350 SBC build for Jeep. Need Help !!! Intake, carb, cam, efi and mileage.
Hello. This is my second technical post here on this awesome site, Since the other went south, to a discuss about some Regal alternator's, But then again I really appreciate them answer whom came into the other thread ! before it turned into a Buick Regal 2.5 alternator spagetti thread :pimp:
Here's the thing. I'we recently came across TBI 350 SBC engine. as in a matter of fact. I don't know anything about the engine aside from that it came out of a Suburban.
My plans are to put this engine into a CJ-5 Jeep that's on 38" Mudder tire's and I am going to use this Jeep mostly for trip's, highway and off-road. Because of where I live I need to drive on the highway for hours just to get to play in snow/sand whatever. So basically I need to get as good gas mileage as possible.
The Jeep itself is around 3500 lbs. and as mentioned above is on 38" tires and I will be using TH-350 Transmission with stock converter. The Jeep has 4.10:1 gears in the Dana axles. What about my gearing is it somewhere in line with what I'm going to do, As from what I'we seen I can't go much lower (higher numerical ratio) I'f I'm going to run that 3 speed transmission and get somewhat decent mileage, and thus having fairly light Jeep compared to other's running similar tire size's and 350 engine's. It would just be good to run the 4.10's with an engine that has somewhat of good low end power ?
Are there any modifications i could do to the engine, to get the gas mileage as low as possible ? I'm open running both TBI or small carb.
The engine is as above mentioned a Bone stock 350 TBI from the Suburban truck. I am going to run exhaust manifolds that hopefully will run into dual 2.1/2" exhaust (or what do you recommend) ?
I had thoughts about running an Aluminium intake manifold with good Quadrajet over the stock TBI system. and then i would change the ignition to GM-Hei. would you recommend running an MSD ignition box with the HEI for improved spark and durability ? what do you say about that, would the stock HEI be acceptable or would it need some tuning ?
I would like to use them Swirl Port Tbi head's, no matter if I go the 4bbl route or vice versa. Because what I really like about them is that the are supposed to have 64cc combustion chambers and 1.94"/1.5" valves, I mean though there are plenty of better heads out there, these are by far not the worst set. They seam to run out of steam at around 4500 rpm, which is completely fine for this application as I'm only seeking for good mileage as along with good low end torque, also they seem to be good for mileage which is a BIG plus for this application. Also I'we heard that going with an early 4 barrel manifold would need some modification's around few bolt holes. Is that true ? Because of '87 cast iron head's having a bit different bolt holes/pattern/angle...
So to give it to you easy, I would like to get as good mileage as i possibly can without having to tear the engine around completely. So the Biggest thing i would like to do for now is to MAYBE change the camshaft. It seem's this model of engine (1988) accept's factory equipped hydraulic roller camshaft, and accessories. But then again If it's better for me I would like to go to maybe a good Aluminium Intake Manifold, and small 4 barrel carburetor or Q-jet, and HEI distributor with MSD ignition box for hotter spark, and therefor maybe better mileage !
If I'm not clear on some things, Please ask.
The bottom line is I need as good mileage as i can get along with low end torque and reliability.
So Before I do anything I would like to discuss it a little here, I now about the search button and all that, and believe me I'we tried to search, but as they say "every application is different,, I thought It would give me the best result just to ask them experienced Jeepers.
Also one thing to consider... That's what would be realistic gas mileage for a Jeep like mine on the interstate 50 Mp/h limit. some say I would be lucky to get 15 Mpg... Also considering what would be acceptable vacuum for the engine, when running at 50 Mp/h on the highway ? I'm assuming as high as possible but what would be realistic for an original cammed Small Block Chevy that's driven 60.000 miles ?
Here are two picture's so you can get a picture of what the jeep would mostly be used to. (the muddy picture is just there for fun, this is not heavy mud as you can see, just basically a dirty water)
Greetings from Iceland.
