Racecar Rebuild: its been awhile!

**6G72gearhead** · 05-28-2014, 08:54 PM

I want to build an intake manifold for 6 jenvey throttles, go even farther on my current port work and so on and so forth.

I'm just unsure what cam profile will really be optimal. There hasn't been much done with these engines in the world of natural aspiration, at least not to the extent of the likes of the VQ world and other V6 platforms that have made a lot of horsepower n/a.

I think it can be done with this one, it won't be cheap and it won't be easy and I'll probably blow up a few engines doing it, but once I'm out of school I don't have much of a problem with making that investment.

I'd like to see where that 3.7 came into existence, that sounds like a build I need to read.

**Silvertune** · 05-28-2014, 09:50 PM

The four banger guys aren't the only ones who can mix and match cranks and blocks with custom rods. If you're ballsy you can run a 97mm bore over the 85.8mm stroke. Put that under a set of ported and cammed MIVEC heads or even a ridiculously cammed up set of non mivec heads (they have identical flow potentials as far as ports go) with the breathing support above them and the sky is the limit. The 6g75's react to modifications the same if not better than most other V6's. People are making 30+whp/wtq over advertised crank numbers at the wheels with basic port work and decent bolt ons with stock cams. Hopefully I'll have M-rod set for the dyno soon here. Between him and Bhuddalawton on the other forum it should be possible to get a pretty good idea of where the 3.8's capabilities lie.

**demond0d5** · 05-29-2014, 01:15 PM

idk if it would work but:
http://www.3sx.com/store/comersus_vi...dProduct=28777
could be worth looking into, idk much about engines and stuff though.....happen to find that looking for some stuff a while back

**oakrdrs187** · 05-29-2014, 01:27 PM

^^^$5000!

Screw that!

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**Galantman03** · 05-29-2014, 02:37 PM

That's a little pricey IMO lol. Even though it would be cool.

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**wetamup2k3g** · 05-29-2014, 05:13 PM

Looking at that kit, I saw this:

Pistons are set to 8.5:1 compression ratio.

That's not what you want for an NA build on this platform. That's for turbo. Seeing as how that's 3SX, it's targeted to 3KGT's and Stealth builds, though I think it would work in our blocks (correct me if I'm wrong).

**Silvertune** · 05-29-2014, 05:24 PM

Zone DOHC shouldn't even cross the minds of us SOHC guys anymore. Stock cam non mivec 3.8s are putting down about the same power as the most powerful all motor DOHC of all time that has well over 15 grand into the engine alone. Heck put 3k I to the heads and you're looking at well over 300whp. You can spin the 3.8s really but when you're power band is a breath above idle to 6 grand you don't need it.

**6G72gearhead** · 05-29-2014, 07:07 PM

That is what I like about the 3.8, the fact that power is well set in at 3k ish rpm and I imagine it carry's to 6k rpm, which is where I need power, but I need to be able to let it rev to 7500 ish and have it hold up, since its, many times, faster to let it rev or leave it on the limiter then to upshift and downshift. With my current gearing I drop to about 2800 rpm at lowest and wind it to 7500 rpm, so making a good curve through that is ideal. It doesn't need to idle at all or make any power below that though, lol.

**Silvertune** · 05-29-2014, 08:38 PM

You're revving a stock shortblock to 7500? Livin on the edge! Lol.

**demond0d5** · 05-29-2014, 11:54 PM

Originally Posted by wetamup2k3g

Looking at that kit, I saw this:

That's not what you want for an NA build on this platform. That's for turbo. Seeing as how that's 3SX, it's targeted to 3KGT's and Stealth builds, though I think it would work in our blocks (correct me if I'm wrong).

yeah yeah I know its for FI and 3sx is for 3000gt's and such but figured it might be worth sparking some ideas or conversations ^.^ and it should work on ours, I've no idea why it wouldn't I mean that's the absolute center so even though its all flipped around the middle doesn't really change ya know.
like silvertune said, no reason 4 cyl should be the only guys that can't mix and match parts. if you need everything you can get out of a n/a then you gotta do what you gotta do...

now what would stop you from using the crank but using say...wiseco pistons or something? that even possible? like I said before, im not much of an internal engine guy, more about add on stuff and aftermarket but im learning =]

**demond0d5** · 05-29-2014, 11:57 PM

and while we are at it, would this fuel rail work? Id guess its for 3kgt but should be about the same right
http://www.3sx.com/store/comersus_vi...dProduct=34385
the mani they have pictured looks about like the diamonte mani doesn't it?

and I've been looking for pistons but the wiseco site is confusing as shit, would these work too
http://www.3sx.com/store/comersus_vi...dProduct=28405

**Silvertune** · 05-30-2014, 10:20 AM

Nothing you've shared from 3sx is worth even considering. By mixing and matching parts I'm talking about putting a 3.5 crank in a 3.8 block, under 3.8 pistons with custom long rods. Billet 3.4 liter stroker kits are a WASTE when you can buy a whole 3.5 for $200 and still spin it higher. Billet fuel rails are a WASTE when the $20 stock rail upgrades are found like grains of sand in yards nationally that are already bigger than AN six. And unless you personally are going to show proof that the DOHC pistons don't hit SOHC valves don't even think about recommending someone else do so.

