J1MMY
Well-Known Member
Well I’m guessing these aren’t KB167s like the now folklore surrounding this engine once suggested. I’ve done some searching but the eyebrows and centre relief doesn’t match anything…
Deciding on replacement intake (318, details in post)
- Thread starter J1MMY
- Start date
-
No that just the basic summary of those 4 400 hp 318 builds.
Your mostly there depending how well your heads are ported.
Sealed Power. Good slugs. They look real close to zero deck.
J1MMY
Well-Known Member
Well that’s nice to know
junkyardhero
Well-Known Member
having built the fabled 400hp 318 (twice, natch) your make or break is going to be the heads. to note, that 400 was just barely and everything has to be dress-right-dress to get there. and i honestly don't know if the air gap will do it over the single plane. i can tell you that i took the single plane off and wound up putting on an airgap the second time (it wasn't available the first time i built one) and that made the car much more driveable.
anyway, onto what you've got cooking. if you're not looking to spend a ton of dough or re-engineer the whole enchartio, i'd say you probably have enough cam to get there. those sealed power slugs aren't a bazillion miles in the hole and are up to the task.
so, heads. either you work the F out of your 915's or... flip for some eddy's, speedmaster or trick flow. given your locale i think by the time you splash the pot for some magnum heads you're pounds ahead just biting the bullet and getting something aftermarket that'll support your cam (or the air flow requirement) needed to hit the number without a bunch of additional work.
with that combo, plus an airgap and 750 i say you'll tickle just shy of 400
anyway, onto what you've got cooking. if you're not looking to spend a ton of dough or re-engineer the whole enchartio, i'd say you probably have enough cam to get there. those sealed power slugs aren't a bazillion miles in the hole and are up to the task.
so, heads. either you work the F out of your 915's or... flip for some eddy's, speedmaster or trick flow. given your locale i think by the time you splash the pot for some magnum heads you're pounds ahead just biting the bullet and getting something aftermarket that'll support your cam (or the air flow requirement) needed to hit the number without a bunch of additional work.
with that combo, plus an airgap and 750 i say you'll tickle just shy of 400
J1MMY
Well-Known Member
J1MMY
Well-Known Member
I was looking at the cost of heads on the Summit app this afternoon. I did notice that Trickflow are quoting higher flow rates than Edelbrock so could be more of a goer straight out of the box?
Flipped the block and pulled #1 piston and rod this evening, noticed the big end and the big end bearings are pretty scratched up, the crank is also .010 undersized. Rods are the usual 318 items the part no. now escapes me but there have been plenty of posts discussing them (not bushed at the little end). The crank has been ground, I can’t find any numbers of meaning, 616 on the end of a counterweight, 5389 on the side of the counterweight at the balancer end but nothing else.
This has given me some uncertainty and perhaps increased the shopping list.
Hopefully tmw I’ll get the remainder out and have a good look at the bores.
BTW, I’m grateful for everyone’s input and patience - the continual ‘oh and today I found….’ is a bit tedious but I don’t get much time outside of work on weekdays.
junkyardhero
Well-Known Member
stock magnums flow okay, but they have their limits. if you're going to port something stock the mags have quite a bit more upside than stock LA heads. but then you're talking about the incurred cost of heads, rockers and that work. the other side of that coin is some aftermarket heads which should (in theory) flow at least or better than magnums all across the board. so there's that?
i'm gonna use some very loose numbers here, but on that particular 400hp build the magnum RT heads used have an intake runner of 180 and flow about 220-230 out of the box, so a wild *** scientific guess would say you need "about that", so there would be my target range for deciding aftermarket heads. well, that and rocker gear-- i don't know if you've got something decent you can reuse or if you wanted to upgrade.
if you can get away with a polish, then i'd just slam bearings in and ship it. but if it's beyond that or needs another cut, then it's decision time. i can't wholly make a recommendation because i don't know what availability is like over yonder, but if you've got a crank requiring work and those bores hold unexpected surprises then it may be time to rethink the path forward, especially with the block already being 40 over.
babies n' bath water n' all that.
that's just the way the scone crumbles homie. set out to do it one way and the script gets flipped on ya. we fully expect an update on the bores and i look forward to help spending your money for you!
