Street/Strip stroker?

[jnordness]

Hi guys. I frequent other AMC boards, but I think this is my first post on here. I have a 78 AMX I'd like to hop up someday and I'm trying to do a little research on my engine choices. It has the 258 in there at the moment, with some Clifford goodies, like a single plane intake with Holley 390 and the dual exhaust headers. I may just go with a V8 eventually, but I'd like to know how good of a street/strip engine I can make out of a 4.7l stroker.

I've been playing around with some DD2000 numbers, but I know that it's just a guideline. I'm looking to run either of the big Crower solid camshafts, and the biggest one, according to DD, peaks at 6500 rpm. If I go the stroker route I'll just be using the 258 crank and rods, and I'm having some doubts about the ability of the rods to rev that high with such a long stroke. I plan on keeping the carbureted intake and headers, but I may need to modify them some for the 4.0l head. I know Sixpak has built a pretty wicked strip motor, so I don't know if he's around to give me some input. My goal would be to try to break into the 12's with a T5 trans and 4.11 to 4.56 gears. Think that's possible with a 4.7l?

Joel

[amcinstaller]

if you frequent some of the main amc forums, youre probly also familiar with turbo tom. his turbo charged 4.0 is moving his spirit pretty quickly down the 1/4. seems to me his fastest is around 10.89?? this is an awesome place to get info on the stroker engine though, and if you search you may find the thread about crank harmonics and where the limit is for rpms.

[Plechtan]

Most 4.7 motors end up around 250-270 hp, your rods will be fine, Six Pac uses stock rods.

I doubt you will be able to get 300 hp. the biggest problem is getting enough airflow through the intake system and the head. More air = more hp.

[SIXPAK]

Back in 1991 my stroker was dynoed at 308 I believe. Stock renix head with a nice valve job, 12 to1, cast roller cam .640 lift, stock intake and TB, stock rods, and 287 c.i., Nothing fancy.

[amcinstaller]

so, with a newer "better" style head and intake, larger throttlebody, and all your same mods, could net a little more. out of curiosity, how long did it run, or is it still running?

[Don H Jr]

That is one irritating avitar you have there.

Jr

[SIXPAK]

Cam had to be replaced about every 1 1/2 yrs. Spring pressure was 160 seat and 360 open. I ran that motor for about 6 yrs. It was reringed twice during that period. It meet it's demise when I started running a bit lean while running some Nitropropane. It broke some ring lands from detonation.

[amcinstaller]

That is one irritating avitar you have there.

Jr

they only get worse from here hun!

thanks sixpack for the answer on the stroker life. good to hear, but sorry to hear the end

[Don H Jr]

Aaaaaaaaa K

Jr

[SIXPAK]

BTW, first year was 1991 and last was 1997. If it wasn't for the nitropropane it would have last many many years.

[SIXPAK]

jnordness, Do yourself a big favor, spend the money on some good pistons and use the 4.0 rods. From my experience the 258 rods are not the best mix for a high reving stroker. The 4.0 rods are plenty strong for what you want to do. Just be sure to get good rod bolts for them.
As far as a cam goes stay around 248 to 252 @.050 for intake duration. Exhaust should be about 252 to 256 @.050. If you are palnning to go the manual trans route have it ground on a 108 lobe sep.

[jnordness]

jnordness, Do yourself a big favor, spend the money on some good pistons and use the 4.0 rods. From my experience the 258 rods are not the best mix for a high reving stroker. The 4.0 rods are plenty strong for what you want to do. Just be sure to get good rod bolts for them.
As far as a cam goes stay around 248 to 252 @.050 for intake duration. Exhaust should be about 252 to 256 @.050. If you are palnning to go the manual trans route have it ground on a 108 lobe sep.

High reving was my concern about the 258 rods. I have been thinking about the good pistons as well, not having a super-ultra-mega high horsepower car on the street, but being able to hit a bit of nitrous at the track. But with the increase in cost, I may as well go the V8 route.

The crower cam I'm looking at is close to those specs, 248 @ .050 intake & 250 @ .050 exhaust, on a 110 CL, but I plan on retarding it a bit. I plan on going about 11:1 compression, and the DCR with the big cam is slightly over 8:1, so hopefully I'll be able to run pump gas.

There's a 4.7l stroker on Youtube that's fairly mild, 8.43 compression with a turbo camshaft, and with the clifford single plane intake and a 750 cfm carb, it went something like 318hp @ 5500. I hope to be able to make ~ 350 hp, but judging from what you said, Sixpak, I don't know if I'll be able to make that. I'd like to be able to turn 12:99's N/A @ 3300lbs.

[SIXPAK]

As far as I can see, 12.99 should be easy. My areodynamic jeep ran 11.16 at 2500lbs.

[Don H Jr]

Your aero-Jeep doesn't break parts, and gets great MPG too.

Don Jr

[johnhalabama]

I'm building one also for the street to go in a 1936 Dodge Sedan. I'll be doing some light towing but it will mostly be highway speed.

96 4.0 w/ Clifford intake and 390 Holley. Still looking at cams also. Running a 904 manual for now but will probably change that out at some point.

John - Chesapeake, VA