AMC V8 Stroker Combinations (using 304 and 360 blocks)

[amundaza]

Hey guys,

I ran a couple of storker combinations through the calculator and came up with some interesting combinations to build.



342” STROKER (304 block & 390 crank)

Offset grind the 390 crank for a 2.10” Chevy rod journal, which allows a 3.782” stroke

Run off the shelf Chevy 5.7” H-beam rod (I Noticed that SBC rods are narrower than 390’s, so a Chevy H-beam 6-cylinder rod could be used, it’s slightly wider than 390 rod width and has a 2.0” journal).

Off the shelf 0.060” over (stock is 3.736”) Keith Black 305 Chevy piston (1.56” pin height & 5.5 CC valve reliefs).

With my current deck height (.010” milled), I get a .002” deck clearance (would be 0.012” on stock 70+ block).

With my current 62cc 304 heads (ported and polished … SBC valves), it comes to 9.94:1 compression.

It can also run their 16 cc dished 305 piston, to get 9.6:1 compression.





435” STROKER (360 block & 390 crank)

Offset grind the 390 crank for a 2.00” Chevy Rod Journal, to a 4.07” stroke.

Run off the shelf KB Chevy 400 pistons at STD bore 4.125” (1.433” pin height & 22 cc D-dish).

Run off the shelf 5.7” H-beam rods for Chevy 6-cylinder (wide big end rod)

Comes out to 9.75:1 compression and 0.030” deck clearance.

It can run an 18cc D-dish piston to achieve 10.1:1 compression



So, what do you think about these combinations?


Sincerely,
GregTaylor
Oxford, MI
1989 Grand Wagoneer : Water/Hydrogen Injection 360-V8. 4.5" lift 31" BFG A/T's. Killer32 front bumper

[tufcj]

The only problem I see is that off the shelf Chevy pistons have the valve reliefs in the wrong place for AMC heads. It might be less pronounced with the 304 heads with 1.94 and 1.50 valves, but running stock 360/401 heads with the 2.02 and 1.65 valves, you'd have to re-cut the reliefs.

You'd probably want the big valves anyway, AMC engines like and need to breathe.

Bob
tufcj

[Wrench Man]

I still don't understand every ones obsession with stroking the AMC's?????
they would make lots of torque but you cant wind them very tight!
The 343 I have SCREAMS!!! and if it had some good heads on it, it would probably make really good power!? it's rated at 280hp and 365ftlbs stock!?

I suppose those combos would make great trail/towing motors for jeeps!

[amundaza]

I still don't understand every ones obsession with stroking the AMC's?????

I already have a 304 stroker started from years ago, for turbocharging in a race car application. Since my project changed directions and I sold the car years ago, I still have the motor to complete and use in SOMETHING! I engineered it back then with a 390 crank in a 0.030" over 304 block and to 7.8:1 compression for high-boost turboing, which I don't want to run on a street/trail driven Jeep.

I may just opt for getting different pistons made up to raise the compression back up, since an 7.8:1 304 'race engine' would be anemic in power. I currently have a forged Venolia piston for the 304, based off of stock specs, but just a tad bit shorter on C/D.

I'm looking to bring it up to 9.5:1-10:1 and then grooving the quench area of the cylinder heads, to improve the burn characteristics.

I've seen some good input from racers doing this on high compression engines, being able to burn 87 octane pump gas with 10.5:1 motors and getting better power and economy due to the increased burn.

For more on the grooves, check out http://speedtalk.com/forum/viewtopic.php?t=4069 & the guy who started it all : http://somender-singh.com

I've also been in contact with one of the posters on the Speedtalk forums (automotivebreath user ID) and he has a stock 95 suburban he built up to 10:1 compression and uses the grooves with 87 octane gas.

Sincerely,
GregTaylor
Oxford, MI
1989 Grand Wagoneer : Water/Hydrogen Injection 360-V8. 4.5" lift 31" BFG A/T's. Killer32 front bumper

[amundaza]

Here are more calculations on the 304 Stroker Motor ...

350” STROKER (304 block & 390 crank) … Now this looks like a killer combination to run.

Offset grind the 390 crank for a 2.10” Chevy rod journal, to a 3.87” stroke

Run off the shelf Chevy 6.0” H-beam rod

Off the shelf 0.060” over (stock is 3.736”) Keith Black 305 Chevy piston (1.261” pin height & 5.5 CC valve reliefs)

With my current deck height of 9.198” (.010” milled), I get a .002” deck clearance (would be 0.012” on stock 70+ block)

With my current 62cc 304 heads (ported and polished … SBC valves), it comes to 10.2:1 compression

This combo can also run the KB 12 cc D-shaped dished 305 piston with a 5.7” rod, to get 9.45:1 compression.

Also, I was incorrect on the AMC 390/401 rods being wider than the SBC. I was thinking of the AMC 327 forged rods, which are 1.00” wide and have the same journal size as the 390/401 (327 rods are 6.375” long and are FORGED).

