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Looking for some advice on a stock sbc 350 build
77cruiser:
My 95 truck had a flat tappet, I think 96 when Vortec came out were all roller after that.
Mudsport96:
--- Quote from: tschmitt on August 05, 2023, 11:56:31 AM ---It has a flat tappet. From the research I have gathered some trucks in the early 90's still had a flat tappet cam. All car 350's in the early 90's had roller cams though. They were still phasing them out in trucks in the early 90's though.
--- End quote ---
Well that is a downer, but is the valley drilled and tapped for the hold downs? Some of the flat tappet engines were already drilled and tapped for the roller setup.But if they went down the truck line instead of the car line they got the non roller camshaft. So it is possible that you could junkyard dive for the lifter hold downs, pushrods, and maybe even lifters if you are brave.
Then get a copy of an L98 TPI cam. Broad tq and easy driving as it is a stock cam. I think the Engine tech ES808 o. Rockauto.com is the one.
Cliff Ruggles:
The heavy duty truck engines from 87-94 came with flat tappet camshafts but the block is set up for HR cams. You can buy everything to install a roller cam in a "kit". Summit used to have them and probably still does. It will come with the retaining plate for the cam, forks to hold the lifters from turning and the spider to hold them in place. You will need shorter pushrods, HR lifters, and a HR cam. A stock replacement truck cam would be fine for what you are doing. They are really low lift and easy on the valve train.
If you stick with a flat cam you already have the right one. Nothing out there will work better than the CS-274 cam, it is basically a duplicate of the factory 350/300hp cam.
Nothing special needed for the build, stock oil pump, stock timing set (I would NOT use any type of double roller chain set-up), stock pushrods and rocker arms.
The key to success with the SBC is tight squish so the .020" steel gaskets are a good choice. Here I keep the quench under .040" no matter what it takes to get there.
Flat top pistons would be a huge upgrade for what you are doing. I did the exact same engine build for my dad's 1991 3/4 ton engine about 25 years ago. I kept the early swirl port Vortec heads, but bought a stock roller cam, lifters, pushrods and the kit to install it. We bored it .030" over as it had over 250,000 miles on it and broke a piston ring land. Otherwise the engine was in pretty good shape. I went back with all stock replacement parts, put new stock valve springs in the heads, valves and valve guides.
The improvement in performance was remarkable, most coming from the increase in compression. I doubt if the roller cam did much but they do free things up some with less friction than a flat cam.
Dad used that truck to pull a 24' horse trailer with 4 mules in it, all their tack, and another small trailer behind it with a wagon on it. He went to parades and events where they hitch up the mules and such.
Before the engine "upgrades" it really had it's tongue hanging out pulling that much weight. The new build did really good with it and made gobs of low end and mid range power. The truck had 3.73 gears and a NV4500 5 speed so all the power was on the pavement......
tschmitt:
--- Quote from: Cliff Ruggles on August 16, 2023, 02:59:04 AM ---The heavy duty truck engines from 87-94 came with flat tappet camshafts but the block is set up for HR cams. You can buy everything to install a roller cam in a "kit". Summit used to have them and probably still does. It will come with the retaining plate for the cam, forks to hold the lifters from turning and the spider to hold them in place. You will need shorter pushrods, HR lifters, and a HR cam. A stock replacement truck cam would be fine for what you are doing. They are really low lift and easy on the valve train.
If you stick with a flat cam you already have the right one. Nothing out there will work better than the CS-274 cam, it is basically a duplicate of the factory 350/300hp cam.
Nothing special needed for the build, stock oil pump, stock timing set (I would NOT use any type of double roller chain set-up), stock pushrods and rocker arms.
The key to success with the SBC is tight squish so the .020" steel gaskets are a good choice. Here I keep the quench under .040" no matter what it takes to get there.
Flat top pistons would be a huge upgrade for what you are doing. I did the exact same engine build for my dad's 1991 3/4 ton engine about 25 years ago. I kept the early swirl port Vortec heads, but bought a stock roller cam, lifters, pushrods and the kit to install it. We bored in .030" over as it had over 250,000 miles on it and broke a piston ring land. Otherwise the engine was in pretty good shape. I went back with all stock replacement parts, put new stock valve springs in the heads, valves and valve guides.
The improvement in performance was remarkable, most coming from the increase in compression. I doubt if the roller cam did much but they do free things up some with less friction than a flat cam.
Dad used that truck to pull a 24' horse trailer with 4 mules in it, all their tack, and another small trailer behind it with a wagon on it. He went to parades and events where they hitch up the mules and such.
Before the engine "upgrades" it really had it's tongue hanging out pulling that much weight. The new build did really good with it and made gobs of low end and mid range power. The truck had 3.73 gears and a NV4500 5 speed so all the power was on the pavement......
--- End quote ---
Thank you very much for the advice Cliff, I'll be sticking with a flat tappet cam vs roller but doing exactly what you said other than that. In regards to the quench is there a recommended range you would stay within for a street engine? I've seen some guys run from a 0.030" up to 0.045" but I want to be safe and not risk damaging anything. Thank you again for your advice, I'll be calling in the near future to order a kit for the quadrajet once I get it apart and see what all it needs.
Cliff Ruggles:
Here I target .035", and never over .040" for any reason. .030" is plenty with cast pistons as they don't "rock" much in the bores. I know a few engine builder (very good ones) that go a little tighter with quench.
The vast majority of folks doing this, guru's, machine shop folks, engine "builders", etc, don't have a clue about establishing tight quench and the benefits that come from it.
Quench area is NOT your friend with these things. I've had some ill fated engines brought in here that ran hot, overheated and pinged easily on pump gas simply because they had WAY too much quench in them.
It's not uncommon with some aftermarket cast pistons to have them end up .030-.050" in the holes at TDC. For some reason, and even TRW/Speed Pro forged pistons will be like this, they decreased the pin distance to compensate for the overbore so the compression ratio wasn't increased. How STOOPID is that?
In any case all of my engine builds get the block decked and squared. This establishes a true distance to center from the heads and equal distance to the crank on both sides of the block. I've seen untouched factory blocks off as far as .035" bank to bank and nearly that much front to rear.
So NEVER assume the factory got it right, ALWAYS check everything.
The easiest way to accomplish tight quench and equal distances side to side is to buy pistons that come up pretty close to the top of the block right to start with. Before you take the engine apart roll it over to TDC on a couple of pistons on both banks and measure how far down they are in the holes. Once they are out measure the pin height or distance from the pin to the top of the piston.
Do some math at this point to insure that the new pistons will be close to the top of the block at TDC when assembled.
Have the block bored for the new pistons, do a quick assembly by installing the crankshaft with only the thrust bearing and front main bearing. Install the outer four pistons/rods with no rings on the pistons and measure how far down in the holes they are. Using a paint marker write the distance at each corner of the block. Then carry it back to the machine shop for decking and squaring.
A really good shop with a skilled machinist can forego those steps using calculations, but I much prefer to mock the assembly up and measure it myself.
Anyhow, at this point you have choices and can decide how much is needed to straighten up the block, plus how thick the head gaskets will need to be to hit the target quench distance on assembly.
Continued......
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