[77TA]

ok I was just thinking about this and thought Id share some observations and get some input. I recently replaced my 400 with a 455. I was expecting great changes in power but I don't seem to feel like that great a diffrence. I Have not been real hard on the new motor yet but a couple of full throtle passes have been made but none on a drag strip this is all seat of the pants stuff.
This is what I was running in the 400. 412cid 6x heads 8.2 compression 268 comp cams cam. 1 5/8 headers 72 intake and quadratjet carb. timing 36 degrees total. it was a good running motor and had just a hint of a lope to it at idle. It would spin the tires fron a 1st gear roll. the car is a 77ta with 4 speed and 3.42 posi rear end and 255/60 tires. The 455 specs at 462cid 71 96 heads 9.6 compression comp cams extreme energy 274 cam 230/236 @.050 and .490 lift. Ferra valves and 995 spring in the heads with a fresh valve job. Eagle rods and trw forged pistons. same intake,carb and headers. This combanation will also spin the tires from a 1st gear roll most of the time and sometimes break second loose a little. It idles really smooth smoother than the 400 but only has about 14 inches of vacume at 750 rpm idle and is very steady the 400 was very jumpy. I read a lot on the web sites about how much more power the 455 would make at low to mid rpms than a 400 but I am not seeing a great difference. I felt like my old 400 was about equal to a new Camero with and lt1 and this new 455 seems about the same or just a tad faster. The new engine does seem to pull to a higher rpm the 400 was done at 5000 the 455 pulls hard to 5500. I am running about 34 degrees total timming now with the 455.

[77TA]

ok I was just thinking about this and thought Id share some observations and get some input. I recently replaced my 400 with a 455. I was expecting great changes in power but I don't seem to feel like that great a diffrence. I Have not been real hard on the new motor yet but a couple of full throtle passes have been made but none on a drag strip this is all seat of the pants stuff.
This is what I was running in the 400. 412cid 6x heads 8.2 compression 268 comp cams cam. 1 5/8 headers 72 intake and quadratjet carb. timing 36 degrees total. it was a good running motor and had just a hint of a lope to it at idle. It would spin the tires fron a 1st gear roll. the car is a 77ta with 4 speed and 3.42 posi rear end and 255/60 tires. The 455 specs at 462cid 71 96 heads 9.6 compression comp cams extreme energy 274 cam 230/236 @.050 and .490 lift. Ferra valves and 995 spring in the heads with a fresh valve job. Eagle rods and trw forged pistons. same intake,carb and headers. This combanation will also spin the tires from a 1st gear roll most of the time and sometimes break second loose a little. It idles really smooth smoother than the 400 but only has about 14 inches of vacume at 750 rpm idle and is very steady the 400 was very jumpy. I read a lot on the web sites about how much more power the 455 would make at low to mid rpms than a 400 but I am not seeing a great difference. I felt like my old 400 was about equal to a new Camero with and lt1 and this new 455 seems about the same or just a tad faster. The new engine does seem to pull to a higher rpm the 400 was done at 5000 the 455 pulls hard to 5500. I am running about 34 degrees total timming now with the 455.

[David Holmberg]

The 455 will make more torque and torque is not nearly as addictive as the feel of higher rev's. The ONLY way to judge the performance of the car is at the track, torque is mis-leading in that area that's why people want to over rev a 455. Your combo is very nice for the street and should run mid 12's in street trim with some traction. Try shifting at 5000 then move up slowly if it improves, but don't feel bad if it runs faster at 4800. If you just swapped the intake and carb over from the 400 you will need to check the plugs for proper jetting. Good luck...

[Michael Farich]

Ditto on the take-it-to-the-track advice. 15 years ago I swapped an LS6 454 in place of a 396/350hp motor and hit the street with it. With such excitement and hence huge expectations I wasn't sure if the new motor ran much better after all. That was until that weekend when it made its first pass at the strip. Using the old familiar starting procedure I wasted the first two hundred feet (street radials) with wheel spin and thought it was a lousy run. What a shock I got when the girl handed me the time card showing a lower ET and faster MPH than the best ever run with the old motor! With all the emotion we gearheads put into a new motor it could take weeks of daily driving for us to overcome our emotions and be able to tell the difference.

