I have an '86 305 TPI that needs some work. Its burning coolant and blowing it out the exhaust. I'm not sure at this point what the problem is, but I'm pretty sure its a head gasket or warped/cracked head. Either way, I'm in the process of tearing the motor down to find the problem so I was thinking of taking the opportunity to maybe make some improvements while I'm in there Does anybody know of any cheap and/or easy mods I can do for a bit of a performance boost while I've got the intake and heads off? I'd prefer to mod for torque and stay away from anything that would require ECM changes or anything deeper into the motor than the heads or intake (I didn't take the motor out to tear it down and I'm not sure if I'd be able to get at the cam easily from this point so I'll probably stay away from that).

Also, when I pulled the fuel rail and injectors off, I noticed that the rubber or plastic caps on tips of the injectors were cracked, dirty, or missing altogether. Can those be purchased and replaced separately, and if so, what are they called? I can't find anything like that in a parts listing anywhere (rock auto, autozone, etc...)

Thanks!

 

As far as mods ide say your best bet is to put a cam in it. That will give you a nice bump in hp. Not exactly cheap but not really expensive either. I think that would be your best value. Also maybe the free stuff (port heads, plenium, base ect). Wouldn't get too crazy with it just clean up the castings but you get the idea.

 

Thanks for the ideas. I'll definitely have the heads cleaned up, and depending on what is left in the budget after fixing the coolant leak, I might consider upgrading the cam. Any particular cam you'd recommend?

 

Well what I would recommend and the cam I will be using is comp cams 12-256-4. Its a 50 state street legal cam thats designed specifically for TPI motors to build power in the 1200-5300 range. This would be great for a street car and really complements the TPI intake well. I dont believe the ECM will even need to be retuned although it will be a good idea anyways. It will require new springs and all as the factory ones wont cut it so it starts to add up price wise but considering how small the factory TPI cam was and how much better this one is you will see a very nice gain from this mod even with everything else factory. Although doing exhaust work would help out a lot. Gains from seeing other tests with cams similar on these motors I would expect at the very least 30 hp but not more than 60 hp. I would guess about 40hp to stay on the conservative side. Even earlier 85 305 TPI factory cams allowed these motors to produce 215 (vs your 190 a 25 hp gain just using a factory piece!) and this cam is considerably better than that one. Sorry for the long post i just cannot begin to describe how bad our factory cams are.

 

Thanks for posting that lil peragraph you did there, I got some ideas for a cam now that I would love to go with now, First is that cam street legal for use in california? and that part number is it good on jegs or summit racing? My next upgrade would defenetly be a cam, but never knew which ones to go with and have you done this your ride by any chance?

Thanks. Tony.

 

Well for starters yes as i said it is 50 state legal which means even in California it is fully legal! Now as for if ive done it? No not yet being that flat tappet cams have a tendency to go at roughly 160 k and im alittle over 110k im waiting for it to fail and then will swap to this cam. However I have experimented with engine dyno software and the results seem very promising which the results seem to coincide with other similar cams that have been actually dyno tested. You can tinker around with it yourselves with comp cams cam quest (its a free program so go ahead and give it a try). Now for part numbers the one i listed is comp cams grind number although they are available as a kit with springs and all that through places like summit racing and jegs. Their part numbers will be different but it will still have the 256 number in the actual part number. For example it might be listed as a EX256H or something like that. However comp cams official grind number will most likely be listed in the add for the part (especially online there's usually more info) but if in doubt though you can always call and ask them what is the cam grind number. One thing to consider though this is a hydrolic flat tappet cam as the original poster has an 86 if you have hydrolic rollers valve train this is not the cam i would use. I would use its hydrolic roller equivalent.

 

Excellent info on that cam! That sounds like its exactly what I am looking for. I always wondered about the factory setup too, it amazed me that a person could take a 305 v8, stick fuel injection on it, and only produce 190hp?! ...Anyway, I got the heads off now but didn't see any visible problem with the head gaskets, and I didn't see any cracks or anything upon visible inspection so I'll have to let a shop examine the heads and intake and see what they come up with before I go forward with the project. I'm surprised I didn't see anything because the motor was burning through about a half gallon of coolant on a 40 mile drive...

 

Well yea i mean 190 dosnt sound like a lot but concidering the time TPI was a huge recolutionary intake. At the time when they just put TIP onto already exsisting motors like the crossfire fuel injectioned 350 vett motor and it just blew them away and got better fuel economy!

"The first production TUNED PORT INJECTION (TPI) appeared on General Motors vehicles in 1985. The GM vehicles built with these systems were Corvette, Pontiac Firebird & Trans AM, and the Chevrolet Camaro. These systems according to the manufacturer rendered up to 30 % improvement in Horsepower, torque and economy over carbureted systems, Independent laboratories conducted numerous test on the TPI systems and indicated these claims were conservative and that increases of up to 35% in these three areas are attainable."

http://www.fuelinjection.com/portinj.html

Beyond that TPI is an amazing street intake allowing even 305s with alittle work to produce around 400 foot pounds of torque in the low RPMS and 350s around 500 foot pounds! Thats big block torque from something you could afford to drive every day. Top end hp is not really the greatest even with aftermarket systems allowing them to build power to about 5k on 350s but thats why i say its a great street intake. Concidering how often do you really hit 5k on the streets and the fact 350s can get 500 ftlbs of torque in the low RPMs where you actually do spend 95% or your time its a great set up. Why they only produced 190 from the factory. You can thanks emmissions regulations for that and engineering constraints. The cam was so small to me its amazing that it worked as well as it did. The exhaust is terrable from the factory. The intake is pretty good on a 305 and the heads are OK not great but ok. Swapping the cam and exhaust you will see a big leap in performance. Doing a little port work to the heads and cleaning up the castings on the intake will also help considerably. I figure with the cam posted, some exhaust work, cleaning of the castings on the intake, and maybe even a little head work i dont think it would be unreasonable to expect atleast 250-260 but probably not exceed more 300. I think 280 hp would be a good guess with about 380 torque down around 3000 rpms.

 

Well you have to keep in mind even a pin hole would allow alot of coolent to flow through because the coolent system is under pressure. Also its not just a torn headgasket that can cause a leak things like the intake manifold could be leaking, the bolts that thread into the water jacket could be leaking (which is virtually every head bolt and intake manifold bolt i believe), the block or heads could be cracked. Even if the gasket wasn't torn it can still leak.