Verified answer

from 350 to 400 hp

is it a 351w, m, or c? It totally matters. Being that it is a 77 I am putting my money on the 100 hp m engine. When you say "lengthened" pistons do you mean it is stroked? If so how much? What kind of heads are you running and what has been done to them, what cc are they? What is the compression ratio? What kind of cam? What is a turbopack? What kind of intake and carburetor are you using? What are you installing for exhaust? You need to give us more input if you want some answers. I downloaded for free a desktop dyno program to check it for accuracy. As I have never had my engine dyno'd I did have a time slip for my car and the program figured 1/4 mile et's also. I inputed all the pertinent info into the computer and vioala it gave me a number, is it right? I don't know but I'll bet it's close because it's et estimate was right on. Download the program and give it a try. It will come closer than anyone of us just tossing a guess.

man u asked this question the other day. your still not giving enough numbers and other essential information. you need to get your self a desk top dyno or take it in to a real dyno to get it tested to find the real number. i still guess that you only got about 240 hp at the fly at the absolute most. then again i don't know what kind of induction, heads, cam, transmission or anything else other than you stroked it. truth be told unless it is a cleveland all the 351's sucked. that is the plain and simple truth. you would be much better off stroking a 302.

it matters how much theyre bored over, and what kinda pistons are in it. Im also curious as to what you mean by Turbopack. If you mean a turbo kit, then it could be damn near any amount.

its pretty hard to judge. the 351 was a pretty common engine. Its almost like asking how much hp a chevy 350 has (theyve made it for like 50 years in prob 100+incarnations)

I dont know Im not a dyno meter.

diffenitly not enough info