# 400 stroker rebuild



## Kenta32 (Jan 17, 2021)

Hi, need some advice for my rebuild. Have a -71 400 YS engine and #96 (96 cc) heads in my -68 Firebird with a M20 and 3.36 in the rear BOP 8.2. No PB.
Thinking of a stroker-kit 4.115 bore, 4.250 stroke to 461cui. Forged rods and pistons. Aiming to get much better low/mid range torque for street-use, calm idle and strong car in the rpm-range idle to 5000/5500 rpm. With stock heads and manifolds. New stainless steel valves (2.11/1.77) and 3-angle valve job. Think I get about 9.3-9.5:1 in static compression ratio (Wallaceracing calculator), good for using pump-gas.

what recommendations for suitable hydraulic flat-tapped cam?
can I go for a cast crank in the stroker-kit?
the pistons is now 0.020 “in the hole”. Will that be the same with the stroker-kit?
is it a good idea for my build to topdeck to 0 for better quench?
a hard question to answer probably, but will my 4-speed Muncie and rear end hold for the torque?


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## PontiacJim (Dec 29, 2012)

Kenta32 said:


> Hi, need some advice for my rebuild. Have a -71 400 YS engine and #96 (96 cc) heads in my -68 Firebird with a M20 and 3.36 in the rear BOP 8.2. No PB.
> Thinking of a stroker-kit 4.115 bore, 4.250 stroke to 461cui. Forged rods and pistons. Aiming to get much better low/mid range torque for street-use, calm idle and strong car in the rpm-range idle to 5000/5500 rpm. With stock heads and manifolds. New stainless steel valves (2.11/1.77) and 3-angle valve job. Think I get about 9.3-9.5:1 in static compression ratio (Wallaceracing calculator), good for using pump-gas.
> 
> what recommendations for suitable hydraulic flat-tapped cam?
> ...



cast crank will be fine
not sure how far down in the hole the pistons will be as th stroker kit uses a longer BB rod and Ross pistons. Contact whomever you get your stroker kit from to answer that one. If you "zero-deck" the block, it may affect compression, so recalculate your numbers if you do. Zero deck is a personal choice unless the block needs to be decked/squared. It is an $extra operation, but can make it easier to get a good quench/squish distance of .040"-.045" between piston and head. So something to consult on with your machinist.
-Tranny and rear may hold up, but may not, depends on how hard you like to drive the car, posi or non-posi, wide tires or factory skinnies. Use it until something pops, if it does, then go with something more rugged.
- Cam choice is many. It depends on what the compression is - my opinion on selecting a cam. I like the cams with a 112 LSA, but 114 LSA can be good, and then look at your overlap numbers. The more overlap, the more lumpy the cam, but it generally means more duration and that means the power band goes up for useable HP. I think overlap in the 63-70 range might be good. Closing of the intake valve is a key component of a cam - too early and you can build too much cylinder pressure and have detonation. Too late and you will be blowing power out the exhaust on the lower RPM's and picking it up at the higher RPM's and not enjoying the lower side of the engine. If stock heads and no port/flow work, going over .450" lift is about it for flow. The 3-angle valve job will help flow, so a cam with lift around .480"ish would be good. I like around a 280 duration, but you can probably go a little more. The larger cubes will tame down a cam. I would not overthink cam selection as there are at least 100 you could choose from.


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## Kenta32 (Jan 17, 2021)

Thanks for the quick reply and input. Yes there are LOT of cam choices out there.
I have earlier looked at a Crower 60243 that seems to be pretty close your good recommendations. Adv duration 284/290, lift 0.479/0.494, LSA 112. Not sure of the overlap but could be in the 63 range. Crower 60242 seems to be a bit milder but also close.

Could Crower 60243 or 60242 be a good choice for my build?


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## deanhickey (Apr 6, 2015)

I just completed a very similar build to the one you are contemplating. I chose a "086" Pontiac grind cam, very smooth idle and street manners and it can still spin the tires when I come down on the pedal. My goal was a cruiser not a racer. That cam might be too mild for you but it gives you a reference point. LSA-116 OVERLAP 63, DURATION 288/302 (I think)

a good article about Pontiac cams. lhttp://www.silverstatepontiacs.com/jharticles/jharticles5.html 

Good luck with your build and enjoy the ride.


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## Old Man Taylor (May 9, 2011)

I think you mean 068, not 086.


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## Kenta32 (Jan 17, 2021)

Good reference and I also read the article. I’m not going for the worst street-racer either and wants, as you point out, smooth idle and street manners. But at the same time get a good use of the 461 cui. The 068 / Melling SPC-7 could perhaps be an alternative. 
Deanhicky, did you also build with a manual M20?

If I would go for one of the Crower cams 60442 or 60243, which I translates to be a bit bigger cams compared to the 068, could those work fine for me too or do I have to consider something else?


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## Old Man Taylor (May 9, 2011)

I would not get the exact 068. I would get a new grind that has the same specs. The shape of the lobes is much better than the old factory grinds. I can go into some more detail later.


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## Atarchus (Aug 4, 2020)

I just rebuild my 400 into a 461 stroker. I went with at 230/236 @ .050 with 112LSA hydraulic roller cam. My car is an automatic, street driven cruiser with a 2500rpm stall converter. This is definitely as large as I would go for a cam for a street driven automatic. If you have a manual, you might be able to go one or two steps bigger. Also, with my ported Edelbrock heads and Torquer II intake I made peak hp at 5200rpm. A larger cam would push peak hp and torque up even higher, so all things considered I am very happy with my cam selection and it sounds great. Hopefully this helps with your choice in cam.


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## PontiacJim (Dec 29, 2012)

Kenta32 said:


> Good reference and I also read the article. I’m not going for the worst street-racer either and wants, as you point out, smooth idle and street manners. But at the same time get a good use of the 461 cui. The 068 / Melling SPC-7 could perhaps be an alternative.
> Deanhicky, did you also build with a manual M20?
> 
> If I would go for one of the Crower cams 60442 or 60243, which I translates to be a bit bigger cams compared to the 068, could those work fine for me too or do I have to consider something else?


The 60242 shows to have 59 degrees of overlap. The 60243 has 63 degrees of overlap. The 243 will have less vacuum, be a little more lumpy, and pull harder as RPM's increase. The 242 might be a good automatic cam, have better vacuum, and pull harder on the bottom end and up. BUT, the 461 will have plenty of bottom end torque as is and the 243 would most likely pick up the difference from low-mid to upper RPM's of the engine.

So the cams are similar, but I like the "bigger is better" thinking and would pick the 243.


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## Kenta32 (Jan 17, 2021)

Thank you all for the inputs for my rebuild and cam choice!


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## deanhickey (Apr 6, 2015)

Kenta32 said:


> Good reference and I also read the article. I’m not going for the worst street-racer either and wants, as you point out, smooth idle and street manners. But at the same time get a good use of the 461 cui. The 068 / Melling SPC-7 could perhaps be an alternative.
> Deanhicky, did you also build with a manual M20?
> 
> If I would go for one of the Crower cams 60442 or 60243, which I translates to be a bit bigger cams compared to the 068, could those work fine for me too or do I have to consider something else?


my build was for a th400


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