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Thread: 350 SBC build for Jeep. Need Help !!! Intake, carb, cam, efi and mileage. Reply to Thread
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Topic Review (Newest First)
12-18-2011 01:59 PM
Icejeep Finally time for updates here.
I did put together a pretty decent 350 engine for my jeep.
350 tbi engine block. 4 bolts main, bored .030" over. Cast crankshaft and factory 5.7" rods. Hypereutectic flat top pistons. Heads are from L98 Corvette #113. 1.94"/1.5" valves and 58cc chambers. Compression is 10.7:1.
The camshaft i did use was a little bit wilder than what was orginally planed. I did use Crane Powermax 272/284 camshaft 216/228 @.50" lift is .454/.480 and LSA is 112'
Intake manifold is an old tried and true Edelbrock Performer intake with 670 cfm truck avenger carburetor sitting on top.
Distributor is new MSD Hei unit. Timing is set at 16' base and 37' at 3000 rpm with vacuum advance connected to full manifold vacuum.
Exhaust is combined with 1.5/8" lomg tube headers with dual 3" exhaust. 4 glasspacks mufflers and 2 flowtech raptors to keep the noise down.

This engine does everything that it should. Vacuum at 700 rpm idle is 16-17" hg. Mileage is 13-14 mpg city with 38" tires and 4.56:1 gears


Best regards
09-12-2010 02:11 PM
Icejeep Thanks for your advice

I did contact Comp Cams this week, and they did recommend Cam #12-234
http://www.summitracing.com/parts/CCA-12-234-2/

Which is 4x4 type cam, that i find rather hot, thus given this is going to a Jeep that's going to be used on regular basis for long trip's where gas mileage and low end power is the main concern.

Would this be acceptable camshaft for my engine, or would it be better suited for me to go to step smaller cam.

Also I would like to be able to throw a little NOS on it once in a while !
Would Edelbrock 500 CFM carb be to little for this application ?

Regards.
08-28-2010 11:06 AM
65smallblock Building for mpg and building for power often take oppisite directions. You are asking for both and most of the advice you are getting is directing you toward power, hence away from mileage.

For a high mpg small block in a Jeep you would be hard pressed to find a better foundation than the 307 that was in it! The first thing I would do is ditch the RPM manifold. And all the hotrodders are reading that and thinking that I am nuts! Do you want a race car engine or a Jeep engine? High HP engines make lots of power, yes. But they are also notorious for making it @ higher rpms and sucking up gobs of petrol. There are things you can do to try to get the best of both worlds, but more often than not the more you lean toward power the farther it will take you away from MPG.

The RPM manifold has a small area cut out of the center divider, that takes away from bottom end power and it is also why it is called an RPM, that is what places it in a higher RPM range. This is BAD for bottom end torque and mileage.. Good for upper RPM power. Good upper RPM power is NOT an ideal engine for a Jeep!!

The GM throttle bodys are some of the best 4wd induction systems on the planet, they place emphasis on bottom end torque and mpg and will run at any angle including upside down. The next best thing IMO would be a very small 4bbl or even a large 2 bbl.

My best friend was a mechanic and they had an old Willys, it had nearly every engine under the sun in it at one time or another. The best one they ever found for it was a big Buick V-6. What a lot of hotrodders dont understand about Jeeps is that in 4 low you can get a boatload of torque from the whimpiest motors around, but 4 low is also murder on MPG. Been there done that.. The distance you can 4 wheel on a tank of gas is as valuable to a Jeeper as a lower ET to a hotrodder...

You want a good jeep motor? Here is what "I" would suggest for you. First of all, if you had an RPM manifold on an otherwise stock 307 then that is an oxymoron. It is a bad mix and it is no wonder that it was weak. A 307 built right could be an EXCELLENT jeep motor.. But what it needs is the right heads and induction. A set of 194 fuelies, 305 HO heads or Vortecs would wake up a 307 nicley without sacrificing any MPG potential. Go with a small cam like 220/440 and a throttle body or a small 4 bbl and youve got an excellent Jeep motor. In other words, if you take a 307, add a couple power features like the right heads and a small cam and an intake that places emphasis on bottom end torque, THEN youve got something..

