jmoney843

Well I picked up a 406sbc through a friend of my fathers. Its a 4 bolt main (casting # 3951511). Although it does need to be honed, it came with the crank (also needs to be honed), a set of forged TRW pistons (part # L-2477F-30) which is a .145 dome piston which seems to be setting my compression pretty high:



Is there a way to be able to drop the compression or do I just need to look into a large CC head or would it be a better route to sell or trade off these pistons for another set?

Also, is there a way to ID the rods? I dont see any markings on them to show a brand or anything

The motor came out of a very quick trailer queen (9 second S-10) or so Im told. I paid 300 bucks for everything as well as a few other odds and ends. I plan to slide this into my 89 Iroc sometime over the next few months. Are there any issues with pulling the entire 350TPI and sliding in the 406? Would I be better to leave the TPI system or run a carb'd setup (id prefer this route). If so what needs to be pulled and what needs to be left for the car to function? Will my stock 700r4 be able to take the abuse from a motor this size or does it need to be beefed up (or swapped? although i want to keep an auto). Are there any guides online on building a 406 from the ground up or even sliding one into a third gen? Any books anyone can recomend? anything to help I would greatly appreciate it.

F-BIRD'88

As you can see from the chart any popular cylinder head combustion chamber size will cause the cr to be way way too high for a pump gas motor using those domed pistons.

For a street driven 400 you want to use flat tops for alarge 76cc heads and dished pistons for any of the popular 64 to 70cc heads.

Keith Black makes both a 22cc D cup piston for the 400 using 5.7 rods and a 18cc d cup for the 5.7 rods. Both are hypers.
Sell off your domed pistons to some one who whats to build a race motor.
The rods are likely stock GM 350 rods (5.7"). Look at the rod bolt heads to see if they were ground for cam lobe clearance.

When you swap to different pistons you'll have to have the crank rebalanced.
Speed Pro also makes dished pistons for this application.

if I was doing this I would use my 350TPI heads (083) and top end. I would select a hyd flat tappet cam for the 400 with wide LSA to be TPI friendly. 114LSA. I would not get crazy with cam size as a TPI induction system is all about low mid torque. Crane cam #113931 H-266-2 (REPLACES HMV-266-2) is a good match. You could even swap to 1.6 rockers.
I'd build for a 9.5 to 9.8 finished cr. KB 168 pistons will get your there using your 64cc tpi heads.
I would moderately port your 350 TPI heads and get new 2.02x 1.60 valves. You can do the porting at home and have a machine shop do the machining and valve job for the new valves. These heads respond very well to home porting.

The TPi EFI computer should run fine with this cam as it will have strong idle vacuum. The TPI computer will need the chip fuel curve program re tuned as the 400 will use more airflow than a stock 350 ci motor. I would get some shorty headers for this motor. may/ or may not, have to go up 1 size in injectors.

You can use your stock rear gear ratio, trans and stock torque converter as this motor will have a ton of torque.
A trans shift kit and cooler will help your trans live a long life behind a 400.

Keep it Stealthy by sliding a mild built 400 ci motor under your stock appearing TPI/ head top end package.
You'll retain all the good points of the TPI combo but run like no other. Emissions legal too.
Many here from the TPI board can help you with the specifics of setting up your EFI computer for your new motor.

You did not mention what heads you got with the 400 motor.

jmoney843

How much could I ask for them, the pistons are in flawless shape, as are the rods also has chrome moly rings.

Yes, they are...this a good or bad thing?

Im sure this is the fastest way to get the motor in the care, and one of the cheapest, but it seems like it would strangle the motor for power, although on torque im sure it would be a monster.

Where or who would be able to burn my chip? Is there a place online to have this done?

There were no heads, but I bought the motor the guy asked if it was gonna be street driving or a track car, I told him it would be a street driven weekend toy, in which he insisted the heads would give me a far too high compression ratio to drive on the street, so I wouldnt need them.


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Also using the TPI and the setup you mentioned how much power would I be putting down?