**6G72gearhead** · 05-30-2014, 11:57 AM

Haha, yes this thing see's 7500 regularly and doesn't gripe about it, but I know going any higher is looking for trouble.

So when you go with a 6g74 crank in a 6g75 it ill increase the rod stroke ratio and ease some issues that go along with having a small one, but will there still be any of the bearing issues you mentioned beforehand, or is that just solved in the rebuild?

The 6G72 just seems like it was built to rev, long rods, big bore, super short stroke. I'd like to see where power can be found there. However as much as I want that right now I want to win, so I'm after whatever will build good usable power.

Maybe its been found otherwise, but I don't see the n/a V6's needing more fuel flow than the stock fuel rail can support, bigger injectors yes, adjustable pressure regulator, probably, but the fuel supply won't be near what an FI engine will require.

**demond0d5** · 05-30-2014, 11:49 PM

hey silvertune that's exactly why I often state I don't know anything about the engine stuff. hell I see it as beneficial cuz a lot more people out there like me that don't know this stuff and now, if they read this, they will know it wont work ya know. maybe we just saved somebody from wasting a bunch of cash on something that wont work ^.^

**mysticj** · 05-31-2014, 12:40 PM

Originally Posted by 6G72gearhead

Haha, yes this thing see's 7500 regularly and doesn't gripe about it, but I know going any higher is looking for trouble.

So when you go with a 6g74 crank in a 6g75 it ill increase the rod stroke ratio and ease some issues that go along with having a small one, but will there still be any of the bearing issues you mentioned beforehand, or is that just solved in the rebuild?

The 6G72 just seems like it was built to rev, long rods, big bore, super short stroke. I'd like to see where power can be found there. However as much as I want that right now I want to win, so I'm after whatever will build good usable power.

Maybe its been found otherwise, but I don't see the n/a V6's needing more fuel flow than the stock fuel rail can support, bigger injectors yes, adjustable pressure regulator, probably, but the fuel supply won't be near what an FI engine will require.

Modified some Chevy 6.125" rods with the 6g74 crank and you will not only increase the R/S ratio but also gain a little bump in compression with the 6g75 pistons.

6g75 are limited to 6800rpm and even then the thin bearings overheat, worse on a FI build. 7200rpm is max with better bearings on the 90mm stroke or end up like that 6g75 drag Mirage: parted out.

**Silvertune** · 05-31-2014, 02:27 PM

Originally Posted by mysticj

end up like that 6g75 drag Mirage: parted out.

You should PM me with the story on this.

**6G72gearhead** · 06-02-2014, 09:20 PM

Shit just post it here, I'd like to see this!

Well I've been having an input shaft bearing noise for some time now and finally decided to do something about it. Well since my buddy wanted to know how long it takes to get the gearbox out I timed myself, 50 minutes on the nose, not bad for hand tools and jackstands. Got the box apart shortly after, the input bearing is the only one making noise, the others look to be in really good shape, so I got that one on order and it should be here soon. Since the other side uses a sealed bearing I shouldn't have to reshim the diff or the output shaft, right?

I ordered an Ultra-Shield spec miata seat today, I'll be sure to post pictures of that when I get it.

So some stupid raccoon ran out in front of me last night and I blasted him with my drivers corner, most of it was just plastic and he didn't get my bumper cover, but the inner fender liner, and the liner between the wheel well and the gearbox got destroyed.

This past Sunday was event #4 for me, unfortunately I only got the first 2 runs, if that, so no kick ass video. It turns out one of my front swaybar links broke recently, the car felt funny on the highway, but I couldn't see anything wrong when I inspected it. Well, turns out the bottom stud broke and the thing would slip back in when the car was sitting still, and look like it was attached.

In spite of that set back I managed to place 16th out of 113, which isn't too bad, considering if the backend would have behaved and I didn't cone (by just barely) on my fastest run I would have placed 11th.

So I'm hoping with the new seat I can keep my struggles with sliding around on the seat to a minimum and hopefully start getting into top 10 positions. If I can start competing with the likes of Mark Hill, Craig Wilcox and some of our regions national champion drivers I should be standing on a good shot at breathing down the necks of the Civics at nationals.

**demond0d5** · 06-02-2014, 11:48 PM

Originally Posted by 6G72gearhead

Shit just post it here, I'd like to see this!

seconded! always nice to read up on another build, never know what you're gonna learn!

sucks about the raccoon bro, I got some links at oreilly the other day that were like twice as big as the ones that were on the car...not sure if you're looking for something massive or what but the masterpro ones they had seemed pretty beefy