Gentlemen and Ladies
When I bought my car the po had installed a blueprint short block 355. He reused the heads with a quicky valve job, and bolted everything back on as is. The new engine lacks power and runs rough. It goes to the diagnostic shop next week. I want something to really scoot along. I was thinking about bolting in a Blueprint 383, 420 HP long block, but don't know if the induction system can handle that. Any observations?

 

I doubt it will be a 420 HP 383 after you bolt up the TPI. I would change it. And you also have to remember, anything with fuel injection requires a tune to accommodate any changes.

 

If you are going to do that change the intake. The TPI will work I'm not saying it wont but you will be choked down.

 

Turbo charged LSx... Problem solved...

 

Cost vs benefit. I'm looking for around a true 300+ HP at the wheel. Enough to chirp the tires. The LS swap would have to be a 8K to 10K price tag when all is said and done. The 420 swap would be under 5K. The car goes to the Corvette shop next week for a through inspection and all the diagnostics including compression and leak down. It's not that I don't believe the po that the engine is new.....just trust but verify. (Whew, I'm glad I'm retired. Any more corporate/political clichés and I won't be speaking English anymore). I love the car, but I don't want to overspend on it. Thanks for the observation about the fuel injection. I will ask the shop what I can do. KM

 

Firstly you should take the car for a quarter mile run, the 85-91 TPI C4's should do a 13.9-14.5 standard depending on the year.

I know with long tube headers, cut airfilter lid and an adjustable fuel pressure regulator set to 45-48 psi really waked the std engine and cut it down to 13.2 from the standard 14.4 quarter mile before i added a blower.

So once you have done a quarter mile run you will know where you stand with your vette, of course a 383 bottom end is a straight forward swap nowadays.
The TPI inlet manifold is not suited for a high RPM engine which a 383 should not need to be, i have no issues (mainly because i cheat having a blower) there are plenty of naturally aspirated TPI vettes in the 12 second quarter mile times.

If you want a 10-12 second quarter mile screamer high rpm engine you will need to go with a miniram (LT1 style) inlet manifold.

 

You didn't specify. Ya kinda just left it wide open.....

 

I know the 383 should provide for more torque. The usual place I like to feel a healthy engine is off the line and pulling through the gears. I haven't been interested in the 1/4 mile for a long time. I thank you for your observation. Quarter mile results are a great indicator of overall engine power, but the quarter mile is not really what I'm looking for. I want a powerful cruiser with no annoying habits, no loping cams and good vacuum. Decent gas mileage. It has been my experience that without power adders (blowers, nitrous, etc..) the quickest way to more power are more cubic inches. The car is for cruising comfortably. I really worry about the injection system negating the increase in cubic inches. It would defeat my purpose. Does anyone have direct experience with a 383 and the stock injection? Thanks KM

 

True, true. Wish I had the dinero for such a swap. The "new" LS motors are just fantastic. I'm just a low budget operation.

 

The stock TPI on your 383 will haul like a cut cat. You'll be able to light the tires in 1st and get a solid chirp into 2nd no trouble (auto) but you probably won't want to make a habit of pushing a Dana 36 diff too much. (not an issue if you have the stronger manual tranny equipped Dana 44).

Because of the high low down torque this combo will produce I think you'll be very happy and should out power most other cars off the line. You just won't have much left after about 4500 rpm which for most street cars and judging by your own described use is seldom called upon anyway.

If you find the TPI a restriction then it can always be changed at a later date but to get the same 'off the line' performance you'll then need to invest in at least a high stall speed converter.

There will be varying opinions but I would estimate 28lb to 30lb injectors would be about right to give good performance but you may need to keep it at the lower end to meet emissions. Either way I think for what you're asking you'll be very happy. Its hard to beat a TPI for normal low down street performance