350 generic crate, rebuild?
Hi folks I wanted to see if there is some thing else I should do or maybe some thing I should not do on this rebuild.
Here is what I have
1984 C-10 Short bed
All original components work, AC,power brakes ,etc.
rear end ratio, 2.73
truck weight , 4000Lbs
trans, turbo 350
tires , 31" tall
stock exhaust system, 2 pipes into one then cat and muffler.
Engine Name: 350 LM1
Horsepower: 249 HP @ 5,000 RPM
Torque: 304 Ft/Lbs @ 3,500 RPM
Compression Ratio: 8.50 to 1
Block: 4 – Bolt, 2 Piece Rear Seal, 4.000” Bore
Crankshaft: Cast Nodular 3.480” Stroke
Heads: Cast Iron, 76cc
Valves: 1.940” / 1.500”
Camshaft lift: 0.390” / 0.410” Hydraulic
Duration @ 0.050”: 195° / 202°
I am going to try and keep it simple and use the same 882 style heads. I talked to the guys up at the motor shop and told them I am looking for low end, raised compression, 87 octane.
They said to go with flat tops with the 4 valve relief, heads will be surfaced and compression should be good with 87 octane. Does this look about right?
I am also stuck with a mellings MTC-1 cam, the motor will not be warrantied if I go aftermarket. 1 year,12,000 warranty. Heres the specs on the cam,
Cam Style Hydraulic flat tappet
Basic Operating RPM Range Idle-4,500
Intake Duration at 050 inch Lift 204
Exhaust Duration at 050 inch Lift 214
Duration at 050 inch Lift 204 int./214 exh.
Advertised Intake Duration 278
Advertised Exhaust Duration 288
Advertised Duration 278 int./288 exh.
Intake Valve Lift with Factory Rocker Arm Ratio 0.420 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio 0.433 in.
Valve Lift with Factory Rocker Arm Ratio 0.420 int./0.433 exh.
Lobe Separation (degrees) 112
Computer-Controlled Compatible No
Valve Springs Required Yes
Anything else I should add or take away on this rebuild that some of the more experienced folks see? I trust the guy at the sales counter as much as I trust any other salesman, not that he is wrong , but we can all miss some thing. So I thought I would run passed here also. Thanks
With flat top pistons there is something you have to be aware of and that is the compression height. Factory 350 pistons have a height of 1.560.
Some of the aftermarket "rebuilder" pistons have flat tops but the compression height is 1.540. This kills quench and compression.
You can usually get a real good deal on Ebay on 2 valve relief coated skirt pistons from Speed Pro, these pistons with 882 heads would put you around a 9:1 compression ratio. I would also use a thin head gasket such as GM's .028 thickness head gaskets. The melling cam will work fine, it's specs are almost identical to the Edelbrock Performer cam which will give you good torque. I would use a cloyes double roller timing set. Last but not least, add a set of headers, the headers alone will give you a 15 horsepower kick.
Make sure you get a set of valve springs to match the cam. What is hurting you most of all is the tall 31 inch tire and the awful high 2.73 rear gear ratio.
It would be a huge improvement to power and torque if you went with around a 3.55 or 3.73:1 ratio rear gear.
X2 on the above; the easiest way to increase performance is to put some gears in the back. Even a 3.42 or 3.23 will amaze you at this point. You could also go to a 28" tall tire.
Depending on what you want to do, the 882s arent the worst head, but a set of vortec's might be better.
I'll add that I'm not a big fan of the 883 head it just isn't very effecient at burning fuel, compared to the Vortec with this cam the 883's leave about 30 horses and a couple/three miles to the gallon on the floor.
You can brighten up the Melling cam with 1.6 rockers, if you run a stock type rocker with a ball fulcrum and sliding tip this change can be made cheaply.
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