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Old 06-06-2019, 10:47 AM   #1
vince1
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79 350 overhaul

I pulled the heads and found they are numbered 462624 which makes them 76cc and as some people say the worst smog heads GM ever made. My intent was to disassemble and check them for cracks before reassembling with new valve seals. Or should I look for different heads?

With a cam upgrade can this engine make any power? It has a quadrajet and will get dual exhaust.

It will go in my 66 fleetside. All I am looking for is about 250 HP. I compare it to the the 65 Merc we had on the farm that had a 352 2 barrel with 208HP.

Thanks.

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Old 06-06-2019, 11:44 AM   #2
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Re: 79 350 overhaul

Get a decent cam like a 266 or a 268 (duration) get the heads done and enjoy it. Put an HEI electronic ign on it. You'll get the 250hp you want easily. You don't need to spend a ton of money to get a good runner. 3'' single exhaust from the iron manifolds is more than enough for a truck (if that's what you are using it for)
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Old 06-06-2019, 11:52 AM   #3
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Re: 79 350 overhaul

I reused the same heads on a stoock 1979 350 I rebuilt in a '79 GMC K25 High Sierra I had. I used a Comp 268H cam in it and it ran great with those stock heads. I had an Edelbrock EPS intake with a crappy Edelbrock carb on it too. Still ran dang good.

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My 1972 GMC 1500 Super Custom (Creeping Death) "long term" build thread.

The Rebuild of Creeping Death after the wreck

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I would never rebuild a 305.
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I love using vacuum gauges as part of the carb tuning process. I hook the gauge to the inside of my garbage can and leave it there.
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Remember Murphys 2nd law of mechanical relationships... "OPPOSING COMPONENTS ATTEMPTING TO OCCUPY THE SAME SPACE, AT THE SAME TIME, GENERALLY END UP OCCUPYING ADJOINING SPACE AT THE BOTTOM OF THE OIL PAN"
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Old 06-07-2019, 07:31 PM   #4
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Re: 79 350 overhaul

Well I was thinking for a while that I was taking this engine apart for nothing, until I found the second from the back cam lobe worn off.
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Old 06-07-2019, 08:47 PM   #5
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Re: 79 350 overhaul

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Well I was thinking for a while that I was taking this engine apart for nothing, until I found the second from the back cam lobe worn off.
Besides pulling the heads, did you tear it down completely and get it hot tanked?
If not, All that fine medal will come back and take a big chunk out of your wallet!
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Old 06-07-2019, 09:52 PM   #6
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Re: 79 350 overhaul

That must be where some small scratches in the bearings came from. Thanks for the advice. I'll get it hot tanked. Will the cam bearings have to come out?

Will 283/327 heads work? The numbers I was given don't correspond totally but I am thinking they may be 3795896 and that would be 60cc according to what I am reading. Maybe they won't have enough accessory holes?

Last edited by vince1; 06-07-2019 at 10:06 PM.
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Old 06-07-2019, 10:06 PM   #7
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Re: 79 350 overhaul

All the bearings will need replaced.
Plus a new oil pump and timing chain.
Basically a bare block build.
Can’t find your head numbers.
283 would have small valves.
Look here for some choices.

https://www.mortec.com/castnum.htm
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Old 06-08-2019, 05:36 PM   #8
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Re: 79 350 overhaul

250hp is what a stock 350 will dyno at with headers. 300hp is pretty easy with a good cam [read: not generic old ass tech that everyone keeps using for who knows what reason, which is basically anything melling or the flat tappets GM puts in its crate engines for some weird reason]
If the currents heads need any machine work, they aren't worth the time. If its just new seals then sure go ahead and run them.
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Old 06-09-2019, 12:39 PM   #9
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Re: 79 350 overhaul

I ordered a bunch of parts from Rockauto so it will have a #274 cam .202 dur .390/.409 lift and std rings, brgs and new oil pump and chain set. I don't know much what the cam no's mean so I hope I get my 250HP. In any case it's ordered and that's what's going in. Or if they haven't filled my order should I cancel it? Cancelled, I'll look again. Melling MTC1 ? OR enginetech ECK1014R?

I've degreased, washed and scrubbed the heads so now I'll wire wheel the valves, lap them in with compound, then clean and put them back in with new seals. Final check is to do a solvent check and hope none leak.

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Old 06-09-2019, 09:49 PM   #10
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Re: 79 350 overhaul

I got the heads back together with valves cleaned up and new seals. There is something good about them I am not used to seeing. The valves and seats are way harder than the old stuff I remember. No lapping compound needed on these.

I think the valve lifters were way too soft though. Probably just as bad as the cam.

Last edited by vince1; 06-13-2019 at 08:50 PM.
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Old 06-10-2019, 08:32 PM   #11
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Re: 79 350 overhaul

You ordered a stock cam. It will be no different then whats in there now.

Pick something from a cam company. A Lunati, a comp cams etc. The smallest XE from comp or smallest voodoo from Lunati would both get you excellent power compared to anything melling makes.
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Old 06-10-2019, 09:52 PM   #12
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Re: 79 350 overhaul

Thanks.

