496 stroker

[puckhead]

I just got off the phone with the local machine shop i was told that it is very hard to build a 12:1 pump gas engine... silly me I thought people did this all the time...

after talking to the guy a few minutes we were throwing some #'s around and this is what I and the other guy think will work

so heres the plan:

1 454 4 bolt main block bored .060 over stuffed with a calles 4.25 stroke 4340 forged crank custom ross pistons some 6.535 h beam rods open chamber heads (style to be determined) soild roller cam with a relativly low duration

 

[Ryan B.]

yep my 11:1 469 pings and detonates like crazy at about 3/4 throttle on 91 octane. I could cruise just no getting my foot in it without race fuel!
Hydraulic roller= set the valve lash once or twice and your golden for years.
Solid roller= Gonna get good at adjusting/checking them every month or two, for the benefit of more TQ/HP.

 

[sled_dog]

what is this for? You say low duration but solid lifter? I don't see the purpose in that in most applications.

And yes, iron head 12:1 on pump gas, good luck.

 

[puckhead]

They said low duration so cylinder pressure isnt so high its gonna be for street and trails I'd like some good reliability also

 

[blazin_blazer]

12.5 sbc

i have 12.5:1 in a 383 and it takes 2 bottles of 104+ octane booster to about 12 gallons of gas and have no problem except on wallet or when pulling to tall a gear

 

[blazinzuk]

I have heard of people having better succes running higher compresion ratios with the new coatings that are out. These are just dyno tests though no real world stuff. One company said you could run a full point of compression higher because of their coatings, don't know if this is true or not but something worth looking into

 

[smalltruckbigcid]

If you use aluminum heads the heat transfer will reduce the cr about 1 point.
George

 

[4X4HIGH]

They said low duration so cylinder pressure isnt so high its gonna be for street and trails I'd like some good reliability also

Are you sure they didn't say long duration? The long duration is what bleeds off low end cylinder pressures allowing more compression ratio to be run, but this also makes for a real choppy idle and starts to make it not so street friendly and reliable as you want. You can't have the best of both worlds, you give up some dependability and mileage for performance and horsepower.

 

[moturbopar]

Are you planning on running stock head castings? If so I dont see anyway that those crapy combustion chambers will work. I think the only way would be a set of modern heads and coatings and you might get away with it, but I doubt it. if you run aluminum heads, you might but I doubt it also. Also low duration cams and high compression dont mix, usually it takes a pretty big cam to work with higher compression, or a very wide lobe seperation something to bleed off cylinder pressure. Why not just forget the high compression and spend the $$$ on a few more extra cubes? Or spend a little extra on the heads?

 

[k20]

If you want low end, and for trails. Whats the need for the 12:1? I have a 496 runnin 9.7:1, on large valve, slightly ported 049s, and it has all the power Id ever need. Lights em up realllll good lol. Desktop dyno says 460hp, 600ft/lbs. I think that the tq is rated a little high, but 3 broken th400s, it might not be .

I say lose the idea of 12:1. Kick back to 10:1 max, that is, unless you have the $$ to pony up for 100 octane at 6.00 a gallon.

 

[unclematty]

I'm runnin a 10:1 , .060 over 513 caddy motor, that runs on 87 octane all day long and offers more power then can use in my 7000 lb rig, no lumpy cam fairly inexpensive to build and great to maintain. Forget that hi comp paperweight get a caddy! just one mans .02 cents

 

[moturbopar]

I'm runnin a 10:1 , .060 over 513 caddy motor, that runs on 87 octane all day long and offers more power then can use in my 7000 lb rig, no lumpy cam fairly inexpensive to build and great to maintain. Forget that hi comp paperweight get a caddy! just one mans .02 cents

Its true even the bad cad heads have pretty good combustion chambers. The 76cc heads are very nice, and look similar to many of the modern heart shaped chambers. I built a 500 with the large chamber heads, it had around 9.0-1 compression when built, ran on 87 all day and didnt even ping with 50deg toal timing(dont ask)! The best power was with total set at 38 deg. The engine was a 200,000 mile junkyard motor, put fresh rings and bearings in, mt10 cam, home ported big chamber heads, edelbrock intake, headers and milled the heads. pushing through a built 700r4 and a dana60 the truck made 380rwhp at 4200rpm and 510ftlb at 2600rpm. had a total of $1200into the engine.