quote Originally posted by FieroWannaBe: I will have to keep that all in mind down the road, if I find the I6 balancer lacking.

Good Luck on your project. Seems like you are making good progress.

Not sure if you came across my build a few years ago (https://www.fiero.nl/forum/Forum2/HTML/133921.html) if not, here's the link. Maybe you can avoid a few of the mistakes I made. My SD4 is still running (knock on wood) but I get too much detonation / spark knock from 93 octane gas. I've had to start using a mix of 50% E85 and 50% regular gas to get high enough octane to get rid of the knock. I was able to tune for this, without too much problem. Only issue is that the E85 is not available near by and I have to travel a bit to get it. But still cheaper than trying to get racing fuel.

FYI, the EPA legal amount of an MMT octane booster (like Lucas) will give about 1 number octane boost. Lucas's recomended amount for "off-road use only" is about 5 times the legal amount and will give a 2-3 mumber boost. High amounts of MMT can create manganese deposits so buyer beware. I 'm planning a Quad 4 project with either boost or high compression and plan to dose 93 pump gas to 94 with MMT.

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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged

quote Originally posted by edfiero: Good Luck on your project. Seems like you are making good progress. Not sure if you came across my build a few years ago (https://www.fiero.nl/forum/Forum2/HTML/133921.html) if not, here's the link. Maybe you can avoid a few of the mistakes I made. My SD4 is still running (knock on wood) but I get too much detonation / spark knock from 93 octane gas. I've had to start using a mix of 50% E85 and 50% regular gas to get high enough octane to get rid of the knock. I was able to tune for this, without too much problem. Only issue is that the E85 is not available near by and I have to travel a bit to get it. But still cheaper than trying to get racing fuel.

I have seen your thread, Im sure some of the data point have played into my decision making, like just planning on custom pistons from the start. the big issue I am not over yet is figuring out what CC to finish the head at to bring my compression ratio to a usable level for 93 octane. I do have e85 available at 1 pump near me. But that's limits my range for travel a lot.
I have been exploring modifications to increase quench as well to make the pump gas more detonation resistant.

I just put my Iron SD4 head and the 2 barrel intake up on EBay.
https://www.ebay.com/itm/12...r=artemis&media=COPY

https://www.ebay.com/itm/12...r=artemis&media=COPY

The Iron EGR head is with it's new owner, and the 2 Barrel Intake is lost in UPS hell.

I did work on tearing the block down further.

I found a dirty little trick I am not too happy with:
A welding Main saddle, but it appears to be an adequate repair.



Unfortunately the builder of the engine decided to forgo the prescribed 1/2" main studs and Heli-coiled the block for 7/16 studs in all the holes to replace the 11mm threads the SD4 came machined with.

The OD of a 7/16-14 Helicoil should be 17/32, which is the drill size for a 1/2-13" Helicoil.
The problem is, I have to Helicoil if I want the use the "proper" 1/2in stud since the 7/16-14 Helicoil is larger than a 1/2-13" thread. I don't see there being enough meat in the block at the main bearing split for the 1/2"-13 Helicoil, which has an OD of 39/64".



I don't want a crack to develop if the hole intersects the notch for the bearing tangs.

I most likely need to keep the smaller main studs.