)
Duration @ 50: 202/207
Lift (1.5): 413/428
LSA: 114.5
GM Part #10111773

My buddy replaced the cam in his 86 LB9 TA (*** only knows why), and what did he replace it with? Another stock 86 LB9 cam.

jmd

iTrader: (4)

the L69 (305 H.O) was produced in 83-85, and I thought there were a handful in 1986.



I didn't think there was a 1986 manual TPI 305 combination certified and sold.



They will work fine with it.

Since the 85 LB9 had iron heads, you do not need, nor want to run self-aligning rockers with it's stock heads, pushrods, etc. Seals are always a good idea if you have the heads partially apart like that. Go full roller if you can swing it. There are tonnes of rocker covers to fit the 85 heads w/ clearance for the rockers if the stock ones don't do it.

Wishmaster's87IROC

iTrader: (4)

Did the 87 Auto 305 HO motors come with the so called "peanut cam" The 87 has roller rockers? So it would be a good idea to change the cam in my engine? thanks

Jim85IROC

iTrader: (2)

Yes, the 87 305 autos still had a peanut cam. They used the following cam:

1987 (LB9 Auto)
Duration @ 50: 179/194
Lift (1.5): 350/384
LSA: 109.0
GM Part #14094097

1988-90 (LB9 Auto)
Duration @ 50: 179/194
Lift (1.5): 350/384
LSA: 109.0
GM Part #10088155

I'm not sure what's different about the 88-90 cam, but it's got a different part number. The ramp profile may be different.

Wishmaster's87IROC

iTrader: (4)

Is the 87 TPI 305 and the TPI 305HO the same motor? is so then why did they add the "HO" which I know mean High Output. but why did they refer to this motor as such?
Is it positive that the 87 305HO came with the peanut cam? So putting any other cam better would make a big improvement?


thanks

The Anvil

No the HO is *not* the TPI 305. The HO is the carbed L-69 (High Output), which never got the peanut cam.

Dave

The Anvil

Self-aligning rockers have nothing to do with whether or not the heads are iron or aluminum; rather it has to do with whether or not the engine was originally equipped with a roller-cam or not. Since 1985 still used a flat-tappet cam, in this case no, you do not need the self-aligning rockers.

Just a clarification.

Dave

Wishmaster's87IROC

iTrader: (4)

Well then how come when I pulled my VIn# on Carfax it says HO and also some people that Ive talked say I have an HO motor. ITs a TPI too. Like one guy that used to work at the Chevy place years ago and did some work on my car. He says told me a bunch of reason that I have an HO motor and he used to have an IROC back in the day when they came out. Bought it dirt cheap thru Chevy, cause he was an employer... Ive heard a bunch of people talk about HO and never said that they just came out in "carbed" cars.

Jim85IROC

iTrader: (2)

Because we all know that Carfax is the most accurate resource for thirdgen information.

In a lot of cases, all TPI motors were referred to as "HO" motors, because compared to the LG4s, they were. Officially, the only motor to get the HO designation was the L69.

The Anvil

Jim, you took the words right out of my mouth.

Dave

Guest

Thats not even true. 87's dont have self aligning rockers, but do have a roller cam. The only sure fire way is to look at the head.

Wishmaster's87IROC

iTrader: (4)

Im just rying to figure out which higher/better cam I can use without changing anything esle. I just want to be able to slid the old cam out and put the new cam in....is that possible?

The Anvil

Then what years exactly, came with the self-aligning rockers, and in which applications?

Dave

Guest

Well, supposedly GM used them on anything SBC 88 and newer. Given GM's consistency, I will not call that a hard and fast rule, but there werent any in 87. At least not any from GM. Someone could always have swapped some in later (and stuff like that happens all the time).