I re-ordered my bunch of parts from RA and the Melling MTC-1 is on its way, with I think a good set of lifters and I hope it is an improvement over original. Check out the specs and let me know what you think. Up here I have gotten into so much trouble with shipping and customs and waiting when ordering from new sources.

The next thing on my agenda is to get the cam bearings out and try to clean out the oil passages.
I watched a Youtube where a guy cut the front journal off an old cam, cut and ground down an old cam gear to push the bearing, bolt the two together and weld a bar on to them. I think I'll try that.

I checked out the Lunati site. I like the high efficiency kit # 10120215 or street master # 10120316.

Last edited by vince1; 06-11-2019 at 09:47 AM.
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Old 06-13-2019, 05:45 PM   #13
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Re: 79 350 overhaul

That Melling MTC-1 will get you your 250hp and then some, provided you have a set of headers, a 600 cfm Holley or Edelbrock or a Q-jet, and a decent dual-plane intake ( Edelbrock Performer or a cast iron Q-jet will work here). That cam may not be the latest tech, as far as lobe intensity goes, but will be better, as far as longitivity goes, with todays oils. The more aggressive lobe-cams have more of a tendency to wear lobes out quicker with the zinc-less oils of today compared to the old-school lazier lobes like the Melling you have picked out.
Either way, make sure you follow the cam break-in procedures and run a zinc additive of some sort and that cam should last a long time. It will make for a nice driver. Have fun with it!
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Old 06-14-2019, 06:11 PM   #14
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Re: 79 350 overhaul

Just because a head has small chambers (higher compression) doesn't mean it will flow well. The crappy flow will negate any compression gain you get.

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My 1972 GMC 1500 Super Custom (Creeping Death) "long term" build thread.

The Rebuild of Creeping Death after the wreck

Quote:
Originally Posted by LONGHAIR View Post
I would never rebuild a 305.
Quote:
Originally Posted by prostreetC-10 View Post
I love using vacuum gauges as part of the carb tuning process. I hook the gauge to the inside of my garbage can and leave it there.
Quote:
Originally Posted by Marv D View Post
Remember Murphys 2nd law of mechanical relationships... "OPPOSING COMPONENTS ATTEMPTING TO OCCUPY THE SAME SPACE, AT THE SAME TIME, GENERALLY END UP OCCUPYING ADJOINING SPACE AT THE BOTTOM OF THE OIL PAN"
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Old 06-15-2019, 09:00 AM   #15
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Re: 79 350 overhaul

Good thing you did not magnaflux those "scalloped" light duty twin cross over port heads to disappoint yourself. Cracks in the center exhaust seats at 1 and 11 o'clock positions were/are the norm raher than exception. Hopefully they won't worsen and result in burnt valves any time soon. And hope you removed all block plugs so as the clean lobe metal from all the oil galleys. Much work but will save your wallet later on as said.
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Old 06-15-2019, 10:16 AM   #16
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Re: 79 350 overhaul

Heads are easy to remove should that happen. I think I have three more of the same stored next province over that someone gave me years ago.

I did remove the cam bearings and the three screw in plugs at the back end of the galleries. Maybe still do the push in plugs from the front? I've been at it pretty good with engine degreaser and water followed by carb cleaner and compressed air. WD 40 to stop it from rusting. I just bought a cylinder hone so could knock out the front plugs and do another clean after the honing.

With the block upside down does the front bearing go in with holes at 4 and 8 and the rest at 8 o'clock?

I used to time the old magnetos on motorcycles or distributors with a cigarette paper or light between the points. How does one set up the initial timing on the HEI's? And as for wire position, #1 at about 11 o'clock? I can't remember if the cap is labeled or not.

I've got my parts but can't get at it again for another week.

On the up side I am pretty sure that the TH400 behind it has had a rebuild. Hopefully I can do the exchange before the summer is over.

Last edited by vince1; 06-15-2019 at 10:42 AM.
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Old 06-15-2019, 07:14 PM   #17
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Re: 79 350 overhaul

My 69 350 is rated at 255 hp and it has 76 cc small valve heads ( 991) it has a quadrajet but I think as far as I’m aware it’s got flat top pistons as it’s a 9-1 compression engine. ( pre smog era) so I’m thinking if you could bump your compression up using flat top pistons and reach your goal. Just as gm did in 1969. Also bigger cams bleed of cylinder pressure so won’t like your low compression motor much
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Old 06-16-2019, 07:33 AM   #18
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Re: 79 350 overhaul

After thinking back to the 1967 750cc (45ci) Norton Atlas motorcycle I used to have I am no longer so concerned about the lower compression. It had 7.6 to 1, red lined at 6800RPM and was rated at 49HP.

Last edited by vince1; 06-16-2019 at 07:50 AM.
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Old 06-16-2019, 08:51 AM   #19
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Re: 79 350 overhaul

Without knowing how you plan to use your truck, as well as transmission type, tire height, and axle ratio, it's pretty hard to recommend a cam other than stock or near stock.