If you already have the 350 built and want to go that direction then you have already given up considerable MPG potential. But what you DONT want to do from there is use an RPM or single plane manifold, use a big Holley or similar carb, or use to big of a cam. The reason smaller performance cams were dubbed "RV" cams is because the work really well for off roading/ lower RPMs. In short you want a cam that is designed to operate in lower RPM ranges. For your application you would be much better off with a stock 929 cam then too big of a cam..

If you go with the 350 then I would even consider the swirl port heads and throttle body. They will NOT make the best power, but they will get better MPG and they are BIG on bottom end torque.. However Vortec or fuelie heads will also deliver good mpg and much more overall power.. If I were building a Jeep motor I would look no further then the set of 305 HO heads I have in my shed, give them a good porting job and slap them on a stout 307. That would make FAR more power than any 305 or 6 cylinder Jeep motor and still be capable of really good mileage..

Good luck with your project and remember you are getting advice from people who build race cars here..
08-28-2010 10:02 AM
Icejeep I'we been doing a little research on my own, I went to Comp cams website and found this cam which as you can see is rather mild - http://www.compcams.com/Company/CC/c...x?csid=95&sb=2

And based to you opinions this would be a good cam for my application. It's not to mild and not to wild.
But I recently found this dynamic comp calculator that i'm using - http://www.wallaceracing.com/dynamic-cr.php
And by inserting my Engine in this form, with this cam then i get a blazing 8.06:1 DCR which i find rather high if you look at that i'm only getting 160 psi Dynamic cranking pressure ! Which maybe is ok ?

What's the highest DCR that i can run on 91 Oct gas ?

And by going with this Crane Energizer 266 That Mr. Monzter recommended - http://cranecams.com/?show=browsePar...tType=camshaft
then my DCR would be at 7.75:1 with Cranking PSI of 152 Psi Which might be better for my Pump gas engine ?

When browsing at Crane Cams web site I found this Crane Cams Z Cams to bee interesting so i thought i put one of them as well into this formula. The particular cam i'm interested in - http://cranecams.com/?show=browsePar...tType=camshaft
When inserted in the formula it looks to be on pair with the Comp's 4x4 Cam, Thus i'm getting 8.01:1 DCR with 159 Psi Cranking compression.

Also another thought, I recently found a 500 CFM Edelbrock 4 BBL carb # 1404, Would it be a good idea to use this kind of carb on my SBC ?
Since low end power and MPG is the main factor !



Just a thought
Icejeep...
08-25-2010 09:11 AM
monzter I once heard that if on a motor that's got decent set of heads than you might get better results in low end power and MPG by using single pattern cam VS Dual patterned. So in my opinion that's something you should check out, And another thing to check is to get the most lift for given duration. But another thing is that with these new lobes like Comp's XE and Lunati Voodoo line is that these lobes tend to go flat out after minimal driving. (me myself have never tried out these new line of cams but I'm dying to try one out myself)
On other hand if you are willing to sacrifice some Power for reliability then I would check out these old cams like Crane's Energizer series for single patterned OR Crane Powermax series for Dual patterned.
My friend has got 266 Crane Energizer in his Toyota Land_cruiser and it's delivering some serious low to midrange power along with good mileage, He's running a 350 Chevy with 10:1 compression 416 305 heads and performer intake with 600 Holley on top... But on the other hand he's running manual transmission. So maybe you it would be better for you to run the 260 version, Since you got these big and heavy tires and Automatic transmission with stock stall converter.