Any Jeepers here ?
i think that you have some of your information wrong, the swirl port heads produced by GM were amoung the worst performing heads they ever produced. i think you want the vortec heads these are the best performing heads that GM ever produced, you would be looking for either the 906 or 062 heads castings. these would even help you with gas mileage as they have an extremely efficient burn chamber and take full advatage of all the fuel in the cylinders during combustion, and they can be had for a few hundred $.
above would be my strongest recomendation
next you mentioned 4.10's with 38" tires (without doing the math) that is about like running a 31" tire (most stock truck size tires) with about a 3.23 gear, it's a little small to me i would look more into a setof 4.56's or 4.88's but then again that would reduce you mpg's. with running the 4.10's i wouldn't look at a cam with any more than 212 advanced duration otherwise your bottem end will be soggy. and yes you have a hyd roller cam in it. personlly i would scrap the TBI/FI and go after a performer or RPM intake with either a 650 holley or if you can find a good 750 Q-jet then i would go after that, the trick is finding one still in decent condition cause to buy one brand new will you about 500.00 vs 250-300 for the holley.
above would be A sugestion as well, but really i am always in favor of rebuilding the motor before you put much money into it. here is a quote i've heard many times "you wouldn't build a castle on a foundation of sand"
That Quote is awesome :) and make's good sense too !
Well that's just what I heart about them swirl port heads, thus they would deliver good low end power along with good mileage. I'm not building a race car motor so I would really like to keep the stock heads. It's only because here in Iceland you can take the dollar price an multiply it by 2. That would be nearer the price for me, to have the part's shipped over seas and all.
I could get a Holley 600 vacuum carb. for good price here in Iceland, it's supposed to be in good condition, other vice I'm kinda a Holley guy so giving it a rebuilt wouldn't be a problem at all, I'we never messed up with Q-jet though, just like them because of them small primary's !
Wouldn't Performer or similar intake be better choice for me ?
Because we're only talking about rpm range of 0-4500 !
So I would like to get as much low end grunt as possible with what i have. and it must be good to use with stock stall converter and get good mileage.
you would really like the added power from the vortecs but i can understand the budget constraints. if you have a local machine shop then i would recomend having them do some bowl work on the heads this will help with the flow. i'm a holley man as well so we're good there and a 600 will do just fine since you really dont plan on turning over 4500 or so. oddly i like the Q-jets as well they are good for fuel economy but in my experiance once they go bad and you rebuild them they wont ever be the same again. i used to have one in my old camaro years ago and i ended up rebuilding it cause the accelorator pump went up and i did a pretty good job rebuilding it but it didn't last long and i had to rebuild it again within another 18 months. well it went bad again shortly after and that is about the time i ended up rebuilding the whole motor (.030 355) and used a holley 650 vac sec carb. i never had another problem with the carb agian.
Ok, I'm not sure about if there's any machine shop here in Iceland who can do decent valve jobs, here in Iceland, we're like don't have any thing at all that would ease us hotrodders the life here, for example here is no shop yet that can do balancing on rotating assembly's !!!
So I think in this budget oriented build for good mph, I must just use what I have, since I'm only looking for good low end power, decent mileage and reliability it might work like a charm.
So you advice me not to go to Q'Jet because they tend to go bad after short time !
Greetings from Iceland.
Do any other Hotrodders have an opinion on this engine build ?
Nice Jeep's there :thumbup:
My thought's would be to go with the Edelbrock Performer Plus Cam kit, I think that is very well matched for what you are going to do with your Jeep.
Partner this cam with Performer intake manifold or GM aluminium one with small 4bbl (600 cfm 4160 Holley) and you will have one heck of a low end brute motor that would be good on gas too.
But then again these are just my thought's, Not sure if other hotrodders agree.
Where would the jeep spend most of its life in?
For off roading I would keep the efi. EFI will work perfectly no matter what angle or elevation your jeep is in but I would change it to TPI instead of TBI with vortec heads as mentioned above. Also as mentioned above you would be better off with 4.56 or 4.88 gears but that's only if most of the time you would be off road. For highway, leave it as is or change to a carb with the 4.10's. Either way with the lift and tires you have mpg's will suffer.
Any vehicle built for too many different applications will not be perfect at any of them so try to build it for the application where the vehicle will spend most of its life in.
Yes I'm was aware of that I wouldn't get 25 mpg, But then again someone said that 15-17 mpg wouldn't be far out if everything is in good condition.
My Jeep is not the typical American show built Jeep. you know, with 10" lift-kit and so on. But then again I'm running on these big 38" Mudder Radial tires.
Similar Jeep to mine, as you see here, these are not lifted to the sky !
Where I live, The Jeep would be used more on the street/road, as I need to drive for hour's just to get to play off-road, when I go in trip's. and it's just as simple as that, more mileage = more you get to play in the snow :)
Then would it be better for me use a decent carburetor on a good, well flowing intake manifold ?
Would you guys recommend any Camshaft that would be good for my application, where good low end torque and decent mileage is a must ?
I would NOT use a carb in this application. If you want good 4wheeling, reliability, and MPG's then even a TBI unit wins over a carb.
