• To ALL forum users - As of late I have been getting quite a few private messages with questions about build ups here on the forum, or tech questions about your personal project. While I appreciate the interest, sending me a private message about these topics distracts from, and undermines the purpose of having a forum here. During the day I wear many hats as a small business owner-operator and I work tirelessly to provide the absolute best service possible to you, our valued customer. When I created this forum I rounded up some of the best minds I knew so that any tech question you might have could be asked and answered by either myself or one of my highly experienced moderators, this way the next time this same question is asked the answer can be easily found and utilized by the next IH enthusiast having the same question. This allows me the freedom to run the day to day operations of the business and minimize the impact to shipments and shop activities that these distractions can cause. It is of the up most importance for me to complete the daily tasks in order to best take care of you our customer, all the while providing you a forum to get the level advice and input you have come to expect and deserve from the premier IH shop in the country.

    So with that I ask that anyone with a question about one of our build ups or a general tech question to please use the forum as it was intended. I am absolutely available by telephone to answer your questions as well but at times may direct you back to our website to better field your question or questions. Most other private messages I will be glad to answer for you.

    Thank you for your understanding.

    Jeff Ismail

Which Injectors ?

I am looking to go fuel injection for my wife's 77ssii. She hates the carb and manual choke. Elevation differences are a factor also. It is nothing to go from 2000' to 10,000'. Was looking for input on if I needed to go with the performance injectors of if the standard option would work. This is a trail run Scout, as in, unimproved dirt roads. No major rock crawling or anything like that. Right now it is running a stock, non improved cooling 392/727 combo. Holley points distributer. (because the gold box had issues) 4.27 gears and 31 in tires. When the tires wear out I will probably go 32", when and if the 727 ever dies, a 700r4 swap is something I would consider. The old 345 is in the corner needs to be rebuilt. It ran a 272h schneider cam. Love the 392 but I miss the top end of that 345 a bit. I might go high compression with a head and cam swap. So, should I order the performance injectors? Anything else? I would be tempted to go aluminum intake if that would be an improvement. I want the engine to stay IH. Right now I am running stock square bore 4v intakes. It would be nice to drop a few pounds on the front end.

Bill USN-1

F.I. Moderator
Not sure what your referring to as performance injectors.
The stock 392 can run on the stock 350 TBI and I set the regulator pressure to 15psi.
you can use the 454 throttle body.
If your going to be upgrading and looking for more top end then lean towards the 454.
If you do more trail crawling then the 350 is fine for the low end throttle response.

The 350 is about 500cfm and the 454 about 700cfm.

Maximum engine rpm : 4000
engine size in cubic inches : 392
street carb cfm : 385.65
racing carb cfm : 499.07

as you can see the engine really doesn't need a big carb.
On IH only they refer to a performance throttle body in addition to the regular throttle body. That is why I asked . Unsure if future changes would justify going larger. The 345, when it was running well, would go 5000 rpms without issue.

Bill USN-1

F.I. Moderator
If your looking at the efi kits then the performance upgrade is the 454 throttle body.
The tuning will be different between the 345 and the 392.

And when you start making cam and manifold swaps it also changes the air flow of the engine.

I used the cfm calculator at summitracing.com
you can punch in the numbers you plan to run and get an idea of the requirements.

I do a lot of towing with my 345 and 392 and my 345 has a few upgrades during the build so I went to the performance/454 throttle body.
But even with the standard throttle body I pulled over 5500 rpm with no problem on the chassis dyno with my 345 when I first built it.
Thanks for the quick response. I will probably order within the next couple of months if not sooner. I do a little towing with mine also. 2 horse slant load. I will look at the calculator at summit. I take it that any changes down the road can be addressed by burning another chip.