Looking for some advice on a stock sbc 350 build

[tschmitt]

Hi All, looking to rebuild a 1992 sbc 350 with 193 heads. This is going to be a very basic stock rebuild, not changing heads (will be using .015 or .020 steel shim head gaskets), reusing the stock pistons, but will be looking to change the intake since I am going with a quadrajet (1705 series) that I will rebuild with parts from Cliff. This motor is going into a 1800-1900# tbucket with a TH350, 4.10ish rear end ratio with 32-33 inch tall tires in the back, manual steering, manual brakes. This engine will also have open headers. Will be mostly used around town and driven to the local car shows, no drag races, no long hauls, just a fun little rig to play around in. I am looking for advice on what cam to use and for what intake to use. I can find all kinds of used SBC intakes locally so just a couple of recommendations would be nice that would fit this build and head combo. I am looking at a Speed Pro CS-274 camshaft (basically stock from what I can tell) with new lifters and new stock valve springs. I don't want a cam with a lot of lope as the open headers will be plenty enough and I want it to be easy to dial in with good idle vacuum and great throttle response. Wanting to have most of the power down low as I know these heads don't make much past 4000 rpms which is ok with me for this small of toy.

Just wanting a nice streetable engine that is easy to tune and has a great/crisp throttle response.

So to sum it up, camshaft recommendation and intake recommendation that might best fit this build. I appreciate any advice you all might have. Thank you

[quadrajam]

I have that same cam in my 92 s10. Its a DD, Idles smooth as silk and way down low.
That will actually sound good with your open headers. As for an intake your heads will require
an intake with the 4 center bolts straight down. There is a factory GM Q-Jet aluminum intake
that will work. Casting # 14101074 . Also several aftermarket available.

QJ 

[tschmitt]

I have that same cam in my 92 s10. Its a DD, Idles smooth as silk and way down low.
That will actually sound good with your open headers. As for an intake your heads will require
an intake with the 4 center bolts straight down. There is a factory GM Q-Jet aluminum intake
that will work. Casting # 14101074 . Also several aftermarket available.

QJ

Thank you very much for the advice, I'll do some checking around on the that intake and see what I find. Thanks again!

[Mudsport96]

A 92 block should be a roller cam, what camshaft does it currently have in it?

[tschmitt]

A 92 block should be a roller cam, what camshaft does it currently have in it?

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.

[77cruiser]

My 95 truck had a flat tappet, I think 96 when Vortec came out were all roller after that.

[Mudsport96]

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.

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]

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......

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......

[Cliff Ruggles]

In most cases here I'll simply have the blocked decked and squared for zero and use a Felpro .039" thick head gasket.  This gets me .039" quench distance and the Felpro stock blue gaskets are EXCELLENT parts.  I am NOT fond of most of the others out there, unless you get into really high end stuff like Cometic or multiple layer shim type gaskets. 

Nothing at all wrong with stock steel .020" shim SBC gaskets, just be aware that the "finish" on the block and heads MUST be pretty fine/smooth or they may seep some coolant even if they are a coated variety or you spray them with High Tac.

In any case I don't want to write a book here on engine building.  Even so it is worth the time and expense to do these steps.  Your new engine will last longer, less prone to detonation, increased power, running cooler, LESS timing required to make peak power, and using LESS fuel to make the power, plus improved fuel economy. 


So it's a no-brainer, IMHO.  I'll also add that I get all sorts of inquiries from folks who just did an engine "build" and did NONE of the above.  Instead they put it together with the pistons WAY down in the holes at TDC, added a thick "builder" head gasket, some aftermarket short seat timing fast ramp cam on a tight LSA.  A high rise aluminum intake, headers, and very disappointed with the end result.  They can't figure out why it's a complete "turd" everyplace, runs hot, overheats, pings on pump gas, and wouldn't spin the rear tires if you dropped it off a floor jack at WOT!

Good results start with good engine building practices, attention to detail, and making good choices for compression, head flow and camshaft events.   Tight squish is NOT an option, neither is not establishing equal distance from the deck to the crankshaft centerline on both banks. 

Since I tune for a living I could put up HUNDREDS of stories hear where I get involved with these engine builds after very poor decisions were made.  At that point way too much quench, not enough compression, and a poor cam choice only allow us to "crutch" the tune to get things to work well, and the end results are NEVER nearly as good as they could have been......hope this helps some.......

[tschmitt]

Thank you so much for the advice and education Cliff, as always I truly appreciate learning from you and take your advice to heart. This place is an amazing place to learn from and hopefully someday you will have time to right a book on engine building and tuning, I am sure it would be a great success! Thank you again!

[Cliff Ruggles]

I've been asked to write a couple more books but don't have time for it.  It takes a  year to do one, and that's putting quite a few hours into it each day.  The parts business is keeping me a LOT busier than I want to be, so for now no book writing on the horizon......

[tayto]

these heads don't like more than 30* all in timing. i built a 350 w/ flat top pistons and these heads and nake peak hp/tq @ 25*

[Cliff Ruggles]

Since I started establishing tight quench with these engines and making good cam choices almost all of them make best power at heavy/WOT at 28-32 degrees total timing.  That's a good place to be instead of clear up at 36-38 degrees and tells us we've done a good job with our choices for the engine. 

I also add in about 10-15 degrees vacuum advance, almost always from a ported source simply because a well thought out engine with optimum compression for pump gas and well chosen cam is not going to like, want, need or respond well to a butt-load of timing at idle speed.

Most of my engine are fine with about 10-12 degrees initial timing, 28-30 total, and 40-45 at cruise/light engine load.......