Dang, now I'm going to need to look around for the out of the box Speedmaster flow numbers.
junkyardhero
Well-Known Member
i think @MOPAROFFICIAL posted some at one time? or he had a reader's digest on them that was something along the lines of: trash downtown, but okay-ish numbers were you want them up top for a street motor. needs cleanup here, here & here.
junkyardhero
Well-Known Member
J1MMY
Well-Known Member
Magnum heads - I could spend who knows how long trying to find some over here, assuming I did and they were in serviceable order there is the cost of bringing in the parts to refurbish, machining and from what I’ve seen, intake etc are specific to fit it? Would be quicker and perhaps work out not far off the same cost to ship in new heads.
Crank and bore - will update, hopefully get it fully apart tonight. I do have another 318 from a ‘71 Aussie Valiant which I parted out and kept as a spare. I’d need to strip it down and check it out.
MopaR&D
Nerd Member
I feel like at your current power level, significant gains could only be had with a "complete package" rebuild, at least in regards to cam/heads/intake. IMO going from cleaned up and milled J heads to unported Trick Flows will give an incremental boost, maybe 30 HP? If it were mine I'd go for some heavily ported Speedmasters, get that intake flow up in the high 200s CFM range (at least). You're at the point in the "Cost vs. Power" curve where it starts getting a lot more expensive to make solid appreciable gains in performance.
J1MMY
Well-Known Member
That strikes me as a fair question
if I have any more unwelcome news when the bottom end comes apart I’ll be fitting a 400hp BMW I6 diesel engine
but seriously, I will know more later. If I cannot reuse much of the engine in its last guise I will need to prioritise replacement of bad before replacing currently usable which will draw things out. It’s not the end of the world, I’m in no hurry.
J1MMY
Well-Known Member
I didn’t get much time last night, block is now stripped. Pics below hopefully. I will give everything a good clean over the weekend. Can’t see in the bores very well right now
J1MMY
Well-Known Member
Looks like I may have caught head gasket failure over cylinder 7, also the coolant was more water than coolant in the system, fuel in the oil (gulp) and the oil hadn’t been changed in a long time.
I've never owned an American vehicle that hadn’t suffered some sort of neglect under British ownership (don’t know why, they’re not really any different to maintain than anything else) and I’ve had around twenty over the years. I generally assume that bad things have happened whenever I buy one.
I've never owned an American vehicle that hadn’t suffered some sort of neglect under British ownership (don’t know why, they’re not really any different to maintain than anything else) and I’ve had around twenty over the years. I generally assume that bad things have happened whenever I buy one.
mygasser
Well-Known Member
has anyone mentioned a 390 (392? at your 40 over) stroker kit yet? it'll get you to 400hp easier, again with decent heads of course.
neil.
neil.
J1MMY
Well-Known Member
Yep and I initially dismissed it as I want to keep it a screamer. If the bores cannot be honed and the spare 318 I have isn’t economically worth the work I will consider the options.
Mad isn’t it that big blocks are everywhere over here but try finding 360s…that said I’d still put the same effort and money into one.
J1MMY
Well-Known Member
mygasser
Well-Known Member
who told you a stroker won't rev? at 3.95" bore and 4" stroke it's pretty much 'square' after all. revs are down to cam, heads, induction and exhaust as you know. the limiting factor with a higher hp/revving small block mopar is heads not stroke. the reason some say strokers won't rev is they don't know what they're talking about. yes a stroker can make the same power/torque at lower revs as a stock stroke motor, but you then have the potential for more hp/torque if you build it for revs.
lastly is your 318 already in a high state of tune? you say 'keep it a screamer' but a 318 was never that from the factory. did you say your intended useage of the car it's going in? unless it's a dedicated drag/race car how often (be honest) will you rev it past 6k anyway? if you build for best power at 7k and it's primarily a road car you may be dissapointed with it's road manners.
neil.
ps have you spoken to dave billadeau for advice and parts?
You can definitely make larger displacements rev, a 408 is about 28% bigger than a 318 so it needs to be able to move about 28% more air flow to rev the same and that would reward you about 28% more power and a 318 could do similar power but it would need to turn about 28% more rpms, if efficiency were similar for each.
mygasser
Well-Known Member
-
