Put 3400 heads on a 3100 now its running weird

[maverickdog8]

So I recently had to get some new heads for my 3100 engine and I decided to go the easy route and pull the brand new 3400 heads off my gf's totalled car. Had them checked at a local shop and they are still perfect.

Problem is I put them on the car and it runs like a dog. I hit the gas to accelerate and it barely wants to move. Does fine at like 25mph+ though. I am wondering what it could be causing the car to run this horribly. Noone locally can give me any advice on it at all, not even the local shops. Does anyone know something that I have been missing or is this engine just shot.

 

[maverickdog8]

what I forgot to mention is when im sitting somewhere and it is idling it bounces around and idles horribly rough. between 600-1200 rpm.

 

[Bio248]

sounds like you got a vacuum leak if the idle is erratic like that.

 

[maverickdog8]

I've checked and there is no vaccum leak. all the hoses are on the right place and good.

 

[BillBoost37]

I'd check again. It sounds like a vacuum leak, but since we aren't there..you are our eyes, ears and hands... back to work you go. :th_thumbsup-wink:

 

[maverickdog8]

So I checked for vaccum leak. Cant find anything. Im swapping the fuel pump today(mine doesnt read that I have gas so i gotta do it). Lets see if having a different fuel pump changed anything.

 

[91gpse]

could be a fuel problem as well. 3400 heads are bigger so it could be running lean.