So once agian this new motor is causing me issues...... The issue is at about 4500 RPM I get what feels like a misfire, my A/F meter go lean and so on....... ifI hold the pedel down it sometimes comes and go's when it pulls agian with pedel down the A/F meter go's rich.. so I do not think it is a fuel issue..(carb. car)... it has ngk plugs and I think one may be going down at high sprak load..... and input would be great!!!!

 

I ran NGK's once with an MSD 6... they sucked.

 

I changed the plugs at lunch and drove the car and no change the only other thing that it could be is fuel starvation I tested my fuel pump when I had my valve spring problem and it was ok at idle. I will be rechecking it tonight at high RPM and I will also be setting the float a little higher......the funny part is, is that this car with the old 83 H.O. motor ran faster.....with the same carb. set-up..

 

What engine and carb config are you running right now? You could also be experiencing Vapor Lock this time of year. (Heat + mechanical fuel pump = vaporization of fuel in the line or carb that bascially starves the engine)

 

Could be vapor lock, but it's almost certainly a fuel related problem. Maybe it need to be jetted. Need more info

 

The motor is a 90 roller 302 block .030 over, forged flat tops, heart shaped cylinder heads, compucam 2020, and an edelbrock 1405 600 cfm carb....The old stock 302 H.O. use to run 13.5 on street tires with 3:73 and 5spd......now car has 4:10 and only runs 14.5 with this issue......I'll test fuel pressure on the way home which is now.....report back later.....

 

Did you use the same car with the same jetting? If the new engine is more powerful, it's unlikely the same jetting will work. Are you sure your fuel system is in good repair? Pump, filter etc

 

Could be a coil incompatibility as well.

 

Same car... I did have to jet a little more.... I found on my ride home with a fuel pressure gauge between the filter and the carb.,,that when I hit4200 to 4500 RPM at WOT I can make the gauge bottom out(0 to 1psi) ......pump can not keep up.....(should have keep the old one!!!!)....I have changed the location of the gauge to in front of the fuel filter to see if it's a pump or a plugged filter....So thanks for all the help....I will report on what I find.... and list my times if after 3 week of play'n and tweek'n finally get me back to were this car should be....thanks again.

 

So after installing a new fuel pump with more flow, 110 GPH, I drove the car home and it was better but not gone, so at home I adjusted the floats higher and no change......the only other thing I can think of is "TNT" ohhh!!! I mean timing I have a MSD Billit dist. and 6AL box I think the engine shop that curved the dist. for me maybe when to high.......it has the red bushing one heavy and one light silver spring and 14d of base timing......so in the end it has 42d of total timing at 4400 to 4600 RPM.....any thing that I have read or heard about thesemotors is they run best at 34d of total timing.... could this be my issue????