Cascade Crew

[Project_1986_TA]

In August 2002 I had the old siezed 305 taken out of the car and had a longblock 350 with a mild (268*) comp cam put in along with a 180* TS. I had the old 305 TPI setup put back on but with new 21lb Accel Injectors. The shop said the put in new plugs/wires/cap/rotor ect. and balanced the motor. When i got the car back it ran like crap, overheated, and got 7-8MPG. I then had Blood Enterprises (www.bloodenterprises.com) install a custom computer chip wich they did using the dyno and a laptop. It only put down 160.5RWHP and 275.3RWTQ but ran great and hasn't overheated or come close once. Since i have changed a few things such as Fuel filter, air filter, changed the bad muffler, put in a good high flo cat. cuz mine was F'd up, and also the o2 sensor it has picked up a bit of power but still only get 12-13MPG at best city and 20mpg highway. When the car was dyno'd it had a 2.77 posi (posi didnt work) rear that was on its last leg and also the tranny is probably on its last leg (700R4). I have put over 8k miles on it and cant figure out why the milage is so bad and why a mild 350 TPI only put down 160HP and 275TQ to the ground. I talked to Schultzy and he said to check the cap/rotor and plugs/wires wich i will later today. Anyone else have guess of what it could be? Just a bad block?

*It also has an exhaust leak on the passenger side manifold wich 2 shops said its just noise, its not robbing power or sucking any gas.

Any help would be appreciated, thanks!

[Twilightoptics]

I had an exhaust leak on the S10 and when I repaired it it felt a tad quicker.

What heads and what compression is the motor?

IMHO the 268 is too big for stock heads. I ran the 262 cam, which is still in there, and ran 14.0 with a failing tranny, and fouled plugs.

20hwy seems okay. I get 17HWY without overdrive.

If they made a custom chip for you, they should have enabled highway mode, which when you cruise at a steady rate, will lean out your mixture to increase milage.

Find someone that has a laptop and cable, or an autoxray and see what your BLM readings are. If they are under 128, you're always running rich.

As Schultzy said, check your plugs cap rotor and wires.

Pull the plugs, try to make the distiction if they are wet if its fuel or oil. If they are dry and maybe pinkish you should be alright. Look at the cap to see if the terminals on the inside are all corroded. Open your hood at night and see if the wires are arcing (sparks you'll see if they are).

Also, your gear is way too low. It would help for hwy milage, but your engine has to work harder to get to the speed. As for the dyno, a higher gear would give you more power. It's a mechanical advantage.

Think of a bike, you put it on a smaller/higher ratio gear to get up a hill easier. So the motor spins up faster applying that power.

But yes, 160RWHP out of a 350 sucks. But I think that cam is too big for you. What did the Bloodenterprises say about the lack of power?

How in order is your transmission?
Is your Ignition Coil Stock? Do you have small or large cap distributor (small cap coil mounted outside, large cap coil mounted ontop of hte cap)

If its stock, buy an aftermarket coil.

Without diagnosing in person I say that cam is too big, your gear is too numerically small, and your chip might be off.

But do a tuneup first! Check fuel pressure too.

[chevymad]

I dont think that the 268 is too big myself. Its actually the preferred head for stock vortec heads. What year is the 350 and heads? I'm bettin late 70s. Probably has 76 cc chambers and you've only got 8:1 compression or even less. Vortec heads would work sweet but you'd need a new lower intake. You're old 305 heads would work pretty good with larger valves and porting. Or find yourself a set of L98 iron heads, they're not too bad out of hte box(not like vortecs though) and can be ported pretty sweet.

If you have extra cash buy yourself a set of modern heads. AFR or Pro i'd say are tops for small block. But I'm not sure how easy it will be to get Protopline heads right now, they seem to be out of business. Rumor is its only temporary but we'll see. Dart makes a good head too, but to equal the others you'll need porting again. Nice thing with darts is theres lots of meat so you dont have to worry so much bout grinding through.

What pistons are in the shortblock? flat tops, dished, 4 valve releif, d-dish, 2 relief? That will also make a huge difference in your power. The pistons will also determine just what size head you'll need to get. The 268 cam is probably just big enough that without good compression you'll actually be lowering your horsepower. As Paul was leading to if you have 8:1 compression that cam will bleed off even more and be a dog. A 262 or 256 will gain more dynamic compression on a motor with a low static compression ratio.

[Project_1986_TA]

I wish i new more specs on the motor but i dont. The shop said they were putting in a rebuilt 350 longblock (87 and up block for TPI base but never said wich year) and put in a 4bolt main as i requested. Dont know what heads or pistons i have but the cam is for a 350 with modified computer wich i did after the engine swap. I did forget to mention but is in my sig that i have a new GM 10bolt rear with 3.73 gears and an eaton posi.
I didn't have time to check the plugs, wires, cap or rotor and probably wont have time this week.
The tranny is slipping a bit and seems to go into nuetral before shifting when its cold. When its warmed up it just slips a little. It doesn't have a good firm shift, just kinda sloppy. The fluid and levels are fine.
I have a laptop but none of the programs to use for my car. When Blood Enterprises did the chip it was running way lean so they richend it out and now it is suposedly fine.

[Twilightoptics]

With that cam you should have gotten more lean, and then they would add fuel to compensate.

Even with OD 3.73 are tall gears for the back if you are concerned about milage.

If it is indeed an '87 + longblock you have an L98. 9.3:1 compression. Which should put down 200+ stock with TPI. Try a set of headers and exhaust next and see what your HP would do.

AS for milage, now that you say you have those gears, you're probably close to what youre going to get. Th700R4 take ~80HP to drive, TH350 take ~40hp to drive.

I think L98s got like 22HWY, 17in town

[Project_1986_TA]

with the 2.77 rear i still got the same milage city. I do have a Magnaflow muffler and 3'' high flow cat but do need some headers and will get some as soon as i get a job.
Were all 87 and up blocks L98's?

[Twilightoptics]

Did you buy the camshaft? If so you'll know if its a roller cam or flat tappet cam.

If its a roller cam, you should have an l98 block because it was set for TPI

If its a flat tappet cam, you might have gotten a truck block.

[Project_1986_TA]

Not sure, he just said he was putting in a 268* comp cam. For the next build up im doing everything myself so i know exactly what is going in and what parts are the best to go together. Im never going to have just some shop do anything such as this again. Thanks for the help, i'll keep you guys posted if i find anything or not.