Thread: 350 rebuild head advice

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I bought a "new" daily driver over the weekend, and it doesn't have quite the hp I would like, and the 305 in it smokes a bit. Good reason to upgrade some ponies. Its an 86 C10 step side with 2.73 gears, runs like a champ on the hwy but slow off the line. Now I have re-built a few (4) engines but never screwed with head combinations/cam upgrade, so I come to you for input. I have a virgin 350 block (3970014) w/ 4bolt main. I have 3 sets of heads, 882 which came on the motor which were probably stock does not have the screw in studs so its not the 881 heads I was hoping they were, set of 462 camel hump (don't really want to screw with finding/making brackets for all of the accessories) and then a set of 305 heads. Cam flat tappet 262/270 duration, lift .462/.469. Performer Intake, Holly 650. Ok, I hear that if you use 305 heads you up the compression and makes for a torque monster but peters out around 5000rpm. But if I am running 2.73 gears, I should be good for all around off the line and at highway speeds. I am running on small budget, have to use what I have or sell what I have and buy other heads, I would love to buy some aluminum or dart iron eagle blem heads, I just don't have the cash. Most of the money for this build will be at the machine shop making sure everything is true, polished and magnufluxed. Please let me know if I am way off base or close but need to make an adjustment. Thanks for your help in advance.

Lance

are you sure its 2.73 gears??????? your not going anywhere in a hurry with those gears and a 3o5 OR 350----------

Love the truck, Lance! Good lines and looks like the tin is in great shape. I think you’re headed in the right direction i.e., the 350 engine. I’d have the block bored .030 and all the surfaces squared up. Have your machinist install your cam bearings as well. The cam you’re looking at is probably okay – however, if you’ve read anything here at all you’ll know the pitfalls of flat tappet cams and make sure you follow manufacturer’s break in instructions to the letter!

In my opinion, the only big issue with the 882 head is that the casting quality can be a bit sloppy. There seems to be a lot flash at the intake ports. You can clean them up yourself with a die grinder and carbide bits. Start by placing a gasket on the head and lightly dusting the surface with black spray paint and then matching to the gasket outline. Go slow and vacuum as you grind (use a mask and goggles too!).

There are some who complain about cracking but I have built a lot engines with 882 heads as they’re plentiful in bone yards and just fine for stock or near stock applications. The local yard that I’m most familiar with allows a swap if you have a cracked head, but I’ve yet to have one – maybe I’m lucky. I also wouldn’t worry about press in studs. If your budget allows, you can either pin them or have your machinist tap the holes.

The 305 heads can certainly raise compression, but they will definitely run out of steam early in the RPMs. Reason being is smaller intake runners. Stay with the 882 heads.

Use a Performer RPM manifold and a 650 CFM. As an alternate – I’d rather see a Q-Jet as I think they’re a fantastic carburetor and I love the sound and snap of the big secondaries opening. Go with some good headers – I love ceramic coated Hookers. They look great forever and fit very well. Use a cross over pipe and 2-1/4 inch exhaust to the outside of the truck – dumping exhaust under any vehicle is just bad juju!

I’m assuming you’re running a 350 transmission. The stock converter is probably okay, but your 2:73 will be a problem. If you want any snap at all from dead stop, you’ll need to go taller in the gears. This is an area where you may want to spend a few bucks. Complete hub-to-hub rear ends can be had for $300-$500 at most wrecking yards and on Craig’slist/e-bay. Common rations are 3:42 or 3:73 – either would give you a bit excitement from dead stop. If by chance you have a 700R4 or 4L60 transmission the 3:42 would be my choice.

Have fun and keep us posted!
Glenn

We just got rid of a 2.73 rear and put a 3.73 into an 85 C10.....night and day, really made the truck fun with
a lower gear. Earlier, a 700R4 had been put in but with the bonneville gears, overdrive was useless. Now, it is
working great. AND, it was really cheap to find an entire axle to swap in.

