just wondered what kinda gains i could expect from an lt1 intake on my 305. thanx

 

You'll definatly lose torque. Unless your running steeper gears, higher lift cam and shifting at 5800 rpm, your car will be dissapointing after all your hard work of installing it on your 305. Your better off porting your stock heads or saving the LT1 manifold for your 350 upgrade.

 

Where's your facts or is this just opinion?

They put "LT1" style intakes on the little 4.3L V-8 (Caprice). It was called L99 and looks exactly like the LT1 intake except with slightly smaller ports.

 

The shorter runners of the LT1 intake will have a higher tuning (resonance) frequency than a TPI intake, this will move the torque peak up the powerband. Where the TPI intake is limited on it's ability to breathe on the top end, the LT1's low end will be limited by the fact that it has a much shorter runner which moves the "tuning" frequency of the manifold up the powerband. This will cause a reasonably signifigant drop in low end torque. There is no free lunch, an intake that works well on the low end will not work as well on the top end and the reverse is also true. Now, someone may say "the LS1 does it", but it really is a compromise design (that works very well) that uses roughly a 9" intake runner (tpi is about 21", LT1 is about 4") and large ports to make good torque and horsepower, this is helped by an excellent set of cylinder heads, cam choice, etc. The difference in these designs is is why there is nothing like driving a TPI 350 for around town use. The extreme low end torque of that motor is great fun for "point and squirt" in traffic. I've seen a few people claim that their stock TPI 350 made 310 ft lbs and 210 hp on a chassis dyno. If this is correct, this is very nearly the same amount of torque as the LS1 (mine dynoed 317 ft lbs and 299.7 hp, stock), but usually at a lower RPM (again, fun in traffic), however the manifold and cylinder heads of the TPI 350 can't keep up on the top end and the horsepower suffers. I suspect an LT1 manifold will kill a bunch of that low end torque, but it could be good for a fair amount of hp on the top end. On the 305, I'm not sure the trade off will be worth it (since you are still very limited on cylinder head flow and the lack of cubic inches is already a torque penalty), but, as I've never done this swap, this is based on intake manifold design theory and not dyno results of a 305 LT1 intake swap.

The 4.3 motor you spoke of most likley has different cylinder head flow and tuning numbers (I've not seen them, and never cared to look), as GM designed it as a package. So,though it is limited on cubic inches, it was tuned for the maximum benefit of those cubic inches. The manifold from the smaller engine may be a better match for a 305 (assuming it is truly smaller, but without knowing the specifics, it could be too small), but that is just speculation. I don't think it would be worth the time to swap on that manifold since most people plan to upgrade to a 350 or larger at some later date.

My thoughts.

 

Well we will see. I have a customer that is doing a before and after dyno using the L99 intake on his stock 305. Results will be posted good or bad on my website.

I have done many LT1 intakes for customers with 305's and they are extreamly happy with the results. I have never had the chance to get numbers till now.

I do have numbers for a LT1 on a slightly modified 355 and the tq curve is very flat. I am very interested in how it will look on a 305.

BTW, the L99 can be ported to match the LT1's port size. Here's pictures of all 3 LTx style intake ports.

http://www.lt1intake.com/intakeports.htm

 

I'd think the l99 could be a good match for a 305 (as I stated), but that is based on a "best guess" about runner size, etc (based on the way GM does or may do things). As I have no concrete info on the size difference between the two as far as the runners are concerned, I would be very interested in seeing the results (as well as specs on both intakes).

Keep us posted!

 

LT1 and LT1 style are two different things.

 

You are correct. But as I said, the L99 is just the same as the LT1 except for slightly smaller ports. I can say this because I have had more Lxx intakes in my shop then anyone on this board.

 

Ok, but you are still comparing an intake with a smaller port, to an intake with a larger port, and denying the fact that the LT1 intake is most likely too big for the 305.

Maybe instead of "dropping rank", you could try to add to the knowledge base of the forum by educating us with facts? You seem like a nice guy- you could provide us with some info?

S.

 

i might just stay tpi then, untill i can do my hotcam experiment with some ported l98 heads on m 305. see what it'll bring then. well, i love the low end torque of the tpi. i can spin the tires at a 15mph punch with 2.73's right now. pretty decent considering 2.73's and a 305. i dunno what to do. i'm going to wait and see those 305 dyno gains

 

Steve,

I recommend the L99 intake for a 305 if you are modifing the engine. If that customer wants to drop in a 350 later he can and just port match the intake to his 350 heads. It will essensially be a "LT1" intake.

I am waiting on dyno results on a 305.



Of course for a 350+ you would want to start with the LT1 intake. It can't be ported past a felpro 1205 though unless you weld.

Dyno results on a Superram 350 can be found here in the Aug 03 issue of PHR. I converted Tom's intake for him and he wrote the article.
http://www.popularhotrodding.com/tech/0803phr_beast/