I'm going to swap in my LT1+T56 and get it running before I do any performance mods to it. So I'll be re-using my stock 305 TBI exhaust manifolds if they'll fit. Will they?...it's only a temporary thing, don't worry

 

Couldnt you just save yourself alot of time and put headers on while the motor is out? Then just drop it in?

 

Do not use the stock exhaust manifolds. They will not clear the D-ports on the LT1 heads and you could have an exaust leak. The motor will be detuned about 50hp or more with your stock manifolds. Just wait and save up some money for some better headers. You cannot skimp on any LT1 swap.

 

Yes they will bolt up just fine and work just fine.

 

If by fine you mean horrible. The stock LO3 manifolds cannot even support the stock 170hp no less a motor that makes almost twice that. 3rd gen 1 5/8" headers barely clear the D-ports on a LT1 swap. The stock manifolds will not.

 

he said it will only be temporary, in which case they will work fine.

Its not like the engine is going to have a catastrophic failure because the stock manifolds dont flow well.

 

Yea I understand that but I am pretty sure the manifolds will not cover the D-port. Meaning he will have a huge exahust leak at every port. If round 1 5/8" headers barely clear the D-ports on the LT1 heads than LO3 manifolds will not. They are at the most 1.5" round.

 

Manufacturers make specific manifolds/headers for D-port heads. having leaks at every port would be the same as not having manifolds on the engine resulting in lack of power, increased noise and possibly unburned fuel being dumped in the engine bay.

 

Yea you are right but there is only one or two sets of headers out there that are tailored to 3rd gens with D-port heads. Every other header out there for 3rd gens are round or squarish. The problems that you listed would apply to using small round primaries mated to larger D-ports. This is the problem he will face.

 

Look quit posting this BS, im sure you havent done any lining up of any gaskets, and if im not mistaken you havent even done the swap, the LT1 port must not be in the same location as the fast burn heads which seem to be the main other D port head that pops up around here, the roof isnt any higher than a L03 exhaust port, and the LT1 port doesnt even make it as low, so there will be no sealing issues, yes they wont flow as good cause its a tiny stock log manifold, however they will work just fine and seal just fine, and for the record as far as aftermarket headers go, SLP 1 3/4's EAT the LT1 ports.

 

The SLP's will cover them fine because of thier large size. I am just concerend that the small 1.5" stock ones would not. The people that do the swap always say that they re-weld the outside flange of 1 5/8" headers so that they can grind down the inside lip. I am not worried about the roof sealing but instead the bottom where the D shape widens out. So if 1 5/8" brealy covers I don't see how 1.5" would. I am just using common sense here. It may line up fine but I am sugesting a possible problem. Yea I have never done the swap but I do own both type of motors and are extremely familiar with both. I wouldn't be so quick to call BS.

 

Well I'd really like to get this thing running as soon as possible. If there is a serious problem with the manifolds clearing the heads, I'll bite the bullet and wait to install it until I get headers. BTW, what's the best headers+y-pipe combo for the LT1 swap?

 

Just line them up and see for yourself. I am gonna try to show a pic with my old manifolds up against some LT1 ports. I have to get the measurement of the width of the lower d port of the head.

 

I call BS cause i've already done it, done the measuring, done the swap 3 times, about to do the 4th and i've got someone who is arguing with me due to hearsay, matt, bolt em up do the swap, when you get the cash get yourself some SLP 1 3/4's.

and they are both 1 5/16 at the bottom of the port since you wanted to know shifty...

i have both motors sitting beside each other right here in the shop.

 

That is all you had to say in the first place. I was just being cautious.