Yeah.. truck motors are great.. but a set of ls7 heads work like a charm.

So really.. my "local" machine shop told me they could sleeve it to 427 w/o problems... I have a block laying around there that needs to be finished... maybe i'll go ahead and do it with a 3.75" stroke and some 15º heads with a supercharger.

 

Call me a jabronie, but I'll never get sick of hearing about LT1s over 400 cubes.

ARE YOU LISTENING, BRET?!

 

Dave, I think a sprint car/street car comparison is invalid, not that there's any problem with batch firing injectors.

 

I dont see why you would want to use a LTx block. I would just go with a 400 SBC block bored to 4.185 and a nice 4.125 sroke for a 454. Its entirely possible.

I would then use SBC standard cooling. If you are good with electronics, you could set up a crank trigger off of the pulley to replicate the opti signal and then use a Delteq or LTCC system for spark. Its not that hard, you would just need to copy the internals of the opti and use LEDs and light-diode recievers. We use them all the time in our research and the wiring isnt that tough... they just send voltage signals when light hits them. Getting the voltages right shoudnt be hard either.

The hardest part is getting past the double speed of the crank vs the cam, but Im sure there would be a way around that.

 

You can't use a crank signal off the pulley to replicate the Opti signals. You need true cam position to run sequential injection and direct-fire ignition.

 

I just though of a major problem running a Large cube motor off of a Gen III PCM. The Gen III has no provisions for Acceleration Enrichment (AE) All of the AE stuff seems to be hard coded for the intake characteristics of the LT1. My guess is a big cube SBC would stumble on tip in and thats something that may be hard to get around. Perhaps a strategy of early onset PE or a couple whacky cells in the VE table could help but that's a poor work-around in my book. Will DFI or Big Stuff drive LS1 coils?

Steve

 

You guys worry too much.

I did a conversion on a 400 sbc to use LT1 management. It's actually very cheap and easy and when I get back from the sandbox I plan on putting up a 'how-to' thread with some pics

You need some 1" water pump spacers, and electric low profile pump, internally balanced rotating assembly, a custom timing cover and adapter, and heads. Ignition and valvetrain depends on how much you want to spend and what you want to do. The conversion could work a dozen different ways. For example, I have an LT1 running TPI components in my '86 iroc-z right now. No butchery.

My plan was at first a 420 ci. sbc. I was going to just put on some good heads, single plane, and tune the PCM for the combo. I was going to make it roughly the same as my current 383 LT1 but proportionately bigger and compare the power and mileage differences.

Since I'm deployed, the project has stalled. But I have gotten it together to know that the engine bolts together fine as a package, so I dont see why it wouldnt work. The whole point is to do this, then duplicate it on a 454 sbc with some nasty heads. And say it's a 350 This has been together with the accessories, opti, and water pump. I added a mount to the lifter valley for the factory oil pump driveshaft adapter, but you could use a distributor if you wanted to.

Food for thought.

Oh yes, and the water pump clears the radiator, but barely. Only some types of pumps will work depending on how long they are. The conversion is easier than it looks...anyone with enough knowledge to build an engine could easily do it. It looks more intimidating than it really is.

 

Grrr. . . this is one of my pet peave's. I've been living with a lean bog on tip-in for a few years now. It's better in open loop, so I disabled closed loop. I sure wish someone would figure out how to fix this. If I ever switch to a standalone, it will be for this reason.

Mike

 

Open loops should take care of that and i think that can be taken care of with the obd2 pcm.. i will check out which tables are there for that...

Acceleration enrichment is used a lot with the V6 crowd.

 

Another possible solution to the AE dilemma on the PCM is to step back to a 93 SD PCM. All of the AE tables are mapped out for those. Then you've got the speedo inputs to deal with (unless you own a 93 obviously)

Steve

 

Can you specify which pump is short enough to clear stuff? Also did you start with an LT1 timing cover for your modifications or something else?

Thanks

Steve