another 318 hop up

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mygasser

mygasser

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hi all,
i've bought a 318/904 to fit in my '63 vauxhall cresta gasser project. the motor's from a 72 plymouth scamp and is stock. i'm collecting parts as cheap as i can to give it some more 'pep'. it'll never be a race car, i'm just after..... more, lol. so far i have a nos lunati voodoo 60403 cam, new lifters, chevy fenderwell headers (i have sbm head flanges to swap over), 360 heads, a weiand stealth dual plane inlet and a 750 vac sec holley. the stock electronic dizzy will be getting an uprated hei module and e-core coil. i have a 2500 stall convertor and will fit a shift kit to the box.
now don't give me the 'those heads will make the low compression even worse' crap, i know that but the increased flow/valve sizes outweigh that loss more than not so...
apart from that does this pile of mismatched parts sound reasonable?
neil.
1746051622208.png
 
It sounds like a decent setup to me. Not sure on the cam specs but if you can deck the block and/or mill the heads a little to increase compression all the better. With enough gear it should be a fun ride.

Maybe advance the cam some more from the recommended intake centerline.
 
If you get some daytime pics please snap some.. i don't know that car, looks like a nice bodystyle though
 
Assuming your at 1000 ft elevation and that camshaft,
At 9:1 static compression ratio, your dynamic compression ratio will be 7.4:1.
At 8:1 static compression ratio,your dynamic compression ratio will be 6.62:1.
At 7:1 static compression ratio, your dynamic compression ratio will be 5.82:1.

Higher in altitude, your compression will be less and lower altitude it will be higher.

Consequences of too low dynamic compression ratio will be you run out of horsepower in top gear before you hit the cams top rpm and to low mph. It might be 80mph or it might be 100mph. Hard to say till you get it together and give it a rip.
 
Like been said I'd mill some off head and or block, what gears ?
Sound ok for what it is.
 
ch1ll said:
Consequences of too low dynamic compression ratio will be you run out of horsepower in top gear before you hit the cams top rpm and to low mph. It might be 80mph or it might be 100mph. Hard to say till you get it together and give it a rip.
Click to expand...
How? I don't know what the OP has for gearing but lets say he has 3.91 with 26" tires that's about 4050 rpm @ 80 mph and 5050 rpm @ 100 mph plus some for slip, so he's gonna run out of hp ? guess you mean useable rpm, I don't see that, obviously less cr gonna make less power at those rpms but it still gonna make a reasonable amount of hp way over a stock 318 will at those rpms. Now if he's running even deeper gears he could run out of useable rpm but it won't be from low cr.
 
ch1ll said:
Assuming your at 1000 ft elevation and that camshaft,
At 9:1 static compression ratio, your dynamic compression ratio will be 7.4:1.
At 8:1 static compression ratio,your dynamic compression ratio will be 6.62:1.
At 7:1 static compression ratio, your dynamic compression ratio will be 5.82:1.

Higher in altitude, your compression will be less and lower altitude it will be higher.

Consequences of too low dynamic compression ratio will be you run out of horsepower in top gear before you hit the cams top rpm and to low mph. It might be 80mph or it might be 100mph. Hard to say till you get it together and give it a rip.
Click to expand...
i'm about 50ft above sea level so that'll help, lol.
 
the lunati cam fell through so bought an early 340 cam instead. i've also just bought a set of kb399 pistons for the 318. they're the domed top ones which will help regain some of the lost compression with the 360 head's bigger chambers.
:thumbright:

neil.

kb399_pair_1.jpg
 
re the new pistons... i had 2 choices to regain the lost compression. 1) these domed pistons or 2) turbo the engine. the pistons are (even with the cost of a rebore) much cheaper and although the turbo choice would make more power, to be honest i don't need it.
there.... i said it, i don't 'need' more power
lol.gif

neil.
 
mygasser said:
the lunati cam fell through so bought an early 340 cam instead. i've also just bought a set of kb399 pistons for the 318. they're the domed top ones which will help regain some of the lost compression with the 360 head's bigger chambers.
:thumbright:

neil.

