Mild 350 sbc build, what do you think?

[mjrwraith]

Ok so I have just acquired a 1972 GMC C15 long bed fleetside. I want to do just a simple restore job with a focus more on comfort than a fancy paint job or hot rod motor. I do however want to add a little extra power and a few more mpg out of it. So after some research I wanted to throw my idea on how to set this up out there and get some of your opinions. So here it is, I'm going to take the stock motor with all the lower end being factory spec, and put a COMPCams 252he cam with the new valve train and all to match. Then take the stock intake manifold off and put on an edelbrock rpm intake with the stock quadrajet. Leave the stock exhaust manifolds on and put a b&m shift kit in the TH350 tranny. I'm only looking to get around 25 more horse and maybe 2-3 mpg more out of it. Compression will be stock, which I believe is 9.5:1 may be wrong I'll have to double check. I think that covers everything so any tips or advice would be helpful thanks.

[DonnieB]

I would consider exhaust too.

[adricar1]

personally with that cam i would go with a performer manifold over the rpm, as that cam will not the rpm up top.Exhaust would as mentioned be a consideration as well. have you looked at there 260 cams ? pull well and a little more rpm.

[mjrwraith]

Yeah I am looking at exhaust just forgot to to add it to the list. I'm looking at going with true dials. After looking back over my parts list and the edelbrock site I'm definitely going with the performer. I had one on one of my old grandwagoneers and loved it. I want the rpm range of the 252 I compared the two and the 252 is in the rpm range I'm wanting.

[hugger6933]

I would consider the 260h. I have used the 268H in many cases and it has never let me down. Even going with one that far from the stock spec it helped the motor run so much better in all cases it got better gas mileage. and power boy howdy!!the expectations you have are fine if not just a little low but being low is ok so your not disappointed if it doesn't do great, but it will. Jim

[mjrwraith]

Originally Posted by hugger6933

I would consider the 260h. I have used the 268H in many cases and it has never let me down. Even going with one that far from the stock spec it helped the motor run so much better in all cases it got better gas mileage. and power boy howdy!!the expectations you have are fine if not just a little low but being low is ok so your not disappointed if it doesn't do great, but it will. Jim

My reasoning for the low duration and all is along the fact of the last motor I built, which was an AMC 360 in a Grand Wagoneer, I put the 270H cam in it and it was too much. The motor got horrible mileage I had to put a 750 CFM carb on it just to keep the poor thing from falling on its face.

[mjrwraith]

Ok so I ended up going with an already built motor. My wife's uncle had a svc 350 that had already had the heads milled to bring the compression up to 10:1, it has the 268HE COMPcams cam, a demon intake, and hooker shortly headers. Only had to give him $350 for the whole setup. So I figured I'd go with it since there's no wat I could've built the motor for that price. Now all I've gotta do is put new cab mounts in, put my rebuilt TH350 with a b&m shift kit in, and rebuild the front end and she'll be ready to go. Thanks for all the input!

[mjrwraith]

Well after going to pick up the motor I learned that the reason it was so cheap is cause they put the motor together wrong. When they tried to start it, it had devastating effects. So I'm back to using the original motor, which is no biggie. So I'm going to do some more research and looking at everyones advice and let you know what I'm going to do.

[mechanicalman]

Originally Posted by mjrwraith

Ok so I have just acquired a 1972 GMC C15 long bed fleetside. I want to do just a simple restore job with a focus more on comfort than a fancy paint job or hot rod motor. I do however want to add a little extra power and a few more mpg out of it. So after some research I wanted to throw my idea on how to set this up out there and get some of your opinions. So here it is, I'm going to take the stock motor with all the lower end being factory spec, and put a COMPCams 252he cam with the new valve train and all to match. Then take the stock intake manifold off and put on an edelbrock rpm intake with the stock quadrajet. Leave the stock exhaust manifolds on and put a b&m shift kit in the TH350 tranny. I'm only looking to get around 25 more horse and maybe 2-3 mpg more out of it. Compression will be stock, which I believe is 9.5:1 may be wrong I'll have to double check. I think that covers everything so any tips or advice would be helpful thanks.

Stock compression ratio that year stock was advertised at 8.5 but if you checked the head chamber size and with the stock head gasket it was closer to 8.0 than 8.5.

