Cliff's Quadrajet Parts and Rebuild Kits
General Category => Lobby => Topic started by: tschmitt on August 04, 2023, 07:12:04 AM
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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
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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
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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!
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A 92 block should be a roller cam, what camshaft does it currently have in it?
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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.
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My 95 truck had a flat tappet, I think 96 when Vortec came out were all roller after that.
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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.
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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......
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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.
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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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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.......
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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!
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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......
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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*
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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.......
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...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...
Hey Cliff,
I'm building almost the exact same engine RN, and just installed a Melling Double roller timing set. I've used lots of them and always thought that was "the way", but TBH I never really looked into it and just took it as gosple.
What's wrong with them? drag? quality? harmonics? weight?
I'm inclined to just run it, but legitimately curious why you don't recommend them.
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Right to start with a roller chain isn't nearly as strong. They are not "constant tooth contact" so you get more spark scatter from the distributor. There is also no tensioner to keep them from flopping around when they get loose, and they do get loose in a hurry. It's my opinion that lacking a tensioning system allows them to really start flopping around when they get loose and accellerates the wear.
If you've ever peaked into a chain driven 4 X 4 transfer case you will NEVER see a roller chain there. It wouldn't last to the bottom of my driveway in a 6000 lb truck on hard pavement in four wheel drive mode.
The roller chains also have multiple wear points, and many are low quality. The only one I'd even look at for any of these engines would be the high end Cloye's or Rollmaster with the IWIS chain on it.
I've pulled down a good many engines several years after full rebuilds and you'd be surprised at how loose the roller timing sets are. We don't get accurate feedback with this sort of thing simply due to the way these vehicle are used. Most don't see much more than a couple of car shows every summer, couple of trips to Dairy Queen for ice cream, and maybe one or two trips to the local track to make a few passes on a Friday nigh test & tune session.
I actually tried one of the "high end" Rollmaster 9 keyway double roller sets back in 1999. It was highly recommended to me and came with an engine "package" I bought when building the first 455 that went into my Ventura. I was racing the car a lot back then, and lots of street driving. Four year later it had to be replaced. Got so loose you could just about walk it right off the gears!
I used a 3/4" wide Cloyes in the next 455 build in 2008. In 2022 the timing cover developed a coolant leak and had to be removed. I bought another Cloyes Morse type timing set to replace it. When I got the timing cover off the chain was still pretty tight, with only witness marks on the gears. Put on new gaskets and buttoned it back up and good to go for another 15 years or so......
Pictured below is one I bought off Ebay recently and the type I prefer to use. Steel sprockets and 3/4" wide chain. One of these will easily last the life of the engine......
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Be aware that COMP makes a wide remorse link timing set part # 3200. I used one
for my latest SBC last year and it was a piece of dookie. Slack 1.5 degrees out of the box.
Checked again @ 1500 miles and was 3.5 degrees slack. Got a Cloyes double roller
from LPS and put it back together. I dont think any other company makes the 3/4 wide
chain anymore. You would have to be lucky and find one NOS from ebay or swap meet
etc. ....
QJ
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They still offer the wide link belt sets for SBC and Pontiac.
Try Googling part number 3-489S, Melling or Speed Pro.
Here is an NOS 3/4" wide Pontiac set on Ebay:
https://www.ebay.com/itm/255023708000
I would never use any type of double-roller timing set in one of my engines. Even so I would recommend anyone going that direction to get a set with USA made billet sprockets (9 keyway) and the IWIS chain........Anything less than that is bovine excrement.....IMHO....
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Thats good information to know. I ended up finding a TRW wide set on ebay NOS. One day when
I get caught up I will swap it out.
QJ
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Here is a pic of my favorite timing sets, with steel sprockets and heat treated gears. Very rare these days but the very best timing sets ever made for these engines.....IMHO...
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Any recommendations on what shift points to set with this combo from my first post? I'm considering modifying the governor in the th350 but I'm not for sure what the ideal rpm I should shoot for in regards to shift points with this cam/engine combo.
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Somewhere between 4500 and 5000. That is a pretty small cam on the .050 numbers. Pretty close to a stock late 70s truck cam, so no need to rev it out. Heck, I would just leave to Governor stock and see how it does.
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Somewhere between 4500 and 5000. That is a pretty small cam on the .050 numbers. Pretty close to a stock late 70s truck cam, so no need to rev it out. Heck, I would just leave to Governor stock and see how it does.
Thank you for the information I appreciate it. It currently is shifting around 2500 or so 1st-2nd, 3500 2nd-3rd at WOT so I'm looking to extend both of those out quite a bit further. Very snappy and pulls great but can always try for more. I believe each governor is calibrated to the application it was initially intended for so it may have just been the factory preset for that particular vehicle, whatever this th350 came out of.
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With that info, and the info from the first post saying you have 4.10s, it sounds like you have the same issue my nova has. The calibrations for the governor is for a highway gear. So it is spinning faster and thinks that your road speed is way higher than it really is. I just manually shift the car if I am really wanting to get into the secondaries. You could try trimming or grinding the weights to see if that helps some.
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You have the detent cable hooked up & adjusted?
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Are you running the 4.10s and 32 inch tires yet or still short tires?
Do you know what gear ratio the vehicle that the th350 came from had? If not I'll throw a few random things out.
If it had a 2.56 gear and you are running a 4.10 the governor is spinning roughly 60 percent faster than it would have in the original application.
Most let's say caprice and malibu cars in the 70s to 80s were cammed for economy so at WOT they would probably shift around 4200 to 4500. What is 63% of 4200..... 2700. So if the tach is relatively accurate it should shift where it is. You could try grinding some material off of the flyweights, or see if a local transmission shop can get a governor for a th350 with a higher gear.
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Thanks for the replies fellas. I changed to 3.42 gears, still with 32 inch tall tires though. Kickdown cable is hooked up and adjusted correctly, passing gear works flawless. I'm going take the governor out and slowly take off some material from the inner and outer weights. From what my research shows the inner weights affect more of the 1-2 shift, outer weights more of 2-3 shift. I'll be using a gram scale to measure all of them to start with and slowly come down from there. I'm not sure what the th350 came out of but I'm sure I can get this dialed in to what I'm looking for. Just some trial and error.
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That is one way to go about it.
I just left mine as it is. And like yours at WOT it shifts at like 2500 to 2700 1-2 and 3000ish on the 2-3.
I left it like this so my daughter can drive it and not have it get away from her if she floors it.
So I just manually shift it at 5500. It makes for nice low rpm around town driving shifts.
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That is one way to go about it.
I just left mine as it is. And like yours at WOT it shifts at like 2500 to 2700 1-2 and 3000ish on the 2-3.
I left it like this so my daughter can drive it and not have it get away from her if she floors it.
So I just manually shift it at 5500. It makes for nice low rpm around town driving shifts.
I can understand that. From my understanding with how the th350/th400 works is the vacuum shift modulator has more affect on the part throttle aspect (firmness and RPM range) vs the governor at WOT so it shouldn't have too much of a affect on just daily driving. Not saying it won't change it at all but from what I have gathered it will not change the part throttle shifting to say 4,000+ RPM during daily driving like it will for WOT.