I came across this on another web site............ All 305 TPI (LB9) engines (1985-1992) came with one of two basic cam grind profiles. An easy way to identify the type of cam on an LB9 car is to look at the tach: the lesser cams have a yellow line at 4500 and red line at 5000; the hotter cams have a yellow line at 5000 and red line at 5500. All camshafts 1987 and later use hydraulic roller lifters.


So I ran out to look and sure enough my 85 ta
red lines at 6000 yellow at 5500?????
with all due respect MR. Vader is this atypo
or do i have something rare? I've never driven another 3rd gen.but mine seems to have
tons of toqure.Fun to drive.love this forum.

THANKS

 

That is odd. Sounds like you have a V6 tach, someone must have swapped it at some point.

About the tach and how it relates to the cam... there isn't a direct correlation. It seems that you could get a car with the better cam profile (any 90-92 305 TPI would have it), but the lower RPM tach and 120 MPH speedometer. Mine is this way.

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91 Trans Am WS6
Bright White
5.0 TPI auto
Flowmaster 3" 2 chamber catback
Trans Go shiftkit
2000 stall converter

Built on Wednesday

 

Actually....thats a terrible way to determine the cam.

As for your TA, is it TPI? I know for a FACT the 85 TA's with TPI had a 6000 RPM redline on the tach. My 86 is redlined at 5500, but Vaders car, which has the same engine, is 5000. GM is not consistent at all. The tach has nothing to do with the cam obviously.

BTW, if its a real 85 TA with TPI then it has a pretty good cam stock.

 

Max,

Actually, your cam profile is better than mine (wanna swap for your '85 grind?) The "LA" (LameAss) cam didn't exist until 1986 (thanks a HEAP, GM). My cam MEASURES at .356"/.388" net lift - a few thousandths BETTER than the listed specs for a "LA" camshaft of .350"/.385". Maybe my indicators are screwed, but I doubt that three of them are all bad in the same direction. This just proves the variability of the mass production process.

The '85 305s got the specified .404"/.415" profile, like the later 305 manuals and L98s. Even though the later engines used roller lifters, the basic net profile was the same.

DirtBall is mostly correct - there were two basic cam grinds - with a couple exceptions. The relatively rare 1987 LM1 (SEO/Police package) had a profile that was between the L98 and the "LA" cam - .383"/.404".

Chevy went back to the two basic profiles in 1988, but the displacement didn't necessarily determine the cam profile. While all 350s (L98s) got the better cam, 305s got either one depending on options and marketing packages. Most 305s got the "LA" cam, both automatic and manual transmissions, but the cars with the G92 opition got the L98 cam.

And you're right - the tach yellow/red line method is generally a good indicator, but is not 100% accurate.

I have a listing of five different part numbers for 1986-1992 TPI ThirdGen engines, and they are all correct numbers. I don't have the number for the 1985 TPI, but I do have the specifications.

10088155/Flat;
10088155/Roller;
14093643;
14093640;
10066049;
10111773.

Check out the numbers and their applications - you'll be surprised...

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Later,
Vader
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"Make Me Bad..."
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[This message has been edited by Vader (edited February 04, 2001).]

 

I think you got a signal crossed

I had an 85 before, it had the good cam in it of course.
I pulled the LA cam from my 86 a long time ago. It spec'd out at the LA specs. The date on the back of my gauge cluster has the correct date on it for the car, and it does not appear to be tampered with. But its yellow at 5000, red at 5500. It reads to 8000. My 85 was yellow at 5500, red at 6000, and read to 8000 as well. I know yours reads only to 6000 from a pic you posted a while back. I dont think GM knows what they are doing.

As for an 85 cam, I had one. My friend, who also had an 85, pulled it in 1986 and in 1992 he gave it to me. It had some rust on it, and was a little worn. I took it in for a regrind, and I specifically told them what cam it was and even the specs. I got it back, and they had turned a good cam into a LA. So, if you want my 85 cam, you can have it.

 

My 84 L69 car has a 6000 rpm redline.

 

Max,

Yup, I were purty confuzed!

Too bad about your regrind, but thanks anyway. There's a little place in Tennesee that gets most of my replacement cam traffic.

The tach thing is really screwy. I've read elsewhere that the way to determine the cam profile is the tach yellow/red ranges, but have found out since (like you have) that this is not always reliable. Usually it is, but all those leftover parts in the hands of auto assemblers can yield almost anything in the finished product.

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Later,
Vader
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"I know how to solve your problem, but I can't tell
you since you might use the information illegally..."
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