Regardless of head use the fel pro steel shim 1904 gaskets to enable quench in the combustion chambers.

Those dish piston engines with that size cam just love smaller combustion chambers like the double humps.

For $399.00 you can get these rebuilt 65cc heads, they are likely rebuild 305 castings they have new bronze wall valve guides, stainless valves 1.94"/1.5" valves with new springs that will more than handle your cam.
http://www.aeroheadracing.com/chevy.html

Do you have dual exhaust? I think that engine would like dual exhaust with a crossover pipe. Stock single Y pipe is very restrictive with bad reversion.

Ensure a good distributor on it around 24' mechanical timing at around 2500 RPM (more or less depending on heads and cruise RPM best to have all in at highway cruise for mileage) with about 18' adjustable vacuum advance hooked up to ported. If it pings then set it back as nec.

This should get out of it all it has if the carb is set up right. If it's the original quadrajet with the divorced choke, a new aftermarket manifold will cause problems with that. Edelbrock 7104 Performer RPM quadrajet manifold.
http://www.summitracing.com/parts/EDL-7104
It offers a special choke rod to accommodate the divorced choke, Edelbrock #9172.
http://www.summitracing.com/parts/ed...GoWxoCixnw_wcB

If Vortec heads interest you, let me know I'll tell you what you need.

[slikside]

subd.

[Warrens69GMC]

If I were to do that to my truck I would go with Xe256/vortec heads/ performer manifold

[mechanicalman]

Originally Posted by mjrwraith

Well after going to pick up the motor I learned that the reason it was so cheap is cause they put the motor together wrong. When they tried to start it, it had devastating effects. So I'm back to using the original motor, which is no biggie. So I'm going to do some more research and looking at everyones advice and let you know what I'm going to do.

I think your cam and intake will get you close to your power increase 15-25HP but it will not make much difference in your mileage provided it was already in tune. To do that, you need a more favorable compression ratio (the 65cc heads for $399.00 plus shipping) and a more favorable split lift/split duration cam for that compression that goes well with your performer intake has power band of 1,000-5,500 RPM and produces good vacuum. This will get you around 3MPG.

This camshaft $120.00 shipped
http://www.ebay.com/itm/LUNATI-CHEVY...e1678d&vxp=mtr

Double roller timing chain name brand $27.98 shipped
http://www.ebay.com/itm/New-Cloyes-D...b2b0a7&vxp=mtr

These lifters are the best for durability. $52.33 shipped
http://www.ebay.com/itm/SBC-DELPHI-L...662d12&vxp=mtr

Exhaust cross over $54.92 shipped 2.25"
http://www.ebay.com/itm/Summit-Racin...b29382&vxp=mtr

2.5 "
http://www.ebay.com/itm/Summit-Racin...e81030&vxp=mtr

Intake $155.97 shipped
http://www.ebay.com/itm/Edelbrock-Pe...bfcce2&vxp=mtr

Head gasket (2) $45.94 shipped

Including the heads that's $856.14, plus shipping on the heads.

Then it's down to divorced choke linkage to go with the performer, long slot rockers, pushrods, and remaining gaskets. Get separate intake, timing set, rear main seal and get a good 1pc rubber felpro oil pan gasket.

You are going to spend a little over a thousand 1,200 maybe 1,300. You will have what you want.

Vortec heads would be better all the way around but there are some details involved in using them. You might score a set with rocker arms cheap at a junk yard or u-pull-it. Those rockers would suffice if not worn badly.

[mjrwraith]

Originally Posted by mechanicalman

I think your cam and intake will get you close to your power increase 15-25HP but it will not make much difference in your mileage provided it was already in tune. To do that, you need a more favorable compression ratio (the 65cc heads for $399.00 plus shipping) and a more favorable split lift/split duration cam for that compression that goes well with your performer intake has power band of 1,000-5,500 RPM and produces good vacuum. This will get you around 3MPG.