The 390/401 rods are around 0.92” wide, while SBC are 0.94” wide. This really opens up the possibilities with running a variety of SBC rods on the 390/401 crank.


Sincerely,
GregTaylor
Oxford, MI
1989 Grand Wagoneer : Water/Hydrogen Injection 360-V8. 4.5" lift 31" BFG A/T's. Killer32 front bumper

[jeepsr4ever]

Your stroke cannot be done unless your willing to weld up the crankshaft. The stock stroke of a AMC 390 is 3.577"-3.571" (from factory tolerances). So that is 1.7855-1.7885 from pin center to main center. For a 2.00" chevy rod journal the max stroke you will get out of a completely perfect crank is .1247 more stroke from rod pin center to main which gives you a .2494 increase in overall stroke or a stroke of 3.8264"-3.8204".


Lets say you go down to a .060 racing bearing for a chevy 2.00" journal. From a perfect crank (rods at 2.2495 diameter) you could get .3094 increase in stroke or a possible stroke of 3.8864"-3.8804"....this would be .060 under rod bearings starting with a perfect factory crankshaft and having a crank cutter that was VERY meticulous. I think realistically your looking at a max stroke of 3.800 with a 390 core crank.

3.800 stroke/bore CID possibilities

4.08=397ci
4.115=404ci
4.125=406ci
4.195=420ci
4.250=431ci

I would not use a 327 AMC set of rods for any stroker build. Your better off even with some chinese 4340 H or I beam rods to start with. Now you could try welding and annealing, stress relieving and nitriding (fwew :D ) to gain your stroke but I think in the end the small cheek wall after the radius on the rod journal sides would dissapear at the top end leaving you with the bottom half holding the rod in place (which may be alright...may not).

Alot of crazy strokes have been done already and their is much to learn and rehash but in the end the best choice for a stroker crank is either new, cryo'd used or a billet crank. Forged cranks are so benficial because they take more flexing than a cast crankshaft but they have a finite fatigue life. Once they reach close to the point of breaking the deep cryogenic process can help the molecules settle and re-align.

I like your thinking though!!!

[amundaza]

Thanks for the feedback. I'm not quite following you math here, please correct if I am wrong.

I have an NOS 390 crank, which I have previously had cross-drilled for my engine. The mains/rods have been left at stock diameters, so I assumed the 390 rod journal at 2.248" and half the 390 crank stroke of 3.574" = 1.787".

2.248" - 2.100" = 0.148" (offset available).

0.148" + 1.787" = 1.935"

1.935" x 2 = 3.87" stroke

This is how I calculated the numbers to get a 3.87" stroke. which theoretically seems possible with a 2.100" SBC Rod. You're discussing however, a 2.000" rod and only being able to achieve a 3.800" stroke with said rod and 390 crank ... this is where I am not following your math.

Once again, please advise on my math, compared to yours and if there is something I am missing here with offset grinding a crank in reality (as opposed to on paper).

I still have to get my block deck height re-checked, as it has 0.010" milled from the deck and O-rings installed (originally for turboing). I theoretically calculated my new deck to be 9.198" (stock 9.208" - 0.010"). Since there is a factory deck height tolerance, I'll have to calculate mine exactly, so that I get the stroke, rod and c/d correct, and near a zero deck on the pistons.

Also, I only mentioned the AMC 327 forged rods, as they are the ones that had the wider big end, which I though the 390/401's had.

Thanks for the added feedback.

Sincerely,
GregTaylor
Oxford, MI
1989 Grand Wagoneer : Water/Hydrogen Injection 360-V8. 4.5" lift 31" BFG A/T's. Killer32 front bumper

[jeepsr4ever]

What you missing is you can go down to that 2.100 but its the centerline that will only change so your only gaining .148 in total stroke not .148 x 2.

[amundaza]

What you missing is you can go down to that 2.100 but its the centerline that will only change so your only gaining .148 in total stroke not .148 x 2.

Hello again!
Yeah, I finally figured that out last night. I drew up (in my head) and overlay of the AMC and SBC journal at centerline and realized that, as you pointed out, I'm only gaining half by offsetting the difference. Looks like the theoretical MAX a 2.100 SBC journal could net is a 3.722" stroke from a stock AMC rod journal.

Thanks again for the help ... now back to the drawing board.

I am also considering having my 390 rods offset bushed 0.060" for a SBC pin, to 5.85" and simply running the 305 piston and the stock 390 stroke.

The other option would be to take a 401 rod and offset it back 0.008" to 5.85" and SBC pin size. Do you know who makes the AMC forged 401 rods (I-beam and h-beam) and if they could be direct ordered with said SBC pin size and rod length? Thanks!

Sincerely,
GregTaylor
Oxford, MI
1989 Grand Wagoneer : Water/Hydrogen Injection 360-V8. 4.5" lift 31" BFG A/T's. Killer32 front bumper

[Goose]

Wow, That is a lot of brain power right there..