Ok with gas almost $2.00 a gallon I am looking at trying to get 20 miles per gallon on the highway with what I am driving. Shouldn't be too hard should it. The current overcammed carbed 350 gets 15 and my stock carbed 305 would get 17. I am looking at building my stock 305 since my 350 has developed a slight knock. Apparently broke a piston. I have the originol 305 HO sitting in my garage. I am rebuilding the shortblock. That means .030" overbored, new crank (spun a bearing on the old one), hotanked, new bearings(including cam), to mention a few. I am reusing the 601 ho heads on it. I have a brand new 350 tbi cam that I am planning on using. The headers I am going to use are on the engine now. I am using the hypertech powercharger from my 355 TBI build, as well as the worked TBI, reworked stock regulator (made it adjustable), a set of 305 injectors, and a 747 ecm. It is going to be easier to work with the 747 ecm since I have been unable to find anything for the current 1992 van ecm. I also am going to drop the transmission pan (rebuilt late model 700r4 from TPI camaro)and find out what he did to make it lock up without the computer and switch it back to computer controlled with a manual overide for towing. (Am only going to use it in 3rd gear while towing to lock the converter to keep the heat down since it is a 2,200 stall). Sound like a workable plan? I am going for about 330 ft/lbs @ 2,500 and 240 HP @ 4,000 and good gas mileage.

Oh I am also going with a painless harness to get rid of my cut and spliced togather 1992 chevy van one.

 

Id personally skip rebuilding the 305 and see what you can salvage from the 350. To me, the ideal HD/towing motor would be:

383
short duration cam with a moderatly aggressive profile
dished pistons with smaller CC (CR permitting)
good flowing heads with runners on the smaller side like vortecs
and of course all the other stuff like a good dual plane and free flowing exuast.

This is jsut my opinion, but to me the idea is to get lots of torque in a low rpm band where you can actually use it. It should be efficient there and be able to move heaven and earth without burning a hole in your pocket. I dont think your trans and rear end will like you for it, but it should do a good job towing the boat...

As for the lockup, you can run a switch to ground in parallel with the ecm or set the manditory lockup speed to whatever you like. Basically, the ecm grounds the TCC solenoid to induce lockup.

 

I am only going to tow on occasion so I am not worried about being down on torque. I certainly don't need a 383 for what I am doing. What I tow and where can easily be handled by the 305 TBI with power to spare. The 305 ran better than the 350 that is in there now due to the higher powerband and got about 3 mpg better on average. I am using a stock GM 4 bbl cast iorn intake with a TBI adapter on top. Yes it will clear the EGR valve and allows me to keep my stock throttle cable, TV cable, and cruise linkage. I already have a good set of headers and a good flowing dual exhaust with H pipe.

Any tips on where to start as far as the prom? I know that a stock 305 TBI prom would probably run it OK but am looking for some help in that area.

 

This sounds like a good build up, but I wouldn't over look the stock HO cam. It pulls great through the mid range, which will help keep your foot out of the gas, and head off down shifts before they happen. A properly tuned 305 shouldn't have any problems with turning mid 20's on the highway. Alot will depend on the rear gear and tire size your wanting to run. If you can keep the rpm's down that will help alot. The key to the whole shabang will be tuning. Just getting your VE curves right and fine tuning the timing curves should help gas milage tremendously over a carb. Most truck tunes have very little timing and drown the engine in fuel at the first hint of a load. So running as much timing as the engine wants down low and keeping it from dumping a ton of gas in the engine when it goes into PE mode at low rpm's should be a good strategy.

 

after installing headers and 3" exhaust b4 the lt1 cam and performer rpm intake i got 28 mpg driving from va to ga! i was shocked so i checked it again going back to va and verified it with my wifes car we drove the same amount of miles and it was still 28 mpg the way i drive now and with the mods i have am am positive it is nowhere near there!!!

 

This is actually going in my G20 so 20 would actually be doing real good. High teens is more realistic.

When I say HO it is the 170 HP 305 that came stock in the early 80s chevy van. It is practically identical to the camaro HO but makes more torque. The TBI 350 cam is the same cam except the lobe seperation angle is a little wider which should help with the tuning with the TBI's speed density setup.

 

buy a new plastic lightweight bed for it and take off the doors and hood and it should be alot lighter and get you better gas mileage

 

The only bed it has is in the back and it is made of metal, foam, and cloth upholstery. Its a van not a truck. I am actually probably going to swap my 3.08 gears for 3.90s to help off the line acceleration at part throttle around town. Should help my mileage since I will get the same accleration with less pedal pressure. Might sacrifice a couple of MPG on the highway but help my city alot as well as towing.

 

sorry i thought it was a truck...??? ooppsss

 

a 3.42 gear would be a great gear for you to use. We have a 94 350/4l60e van that gets about 20 on the highway with the a/c on. It has 3.42's and has great acceleration

 

Found out that I broke a piston and the rest of the 355 is fine. I am upping the cam a little and going to some dart iorn eagle 200 cc intake heads. I am thinking the 3.90 will almost be a requirement then. This 355 is going to scream or die trying.

 

What happened to mileage?

 

I figure this combo is probably going to get mid teens for mileage which is good enough for me. I got to thinking about how much stronger the 350 feels (even though it was slower)around town and on the highway. I am staying TBI though. Probably a GM 2" with my 65 lb/hr injectors and the fuel pressure up pretty good. I am swapping to a 747 ecm from the one that a 1992 van uses (can't find any info for it, free dataloging stuff, bin files, ecm file, etc.). Won't be bad at all since I have checked the pinouts and they are the same.

I am going with a cam meant for a TPI engine the TPI specialties ZZ9. So prom tuning is going to be a must.

Anyone actually tried this cam in a tbi?

I got to thinking that with the 5,000 miles I drive a year that I would rather have great performance than the couple of MPG better that the 305 HO TBI would give me.