Would need some more info to give a good recommendation.Do you know for sure the motor is original & never been rebuilt? If it is, you most likely have compression ratio of approx 8:1, so, you would need to stay pretty small on cam choice.Along the lines of an RV type cam.Something like 205* intake duration@ .050".You will also need to use new springs & choose a cam that doesn't have more lift than your heads have clearance for to avoid head work.Do you know the casting # of the heads?

 

Stock Cam vs Aftermarket ????

Thanks for the reply jokerZ71,

Yes it is original and not rebuilt. I bought it in 1977 w/ 46K on it and put a camper on it but had to put it in storage about 15 or so yrs ago when I moved because city would not allow me to park it in front of the house.

About 25 years ago I swapped out the TH350 for a TH400.

Because my son and I promised the wifey we would not go crazy on $$ on the restore and make it a project that she could drive I didn't go into a major overhaul by replacing the heads and lower end, so we could do a good paint job on it.
Block SN#V122TPJ / 3970010

 

Opps, gave you block numbers that I had taken on my phone.
Where would I find the head Case #?

 

Thanks for the reply jokerZ71,

Yes it is original and not rebuilt. I bought it in 1977 w/ 46K on it and put a camper on it but had to put it in storage about 15 or so yrs ago when I moved because city would not allow me to park it in front of the house.

About 25 years ago I swapped out the TH350 for a TH400.

Because my son and I promised the wifey we would not go crazy on $$ on the restore and make it a project that she could drive I didn't go into a major overhaul by replacing the heads and lower end, so we could do a good paint job on it.
Block SN#V122TPJ / 3970010.

Where would I find Head Case number?

 

Under the Valve Cover between the rockers.

 

Thanks, I will check that out tonight when I get home.

 

This is a good all around cam that has been suggested on this forum a lot,good torque for a truck and mileage friendly and EZ on the wallet to make Mama happy. https://www.summitracing.com/parts/sum-k1102/overview/ Good Carb for your intake and also good for MPG is this: https://www.summitracing.com/parts/sum-m08600vs/overview/

 

The 204/214 durations performance truck cams for stock engines mentioned above (and below) are good cams, but bigger than the 194/202 cam you have and will make the MPG problem even worse... The problem is in 1970's, Chevy dropped to early 1950's static compression ratios of high 7's:1, but kept the bigger 1960's cam sizes used for 8.5 - 10:1 compression ratios to keep HP ratings from dropping back so low again... for advertising/competitive reasons... One way for more MPG is going to the heavy truck smaller 184/194 torque cam which will raise the dynamic compression ratio and MPG, but will lower your already tepid HP/RPMs... or maybe Comp Cams has a special truck flat tappet cam with more lift at those same low durations numbers to retain HP... Or could go roller lifters/cam at short durations, but higher lift, like GM did to cure the problem in the 1996 - 2002 Vortec truck engines along with higher compression ratio giving much better MPG and even a boost in power from your current level... but that roller cam setup would cost nearly a $1,000 minimum to do in your engine...

Other solutions:

Change to flat top pistons for a boost in compression ratio to around 9-9.5:1...

https://www.summitracing.com/parts/sum-17350-00/overview/make/chevrolet

Chevy SBC 350 Flat Top Pistons Moly Rings Kit 030 355 | eBay

Swap Vortec heads on for ~8.5:1...

Swap in a new ($2100) or used Vortec engine (9.1:1 and short durations roller lifters/cam)...

Remember, the gas savings will eventually pay for the parts if still driven enough...

The swap from well-tuned Q-Jet carb. to EFI will be expensive and not make a noticeable difference in MPG... the newer engines get vastly better MPG and HP mainly because of internal improvements to the engines as I outlined above... 11:1 compression ratio with aluminum heads is common now... direct extremely high pressure gas injection like a diesel uses is also the top MPG getter now...

Your truck prolly gets about 7 - 9 MPG city and 9 -11 MPG hiway... new trucks are more like 17 city and 23 hiway... simple improvements can prolly get you up to 15 city and 20 hiway... The Q-Jet was the best MPG carb. ever... and can also support a 400+ HP engine...
.

 

Thanks for the very informative reply. I was surprise to here you that the Quadajet was a very good mpg carb.

You were right on regarding my mileage, 10mpg with an 11ft cabover camper and @ 11-12 w/o the camper. I had forgot to mention that I had removed the stock exhaust manifold and install a set for Doug Thorley headers that had given me noticeable improved power when I drove with the camper.

Replacing the heads would be great but an extra $1k-$1.2K would put me way over my budget and Mama would not be happy with that extra cost, but @ $200 for a cam and lifters would work if I saw a modest improvement in performance and mpg.

I going to have to rethink the EFI vs Carb. I have a contact with FI Tech EFI, Riverside, CA and have read and heard a lot of good thinks about their product. A complete system @ $700 including EFI, pump, ECU and handheld programmer. Just about turn-key. But I am going to take your comments into consideration since that will be that last item on the engine to install. I'll have to check out rebuilding the Quad or one of the other suggested carbs from previous posts. Luckily for me the FI Tech Facility is just 30 mins away and are very open answering questions on performance of their products.

I guess I now need to determine the right cam to choose.

Thanks for your feedback

 

Here is another nice camshaft that will fit the application. I have always been really pleased with Isky cams.

https://www.summitracing.com/parts/isk-201256-262/overview/make/chevrolet

I am partial to GM lifters also

https://www.summitracing.com/parts/nal-12371044/overview/

Stick with a camshaft in the 194º-204º intake duration at .050 on a 108-110 LSA.

 

The head casing i have is 3986339

 

Just curious....89 thou and then it sat for 15 years, when you pulled the pan to check the bearings and at least install a new oil pump how did everything look?