Don't go over 215º on the intake duration as noted and no more than 220º on the exhaust (about a 5º split). A good set of long tube headers helps a lot and in that climate/driving I would DEFINITELY get the stainless ones.
I would expect about 15MPG off the details you're describing.
Really a good low buck combo (low buck for around here) would be a Vortec 350 with a zz4 cam. Clean up the head castings a bit, slap on a set of stainless headers and get it tuned and you'd have a VERY reliable engine with great mid range and mileage.
Right now I'm kinda not going to the Vortec's because this is supposed to be budget build. I've heard that IF an after-marked intake manifold is used then you need to modify the bolt holes a little, is this true ?
So the Edelbrock Performer Plus camshaft would suit my needs very well ?
Or maybe the Crane 266 Energizer cam, 210/210 @50. .440 Lift. What's mainly the difference between single and dual pattern camshaft. also what would be acceptable vacuum with a mild camshaft such as these ?
Last Jeep I worked on had 350 SBC. with 272/284 Crane Powermax Camshaft 216/228 @50" And I wasn't satisfied with the low end power in that engine, that was also with 38" tires, 4.10 gears and 3 spd auto trans. That was a mildly built motor with ported #993 Heads, 1.94"/1.5" valves and Edelbrock Torker Intake Manifold. It also had Holley 600 cfm 4160 vacuum carb. The exhaust was "rusty" long tube headers lol with dual 2.1/4" exhaust if I remember correctly. It had acceptable power 2500 and up. I'm thinking it was soggy down low because it didn't had acceptable compression for that powermax cam, It did OK mileage wise if i remember, never checked tho.
Anyhow this is not a thing I want to lend in now, thus it begin soggy down low !!!
Greetings from Iceland.
That Jeep was soggy down low because it comprised of the parts that everyone gives away as they aren't that great, collected together they are still not that great. As far as the Vortec goes, around here it is the easy way to do a budget build, you can get a Vortec longblock for less than $500, for another 5 in gaskets, cam, and some minor stuff you have a 400hp engine that runs excellent and will give you 100,000 miles if tuned properly.
Is there any possibility that I could build a brute low end motor with the long block I have now, Including the swirl port heads ?
That would not be soggy down low and would work well with the stock converter I have ?
Because the matter of fact is that here in Iceland, we don't have many vortec engine's at least not in salvage yard's. and as you know you can multiply the price of the vortec's by 2 at least, to get the price that they would cost me to get, here in Iceland.
Another thing is I don't need 400 Hp in the Jeep, though I know it would be fun :thumbup: 250-275 are just awesome as long as i can get some what of decent mileage !!!
Here on my home we have another thing that we use for drag race, and that includes Big Inch V8 and whole lot of horsepower :thumbup:
If you want to use your long block then use it, you can get 275hp out of even swirl port heads. Bowl work helps a lot on those heads because that's where the choke is, if done properly they can actually work quite well, but that is a lot of time and effort to get there.
I'd stick with the TBI, bowl port the heads, run 4VR pistons and a cam with about 215/215 duration on a 108LSA 6 degrees advanced. I think Isky makes something close to that. Headers are a MUST. probably the single best thing you can do for both power and mileage. That setup, even with a stock TBI unit and intake should be good for 275hp and plenty of torque. Its basically a stock rebuild with flat top pistons, bowl work, and a cam swap.
If you have poor gas quality I may use dish pistons to keep the compression down to 9:1, BUT this will affect you low end torque and throttle response.
These are some grate ideas... :cool:
I will let you know how this all look's like when the engine comes into the garage and I will open it up. Then again we'll know way better what it is that I have in my hand's.
Will update this thread when I begin to tear the engine up.
As curious as I am, I ran a search on summit for a camshaft you recommended and this was the closest I came up with - http://www.summitracing.com/parts/ISK-201264/
You say to have it installed 6° advanced, aren't these "off the shelf" cams advanced from the factory ? also if I need to advance it from the box isn't that a sign I should just get a smaller cam ? (I find the rpm range on this particular cam rather high for given duration 2000-5800, is that in line with stock converter) If I go with the TBI wouldn't I need to have the computer reprogrammed?
Doesn't it apply that the hotter the cam get's in duration the less mpg i would be getting ?
Also what muffler's do you recommend ? I don't wan't it to be crazy loud, just have a very mild tone, barely noticeable... Since It's going to be used for long straight drive at the road / 50 mp/h, had my thought on running dual 2.1/2" exhaust, is that too big ?
Again, thank's for these grate ideas :)
Appreciate them a lot
Greetings from Iceland..
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