Give us your rear tire diameter (circumference is even better), rpm at a given speed like 60mph or 70mph, and tranny output ratio (assume 1:1 with no overdrive?) and we can verify your rear gear number really quick. 2.73 is a really, really high ratio made for high speed highway MPG and not much else.

glensexton, Good deal. I was hoping that I was not to far off with my thoughts. 2.73 is what it says on the inside of the glovebox and I should take that at face value, I will cralw under the rear of the truck and check for a, ID plate on the pumpkin? I have always worked with "9 rear axles, so quick question, how do you change the gearing on the chevy axles? TH350 is what is in the truck now, I have a TH400 that needs rebuilt on my garage floor, but no 700r or 4L60. I ordered some bits for my grinder from eastwood for port work, nice and slow:-) Do you have a better cam in mind? Hooker headers are on the truck now, with 40 series flowmasters, true duals right now, I was planning on putting in a crosstube when I pull the engine for the swap. I appreciate all the advice, and will update progress of truck.

rspears, my speedo doesnt work, and there is no RPM gauge in truck. Luckly there is an app for speedometer with GPS.

Originally Posted by ssgthump

rspears, my speedo doesnt work, and there is no RPM gauge in truck. Luckly there is an app for speedometer with GPS.

Have to resort to the jack up one rear, turn the wheel ten times while counting the driveshaft revolutions.

Good news, Lance – re; headers and 40 series Flowmasters. That’s a great combination. I wouldn’t futz with the TH400 unless you’re having problems with the TH350 – they’re decent transmissions and it’s already in the truck.

A cam kit with the cam and lifters like this one from Summit is fine: http://www.summitracing.com/parts/su...make/chevrolet - again, follow the instruction to the letter as modern oils lack zinc and it’s easy to ruin a cam if not properly seasoned on break-in.

The glove box plate is probably correct. Lots of these trucks (especially the 305 engines) were made for highway cruisers and emphasis was on improving the overall fleet MPG average. It would be easier (in my opinion) to buy a complete rear end from a wrecking yard. Their Hollander reference guide will tell you which ones will fit and you may be able to get a 3:73 posi that’s a straightforward swap. You can then list your old rear end on e-bay for a couple hundred bucks.

Lance, before you spend money on a set of fosdick factory iron heads, please consider a 472/500 Cadillac engine and transmission swap. A bone-stock big Caddy with TH400 will love those tall gears and pull like Jack the Bear. Do some research before you pull the trigger either way. Buy the whole running car, '72-'76 for unleaded fuel, sell the glass, sheet metal and interior on craigslist to recover costs.

Alternately, pop for a set of aftermarket iron heads that will fit your budget. (Honestly, by the time you fix everything on those production heads that will need to be fixed, you will have more money in them than they will ever be worth and they're still subject to cracking). RHS (Racing Head Service), a subsidiary of CompCams, manufactured some iron heads that will do a real good job on a 350 block. I think they discontinued them in favor of producing aluminum products instead, so the last of the inventory was farmed out to different web presences such as Amazon, under the brand name of CompCams instead of RHS. Here is the last part number I know of, 12403. Valves, seals, springs, retainers, keepers are available from Competition Products, listed as a "cylinder head fulfillment" kit. Screw-in studs too.
http://www.amazon.com/Comp-Cams-1240...cylinder+heads

Richard, Thanks for the advise. I will most defintaly look at both options before I do anything. I was talking with momma last night about how much it will cost, she tried to get me to sell my fishing boat! Would the 472/500 be a direct drop in?

Practically nothing, except what was in there originally, will be a direct drop in. Although I love Richard like a brother and have known him since Christ was a Corporal, I'll have to disagree with him on this one. Some of the things to take into consideration are motor mounts, driveshaft compatibility and length, extra added weight on the front end, adequate cooling capacity, and exhaust modifications amongst others. To get an idea look up junkyard girl's thread on putting a Caddy in her 72? Monte Carlo.

Originally Posted by rspears

Have to resort to the jack up one rear, turn the wheel ten times while counting the driveshaft revolutions.

13 1/2 driveshaft revolutions to 10 wheel revolutions, having a 4 yr old spin the tire and count added a huge level of difficulty, good times though!.

Originally Posted by ssgthump

13 1/2 driveshaft revolutions to 10 wheel revolutions, having a 4 yr old spin the tire and count added a huge level of difficulty, good times though!.

Does anyone know how to do this conversion?

Originally Posted by ssgthump

Does anyone know how to do this conversion?

Sent you a reply PM - Open differential splits the action between the two rear wheels, so with one off the ground your ten revolutions becomes five, or if you'd rather your 13.5 becomes 27, and dividing 13.5 by 5 or 27 by 10 confirms your 2.73 gears. Go back and have your son spin that back wheel twenty times and you'll see 27 full turns plus 1/3, but I'd like a video of that process if you can I loved that story, by the way!