compression of a 88 318 with mag heads?

[73scamp318]

any one know? the magnum heads have a 58cc chamber i believe.

thanks
steve

[michaelmopar]

with the pistons in the hole approx .047 and a .030/4.060 gasket and 58 cc heads compression should be around 9.7-9.8:1. the pistons are flatop's on the 318 for that year and the engine is a roller engine cam sucks its 395/395
really needs a little help but the heads are great. i have the exact motor 88 318 and i have close to the same compression i have replaced the cam w/ a 212/218 dur 457/487 lift it has made alot of difference and it does very well. my heads are the 302 castings. motor pulls good i need better gears though.

[TK]

Originally Posted by 73scamp318

any one know? the magnum heads have a 58cc chamber i believe.

thanks
steve

almost 8.5 or somewhere close with a blue felpro gasket.

[michaelmopar]

Originally Posted by dodgetkboy78

almost 8.5 or somewhere close with a blue felpro gasket.

were do you get your numbers? based on if the heads were true 58cc and lets say the pistons were buried .080 and the felpro blue gasket was say .045 compression would still be 8.7:1 theoretically. So lets say with .050 is were the 88's were buried. And a mopar performance gasket is approx. .028 and the 58cc heads on flat top pistons. The compression should be around 9.7:1 all day long. With a .045 felpro blue 9.3:1. I'm not trying to be a smartaxx. I am just trying to understand how you get your numbers on compression.

[racintracy]

Just for the heck of it I ran it on Desktop Dyno to see what it says. I don't know what he specs are for sure but using what Michaelmopar said (58 cc heads, slugs .047 in the hole, fel-pro .042 thick gasket with 4.06 bore) it said 9.56 to 1. If your pistons have valve reliefs of say 5 cc (not sure if they do or not) that drops it to approx. 9.0 to 1.

[TK]

because

i have cc'd lots and lots of 318's put small chamber 675's with a smaller than 58cc after milling heads on and got 9 to 1 (real not dream)
untouched, most are 8 to 1, give or take, mostly give.

the blue felpro gaskets are .075 compressed. i know this because i have MEASURED them!


and, since im on a rampage here. your 9.7 to 1 is just nuts! please cc your engine! did you know that most of my engines with over 9.5 wont even run on premium?? (93) true! and, a 8.5 to 1 318 will ping on regular, period! i have been running, building and racing 318's for a small while, trust me on this one.

im not going to do all the math to come out and argue with you on this, it aint worth th etime, unless i am cc ing a actual engine. so, here it goes. if your roller 318 has STEEL gaskets, wich it probably doesnt, id be willing to bet it is 8.5 or less (from cc ing a few).
as far as the guessing on someones compression? im probably preetty close, but, like i said a few posts/threads back. YOU WONT KNOW UNTILL YOU CC IT!

[73scamp318]

it still has the sock 318 heads right now. but i was thinking about putting some magnums on for now. i ran 14.74 after i coverted it from the 1/8th mile with it stock. i have a big stall converter, m1 single plane and a .513 lift cam i can install with the mag. heads. also i already have a 3.91 gear.

so what would it be really? will the cam work well?

thanks
steve

[TK]

sounds like racintracy has it figured out for teh most part, but, like i said, cc it to be 100 percent sure.
9to1 is possible. i wouldnt go much over that so you can still run premium.
another thing, dont feel like the magnum heads will be a great power gain, they might not be. and, in my oppinion, you might want to port the 318 heads to keep velocity on your side. more than likely you have 302 heads, wich, in all reality, aint really much different than the magnum. they have a good combustion chamber like the magnum.
depending on what compression you end up with, the cam might work ok. what is the duration? center? ect ect.
and, where does your car stall out at?
and, you ran a 14.74 with it stock? like STOCK? if so, how fast do you want to go? sounds like it runs pretty darn good right now.

[73scamp318]

sounds good with the heads. it has an edel. dual plane intake with the exhaust crossover, and with a 4barrel
the stall now is a 2200 or so mp unit.
i guess ill throw in the 3800 with the cam (it came in a 360 short block from mp) with my single plane and port them a little bit.

i want to runs 12's if possible, but 13's would still be great.

thanks
steve

[TK]

run your converter, port the 302's some (bowl work), install 1.88-1.60's (not 2.02's)
a good cam, and your M1, and you will be trying to get the power to the ground. (400+hp)

[73scamp318]

awsome. i have those vavles in my 360 heads..should i maybe just repalce the pistons with forged? i can use a forged crank with eagle rods.(already have both)

thanks
steve

[73scamp318]

maybe these? i don't know the compression hieght in the stock pistons.

steve
http://cgi.ebay.com/ebaymotors/ws/eB...spagename=WD1V

[TK]

what is the casting number on the heads you are going to use?

