I'm building/restoring my friends 1986 IROC-Z for his widow. My friend bought this car in 1996 and drove it until he passed away in 2002. His widow has had the car in storage ever since and is now ready to set it up the way her husband always wanted it. I spent a ton of time wrenching with my friend, and discussing our goals for the cars, so I'm pretty familiar with how he wanted it.

On to the car. It is an 86 305 TPI, 700R4, IROC with open differential and rear drum brakes. It has hotchkis springs, subframe connectors, and thats about it. Goals are T56 swap, keep the car EFI, but more modern performance (300 RWHP is the target). The interior needs some restoration, and the car definitely needs paint. I'm planning to build a mild 350/383 with iron vortec heads and one of the more modern injection intake manifolds. I'll likely use megasquirt or similar ECU to handle the tuning. Once I get an engine built/bought I'll source a T56 and start that conversion.

I'm certainly open to suggestions and ideas, I've been out of the american car scene for a while. I should be getting my hands on the car some time this winter, so until then I'll research and start collecting parts and pieces.

 

You should be able to get it done for that kind of money if you do the majority of the work yourself. Paint and interior is where the majority of my budget will end up being spent.

 

if you are thinking t56 swap and updated fuel injection, id take a good look at finding an lt1/t56 f car and take the whole drive train, you get posi, updated fuel injection, and the trans. If you are patient you can probably find one with some "mechanical" issues for not a whole bunch, then build up the LT1. The LT1 has similar heads to the vortec, and from what i have seen has a decent aftermarket and help for tuning. I never looked into megasquirt, so im not sure how it compares.

just my 0.02. And I can tall ya, the LT1 isnt a bad swap at all, the wiring is tedious, but thats about the toughest part of the swap.

 

I thought about the LT1/T56 swap, but it appears there is an issue with the AC compressor that requires notching the k member?

I picked up what I believe is a L98 tonight. The only block tag I can find says 57LG and CFD. The heads are aluminum 14101128 (L98) with mixed 1.5 and 1.6 roller rockers. I also got a decent set of short tube headers, Accel 30lb injectors, centerforce clutch, and an ECU. The guy said he bought a 3rd gen with that engine and a WC T5 in it and it ran strong. He's not sure what cam is in it, but seemed convinced it had been built and said the heads were ported, etc. I'll get it on a stand and start tearing it down to see exactly what I have. I know the L98 heads will be my limiting factor once I ditch the TPI intake, but I think I could still build a torquey 300+ WHP car that is drivable. I'll still go standalone ECU since I don't want to deal with chip burners and emulators and already have some experience.

The ECU has a hypertech chip in it and I'm assuming they never offered custom tune. How the hell was a L98 running 30lb injectors with an off the shelf chip? fuel pressure turned way down? Planning to get the engine on a stand and pull off all the covers, hopefully ID the cam, and cross my fingers. Engine looks really clean under the valve cover.

Here's my CL find

 

Here is where you can find the #. Remember it doesnt really mean anything tho. You dont know if its been bored, decked, so who knows what you really have.

 

Block casting only lists 5.7LG, nothing else. The VIN may be covered by the intake, will find out soon. My guess is the block and heads belong together (87 Corvette), but who really knows. I just wanted to make sure I got a 350 block. I want to put the engine on a stand tomorrow and begin pulling covers to try and unlock this mystery. Hopefully, it's a lowish mile rebuild that won't require much reworking. I'd like to try and ID the cam, check the bearings and bores and maybe avoid pulling the heads if it all checks out.

 

The LS motor swap AC compressor relocation kit is what you can do instead of notching the cross member
http://www.ebay.com/itm/Truck-sanden...tRiDA2&vxp=mtr

 

Oh well, too late now. Thanks anyway for the info. If this L98 doesn't work out, I may go that way.

 

Someone poke holes in this idea for me please.

Let's assume I go through this L98 and everything is good to go. I know I want to ditch the TPI intake and I plan to go megasquirt. One of the options megasquirt provides is control of individual coils (more on this later). Lets say I spend $100 on a LT1 intake with injectors, rails, FPR, and throttle body. The HSR is basically a copy of the LT1 style intake, so performance should be similar. Can I stick this intake on my L98, ditch the distributor, buy 8 used LS coils, and run a wasted spark config for ignition?

Part of that question was rhetorical, I know I can run 8 coils in a wasted spark config, I'd just need a wheel and pickup for the signal. The part I unsure of, is the LT1 intake on the L98. I like the idea of going distributorless for simplicity, it should make tuning much easier and clean up the engine bay.

