[rkraczek]

The current 350 in my Lemans that I rebuilt 21 years ago decided to hammer a rod bearing, so I'm doing the smart thing and building a stroker with my '68 400 block.

Car is a cruiser, and I do drive it @70-80 on the highway for a couple hundred miles at a time every so often.

Specs:

1971 Lemans convertible
3:36 gears
Th350
Factory A/C with heavy duty radiator, shroud. etc
Power brakes
Car is used exclusively at sea level

I've been reading a ton of posts on here about 455 and up cubic inch builds, and have narrowed down some specs I think will work for a nice streetable 460 sized stroker. I've also built about 50 cam profiles in Desktop Dyno. . .getting cross eyed

Here's the list of what I already have engine wise:

1968 400 block. Recently bored .030 over
1968 big valve #16 heads, recently refreshed with positive valve seals and a light port job. Measured at an actual 72CC
Long tube headers with Pypes 2.5 inch exhaust with x-pipe
Factory '71 4bbl intake and 800cfm Qjet

What I'm thinking of buying and having done:

Butler balanced stroker kit
Zero deck block
Shoot for 9.5 - 10:1 compression depending on the final cam choice

Cam choices:
Either Crower 90243 flat tappet OR
https://crower.com/camshafts/pontiac...amshaft-7.html

Howards 414495 Roller
https://www.howardscams.com/hydrauli...cams-414345-12

I've seen a lot of way more experienced guys than me on here mention cams like these as the correct size for a 455 and bigger street cruiser engine. Looks like I should have about 150-160 psi cranking pressure with either if I stay in that compression range, I assume these cams will idle nice and vacuum will be decent.

Will the #16 heads need to be rechecked if I go with a .560 lift roller?
Am I on the right track here with cam choice and compression?
Are there other cams I should consider? Open to flat tappet OR roller.
Can I go higher on compression without hammering rod bearings if my tune is spot on? What's a "safe" dynamic compression?

Thanks

[65madgoat]

You will be going dished pistons with those heads. Would love to see aluminum heads on there. Nice roller cam like that Howards with 112LSA and some 85cc Kauffman or 87cc E-heads.

[steve25]

If your talking about a solid roller and associated cost I would rather see you put in a flat tappet Hydro Cam and move some of that cost savings into a aftermarket set of D port heads.

You will end up with far more hp then if you even kept the iron heads and ran .650" lift.

You will then also benefit by being able to run 10.5 compression and knocking weight off the nose of the car.

[Lee]

If the car is just a cruiser, and running unported heads, then I'd drop the compression ratio WAY down.

My 455 is just 8.3:1. With a stock torque converter and 3.08 gears, running 87 octane, it has ran 13.12. It doesn't overheat, either.

[Mister Pontiac]

Great question that will get you a hundred different responses. It's hard to answer definitively until a few more questions are answered.

I always say, start with the end in mind...

1. What is my budget?

2. Do I really just want a cruiser, or am I really aiming for more?

3. Is original look desired (cast heads?) or not required (aluminum heads)?

4. Do I then need to upgrade the rest of the drivetrain if I build a lot of power?

As an example, you describe wanting a cruiser primarily with 70-80mph highway runs for hundreds of miles at a time and the occasional full throttle blast. A nice stock 400 with those #16 heads will get that done with a great amount of street power, and ease of operation. No need to go all in on stroker kits, aluminum heads, roller cams, etc...

Hope that helps even though I didn't address your specific questions (yet).

[CROCIE JR]

You are gonna need a 35cc dish with a 72cc head and 0.010 deck clearance to get down to 9 to 1. So thats a custom piston. Probably $1100 said and done. At 9 to 1 thats 91 octane with that head. Use that money for a set of aluminum heads. Do not put a flat tappet cam in it. Find a 2.56-3.08 posi diff.
Personally I would build a 9.25 to 1 aluminum head 87 octane engine with a 230 something roller in it. Dont get to worried about all those cams. The HP difference at this level is maybe 30-45 hp from a 230 to 240 cam at 0.050.
It will make 460hp at like 5100 and 545 ft/lbs at 3200 with a roller cam in that range.

[i82much]

what about maybe finding a 400 crank?