Thoughts on future build?

S

schaferstephen

Well-known member
Hey all, been planning a build for awhile - going to be making some money working for Baker Hughes over the summer, so looks like I'll be able to afford it soon!

Originally (still now a little bit) I really wanted the Offy tri carb just for its looks and sound. But if I'm putting all this time and money into a build, I really want max performance out of it more than anything else, which leads me to strongly consider the CI aluminum head. After that, I'm starting to think about adding a turbo. I don't know a whole lot about this, however. I do know I need to keep a low CR for a turbo. What can yall tell me about adding a turbo, how much boost I can use if I don't bore the cylinders, what type of turbo, etc?

Going to need a new cam and rocker arms as well. Looking at some of the kits from CI, but I'm not really sure which one would be best, or what specs. I'm thinking hydraulic because I believe it's easier to maintain, but I should mention that I don't have power steering or brakes. From what I understand, a solid cam offers better performance but takes away vacuum needed for these accessories. Since I don't have (and don't plan on adding) power brakes/steering, should I consider a solid cam? Either way, what specs?

Also, what type of pistons/rods do yall suggest? I'm thinking that forged is more durable, but I'm not sure if that's really necessary for me.

Ultimately, this will all be mated up to a WC T5. I'm going to try the stock rear end for now, but I'm going to look for an 8" rear and replace the pumpkin with either a 3.0 or a 3.2 posi. The car is only gonna be a semi-daily driver, I'm more focused on performance. The car isn't gonna be raced but I do want something fun for spirited driving on these long, straight, flat Louisiana roads!! Thanks for all the advice yall, I really appreciate it!!
 
Let me add this... Would I be better off considering a supercharger as opposed to a turbo? From what I understand, it's a similar effect from a different cause.
 
Both have pluses and minuses Id like to do a supercharger build but turbos are Easyer to package and can be cheaper but the instant power of a supercharger. Has its advantage
 
1) Turbo vs Super. It's all about preference. If you can, try to find some friends with cars that have both. Don't need to be the same car or type. You are just there to see how they drive. Personally, I love the turbo. I like the fact you can't hear them when they are running properly, and if you size the turbo properly, the lag is pretty much non existant. But, superchargers have advantages as well, but after driving both, I prefer the turbo. Not to mention, for the 200, they are much easier and cheaper to fit up. But, try them both out.

2) Plan on 3.55 or higher gears. I have 3.40s now with a T5 and they are borderline too low. I can't go into 5th until 55 (at a minimum). Remember, the beauty of an overdrive transmission is the ability to run higher gears without sacrificing economy and comfort. 3.55s are pretty standard with T5s, though some go as high as 4.10s and even higher.

3) for cam selection, call. Hands down, all input here is anecdotal at best. Call the people who design cams. Tell them what you are planning. They'll have the good questions for you to answer. Most likely, with a boosted 6 application, you would need a custom grind to get the best set up. They'll also be able to recommend solid/hydraulic. For street engines, IMO you can't go wrong with hydraulics, but for high performance solids may be better.

4) Pistons/Rods are going to be dependent on how much boost you intend to run. If you go to 5-8 psi, stock internals should be fine. Going to 20? then you will need forged internals most likely.

I'd recommend you grab a few books to research turbos. I can't recall the main book right off hand, but it's simply got a title like Turbochargers. It's pretty much the go to reference for turbochargers, sizing, selection, building, etc. I just can't recall the name off the top of my head. And I have it sitting on a shelf in my garage at home.
 
Not really. I suppose you could, but the location of the turbo may not be ideal. You can do custom headers, but most people just save the money and go with the stock manifold as it's relatively easy (from what I've seen anyways) to adapt a turbo exhaust flange to the manifold.
 
schaferstephen":11s7e12h said:
Damn. I already have headers installed. Hmm I'll have to do more research into that. How does a super work with headers?
Click to expand...

8) a supercharger works quite nicely with headers.
 
:unsure: Yes the Aussie 250 block is about .622 of inch taller than our 200's so it's not a big difference, but would require resizing of some parts to fit.
 
IIWIYS...

getting the most out of your i6 is expensive, and difficult, it won't always be so easy unless you have someone else bang thier head against the wall for you...

with the alum head you might not want to go forced induction. it will make alot of power N/A, I would highly try that route first. if not satisfied you can add dished pistons and swap blocks to gain CR before you boost it...

power is great, I love my i6 and for spirited driving you'd never know that i only have 145hp at the tires from the way it takes off and can smoke tires. most guys after a stop light race ask me, 'waht is that thing' or 'nice v8!' and I say 'I6 200ci' ... I even had a few guy's ask me to stop so they can take a look! every one loved it and commented for only 200ci they thought for sure it was boosted but were even more surpised that's it's N/A...

with the alum head, you'll be in the 160-220 rwhp range, depending on how wild you want. more power the harder to get.

now with a turbo, you can easily get a 220-300 rwhp, does10s gets 343 rwhp (450hp crank), but that is all all out 250ci meant for track

I say play with the alum head NA first, then if not enough, go for the turbo, super takes power to make power a two stage turbo setup will make it seem seamless for close to the same boost results from a super... the main difference is the need for an intercooler or not depending on amount of boost.

either way, get ready to spend 2x the cost in parts to get it running and tunned right. so if parts are 4k, it will take 8k to get it finished...
 