Hope this helps.
Btw Again very nice Jeep's you got there.
08-23-2010 12:11 PM
my87Z you are not going to make a ton of power with the limitation of those heads, but it will make decent power, those heads aren't bad for a mild street motor jusst dont be too upset with my power estimations.

with a cam with these charictaristics you could expect to see about 300-325hp and 350-375tq

you should be looking for a cam with specs in these ranges

advertised duration: 258-270
duration @ .050: 206-216
lobe seperation angle (LSA): 110-112
valve lift: .425-.465"
08-22-2010 04:58 PM
Icejeep Finally glad to be back on this awesome forum, Hope it's ok to update this thread...

Well, I'we been really busy this summer, so now I'm planing on getting the Jeep Ready for this winter. I'we ditched the 307 SBC as you know Jeep's need Torque and because of that I'we got my hands over a good 350 SBC Long block and a set of 1.5/8" long tube headers since you guys said it would be better for performance and mileage
I have lowered my gears to 4.56:1 to make it easier to spin these big tires...

The 350 engine is freshly rebuilt and does have Forged pistons (9.5:1) compression, A good sets of rods and crank, It's a 3970010 Block that's got 4 bolt main's.
The heads are a set of 186 Camel humps with 1.94"/1.5" valve's they got fresh valve springs, and valves.
The only thing needed to complete this long block is a good decent 4x4 Camshaft.. Which I don't have a clue what would be best to use.
I had planned on using the same Performer manifold that was going on the 307 SBC, but ditch the carb for 600 CFM Holley vacuum or Edelbrock !
I have also gotten my hands on Mallory Unilite Distributor with Msd 6A Ignition Box and Blaster II Coil, for hotter and better spark.

So right now i'm getting ready to gather these last part's to complete the engine build for my Jeep !
I need a powerful Engine with gobs of low end torque with acceptable horsepower and good mileage !!!

Thanks and greetings from Iceland !
Hope I'm welcome back...
08-22-2010 04:58 PM
Icejeep X2...


06-15-2010 01:08 PM
Icejeep Time for update in this thread !!!

When the time came and i put the TBI 350 in the engine stand it came along that is was stuck and needed a total rebuilt, which i was not ready to do at the time, so back to the basic, I'we got my hands over bone stock 307 SBC, aside from the Edelbrock Performer RPM intake and 650 Holley DP, It has exhaust manifolds and stock heads, not sure about the compression and internals.
What can i do to get the best mileage from this engine in my old Jeep ?
If i'm not clear on things please ask

Best regards.
04-01-2010 01:54 PM
Icejeep Thank's a lot for your help Mr. Ap. I appreciate it a lot
I will update this thread when i'm making some progress with this project.

Greetings from Iceland.
04-01-2010 07:48 AM
ap72 may need to slightly modify the bolt holes, not a big deal. A stock HEI in good condition will be fine. As everyone has already said, 15 MPG is a reasonable goal if everything is in check.
03-31-2010 05:15 PM
Icejeep ?

Regards.
03-30-2010 03:55 PM
Icejeep Thank's again Ap.
I really like the sound of that Jeep in the video, barely noticeable at idle, which is grate and won't drive you crazy during long trip's.

Then the next part Ignition... Is Stock GM Hei with Msd 6Al good enough ?

Also do I need to modify the bolt holes on the pre '87 intake to fit the '87+ heads ?

And the endless question, with the engine this mild and everything in good condition and properly tuned, would 15-17 MPG on the highway be in reach ?

Greetings from Iceland..
03-30-2010 03:14 PM
ap72 I like magnaflows, they make some noise when you hit the lod pedal but cruising they have little interior resonance (Flowmasters have a lot of resonance). With 2 1/4" exhaust into a 3" pipe and then a single magnaflow muffler with a 210/210 cam it'll be pretty mild. noticeably different but not a race sound by far.

Sound pretty close to this:

http://www.youtube.com/watch?v=mqClU...eature=related
03-30-2010 02:59 PM
Icejeep I just took the 200 duration cam at an example, I'we ran with 216/228 cam with no issues and as i'we learned with that cam, is that it's too big to be used with stock converter and these high gear's i'm running. IMHO.

I haven't made up my mind yet about the mufflers, but it must at least be quiet at cruising ! what do you recommend for both application's ?
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