[TK]

Originally Posted by 73scamp318

maybe these? i don't know the compression hieght in the stock pistons.

steve

i think there is spose to be a link?
forgies are always a plus, a whole lot tougher! plus, i have ran forgies in three different engines as the pistons lasted longer than the bore.
TRW are my favs, thre are lighter and better, but, i stick with what i know.
every one i build for myself gets the 800 dollar forgies, so, i dont worry about a shot of bad gas, or lean mixture as much

[73scamp318]

ill hav to check in the morn. they are the stock 88 castings.

steve

[TK]

well, you cant beat the price. cant get a good set of stock cast for that much.
im not a hyper piston fan, but, i dont know everthing either.

[73scamp318]

o the 360's? they are the ones ou tof the mp cat. what ever those are.

stevethe links there now

[TK]

Originally Posted by 73scamp318

ill hav to check in the morn. they are the stock 88 castings.

steve

bet ya a buck they are 302's!

could be 475 big port heads, but not really likely.

[73scamp318]

came out of a van if that matters

steve

[TK]

so, do you have the magnum heads? or were thinking about them.

[73scamp318]

the 360 heads are the 360 hp head. has 1.88 and 1.60 valves

steve

[73scamp318]

i was just thinking about them

steve

[TK]

Originally Posted by 73scamp318

the 360 heads are the 360 hp head. has 1.88 and 1.60 valves

steve

chech the cc's, but, with the block deck at 0, and those heads, it would rum WAY GOOD! and love that single plane manifold!
do you have a cam yet picked out?

[73scamp318]

im going to pull the head of my old 318 soon, so ill check. i was hoping that the .501/.513 came with 288-292

[TK]

just got off the phone with a friend. we had been building him a 340 the last couple of weeks for his demon. he just got back from the strip, ran a best of 12.6? with a smooth idle and a dual plane manifold

[73scamp318]

i have a 340 block that i could use, and 6 ross pistons (have to order 4 more) but the block needs 2 sleeves. maybe ill just build this still it just have honed and lined bored. throw in the crank eagle h-beams and order 4 more pistons at $350 adn throw on my 360 heads till i get some w9's. this motor was turning 8500, and worked well till it spun a rod bearing.

steve

[michaelmopar]

TK - I hope you dont think i am ragging on you but gees man it is just a debate. i know you seem to know alot about mopars and you have been on here awhile and it seems alot of people take your word as the law and i am not questioning it i am just stating facts from variuos resources and i was only basing my info for compression on info given. it was hypothetical on the in the hole amount and the chamber cc and the gasket thickness so i agree until he gives actual real life numbers all this is just a gopod guess on ficticious numbers given so why get all upset about it it is just a motor.

[TK]

im not upset i was just stating how much compression the motors i havre done had, thats all. heck, i had a brain fart last night and totally forgot 360 pistons were dished. dont take my word as law

[skankweirdall]

Hmm, the 1008 FelPro head gaskets I use are .039 compressed, and you can get the thin .024 Detroit Gasket head gasket. The cam in your other 318 is the MP .508 hydraulic flat tappet cam, not the .501 roller. And when did I say you could have my old rods and pistons? Or my new crank for that matter?

On another note the factory published numbers for deck height and combustion chamber cc's are only a generalization. They are used for NHRA blueprint spec's for stockers and it's one of the reasons stock eliminator cars run pretty good because the factory assembled motors aren't usually even close to what they say they are. TK is right about the fact that you have to measure everything, do not take the factory spec for gospel, it's usually not even close to the production piece.

BTW I was thinking that with the Magnum intake I got you could put magnum heads on the 318 with an MP controller than put a Pro Charger supercharger on it. Fuel injected, supercharged and you'd even be able to add an A500 or 518 overdrive to it later.

Have your performance and be able to drive it too.

[racintracy]

I agree totally with the published numbers not always being accurate. They are only a guideline. In some cases they can be way off. That's why you have to cc and measure everything to be sure. If you just need a ballpark figure use them but if you need accuracy cc and measure.