Hey! Looking for some quick answers to a few questions about swapping a 383 into base 305 bird. I searched and did not find these specific questions asked. It is very possible that I'll be buying a 383 crate next month from a local builder who has the engine ready to sell ($3500). Yes, he's reputable and his stuff is proven to work.

So, I've read the stickied 305 to 350 swap thread over and over again and have worked that into my plan. The plan is to keep the TBI and make the suggested upgrades in that thread. But, does that information stay the same with a 383? For example:
1. would the suggested 350 injectors work or Should I go with a 454 injector pod?
2. I'm assuming I should just go with a fuel pump for a 454 since extra gets pumped back in the tank.
3. Can I still use a 746 ECM? How about the chip? I'm assuming I should reach out to tbichips and get a custom burn for the 383 specs..
4. Knock sensor for 350 work?

What else changes with a 383?

Thanks in advance for your time.

Added: Wanted to mention I still have retained lots of advice from my previous threads about transmission, drive, breaks, and rear upgrades with the 383 application and I have considerations in place.

 

If that 383 has a mild,ECM friendly cam,i'd be tempted to reinstall the original TBI with 350 injectors,pickup truck 747 ecm with 350 prom,see how it goes then adjust from there.Probably good to upgrade the pump since the original is pretty lame. If auto and original t700,should install a shift kit with upgraded servo so tranny can handle a mild 383.

 

Sounds good, thanks! I was quoted around 2k to rebuild the 700r4 with corvette servo, etc, to handle up 500hp. I need to call around and compare price still, but not sure I'll get much cheaper around here.

 

Id suggest a bored 46mm unit from SPR with an adjustable fuel pressure regulator and definitely upgrade to a TPI fuel pump because you may need to run much more than the stock 11-13psi. Im running 15psi on basicly stock L98 with the bored 46mm unit and bored stock TBI intake to match. Runs great and pulls way more RPMs than the old L03. Talk with Brian @Tuned Performance and he may can burn you a chip close. Really the 383ci isn't the problem I wouldn't imagine but you really have to watch it with the cam as it needs to be conservative with this map sensor TBI setup.Im running a stock L98 #049 cam 207-213 dur 415-428 lift and I think its a really good choice for these engines as is a stock LT1 type cam. Anything in the 204-218 dur would probably be optimal. You really need to think rear end also. Torque kills these mickey mouse 10 bolts and this will be a weak link.Sub frame connectors will be something you should look into as well. Good luck hope it turns out great.

 

Thanks for the cam info. I need to get with my friend and see about what cam was installed in the 383 he's selling. I guess if it's too aggressive I should either take a pass or scrap the TBI? The guy selling it was going to put it in his nova with a carb, but rebuilt his old 454 he had and is using that instead. What would the cam being aggressive mean to my plans?

As for rear, I plan on doing the 4th gen Z / formula / trans am swap that's suggested here in the How-To's, so I get the posi + 3.42 gears. Would that hold up behind a 383?

Thanks!

 

Can go with a fairly decent cam in a 383 and still pull good vacuum. Especially with the addition of Rhoads lifters.

Personally I would swap the cam and run Rhoads lifters on the new cam.

 

I'm in the process of building a 383 tbi as well. I am glad you asked the question about the knock sensor, it got me to think about something I was about to overlook. 305 and 350 use different knock sensors, I didn't realize this and almost bought the 305 version for my 383 online just now. I'm guessing it's due to differing frequencies related to bore size, as the 350 sensor is listed for the 4.3 v6 as well. Stroke must be a factor as well though, as the baby LT1, the L99 4.3 v8 has 305 bore size with a 3" stroke crank. I think the 350 sensor is likely the best choice we have.

I would suggest picking up a used 454 tbi to start with, it's still bigger than a bored small block unit. According to Dynamic EFI, 305/350 tbi flows 490 cfm @ 1.5inHg, and 454 tbi flows 645 cfm @ 1.5inHg. I just can't see spending the money to have the stock tbi enlarged to still be small on a 383. Also good to know is that the 94-95 454 units use smaller injectors and higher fuel pressure to compensate.

 

There are marine 61 lb/hr high pressure injectors too. Flow 61 lb/hr at about 13 psi but flow about 104 lb/hr at 30 psi. Marine TBIs use the high pressure spring. There are also brazilian TBI I6 injectors that flow close to 120 lb/hr but they use the medium duty truck injector pod. Medium duty truck injector pod is smaller allowing more airflow through the same size TB bores.

 

I tried to the best of my capabilities to find those Brazilian injectors you speak of, using English to Portuguese translators and couldn't find anything resembling tbi injectors. I bought one of those small injector 94-95 454 units, and just installed Standard Motor Products TJ11 injectors for a 1991 454 SS pickup. They are advertised as 90.77 lbs/hr on Rock Auto, but didn't see the flow rate advertised anywhere else.

 

Actually in the middle of dropping my 383 back in myself. Have some engine compartment cleaning, wiring harness repair and reloom as well as a few other things to do before it goes back in.

 

Edit...double posted.