I'm working on converting my LG4 to TPI and I'm also swapping in an LT1 cam and I was wondering where the power will be and maybe what kind of numbers I'll see. Also I was wondering what RPM range people mean when they say low end, midrange, and high end.

Thanks,
Mark

 

Just a guess here, but the LG4 compression ratio was 9.3, same as the LB9 in 87. The LT1 cam is somewhat similar in specs to the cam they put in the 5 speed cars that year (part#14093643) the ratings should be somewhere around the same as the LB9, 215HP @4400 & 295 Ft. Lbs @3200. Of course that would be providing your heads are 081 castings or flow as well as them.

 

the cr might be the same, but the heads are different. LB9 heads or L69(same head) is a cheap cheap upgrade for the LG4. the LG4 heads suck at flow, worse then Lb9's. A good set of ported LB9's would be good, or SR torquers if you wana spring the money for them. You should be at around 200 with your config right there. TPI has a low to mid range band. most power is made from 1k to about 4k. TPI is infamous for killing top end power. Id stick with carb if i were you unless your hell bent on EFI. If thats the case, id go with something with more flow. Also, what is most important is what do you want out of this car? Since your building a 305, i can assume not that much, Just a nice street car with some power. LT1 cam is more for high mid range power as that is what the LT1 engine design is made for. GM realized TPI's total lack of upper range power, and went with a short runner intake. The cam reflects its power range. LT1 cams are good for carb apps because carbs can make power anywhere, the intake and carb just needs to be set right where TPI kind of limits you. good luck with the car.
Alex

 

well right now I'm just looking for a nice street vehicle so I'm not worried about the TPI not breathing above 4500 or wherever it stops since I won't be hitting that alot if at all. Thanks for the help!

Mark
P.S. Just out of curiosity what is the flow rate of the LG4 heads?

 

between sucks and a$$, but i dont have the EXACT numbers for ya...

 

Hey I ran my setup through desktop dyno 2000 and it says that I would be putting out 278hp@5500 and 312tq@4000. I was wondering if these are really far off or what.

305 LG4 converted to TPI
stock except LT1 cam and LT1 rockers

This is with the cam advanced 4 degrees.

I would think this is a little much out of a practically stock car. Is the stock cam really that much of a hold back that I could get these numbers just from the TPI/cam swap? Do I have something wrong or what? I'm not entirely sure what I actually have so I'm kinda sketchy on some variables so any help would be nice.

Thanks,
Mark

 

Alll that I have to say is DD2000 is way off with that!
All stock TPI set ups peak at 4400-4500 in the HP department, no higher! and in the area of around 3500 in TQ reguardless of the engine combo that it is being used on.

 

Ok I found out I had some numbers on the cam way off so after correcting them it gave me 249hp@4000 and 351tq@3000 that is with the cam retarded 4 degrees. This sound more possible or is it still way off on the numbers?

 

torque could be lower then 3k, but i dunno, with the cam, things could change... im gunna see what my engine would do with the mods i wana do with it... i never tested it out... humm. brb.

 

if you put in real flow numbers for your heads and not the default head flow #'s it will make a difference. Also what are the spec's your putting in for the lt1 cam? After putting in the numbers for my stock motor i'm getting 229 hp at 3500 and 4000 and 383 ft/lbs at 2000 (370 at 3000). Also is that with headers or not?

 

I don't know the flow numbers for the heads. The specs for the LT1 cam I found for '95 are:

lift int/ext:
0.450/0.460

Duration int/ext:
202.0/207.0

labeled it as a street/economy
and roller lifter

Mark