This camshaft $120.00 shipped
http://www.ebay.com/itm/LUNATI-CHEVY...e1678d&vxp=mtr

Double roller timing chain name brand $27.98 shipped
http://www.ebay.com/itm/New-Cloyes-D...b2b0a7&vxp=mtr

These lifters are the best for durability. $52.33 shipped
http://www.ebay.com/itm/SBC-DELPHI-L...662d12&vxp=mtr

Exhaust cross over $54.92 shipped 2.25"
http://www.ebay.com/itm/Summit-Racin...b29382&vxp=mtr

2.5 "
http://www.ebay.com/itm/Summit-Racin...e81030&vxp=mtr

Intake $155.97 shipped
http://www.ebay.com/itm/Edelbrock-Pe...bfcce2&vxp=mtr

Head gasket (2) $45.94 shipped

Including the heads that's $856.14, plus shipping on the heads.

Then it's down to divorced choke linkage to go with the performer, long slot rockers, pushrods, and remaining gaskets. Get separate intake, timing set, rear main seal and get a good 1pc rubber felpro oil pan gasket.

You are going to spend a little over a thousand 1,200 maybe 1,300. You will have what you want.

Vortec heads would be better all the way around but there are some details involved in using them. You might score a set with rocker arms cheap at a junk yard or u-pull-it. Those rockers would suffice if not worn badly.

That sounds like pretty close to the setup I was looking for. Out of curiosity how expensive and extensive would going to vortex heads be?

[mechanicalman]

Originally Posted by mjrwraith

That sounds like pretty close to the setup I was looking for. Out of curiosity how expensive and extensive would going to vortex heads be?

Depends, sometimes you can get them at u pull it, craigslist, etc. Lots of times they come with valve covers, rocker arms but the pushrods will not work on flat tappet cams. If you get used, I'd run them through the machine shop to get freshened up unless you are really sure of the condition. Some examples:
https://amarillo.craigslist.org/pts/4802495764.html
https://amarillo.craigslist.org/pts/4797577803.html

$619.98 new shipped.
http://www.ebay.com/itm/Chevrolet-Pe...d29440&vxp=mtr

And rebuilts available many different price ranges.

If you are going to run water temp gauge, you will need to drill out and re-tap the driver's side head temp sender hole from 3/8" NPT out to 1/2" NPT before you install it. If you run temp overheat light, you can get a switch that will fit or you can drill it for your old switch(sender). You also need special intake bolts you can get at summit or jegs or anywhere. You will need a set of 87-98 style valve covers with center bolts. You will need self aligning rocker arms, a cheap set of new head bolts no matter what heads you use (original chevy head bolts damage the heads).

You must utilize a thermostat bypass. Despite the fact your engine block has the bypass port that goes from the passenger side water pump outlet into the block up into the head, the vortec heads are not drilled for it and I don't know if you can drill them. If you do NOT have a heater water control valve, and your heater hoses are flowing all the time, that will function as a bypass.

If you have a/c and a heater water control valve or no heater hoses flowing all the time, you need to run a 3/8" or 5/8" bypass hose from the coolant fitting on the driver's side front of the intake to the top of the water pump. I would prefer a 3/8" bypass hose anything more is overkill plus that is a smaller amount of water being bypassed when the coolant needs to be cooled in a heated situation.

If you have factory a/c you will need to fabricate the bracket off the intake manifold. Vortec heads require a special intake that has only 4 bolts per side instead of the original 6 bolts per side. Scroll down to post 82 and check out the pics and info.
http://67-72chevytrucks.com/vboard/s...=649618&page=4

If you install vortec heads, it would be easier to use a serpentine setup out of an 87-95 C1500 due to the accessory bolt hole configuration.

I'd much sooner spend 620 on a set of new vortec's and go to the trouble to install them plus the more expensive intake than spend the 400 on a set of used rebuilts. They are a much better head, better iron, better manufacturing tolerances, etc. AND they will put out like 30-40HP more than stock heads better mileage, distributor usually will not need extensive modifications (vortec heads require about 4' less total timing). Use the same head gaskets I already recommended, and use the same voodoo cam.

Let me know what you decide to do and if you have any more question.

[67 chevelle]

Originally Posted by Warrens69GMC

If I were to do that to my truck I would go with Xe256/vortec heads/ performer manifold

I think this is great advise , vortec heads are some of the best for all around performance and gas mileage .

performer manifold fits your desires , rpm is more a street strip manifold for higher """rpm"""