usetaboost

iTrader: (1)

I know there's plenty of do's and don'ts on here with the search feat (ure but there's also some unanswered questions I have.

1st, can the carb lg4 be tuned to have equal power to a TPI if exhaust has been upgraded to 2 1/4 manifolds and exhaust?

2nd, can a cam swap be done without swapping springs?

3rd, has anyone here installed lt1 exhaust manifolds on a sbc with any success and what was needed to do it.

My plans for this car is a monte ss trans with d5 converter, performer intake, lt1 manifolds and y pipe from fbody (or 2 1/4 manifolds and y pipe), hooker catback exhaust and test pipe, and step up the cam to maybe something slightly bigger than the HO cam and do the secondary rods and hanger mod. Also planning on building a dual snorkel intake. I may pull the engine to do this since it will make the cam swap easier and clean the motor up and do some gaskets.

Damon

That's not a bad plan, actually. You've obviously done your homework. Let me save you some headache on the exhaust, though. LT1 maifods and their matching y-pipe are not likely to fit. Never tried it personally, but unless they just happen to bolt right in it's not likely worth the hassle. Rarely will G-body and F-body exhaust components interchange without pipes hitting against body or frame parts here and there.

Better solution: Get some shorty headers and a matching 3" Y-pipe designed to fit your G-body chassis (think Monte Carlo SS of the same year as your Elkie). There are several to choose from. Even a crappy set of headers will outflow any stock manifolds by a lot.

Better cam..... Summit K1102 is what you want, and the price can't be argued with. Half a notch more aggressive than the stock L69 cam and it'll work with stock springs. This is a FLAT TAPPET CAM which will bolt in place of your stock LG4 cam in any 86-down application. If you happen to have the rare 1987 LG4 (centerbolt valve covers, factory roller cam) you will be looking for a factory-style roller cam, not a flat tappet to replace it with. A factory LT1 roller cam would be the obvious and cheap choice in that case. Likewise, it's about half a notch hotter than the original L69 cam, but in a roller variety and it'll still work with factory springs.

A quick note about valve springs..... I know you don't want to change them but you should, even with a very mild cam upgrade. They were marginal for even stock cams of the day. A drop-in set of Comp 981 springs is a cheap upgrade and plenty good for 5500 RPM, even 6000 RPMs. Even cheaper and just about as good is a set of eBay "Z28" springs. Reuse all your stock valvetrain gear with them. A true bolt-in upgrade with either set of springs.

You'll want a better tune in the chip to complement it (think: same year L69 chip) but otherwise you should be good to go. Looks like a well thought-out plan. All together and tuned up sharp and you should have "L69-and-a-half" power from it. Definitely the equal of any stock 5.0 TPI engine and pretty darned close to a stock L98 350 TPI.

usetaboost

iTrader: (1)

Maybe I'd be better off finding a complete monte ss exhaust to put on it. I haven't seen any shorty headers for under 200. The bigger manifolds and y pipe have to be a fairly good improvement over the lg4 stuff that's on there now. I remember I had headers on my tpi camaro and the plugs were a pita to change compared to the manifolds. I don't plan on keeping the AIR setup anyway so that stuff will come out. We don't get emissions tested and there is no where close here that does. I do plan on keeping the ecm setup though. I dismantled the AIR setup on my camaro when I got it and it had no ill effects.

I'm sure there's some gain to be had by cleaning up the ports on the stock manifolds and the exhaust side of the heads.

paul_huryk

LG4 motors all suffer from major exhaust back pressure and heavily retarded timing. If you go G-Body headers, 3" cat, and a good cat back, plus an L69 computer, you should pick up 35+ hp easy. You can also do a few additional bolt-ons for power: underdrive pulleys, electric fan(s), and a good cold air intake (dual snorkel or whatever).

Cam - if you go that route, you should change the valvesprings whether the cam has enough lift to require it or not. A 1985 SBC will not have a roller cam, which is a cheaper swap over in terms of component cost. Problem is that a non roller cam won't have enough lift to really add a huge HP increase with the stock heads,

usetaboost

iTrader: (1)

So it's not worth putting a cam in a 305 is what you are saying? Will an 87 monte ss computer work in my 85? What is everyone setting timing and plug gap on the lg4? I did stock plugs and gap and only bumped the timing up 2*

usetaboost

iTrader: (1)

Went to the junkyard today and got 2 air cleaners, one off a 80s truck and the other off a tbi motor and got 2 snorkels off a 80s truck. I'm going to try to use the tbi base since it appears to have less restrictions inside.

five7kid

iTrader: (14)

The cam swap is worth it, but only after you address the other restrictions. The dual snorkel air cleaner is a good start.

I'd say forget any factory exhaust parts. Get aftermarket headers and a cat back made for the chassis.

Bump timing in 2 degree increments until performance falls off, or you get pinging.

usetaboost

iTrader: (1)

I still got that idle/off idle stumble when gets warm also. Still gotta try to figure that out, any suggestions?

I'd like to get this fixed before I make AV adjustments.

usetaboost

iTrader: (1)

Probably gonna buy new stainless for my GN and take the hooker kit off and put it on the el camino. I got a test pipe to that goes with it also so I just really need to find headers and Y for it the elky.

usetaboost

iTrader: (1)

Got the dual snorkel setup finished. A little tight but it works. Excuse the crustiness, I didn't paint it since the engine is still a bit dirty and has a few small leaks. It actually turns a tire over from a dead stop now. Not bad for a 30 dollar investment. I kept the taller top from the truck filter housing and the new air filter that was inside in case I ever get a cowl hood.