Author Topic: Need some of ya'll Engine GuRu's expert opinions! (Read 1003 times)

highspeeddirt · « **on:** February 13, 2006 - 09:27:04 PM »

Ok, The guy I bought my car from already had the engine built. It's the original numbers matching 318. He used the 400hp 318 build out of a Mopar Muscle mag as a guidline. This is basically what they did...... I'm copying this from another post I did....

They bored it .040, put in KB flat top pistons and zero decked the block. They used the later model closed chambered Magnum heads with 1.92/1.625 inch valves. Single plane intake, w/750 demon carb. The cam was a Comp Cam 280H with 230 degrees duration at .050, and .480 lift, but with the Magnum heads 1.6 rockers the lift went to .512 inch lift. Used tti 1 5/8-1 3/4 stepped headers. They got 400hp at 6150 rpm. They played with a 100hp shot of nitrous and got 509Hp at 6000 rpm.

He did everything that they did, except instead of the Magnum heads, It has 1970 340 X heads with the 2.02/1.60 stainless valves, and have been FULLY ported and polished. Also have a LD340 edelbrock dual plane intake instead of the single plane, and a 750 holley, just not a Demon. The magazine made reference that a zero decked block is a waste of time with out a closed chambered head? My heads have only been surfaced. (straightened) Am I gonna have compression issues? Also my cam is a dual profile Comp Cam with 219 degrees intake, 235 degrees exhaust duration at .050. And .462 intake and .482 exhaust lift. And I don't have 1.6 rockers like the Magnum heads. I planned on using the tti 1 5/8-1 3/4 stepped headers like they did.

I'm not gonna be doing a bunch of street racing and no drag racing, but I still want this little "wee18" to be peppy. What are ya'lls opinion on how the differences my build has to theirs, is going to affect my performance?

Thanks!
HSD

matt63 · « **Reply #1 on:** February 13, 2006 - 10:36:51 PM »

Seems like there are quite a few differences here. I can see how a 230 duration cam (which is big for a 318) and a single plane might produce some good peak hp numbers. The guy who wrote this article seems to go for long duration cams- more than the cam mfg's recommend so I don't know who to believe when it comes to cam selection. I think some hp and torque curves would tell a good story as to how streetable his engine builds really are. For your engine, I would calculate the compression ratio as you may be high with zero deck height and you have lost the quench effect with open chamber heads to boot. Max compression on pump gas is approx. 9.5. The trick for a good engine is matching power band for the cam, intake and heads. I think the cam is good for 2000-6000 rpm. If the heads are truly "fully ported" this will be a mismatch. I wouldn't bet on that. The dual plane intake should be ok although i don't know what it is good too - perhaps 1500 - 5500 rpm. The TTI headers are the best. I'm sure Chryco can add to this. It sounds like the engine is already built so you might as well run it see what you get!

Chryco Psycho · « **Reply #2 on:** February 13, 2006 - 10:58:31 PM »

the LD 340 intake is one of the best intakes & will not hurt you much
the Heads will cost you power , I have seen 3 cases where the 308 heads gain 40 + HP over X heads , even ported & the Magnum heads are close to as good as the 308s or better
I feel there are better cams than the Comp too but if you already have the cam you can use it , that will cost 20+ hp as well over other grinds are available

highspeeddirt · « **Reply #3 on:** February 14, 2006 - 07:17:54 AM »

What cc are the X heads? I don't know if the pistons have any valve reliefs of not but should be able to get a close estimate of my compression figured out with that. Also, I'm not opposed to swapping out the cam. What cam would you reccomend with my combination? I'm not worried about vacuum for brakes ect. I plan on running a hydroboost set up on the brakes.

ESGEE · « **Reply #4 on:** February 14, 2006 - 07:33:50 AM »

I did put a sixpack on my 318(with a biggercam not sure what, former owner put it in) and it got real figsty and when the carbs got tuned in it felt like it was gonna blow of it all, i did change to 340 heads that was rebuild and polished and now it sounds much better cant tell how it burs rubber untill winter is over thou

I did not build a motor for racing more fun and hell of it, since it looks like a stock 318 with sixpack on it

Chryco Psycho · « **Reply #5 on:** February 14, 2006 - 10:26:37 PM »

Both the X heads & 308 castings have 68 CC chambers
for hyd cams I use a lot of Engle cams , www.englecams.com
if you look at the K58 hyd grind it has the same 230* @ .050 that the original Comp grind had but offers .520 lift with Only 1.5 ratio rockers , you could also get a split profile with the K 60 exhaust lobe which is 238* @ .050 & .538 valve lift

Author Topic: Need some of ya'll Engine GuRu's expert opinions! (Read 1003 times)

highspeeddirt

Need some of ya'll Engine GuRu's expert opinions!

matt63

Re: Need some of ya'll Engine GuRu's expert opinions!

Chryco Psycho

Re: Need some of ya'll Engine GuRu's expert opinions!

highspeeddirt

Re: Need some of ya'll Engine GuRu's expert opinions!

ESGEE

Re: Need some of ya'll Engine GuRu's expert opinions!

Chryco Psycho

Re: Need some of ya'll Engine GuRu's expert opinions!