Thread: Need some ideas on problem with 377 ci

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Guys I have this lingering problem with my 377 ci destroked 400 small block chevy. The engine flat lines on power and torque at about 5800 rpm. This was felt while driving the car and proven on the dyno. The camshaft rpm range is from 4000 to 7800. I feel there is no way I should reach max horsepower at 5800, something must be wrong.
This is what I have in the motor and have done so far as to trouble shoot the problem.
My compression is at 11.4:1 with flat top pistons. I am running Victor Jr 23 degree aluminum heads and super victor intake. I have a lunati cam with 266 int duration @ .050 and 270 ex duration @ .050, my cam lift is .640 on the intake and .646 on the exhaust with 1.6 rocker arms. I have cam matching valve springs which are set to the specs for the cam on height, the springs were tension tested and met specs. I'm running a MSD 6AL with an MSD billet distibutor and blaster coil. I have a Carb shop holley 750 double pumper carb, that was flow benched according to Carb shop at 928 cfm. I'm running a 4500 stall with 4.88 gears. I have gotten the car to do 11.50's but it ought to do much better considering it's running out of power at 5800 rpm.
Any of you experienced have any ideas what might be the problem with this motor.

[QUOTE]Originally posted by 73RS
[B]Guys I have this lingering problem with my 377 ci destroked 400 small block chevy. The engine flat lines on power and torque at about 5800 rpm.
1- What kind of fuel are You running?
2- How are You getting the fuel to the carb?
3- Is the fuel line big enough to carry the fuel?
4- Have you shut the motor off at the end of a pass and checked
the plugs to make sure you're getting enough fuel? Shut it off
at the line. Do not drive back to the pits. You may be running
out of fuel on top end. Plugs may show a lean condition but if
You lope it back to the pits you may have a false reading. It
might look like you are running rich when you're not.
5- How about temperature? Is it running too hot? This may also
be caused buy running to lean.
6- How about timing? Have you tried backing up on the timing a
just a little to see what happens?
7- Do you drive it on the street? Do you have any heat problems
if you do drive on the street?
8- I have a friend who had a simular problem to yours. He though
it was a cooling problem. Spent $800.00 before deciding to try
bigger jets in the rear. Guess What? Problem solved.
9- These are simple things to look at that dont cost a lot that
could save your motor.
10- I gave you what I consider the simple things first. You may
find some answers there. I keep going back to your thread.
it looks like you have some real nice equipment. The only thing
that keeps jumping out at me is the cam.You didnt say if it is a
roller.being that big it should be . Even so. IT'S TOO DARN BIG!
Bigger is not always better. I think I could take that same
combination except for cam and run away from you.
11- Dont think, I think, I have all the answers, I DONT!! I just
want to give You --- Food For thought-- Good luck !

No Charlie, I must have missed that.

if you got what you say you got then it should pull all the way through the 1/4 mile. where is is playing out at. 1/2 way or 3/4 of the way. like riverhorse and denny i belive id have to be looking at the fuel system also, its gonna take some big fuel lines and pump to turn those rpms. make sure the car roll free and the front end not diging in.

Originally posted by csf03716
hey riv ya not makin fun of my "food for thought are ya?"

Sorry Charlie, I couldnt figure out what You were talking about . After going back and reading Your post twice I finally realized what You meant. If I saw that ,it did not register.I guess I must have completely missed your post but now that I have read it carefully I would agree .I know a guy with a 4000+lb. Monte Carlo with a 406. He runs a much smaller Lunati cam(flat tappet) and runs right on 11 seconds flat. Mike brought out a good point on the converter but I will wait for him to chime in.I just went back to mikes post and he never mentioned what we had talked about.If you dont need that much cam ,why do You need that much converter??

Originally posted by riverhorse59
Sorry Charlie, I couldnt figure out what You were talking about . After going back and reading Your post twice I finally realized what You meant. If I saw that ,it did not register.I guess I must have completely missed your post but now that I have read it carefully I would agree .I know a guy with a 4000+lb. Monte Carlo with a 406. He runs a much smaller Lunati cam(flat tappet) and runs right on 11 seconds flat. Mike brought out a good point on the converter but I will wait for him to chime in.I just went back to mikes post and he never mentioned what we had talked about.If you dont need that much cam ,why do You need that much converter??

i changed my mind, if hes got a good 8000 rpm combination then he ought to be able to go 8000 rpms and then he might need that conv. you'll are detuning his motor but, there is a reason he cant get everything out of his motor the way it is.

He's got a good motor. He hasn't said anything to make us believe he has a great motor. How many passes do you guys give him before we will be picking up scattered parts off the track? I liked both of your thinkings better, earlier. I dont know about Charlie but Mike, When was the last time You had a motor that would pull strong all the way to 8000 RPM. I doubt that I have ever had one and dont think he has one here either.If 73RS had a cam and a converter that would allow him to run strong from a much lower RPM through 6500 he would be much faster and and the engine would last much longer.

Guys thanks for the replies.
I didn't reply back sooner because I have just moved and I can't get a decent internet connection from my new house. Been doing some trouble shooting on that, all I can figure is my phone line is too long from my house to the box near the road. Anyway will have to look into that further. I am at work now and the net moved at lightening speed compare to my house.
I don't feel my setup is that far off, meaning the stall converter and the rpm range of my cam. That is assuming I would make power to 7800 RPM like my cam is supposed too. I go through the 1/4 mile at about 7400 rpm, which is about where I think I should. The real problem is my motor flatlines on power at 5800 rpm.
I did try increasing my rear jets on the carb and am running a 1/2 fuel line from my tank to the pressure regulator on the carb.
I do have and exhaust temp indicator but haven't figured out what a good exhaust temp should be. When I increased the jet size the exhaust temp went way down to 800 from 1250 with the old jets. I think I am probably too rich now and made even less power on the dyno with the smaller jets.
I even rechecked the cam timing at it was timed as per Lunati.
I do use a rev limiter on the 6AL I have a 7600 module in there now.
I do use the car on the street but only to drive to car shows or car club events that are located pretty close to me. The gears are far too low to travel too far.
This rpm problem has plagued this engine from day one. I've put new heads and intake on this thing to no avail. I am feeling like a foolish parts changer at this point.
The problem is probably real simple and looking me right in the face, but I'm too dumb to find it.

Yes Riverhorse, the cam is a roller. I have even tried a smaller cam in the engine, it's a roller also, the darn engine also flatlined at around 5800 rpm so it can't be the cam.

Originally posted by 73RS
Yes Riverhorse, the cam is a roller. I have even tried a smaller cam in the engine, it's a roller also, the darn engine also flatlined at around 5800 rpm so it can't be the cam.

you need to find out what a good exhaust temp. is and that will tell you if you are lean or not, not just jet size, but fuel line size to. i guess you valve springs are ok.

Originally posted by riverhorse59
He's got a good motor. He hasn't said anything to make us believe he has a great motor. How many passes do you guys give him before we will be picking up scattered parts off the track? I liked both of your thinkings better, earlier. I dont know about Charlie but Mike, When was the last time You had a motor that would pull strong all the way to 8000 RPM. I doubt that I have ever had one and dont think he has one here either.If 73RS had a cam and a converter that would allow him to run strong from a much lower RPM through 6500 he would be much faster and and the engine would last much longer.

ive never had a motor that would pull strong to 8000, but if he dont have the good stuff then it should blow up , not quite pulling.