 

This is the first time I have pulled a pan to take a close look but in my opinion it didn't look bad. The oil was dark when it was drained. All the galleries and passages were clear, no sludge found, just a dark film that would wipe off. Since I had a small evidence of oil weepage from the rear main seal, I decided to replace it and while I was at it, also the oil pump. The inside of the pump had no sludge build up. The only bearing I visually looked at was the rear bearing when I replaced the rear seal. The bearing surface looked clean without any visible scratched so I am making an assumption that the other bearings are the same. The oil ports were clean and clear of any debris.

 

Info I get from reading between the lines in your posts tells me you should just leave the motor alone. Run what ya brung sorta thing. And the 'boss' (aka the wife) needs to drive it with no problems.
Rebuild the quadrajet or get Sean Murphy to build one for you. He's also just down the road from you. Excellent carbs.
https://www.smicarburetor.com/

 

This is excellent advice. It's what I was thinking too.

 

The #339 heads are small valve heads(1.72/1.5), so, you may not see a big improvement. A good budget choice for you would be a set of later model (87/95) #193 swirl port heads.These heads can easily be found cheap.They were used on the 87/95 tbi equipped trucks.They are not by any means a performance head.They are designed for good low rpm torque & great milage below 4500 rpm.Combined with a modern profiled cam, they work pretty well in your situation.
I also think the FI Tech system is a great idea.You will see some milage gains & alot of other benefits over your current carb setup.

 

The #339 heads are small valve heads(1.72/1.5), so, you may not see a big improvement. A good budget choice for you would be a set of later model (87/95) #193 swirl port heads.

OK, I hadn't seen Eric's posting when I posted the above... the HP numbers are going to be quite a bit lower than what I posted above and these heads are prolly going to be limited to about a 200 HP max build no matter what you do...

However, changing pistons can still give a good bump up in MPG since they are still big chamber heads giving too low compression ratio...

Too bad you aren't closer to this member who just inherited a brand new Vortec 350" engine... don't know if he has any plans for it or wants it:

http://www.hotrodders.com/forum/motor-448730.html
.

 

In a comparison of a carb vs EFI, with a perfectly tuned carb & motor, EFI milage would similar, but, in the real world, that very seldom the case.The EFI offers alot more benefits.Better, quicker starts, especially in cold weather without running excessively rich & washing the cylinders until warmed up.Better throttle response.Better fuel atomization. Self adjusting for weather/altitude changes.The FI Tech system is very affordable & an easy install.Unless you go too big on the cam, you will see some milage gains over the stock cam you have now.

 

The EFI offers alot more benefits.Better, quicker starts, especially in cold weather

Actually, nothing starts quicker than a Q-Jet warm or cold... the newer EFI cars crank over two or three times as the computer figures out where the engine parts are and then it starts... But a Q-Jet car in good tune just starts most of the time, you don't even hear the engine crank over...

 

Since the gas mpg sucked back when i use to drive it, we thought we would do some easy but moderate improvements under the hood.

we might think about a cam swap since the engine is on a stand. He couldn't recommend which one for my setup since he is a Ford guy.

what does the forum suggest for good mpg and overall torque? Is it worth the $$'s or stay with the stock cam?

I had forgot to mention that I had removed the stock exhaust manifold and install a set for Doug Thorley headers that had given me noticeable improved power...

but @ $200 for a cam and lifters would work if I saw a modest improvement in performance and mpg.

I going to have to rethink the EFI vs Carb.

I guess I now need to determine the right cam to choose.

Mike and Philip

Looks like Mike really wants to make some improvements...

 

Then he ought to save the money to build what he wants. $200-500 is not going to get it done (most everyone here knows that I hope.) If he wants to spend money, then spend it on items that can be used when the money allows for upgrades that are going to make a real difference - i.e. - headers. Cam and heads need to work in unison, otherwise it will be beyond disappointing - been there, done that.

 

If the OP absolutely has to change cams, then this is all the cam I would recommend for use with otherwise stock components and crummy heads....

Crane 113971 (H248-2)
Brute low end torque, smooth idle, daily usage, fuel
economy, 1600-2200 cruise RPM, 7.75 to 8.75 compression
ratio advised. (50 state legal, pre-computer, C.A.R.B.
Operating range 800-4600 rpm's
192/204 0.050" duration
248/260 advertised duration
0.400"/0.427" valve lift

I'm pretty sure that you'd find the stock intake duration back in the 170's somewhere, so 192 would be a substantial change. Always, always, always match the intake duration to the static compression ratio of the motor. You see that this cam calls for a static compression ratio of 7.75 to 8.75. We're pretty sure the stock motor fits into this bracket somewhere, so it should do a great job for you fellows and Mom will never know there's a hotrod cam in the motor.

The OP is hereby cautioned to read and heed this tutorial concerning the life and times of flat tappet cams in today's roller world.....
http://www.crankshaftcoalition.com/wiki/Camshaft_install_tips_and_tricks

He is further cautioned to read and heed cautions about using a flat tappet cam with engine oil that has insufficient phosphorus and zinc.

 

It doesn't appear the OP is trying to spin 6000 rpm at the track, or, win any races.It sounds like he wants improved milage/performance, & reliability. He also mentioned a camper somewhere.
No doubt those heads are the main killer here to any of his goals & even tho the #193's I recommended earlier are not a performance head, they are a cheap (as in sometimes free) upgrade over the current heads.The 65 cc chambers will get the compression up into the 9:1 range & since they were designed & used with throttlebody injection, they will work great with the FI Tech system. Combined with a good cam in the 200 to 205* intake duration & good exhaust, it would make a very good easy, cheap upgrade in performance & milage.The 193's won't flow much past .450" lift, so, no reason to go any farther with lift & a cam that size will fit rite in with compression & rpm range of the heads.