How much of a bore is safe on a 305? The shop who rebuilt mine has it bored 60 oversized. I figured the engine was never rebuilt before so I thought 30 over would be fine. After the rebuild they inform me that it was already 30 over so they took it to 60. They assure me it will be fine, but anything over that will be too dangerous. What is this big bore going to do to my little 305? It's still under warranty and is only 6 months old. I really feel they got me into something bad here. And also not to mention the cam they put in- lift: .442/.465, Duration @.05: 211/221, Separation: 110. I'm not a cam doctor, but this seems a little big for a 305 with stock 305 heads. Any suggestions as to what they have gotten me into would be highly appreciated, thanks.

 

.060" over is fine as long as they checked the wall thickness before hand (which they probably did).

.060" is the most your average guy goes over for longetivity reasons.

As far as the cam, it does seem like a bit much. A smaller cam would help out more with low-mid RPM torque, which the 305 has very little of anyway.

Do you have it running?

 

Less is more here. If all it needs is .030" over, just do that.

 

if it was only 6 months old and under warrenty why did you rebild it or do anything to it? it sure isn't under warrenty now.

 

.060" on a 305 is pretty much the limit; I wouldn't like to take one that far. If I had one of those and the shop told me it had to go that far, I'd find another block; I bet I woulnd't even have to pay for it, but could find somebody willing to pay me to haul one off. But if it's already there and didn't hit water or anything, then it's probably OK.

The cam seems a bit large, but not excessive or anything. In a stick car with 3.73 gears it would probably be a blast. How does the car run? Do you like it? If you do, then it's probably OK. If you feel like it has no nads whatsoever until it hits 4000 RPM, and you fuel economy is measured in gallons per mile instead of the other way around, then it's too much.

 

I think you misunderstood. I took it in to be rebuilt, and THEY bored it .060 over. It is still under warranty, in fact it's at the shop right now having an oil leak looked at.

 

It seems to drive fine. I'm getting around 20ish miles a gallon. As for the nads, I can't really find them. I have an auto in it, and it does not go over about 4000-4200 when WOT. It does like to pick up it's pep later in the RPMs. In fact one of the plugs, #3 to be exact, is collecting oil and carbon. So I'm guessing that injector might be screwed. I'm thinking of just ditching this whole setup altogether and putting a 396 in. I have a post in the Motor Swap board if you're interested in checking it out.

 

Oh...

Based on the fact that #3 cylinder has it's own injector, I'm gonna guess you have TPI.

That could be too much cam for TPI on a 305. TPI is flow limited. That cam is designed to flow air, which the factory TPI isn't made for.

A lot of people who don't know TPI think if they build the engine for upper RPMs, the loss of low-mid RPM grunt will be offset by the TPI. Nothing could be further from the truth.

Put a Greyhound on a 10 ft long race track against a Poodle, and I bet the poodle wins. Greyhounds are made to run fast, not quick. That’s about the equivalent of putting that cam on a 305 TPI.

Besides that, the 110 LSA with 211*/221 might be giving the ECM some trouble with vacuum at idle. Is your TPI SD or MAF?

 

My TPI is MAF. The idle is kind of jumpy between 6-7 if it's a good day, and 5-8 on a bad day.