318 with NOS?

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edward9egan

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So I'm trying to get more out of my 1970 318 for cheaper. I already have 340 J heads that have been ported and have 2.02 intake valves in them. A Holley 750 with vacuum secondary. The bottom end is all stock but is in good shape. I was thinking about putting in some nitrous but had some questions. First is it worth it? If so what kind of intake is going to give me the best results? Will I need to get a mechanical secondary carb? And how should the timing be set so I don't kill the engine?
 
If you have a stock 318 ,unless the J heads are miilled a bunch you will be lowering your compression...
Do you know what size chambers are on the J heads?
Do you know how far the pistons are in the hole i the short block to help you figure out your compression?
 
Hot Rod did a article with a stone stock wore out 318 Duster and kept feeding it more and more nitrous trying to reach the limit of failure. It took quite a bit to fail. Look back in the arcives 10 years or so. I believe Jeff Koch wrote the article.
 
TXDart said:
If you have a stock 318 ,unless the J heads are miilled a bunch you will be lowering your compression...
Do you know what size chambers are on the J heads?
Do you know how far the pistons are in the hole i the short block to help you figure out your compression?
Click to expand...

i know the heads are already milled some but i don't know how much they came off a 1969 360.
 
my bad 1972 360. thats what i get for having too many different year parts on my car.:eek:ops:
 
You don't mention anything about exhaust.. Good exhaust can gain you a lotta H/P, and you need the flow to get rid of all that burnt fuel... my .02
 
inertia said:
You don't mention anything about exhaust.. Good exhaust can gain you a lotta H/P, and you need the flow to get rid of all that burnt fuel... my .02
Click to expand...

thanks for reminding me. i have summit racing block hugger headers into duel pipes.
 
this is just personal experiance..... i freshend up a low compression 72 318 used the stock cast pistons re-ringed new bearings thru-out used a summit racing .420/.442 lift cam edelbrock performer intake stock untouched 72 318 heads other then matched valve springs with a 600 vac.sec. holley. headers and 2 1/2 exhaust with a stock 904 trans and 3.55 gears in my 70 dart timing set to 36* total car ran consistant 14.40's @93/94 mph......

now for the nitrous.... turn back the timing that is key!!
i used an under carb plate wet system... i started at 100 shot and worked my way up to 150 i was down to 30* total timing then. if i remember every 50 hp back it off 2*

unfortunatly i never took it to the track with the nos on it. we had a local airport that would run races on the weekends no times just heads up fun!! i can tell you i beat my buddy's 70 chevy shortbed 2wd at the airport races that ran 12.90's at the track with a mild built 406 small block and 4.11 gears. when we got back he was laughing and saying he couldnt believe how well that little 318 was holding up with the juice on it!! i ran 2 full bottles thru that motor on a 150 shot and the only reason i quit was i noticed the crank was walking forward when i would free rev it under the hood!! guess i didnt get the thrust bearing set right.... oh well a new (used) crank new thrust bearing and it was good as new..... motor still runs like a champ not in the dart anymore tho.... i say dont be afraid of the juice its cheap fun horsepower and my attitude was its a basic 318 if it breaks they made millions of them and are fairly cheap to aquire and build!!
dont get spray happy its like gas the tank runs empty thats the only down side!!

good luck with the build Go for it!!! and let us know what you think of how it runs!!
 
any idea where to start with the rev limit. i was thinking 4000 does that seem high or what.
 
edward9egan said:
any idea where to start with the rev limit. i was thinking 4000 does that seem high or what.
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That seems really low. I don't know what condition your engine is in, but I shift my 440 at 6,100 lol

And I would think you could rev your small block to that pretty easy?
 
ya it is pretty low but i was thinking start low and step it up with the nos i didnt want to go to high with it to start
 
If I was putting juice on the car, get it sorted out so it run tits on engine, then add juice. Don't know the camshaft in your engine, 5000-5500 is usually a decent limiter range for a stockish engine.

I know the instructions on most kits say to pull 2* for every 50hp... pull at least 3* to be safe. I'd rather not have enough timing than too much and encounter detonation.

If the fuel jet is the same size of larger than the n2o jet, it's fat. Fat is worse than lean in most cases regardless of what the internet folks will tell you. Fat will run until it pulls the piston ring lands out. Lean usually barfs on itself and stops running. Can both conditions cause damage, YOU BET.

My 2 cents. If you put a 100 shot on it, usually have a fuel jet about 8-10 sizes smaller than the n2o jet. On an NOS cheater system 02001, run a .047 n2o and .037-.039 fuel jet for a 100 shot. Pull 6-8* of timing. Get the system jetting so it MPH's the best. Then start dialing timing back into the engine, 1* at a time until it slows down. Once you find that decrease point, dial one degree back out and run it.

Bottle pressure and consistent/constant fuel pressure are important.
 
so ive been looking at kits on summit racing. im thinking about either Nitrous Express Mainline or NOS Sniper. anyone tried these out or have any input
 
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