I have tried the search button, but have found nothing to answer my question(s).

1. I have a stock 305 TBI 5-spd. Are SLP's 1 3/4 headers too big for my motor.

2. I plan on possibly putting in a 355 in the future. Are 1 5/8 SLP headers too small for that motor.

3. Which is a better plan of attack, get the 5/8's for the 305 and use them on the 355 if I ever do it, or get the 3/4's and use them on the 305 until I put in the 355?

4. Didnt this month's issue of High Performance Chevy use 1 5/8 headers on a 383 or something like that. And didnt they out perform the 1 3/4?

5. What do you guys recommend. I have found both sets for the same price.

 

I believe that everything you said was correct. I just installed my 1 5/8" headers and they are awesome on my little 305 TBI!

 

Any trouble with the install? Or did you have it done?

 

I would go with the 1-5/8 with your car set up. The smaller tube size will the keep the exhaust velocity up > giving you more bottom end power than the 1- 3/4 tube. You don't have enough flow to reach the full potential of the bigger tube at high rpms. There would be too much air turbulence in the bigger tube, this would cause a decrease in exhaust velocity, which intern lowers the kinetic energy of the exhaust gas, in simple terms this means the big headers won't suck the spent gases out as well as the smaller ones. For example a 2 inch header tube on a stock motor will make way less power than a 1 -5/8.

 

The hardest part was getting spark plugs back on, but that was a simple fix by getting some header plugs at oreilley's by Accel. The second thing was that we had to cut the AIR tube off going to the cat, it had been crimped on.

 

yeah, it was a pretty painles,.........wait..............let's not say painless, because I have some battle wounds, let's say easy install.

 

lOOKS LIKE 1 5/8THS IT IS ... THANKS

 

Would you go 3/4 if the 305 wasn't stock such as what I have and am putting in in my sig.

 

To be honest I would still go will the 5/8, you still wouldn't have that much flow. I run 3/4 on my high 300s hp 350.

 

look at it like this....1 5/8 vs. 1 6/8....... an 1/8 is very little when it comes to tubing.....go bigger...especially if the 305 will get a performance build down the road

 

Be very carefull, just like a cam you can go to far with headers and lose power.

 

There is absolutely nothing wrong with using 1.75" headers on a stock LO3. The loss of torque is slight and is offset by the increase in high end acceleration.

Furthermore, odds are you will probably regret getting the smaller ones after your engine swap/rebuild than if you got the larger headers.

 

Pukka -

Are you happy with the 1.75 SLP's on your L03?

 

I've got 1.75"ers waiting for time to install for my former L03 305. It's got decent heads, single plane intake, 650 carb, big (.482" gross lift) cam (when I get off my lazy *** and install it), and 125 shot of N2O (after I upgrade the fuel pump) so I expect that it won't be to far from optimum. I plan on building something at least 78cid bigger down the road and wanted to make sure that they'd be big enough when needed.

 

All I gotta say if you plan on having over 300 hp go 3/4, anythig less go 5/8.

 

Gotcha

 

i know a kid who wants to put hooker longtubes and a 4" mufflex exhaust on his stock LB9 5 speed trans am. he is very stupid though. he goes by the nickname HOTSTART, any of you guys know him?

 

does this look about right for a SLP Y-pipe?

 

to me they look a little thin coming from each header, no?

 

Yes, very happy . I'll be even happier when I get around to putting in a 350.