[critter]

I would concur with the track time. It's the only real way to quantify changes, whether it's a new motor or changing jets. I would also say that, if this is such a fresh motor, why not give it a little time to loosen up? Mine was extremely tight for the first 500 miles but once it was broken in, WOW. It now wraps up quicker and will fry my street tires through first and well into second gear. That's where a 455 does the nasty, down low in rpm band. While the break in is going on, work on double checking all the tune up items. Make sure the plugs look good. Double check the timing. You get the picture. Good luck.

[77TA]

Thanks for the comments and keep them comming. I was just kinda expecting a real monster. I mean the 400 was rather basic 8.2 compression 268 cam. It seemed to pull about as hard as this motor. I think I am a bit rich on the carb at the moment. I pulled a couple plugs and they are kinda brown on the porcelin. I was fudging to the rich side because of the compression anyway so its not unexpected. 12 degress base timing 16 degrees vacume and 22 degrees mechanic advance seems to be the timing curve detonation and pinging seem to be ok at this point. I am running AC and the thing will idle down to 600 Rpm very easy. I have it set at about 800 though for ease of driving with AC. It just seems a little flat. seems like it I give it a little pedal it feels strong but give it all it just does not pick up that much faster kinda flattens out. Engine sounds great but I would not race a Lt1 firebird with it. I was told this combo should make about 420- 450 hp and about 450-500 ftlbs. my old combo should have been about 300 hp and about 370 ftlbs. I think I got the 280-300 out of the 400 but I thinkim only getting about 300-320 out of this new motor. I have not beat on it much I want to get a few huindred miles on it so maybe it will improve. but just mashing it and running it through the gears a few times does not really impress me like I thought it would. I may be surprised if I go to the track but that will be a while. Thanks for any sugestions I hope to find another 50 hp or so !! But if the thing will hold togeather I will be happy with that with as bad of luck as I have had I should not complain at least its running ! Theres always NOS in the future if I get beat by some of these rice burners I see farting around.

[Will]

77TA, have you thoroughly checked all the really obvious things? You know, the stuff you'd figure couldn't possibly be wrong, like the carb linkage opening the carb all the way when the pedal is floored, sticky advance mechanism in the distributor, partially clogged fuel filter, etc. etc.?? Never hurts to double check.

[77TA]

no I have not checked the throttle linkage yet but what can I do if its not right ? I have not looked at the fuel pressure either so theres lots of possiablities. I just got back from a 150 mile trip in it and it seemd to run very well. on ramps are a blast. I guess I was expecting it to spin crazy like in the first threee gears. I pulled preety good as far as puttting you in the seat. I will start checking those little potential problems though just to be sure. I had the AC blower motor quit while we were on out little trip new motor too! I hope I can change it by taking the inner fender out!Hey I got double digit Gas mileage !!! 10 mpg ! thats a 3 mpg improvement over my last check but I did drive with a lite foot. The wife was in max backseat driver mode. Made me promise to ignor all challenges at red lights even.

[critter]

I'd check my connections to the blower motor and check the relay before tearing that inner fender loose to replace it. My 2 cents.

[T Hutchinson]

77Ta, In addition to above comments I would try a Permformer RPM or even a Torker II, once you are satisified all basic parameters have been dialed in. Running a similar combination to yours, except an even milder cam, I switched from a Torker II to a Performer intake (Similar flow to factory unit) because "the magazines" said over & over that the Performer was best with mild cam & stock heads. Guess what? I slowed down. Stabbing the throttle in first gear at a roll no longer put the car sideways etc. This was with NO other changes. Needless to say I swtchd back to the T2. I havent tried the Performer RPM on this exact combo but in other applications it has proven an all around excellent unit for both torque and RPM capability, either choice could be an improvement. If you know anyone with either one of these units that would be willing to let you try it out, it would be worth taking an afternoon to give it a try. Todd

[This message has been edited by T Hutchinson (edited 06-24-2000).]