383 sbc, LT4 HotCam cheap gas question.

[Orr89rocz]

Hot cam is nice for alot of mild builds. Been in cars with that cam in 350 tpi builds, lt1 builds and a 383 cam only lt1. Always works well

I dont think 1.6 rockers will change much in the tune or idle quality.

[Monzsta]

I finally got to take the truck down the road. with 93 octane in the tank and 30 degrees of timing max in the microsquirt this thing is a beast. I was allowing the autotune to build the ve map and was also doing slow throttle rolls, being careful of the transmission. After a few drives and digs I was pleased to discover the transmission hanging on at WOT, even before the install of the .500 boost valve and Corvette servo I had bought for it. It short shifts into top gear due to the 4.11's I put in the rear but otherwise feels pretty solid, taking WOT 3rd gear pulls that have the truck moving far faster than it wants with it's squishy brakes and rubbery suspension. I actually fooled myself as I have built the exhaust really quiet and in 1st and 2nd, found I had a "miss/skip" at WOT that seemed far short of what it should be doing. A quick look at the datalog showed I was crashing into my 4,000 self imposed break in rev limiter in a hurry.

I'm not seeing any knock in the logs at 30 degrees but I want to make sure my ve map is fully built out before I begin experimenting with timing and fuel octane knock sensitivity. I have a sneaking suspicion it might run on 87 octane after all!

[Monzsta]

Getting the tune worked in and some miles on this thing. After the .500 boost valve and Corvette servo install the transmission feels more sure footed with the power. When I dropped the pan there was nothing scary aside from a tiny little bit of soot and bronze on the bottom of the trans. What I'd considered typical material from a unit with some mileage on it. The fluid was red and smelled healthy.

I'm trying to get OEM driveability out of this so I've spent a lot of time working on the idle and light throttle regions of the fuel and spark map. The throttle response with the 1,000 CFM 4 BBL throttlebody was touchy, hair triggerish. Poking the throttle resulted in a big lurch and chirping tires. That would not be conducive to trying to get a trailer moving on wet grass. I've been watching timing on late model v8's and they will pull out a ton of timing on a throttle poke. The 6.2l I was spying on even went to ATDC momentarily so I watched my timing map and pulled out a bunch of timing where the initial throttle opening occurs and was rewarded with a nice smooth transition and controllable torque on tip in. Even at 700 rpm idle I think I can tiptoe this torque monster around a wet lawn with ease.

I think I'll leave the timing where it is at 32 degrees and move to some mid grade octane fuel and start testing it's fuel tolerance.

[Monzsta]

I am really surprised. I ran through a tank of premium, and on a whim I put in a tankful of 87 and watched the knock sensor like a hawk. Driving easy, I saw nothing register. Crawled under it with a hammer and tap tested the block and saw good activity. Threw some unrealistic timing in it and did a few throttle snaps and the knock sensor logged that. I then put my timing back to 32 degrees and did a few cautious WOT pulls, listening very carefully. I heard nothing, and neither did the knock sensor. The air temperature has been rather cool, in the 40-50's.

I do realize the 87 in the tank does still have some 93 and that air temperature is also playing a factor but I feel like some careful tuning with the intake air temperature sensor and some aggressive knock retard this engine will be pretty comfortable on the cheap stuff.

[Orr89rocz]

Yeah it sounds like it might be ok on some cheap stuff or atleast mid grade if you can find it

[mt-engines]

The LT4 was 10.8:1 with fast burn heads. You should be fine on regular pump.