I have been doing a lot of reading on the board about the 305 TPI and see that there were a number of different camshafts installed from the factory. Some posts have said that the very mild grind "peanut" cams were not used after 87-88, while others say that every 305 w/ an auto trans came with the L98 cam only after 90. I have an 89 IROC convertible with a 700-R4, is there any way to know what cam I have without pulling it? Already have ignition, headers, runners, sfc's, lca's, and Flowmaster catback. Porting intake, heads, and a new cam are next on the list. Trying to figure out how big a priority the cam upgrade should be (If the L98 is in there I might just let it ride). Any help clarifying is greatly appreciated. If any more info about my car is needed, feel free to ask. Thanks

 

LB9/auto cars did not come with the L98 cam. Maybe back in '85, but that's the only year if it did. Beginning in '90, the LB9/autos had 205hp. Only the RPO (G92) equipped 5-speeds had the L98 cam.

Remember though, there were 5-speeds without the G92 package. These cars had 205hp (after '90) just like the autos.

Since your '89 'vert has the LB9/auto, your car will not have the L98 cam from the factory. You either have the famous "peanut" cam or a similar version of it.

 

Wrongo!! All TPI SD cars got the L98 cam.

RagTop, You have an auto maf 5.0 car which means......peanut cam. Don't worry though, when you're ready for a cam swap you'll get something bigger than an L98 cam anyway.

 

[QUOTE]Originally posted by BigWhiteGTP
[B]Wrongo!! All TPI SD cars got the L98 cam.[B][QUOTE]

NOPE!! Do SOME research.

'90-'92 LB9 autos were rated at 205HP/275TQ. LB9 (G92) 5-speed cars have 230hp/300Tq. That's a 25HP and 25TQ difference between the two engines. If all LB9's had the L98 cam, what would account for the 25hp and 25tq difference between the LB9 auto and LB9 5-speed (G92) cars? Exhaust? Heads? Intake? Memcal chip? Nope, it was just the cam.

The N10 dual-converter option was good for 10hp. However, in '91 all LB9 5-speeds with G92 and all L98's had dual-converter exhaust as standard equipment.

'90-'92: L98 and LB9 5-speeds (G92 only) have 203/207 dur/sep .413/.428 lift @.050" + 115* LSA. Part no. 10111773

'90-'92: LB9 autos and LB9 5-speeds (non G92) have 179/194 dur/sep .350/.384 lift @.050" + 109* LSA. Part no. 10088155.

As you can see, the cams were apparently different. 5.7L TPI's and 5.0L TPI's with the G92 package were the ONLY two engines that came with the L98 cam.

 

Thank you both for helping clear that up for me. As I suspected, it looks like the cam has got to go. I have all winter to research and find a better switch. Probably going to go the LT1 or ZZ4 cam route. Would either or these be a suitable replacement, or should I look for something like a custom grind from comp cams for the best results? I would like to go as aggresive as possible without totally killing my bottom end for daily driving. I'd love to get a little lope in the idle too

 

That info is wrong. There was a dude that pulled his stock cam out of his auto/single cat car, mic'd it and it was in fact an L98 cam. Don't look at hp for cam profile. All SD (90-92) cars got the L98 cam. The reason for the difference in HP was exhaust and manual/auto DT loss.

Auto/single cat cars had the crappy exhaust manifolds, were rated at 205hp.
Manual cars with single cat were rated at 215, with the crappy exhaust manifolds
and Manual cars with N10dual got the L98 exhaust manifolds and so power was boosted to 225.

I also had a '91 auto/Tpi/single cat car put down 187whp. You don't do that with a peanut cam.

 

Interesting. Has anyone else mic'd their '90+ LB9/auto cams to confirm this? If so, this info should definitely be included in the tech section on this site.


Ragtop,

You don't really need to port your intake all that much. The 350 guys do it because the TPI intake is severely mismatched for the larger displacement engine as we all know. I'd do just a general cleanup and port match the transition areas between the plenum/runner/base. Knocking down the EGR walls behind the throttle blades would be a excellent idea as well.

The LTR TPI intake was optimized for the smaller 305. So, I wouldn't monkey with it too much. The aftermarket runners may be a waste of $$$. The stock runners work pretty good on modded 305's, but they do become a restriction on modded 350's.

It seems that you are trying to make up for the apparent loss of low-end torque you'll get with those intake/exhaust mods by getting a more aggressive cam and better flowing heads. The problem is, the 305 is still a small-bore long-stroke engine which, by design, doesn't like to rev all that high. The bore of the 305 is, in fact, smaller than the original 265 V8 that debuted in 1955!

Unfortunately, Chevy 305's are not high winding Ford 302's. With this in mind, I wouldn't go too crazy on the cam profile. If it was me, I'd pass on the custom grind and just get an L98 equivalent cam with 1.6:1 rockers. That way, it'll still be very streetable with lots of low-end torque.

 

Chevy 305's can be as high a winding motor as you put heads and cam to feed it to. RPM is made by the heads and the cam, displacement has little to do with it. - It's a common mis-conseption. A motor is an air pump, if you have large enough heads/cam to feed it to 10k, then it'll turn 10k.

back to topic(sorry) - even the L98 cam is pretty much a peanut cam. There's lots of power to be had w/ a good aftermarket cam. As for the motor/cam size war my L98 had the same exhaust manifolds my 87 lb9 car had. Also same manifolds on the 91z I had...