Having installed three Goodwrench 350 crate engines, I can say the much-maligned engine makes very nice street power with a small 4bbl and low restriction dual exhaust, even with it's very small cam (.383"/.401" Lift, 194 / 202 Duration @ .050"). It also makes lots of torque right off idle, typically what you're looking for in a pickup, and 21" vacuum with a smooth, consistent idle.

One customer with a late 60s pickup had me install a Summit K1102 cam (204/214, .421"/.444") in his Goodwrench 350. Not a big cam by hot rodder standards. The engine did pull stronger in the mid-range, and rev around 500 RPM higher, but he lost some torque off-idle, which meant he could no longer spin his tires in low gear (TH350 with 3.08 axle, as I recall.) Gain 500 RPM on top; loose 500 RPM on bottom. That's how cams work. I suspect the next smaller Summit K1101 cam would have been a good compromise. Again, this is with (and because of) the engine's stock heads and low compression. A 204/214 cam with tighter lobes centers might have worked better, but that's another discussion!
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Old 06-18-2019, 04:41 PM   #20
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Re: 79 350 overhaul

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And hope you removed all block plugs so as the clean lobe metal from all the oil galleys. Much work but will save your wallet later on as said.
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Originally Posted by vince1 View Post
I did remove the cam bearings and the three screw in plugs at the back end of the galleries. Maybe still do the push in plugs from the front? I've been at it pretty good with engine degreaser and water followed by carb cleaner and compressed air. WD 40 to stop it from rusting. I just bought a cylinder hone so could knock out the front plugs and do another clean after the honing.
Remove the small front plugs as well. There will be new ones in pretty much any "Freeze Plug" kit you buy. Get yourself a set of long handled engine cleaning brushes and use hot water and dish soap to clean out every oil gallery and nook and cranny.

Use the brushes with soapy water to clean the oil galleries from front to back though the little plug holes. Then rinse the block and oil gallery passages with clean water from a garden hose sprayer, and repeat the process of soapy water... rinse the hell out of that block a couple more times and then blow dry with compressed air.

The you can oil it down once it's completely dry to prevent rusting.

Gary
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My 1972 GMC 1500 Super Custom (Creeping Death) "long term" build thread.

The Rebuild of Creeping Death after the wreck

Quote:
Originally Posted by LONGHAIR View Post
I would never rebuild a 305.
Quote:
Originally Posted by prostreetC-10 View Post
I love using vacuum gauges as part of the carb tuning process. I hook the gauge to the inside of my garbage can and leave it there.
Quote:
Originally Posted by Marv D View Post
Remember Murphys 2nd law of mechanical relationships... "OPPOSING COMPONENTS ATTEMPTING TO OCCUPY THE SAME SPACE, AT THE SAME TIME, GENERALLY END UP OCCUPYING ADJOINING SPACE AT THE BOTTOM OF THE OIL PAN"
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Old 06-21-2019, 12:34 AM   #21
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Re: 79 350 overhaul

I pulled the rest of the plugs including the frost/core plugs. That was a good thing because the slight rust stain from under one engine mount was indeed from a pinhole leak.

It is cleaned as well as I can do it using spiral brushes etc. Next time as has been suggested it will just get hot tanked.

I pushed a new sleeve over the balancer because it was grooved from the seal. At only .013" thick I don't know how long it will last but think it should be OK for a while.

Next jobs are to put in replacement oil/core plugs and the cam bearings. After that I hope it should just be routine assembly.
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Old 06-29-2019, 09:35 PM   #22
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Re: 79 350 overhaul

I don't have time yet to assemble but when dropping my other old car off I had a glance at the manifolds. The left one is cracked. I don't plan on using it but will give the MIG a try just to see what it does. Have any of you tried welding a cracked manifold and had any luck with it?
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Old 06-29-2019, 11:21 PM   #23
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Re: 79 350 overhaul

Yes cast iron can be welded, but with the added carbon in an exhaust manifold, that ins creases the level of difficulty. Either way, cast iron can not successfully be welded with a MIG. You must use either a Nickel rod for stick welding or a nickel rod for TIG welding.
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Old 07-04-2019, 08:24 PM   #24
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Re: 79 350 overhaul

Crank is in but I think I should take the back bearing cap off again because I didn't put any sealant on the ends of the two piece seal halves. Just to confirm, there is not another seal that goes in before the crank is there? Just the one for the pan?

I took another look at the manifold and think it is just exhaust leakage from where the manifold attaches to the head. I suppose the supplied gasket will fix that.
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Old 07-04-2019, 11:39 PM   #25
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Re: 79 350 overhaul

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Originally Posted by vince1 View Post
Crank is in but I think I should take the back bearing cap off again because I didn't put any sealant on the ends of the two piece seal halves. Just to confirm, there is not another seal that goes in before the crank is there? Just the one for the pan?

I took another look at the manifold and think it is just exhaust leakage from where the manifold attaches to the head. I suppose the supplied gasket will fix that.
Be sure the lip seal is positioned leaning inward towards the front of the engine, and the rear seals off-set from the main cap parting line by about 1/4" to reduce the tendency to leak oil.

Also when putting the sealant on.
Here a suggestion from a borrowed Picture
Name:  oilpan.jpg
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