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CarburetorsCarb discussion and questions. Upgrading your Third Gen's carburetor, swapping TBI to carburetor, or TPI to carburetor? Need LG4 or H.O. info? Post it here.
i bought a nice 87 formula, with the carburetor lg4 305 and 52k miles. Engine runs great, leak down test and compression good. I have been toying with a LS swap or a 350 or 383 swap, but after a lot of thought I really like a challenge on building the 305 for max performance. I know a 350 is a better platform to start, but I really want to see what I can do with the 305.
Car has a 9 bolt 3:27 rear, 081 heads, and auto transmission. Compression is stock at 9.3:1. Pretty gutless right now...
I have added a 84 cowl induction setup to the air cleaner plus added a second snorkel to get more fresh air in. I have also removed the a/c ( I was careful in complete removal and stored all pieces). I have installed a steel non air assembly with the correct fan. Looks nice.
I also have removed the ecm wiring harness.
I have started spending some money on the following items
- dyno dons complete exhaust system with magnaflow cat back.
- new vacuum advanced distributor
- 1978 qjet, non computer controlled
i still need a cam, any proven combo would be nice. My goal is 275 rwhp ( 345 crank hp) using the stock 081 heads. Not sure if that is doable with those heads. I have built many engines, pretty good a modifying qjets, but my experience is with traditional Pontiac engines. Cams I was considering was SPO 357, Hot cam, Elgin 1136. With the stock heads not sure if I need more duration to help “fill” the cylinders.
Any thoughts on cams? Or what else I am missing? Thanks
With those heads and that compression ratio, making better than 1.1 HP/CID isn't going to happen.
Heads arguably max out at 220 CFM. There's not a lot of air flow there to support much. If you can get the CR up to 10:1 and have the valve train (and bottom end parts) to spin it to 6000 RPM, you'd get close to that number.
Not bad deal there...
I may just also do the heads to match the cam, either get vortecs or port the 081’s. I think I read that stock vortecs flow well and will still outflow the 081’s after porting. The only reason to keep the 081 would be the stock look then I will have a restriction with the intake. I want to keep my cowl induction so unsure if the vortec intake is same base height as the stock intake manifold.
I thought I read about some one with a 305 that got over 281 rear hp, can’t recall who it was.
....I thought I read about some one with a 305 that got over 281 rear hp, can’t recall who it was.
Go to the "Tech / General Engine" subforum here and look up the member "FireDemonSiC" , he has a thread called "334 TPI Stroker - Dyno Results Are In!!! What next?"
I believe that may be the thread your looking for ....
Go to the "Tech / General Engine" subforum here and look up the member "FireDemonSiC" , he has a thread called "334 TPI Stroker - Dyno Results Are In!!! What next?" 