Found a nice pickup here

Nice affordable ECU and harness here

 

I know the LT1 intake has been used with the standard distributor systems in the past, so from what i remember minimal work will have it on the L98. Your biggest issue will be the thermostat housing. The LT1 intake does not have coolant running through it.

Take a look at other sbc 24x conversions. Sounds like that might something that would work for you. The coil/cylinder. I think you end up getting the vortec style timing cover with a crank shaft position sensor on the snout of the crank shaft. There are all sorts of options to go coil on cylinder for small blocks.

 

Thanks tglennon11, So maybe the LT1 intake may not be as easy as I thought. I'm guessing using the LT1 water pump won't work because of the optispark in the way? I may have to cough up the cash for the HSR and fuel rails, but I'm definitely going to ditch the distributor and go coil-near-plug. I did the same thing on my 87 930 and never looked back, it's really nice not to have to rely on vacuum or mechanical advance/retard (especially when it's retard on boost to avoid blowing the engine to pieces). Thanks again and keep the info coming, it's been a while since I worked on a pushrod engine or an american car.

 

take a look at this thread, you might be able to do it with a "standard" intake for the distributor, should you want to keep the TPI

https://www.thirdgen.org/forums/tpi/...-cylinder.html

 

One piece I forgot about was the oil pump drive. So I'd need an LT1 oil pump drive gear as well. Not needing the distributor hole eliminates the most difficult part of the LT1 conversion according to this info

I'd spend $200 on an LT1 manifold vs the $600 on the HSR stuff I'd need.

The HSR would be cleaner and easier, just more expensive so I need to weigh the pros/cons.



24x timing cover with crank sensor
ECU

 

So, as I'm getting into the engine, I've been able to ID the cam. According to to the markings, I have a comp cam 260AH-14. This appears to be a fairly mild flat tappet cam. Combined with 1.6 int and 1.5 exh roller rockers, what numbers are we looking at with an otherwise stock TPI L98? What would be a better cam for my 350 crank hp goal and HSR?

cam specs: Hyd. Hyd. 1500 to 5500 12-402-4 260AH-14 260 268 212 218.444.444 114°

I also found part numbers on the headers 06 97 L 335 and 06 97 R 335. Anyone know what these headers are? Are the worth cleaning up and coating for this project? They seem to be standard shorty headers and look like the hookers.

 

Got just about everything off but the heads and oil pump. So I have a 2 bolt block with no casting marks other than what I posted before. I found a casting mark on the crank: 14088526 which points to a 350 cast internally balanced crank with 1 piece rear main. I also found a series of casting marks on the rods: F3951 GM 816. The hardware appears to be stock, no ARP goodies that I can see. It appears I have a late 86 corvette L98, aluminum heads, flat tappet cam, and passenger side dipstick. I need to check the bearings, but the rest of the engine seems pretty clean inside. Pistons are part number 14088801. Once I pull the oil pump and windage tray, I'll try to peak up into the cylinders and decide if the heads need to come off.

 

Question time, here's what I have: 350 2 bolt block from an 86 corvette, unported 128 aluminum heads, a 260AH-14 cam, 1.5 exh and 1.6 int roller rockers. Everything inside looks very clean, the engine appears healthy.

Where do I go from here? I'd like to bolt on a HSR, shorty headers, and megasquirt the thing, but can I make 350 crank HP with that combination, or do I need a different cam and/or heads?

The car won't be raced, it just needs to look/sound good and not be embarrassing at the stop light. 350 CHP should put it near 300 RWHP with a T56. That'll be close to double its factory 150ish RWHP.

Thanks in advanced for the help.

 

So my main and rod bearings look excellent, as do the cylinder bores. I've decided not to pull the heads since everything looks great from below. I spoke with comp and they said the 260AH-14 cam will work nicely with the 128 heads, HSR intake, and 3.73 gears. The power band should be 1200-5550 RPMs. With some help, I've been able to identify the headers as Hedman, and have dropped them off to be cleaned and coated. I don't have the Y-pipe, so I'll either buy theirs and replace the single 2.5 pipe with a 3" or fab up my own.

I picked up a 60-2 crank sensor kit to mount on the balancer and will be using a set of LS coils to get ride of the distributor, I'll also use the LS injectors as well. I'm going to go with a microsquirt V3 for engine management. Once I get the engine buttoned up, I begin to look for a LSD disk brake rear end and WCT5 or T56.