What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

question for the engine builders

resurrected_jimmy

resurrected_jimmy

1/2 ton status
Joined
May 23, 2005
Posts
2,241
Reaction score
0
Location
back home in Houston
I would like some opinions on this build plan before I start sinking money into it. Is it too radical for a trail truck? and how long of a life would I get out of a motor like this?

4 bolt main SB bored to 4.125" x 4.00" stroke
5.850" rods, 14cc dish pistons @ 0 deck

aluminum heads, 64cc chambers
170cc intake ports, 70cc exhaust ports
1.94" intake valves, 1.55" exhaust valves

cam, hydraulic roller, 234/238 @ 0.050, 112 LSA

I'm looking at about an 11.0:1 cr so it should run on pump gas. From what I can tell it will be making around 500 hp and 550 lbs of torque. Let me know what ya'll think.
 
11.1 to 1 compression. i don't think that will run on pump gas unless you retard the timing a lot so it won't ping but it won't be making its max power.
I have a 10.95 to 1 469cid big block in my camaro. It pings like crazy on 91 octane. I can drive it around on pump gas, but if i give it more than 3/4 throttle it will start detonating bad. I mix in a few gallons of 114 each tank.
I'd say 10 to 1 might be pushing it.. 9.5 to 1 should be safe. If you're not trying to daily drive it, then i'm sure you won't mind mixing in a little race gas to get the most power out of it if it pings.
I plan on building a 383 for my daily driven k5 and i want to keep it under 10 to 1.
Hell, build it 7.5 or 8 to 1 and then its just waiting for some boost. :grin:
 
Last edited:
yea... I was gonna say the CR was a bit high... I'm running 9.8:1 in my 383... what do you think the best octane would be?
 
Ive been told you can do 10.5:1 with aluminum heads. Im running 10:1 on my 383. I would look at some heads with 2.02/1.6 valves. Maybe 190cc intake ports with it being a over 400 cube small block. Its not too radical so should last a while. The cam isnt exactly a stump pulling low RPM crawler motor. If you want more low RPM torque I would sudgest a 220-ish duration cam. :pimp1:
 
I don't have the program handy to figure dcr, but that static compression may be ok for a cam with that much duration, in a perfect world.... BUT, What are you trying to make? The parts don't match so well..... a 6,000 rpm cam and the small runner heads will not work well together, The 170 cc heads will not support the hp# you are looking for. Also don't like the short rods for the rpm range of the cam. If it was me, I'd get a cam around 220/226 and drop the compression ratio. You could run some larger heads, but using stock rods, I suspect you do not have a sound enough bottom end for the rpm range.

Sorry, that's my $.02. and I'm sure that somebody who know's somebody who know's somebody that's done it will disagree.
 
We need to know what heads you are using( flow #s would be great!) are you using the old aluminum corvette heads? If so they will not support the engine at all, they have a hard time with 380hp. if they are the AFR heads built for a 305 or similar bore they should flow well enough to make around 450hp. If it was me i would look at the pro-flow heads from austrailia(you can get them locally and are hard to beat for the price. They have a 200cc runner head that will do what you want and they are pretty cheap. If you are planning on running the 170cc heads I would run a smaller cam (maybe a 224 228 with a 114lc) with a wider lobe seperation. and drop the compression down to the low 10s, I think this would be much more reliable and make OK power.
 
The heads I am looking at are Edelbrock E-tec 170 (PN 60979) with a 1.6:1 ratio rockers. A friend of mine had these heads on a 383 but tore the engine up and has decided to go big block so I can get a heck of a deal on them. But if they won't work they won't work. My goal is to make 550 lbs of torque with a small block.
 
550 lbs. torque will require cubes and better flowing heads. go to www.airflowresearch.com They are some of the best heads out there. On the top of page click on Dyno Results. Then click Chevy. The have a couple 383's with roller cams that were pulling between 500 and 520 lbs. So with a bit bigger motor you can get up to your goal. If I had to do it over again I would have gotten these but I didnt have the $$$. :doah:
 
Grieby54: what's the specs on your 383 that you are getting 425+ Hp 475+ Ft. Lbs. of Torque?! I'm building a 383 right now and my dyno software says I'm at under 300HP and 418ft-lb torque. :confused:
 
Yes, that's a little radical for a trail rig....

The short rods are not condusive to high rpm operation,
however the small heads are compatitle with the rod ratio
(1.45:1).

The compression is 11.2:1 with -14cc dished pistons and a zero deck height,
i would suggest a -19cc dish and increasing the deck height to .020" which equates to a 10.2:1 static CR and with a .035" head gasket the quench area will be maxed at .055"
(barely streetable on pump gas with iron heads) but the only alternative is a larger dish and i cant find anything bigger than -19cc's...a 25cc inverted dome would yield 10:1 with a zero deck and the same gasket and the .035" quench area would provide excellent ping protection by cancelling the shock waves within the chamber.
the cam is at least 10 degrees too wide @.050" for a short rod stroker and the 112 degree lobe separation angle further dampens torque production in a large dispacement engine.
Dual pattern cams are designed to increase exhaust scavenging at high engine speeds, a single pattern cam will serve you well with no more than 110 degrees LSA.
You're very ambitious and i admire that......
destroke a 400 block with a 350 crank (377cid giant killer) then add some 6.1" rods, custom flat-top pistons and a nasty dual pattern solid roller cam with 240 @ .050" and .570" lift on a 108 LSA, add a pair of 190-200cc intake runners with 2.02/1.60" valves and terrorize the C5 Corvettes with a 4x4....

go back to the drawing board and try it again :<)
 
just go BBC! ;) :D with the 89 crew dually I now have w/ 454tbi I can do cool things. Just a set of heads w/ large valves and a port job and a set ofheaders w/ duals will get me 323hp and 468 ft lb of tq. :yikes: yes just ported and big valved heads w/ headers :D and the tq would pak at about 1800 rpms too :D and thats calculated @ 8:1 comp... 9:1 is better! 345hp 491tq... hmmm and this is with a "stock" cam option lol I would be as bold to say 9.5:1 would be safe on pump gas. I would even personally go as far as to try it w/ regular to see how it ran before making any conclusions. but at 9.5 there is 355/501... I know dd's are to be within 5%... so do the math and it is still impressive what you can do w/ a mild BBC!

as a side note since the motor was over heated and now I believe to have blown head gaskets and have a lifter colapse, it needs rebuilding. and why not put a couple parts in there to make it go even better. cams are cheap. pistons dont cost too much.... ;) I do not have a wide variety of cam specs for bbc though :( maybe I need to buy the latest dd :D
 
I've looked at the Desktop Dyno demos and i cant justify the price (IMHO)

I dont hink the program allows you to enter enough specific information in order to obtain a accurate result or guesstimation of available power and torque figures.
 
they are within 5% so thats fairly acurate in my books. also I paid maybe $20 for desktop dyno 2000 over a year ago. I may get a new one just for the fact that there are more available cams and heads and all the like on a newer one
 
You must log in or register to reply here.

Latest Posts

Top Bottom