View attachment 1716418664
Click to expand...
I don't know how much those will raise the compression ratio with those deep valve reliefs
 
Dan the man said:
I don't know how much those will raise the compression ratio with those deep valve reliefs
Click to expand...
they have the same valve reliefs as the kb167's (flat top) but with the extra .2 inch raised dome/pad. both have a higher compression height than stock pistons which mainly gives the compression bump. plus the kb399's have that dome so even more compression than the kb167's. the deep valve reliefs are probably due to that raised compression height and the valves still needing piston clearance.
neil.
 
we collected all the parts from stu today at santa pod raceway (here in the uk). unfortunately he toasted the trans' in his 70 challenger so was out of the running in nostagia super stock. he did say the car was performing better with his new heads etc so that's good. he also had a pair of nice chrome direct connection valve covers for sale (wouldn't clear his new rockers) so it would've been rude not to have them too, lol.
:thumbright:

neil.
 

another question, this time about the heads removed from the 360 engine fitted in a 70 challenger. did mopar even make a 360 in the 70 model year? so probably not the factory motor. that said the heads from that 360 are J heads which i understand from checking here were 70/71 for 340 and 360. i've not checked valve sizes yet but he also gave me a set of 2.02 valves he had. years ago i had a 74 challenger rallye with a 318/904. i replaced the head gaskets during my ownership and noticed they had the 2.02 valves (maybe they were x/j heads?). anyway that car ran well for the weight and only having a 318. it did have a cam of umknown spec' too and i fitted new headers, an offy port o sonic (remember those?) single plane intake and a 650 dp holley too but i had no issues with low rpm power loss with this combo. from what i've read here the j heads were mostly 1.88 inlet valve size and most agreed that's better for a street motor. i guess that apply's more for my 318 but i am tempted to fit the 2.02 valves if these heads have 1.88's in them now.
any opinions?
cheers, neil.
 
popped out to the mobile shed (my transit van) to have a look at the 360 heads we picked up last weekend at the pod. yes they're 'j' heads as stu told me which is cool. even better they have the larger 2.02" inlet valves which from what i've read means 340 or early 360 heads. also the chambers appear to be smoothed somewhat and the valve keepers and retainers are upgraded too (probably valve springs as well). all in all i'm well pleased with them, thanks stu.
:thumbright:

neil.
 
i ordered a hv oil pump, van/truck pickup tube and rings for the kb pistons yesterday. i went for the van/truck pickup as they have a rear bowl sump. we'll alter my car sump to suit and this'll give more clearance over the front (transverse) spring crossmember in the nash.
neil.
 
mygasser said:
another question, this time about the heads removed from the 360 engine fitted in a 70 challenger. did mopar even make a 360 in the 70 model year? so probably not the factory motor. that said the heads from that 360 are J heads which i understand from checking here were 70/71 for 340 and 360. i've not checked valve sizes yet but he also gave me a set of 2.02 valves he had. years ago i had a 74 challenger rallye with a 318/904. i replaced the head gaskets during my ownership and noticed they had the 2.02 valves (maybe they were x/j heads?). anyway that car ran well for the weight and only having a 318. it did have a cam of umknown spec' too and i fitted new headers, an offy port o sonic (remember those?) single plane intake and a 650 dp holley too but i had no issues with low rpm power loss with this combo. from what i've read here the j heads were mostly 1.88 inlet valve size and most agreed that's better for a street motor. i guess that apply's more for my 318 but i am tempted to fit the 2.02 valves if these heads have 1.88's in them now.
any opinions?
cheers, neil.
Click to expand...
Stock 1.88 valve 360 heads are good for 350-375 hp with reasonable cam and cr, eg.. a comp xe268h and 9:1 should = about 350 hp with the rest of the combo being a match.

If wanting more power especially while keeping cam mild some head work will be needed, it all depends what your after.
 
mygasser said:
popped out to the mobile shed (my transit van) to have a look at the 360 heads we picked up last weekend at the pod. yes they're 'j' heads as stu told me which is cool. even better they have the larger 2.02" inlet valves which from what i've read means 340 or early 360 heads. also the chambers appear to be smoothed somewhat and the valve keepers and retainers are upgraded too (probably valve springs as well). all in all i'm well pleased with them, thanks stu.
:thumbright:

neil.
Click to expand...
All factory 2.02 heads are 340, 360 only had 1.88.
 
273 said:
Stock 1.88 valve 360 heads are good for 350-375 hp with reasonable cam and cr, eg.. a comp xe268h and 9:1 should = about 350 hp with the rest of the combo being a match.

If wanting more power especially while keeping cam mild some head work will be needed, it all depends what your after.
Click to expand...
i have the earlier 340 cam and as above the kb399 pistons. a weiand stealth intake (performer rpm from another mother, lol) and a holley 770 street avenger carb. i'll be making fenderwell headers too so they won't hurt either.
neil.
 
273 said:
All factory 2.02 heads are 340, 360 only had 1.88.
Click to expand...
1970/71 340 heads are a 360 head with 2.02 valves right from the factory. They have the big 360 cast into them on an intake runner. 1970 was a X head. 71 was a J head with 2.02 valves when used on a 340. 71 360 used 1.88 J heads. Yes a 360 did only use 1.88 valves. Kim
 
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