Hm interesting. In hindsight.. a turbo would be smarter than a super, but I went ahead and installed headers, planning on a naturally aspirated build. Pretty sure those headers would make a turbo just about impossible! At any rate.. You're probably right about the aluminum head - that with a new cam and ignition (and a five speed) will probably blow my mind in and of itself. Not at all a bad idea to give that a shot first. What type of CR should I shoot for that can still use pump gas? somewhere just south of 10:1?
 
an easy build IMO... keep it simple

stock alum head, it will come with great valves etc... up the springs little to match the cam
274/274 112* .480 cam or 278/278 112 .480 if possible, think that's the max you can run with hydralic cam installed @ 0* advanced, straight up.
t5
stock chambers on head (think it's 52cc)
a 66-68 block, these usually have 0 decks, bore it to .030 or .040 over
dished or flat pistons, aim for 9.5-9.8 CR to use 91 pump gas with that cam, you'll have to see what you'll need to run piston wise
DSII ignition
and a 2bbl @ 350cfm or 4bbl @ 390 cfm
stock timing chain
stock rockers
stock rod bolts



this will get you up there, the rest is in the tune, so send the DSII to Faron, FalconSedanDelivery, and he'll get you squared away with a great tune
the carb is iffy, a 4bbl is huge for our small i6... so it might run better on autolight.. or IDK, but you'll have to get it dyno tuned. or try a MegaSquirt setup for a perfect tune and the ability to enjoy elevation changes.

people say to beef up parts, well IMO you don't have too, the stock parts and bolts are strong, it's just an opinion tho, if you think it will give you warm fuzzies for going double roller chain and ARP rod bolts then go for it... it's just my opinion. I did, and depends if I would again.
 
Is there any point in having the head ported and doing oversized valves? Also, since I am using a stick, could I run a 108 or 110 cam for a lopier idle and more low RPM power? I don't have any power accessories so I'd just as soon take advantage of not needing that vacuum.
 
As in the current head or large log? Yes. They will both improve flow a bit.
With the aluminium head? Porting will help a bit and they already have intake valves significantly bigger than you can squeeze into the log head.

As far as lobe centers, that is kinda up to you, but it is extremely easy to overcam these engines. Lopey will be more appearant in the aluminium head and way understated in the log.

Like mpg said, 150hp at the wheels will feel insanely higher because of how torquey these lttle engines are just by nature. If you do it right with a good combination of parts, you should have no problem bein far more entertained by your car. I took a mid tune test run in my car with the new head, 274-112* cam and I can say that one of two things will happen this year, either my transmission will explode or my tires will blow out in a burnout that I did not intend to do.
I am truly surprised by how it runs even when it runs so poorly with no tuning time invested.

All of your decisions should be based on the end goal, not what is best on its own. 274 on 110* would be great for the log head as far as drivability goes, but 280 on 110/112 will be great for the aluminium head. But none of that applies if you plan on boosting in the future.

Can't wait to hear what comes of your build.
Gerald.
 
I dont plan on putting any money into this log head. I mean, I think CI offers what they call a street/strip head job for... either 650 or 900 dollars. Do you think that is worthwhile? Also... Good to know about the cam. After reading the CI website, a 274 or 280 110 would probably be pretty tight.. hehe. Also, I'm not sure if I will boost or not.

How does NOS factor in, just out of curiosity? One of my friends told me to check into that.. The more I think about it and hear from yall, naturally aspirated would probably rock my socks in and of itself. But just out of curiosity... How WOULD Nos factor in?
 
Gerald is right, decide your end goal, and the steps you want to take to get there. if you want a two stage then keep in mind what you can reuse and won't use for the 2nd stage.

AFAIK a 274-280 cam is not ideal for any boost, you would have to get a different cam, and if you go with a 'boost' oriented cam all NA will seem pitiful until boost is applied.

FWIW, a stock 72 302ci engine on the dyno gives 115hp and 190tq at the tires, but that's stock and probably tired. the alum head and a cam will put you up to 150+hp easily, depending on cam.

lobe centers...
here is where I stand with your build, you have a long duration planned, 274-280 with a hydraulic cam, this will build a great potential for HP, will pull VERY hard in the upper RPM range, but with that much duration low end TQ will be hit, it's a balancing act. With a 108 lobe you'll rev faster, which is HP AKA top end, with a 112 you'll hinder HP and have more bottom end. I think FWIW, you should go with a 112 to help the low end and the 278 duration to help the top end. all with a lift of .480-.500 on all valves. so in theory, 108* lobe will hurt low end power... IMO go for the 280/280 112 .480 hydraulic cam.

Valves... and porting... short answer yes for all out, no for simple...
Think of valves as a water dam, and Porting as how wide the channel of water is, if that dam all of a sudden disappeared with it holding back all that water, it's going to flow, now think of a bigger dam and wider canal... that is what porting and valves will do. it will let the engine get bigger gulp. now from test shown a stock alum head flows 210cfm and a ported with larger valves flows 231cfm, 21 CFM is huge on the log heads so treat it as such on the alum head. if you're going to get the most out of the engine go for porting/valves. if you want more than stock and Aussie heads and durability and don't need that 'little extra' 21cfm then stay with the stock. valves and proting will help HP and hurt tq, velocity of smaller valves help tq. no point is porting and not going larger valves.

NOS...
When your confident with your NA build, add juice!!! that is a cheap 'turbo' but it costs in fuel. I don't know much but a shot of 50-75HP will make a HUGE difference when on the track. with the alum head I wouldn't try anything higher than a 75hp shot... just because you want to be nice to the engine, too much abuse will cost $$$...

Log...
I had my head done 3 times, same head, mostly for timing issues and testing purposes, in the end I spend close to $1300 on the log head, If I had know at the time I would have just sprung the extra for the alum... I might still in the future and sell my head for $500...

it comes down to what you what, and if you don't know, ask!!!, so you can make the best decision with your money and have it feel worth your time.
remember do it once and do it right. and always stick to a plan!
 
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