Have I got my bases covered? 305/350 swap.

[CAChevy]

Hey Gang…new on the forum here. I’ve been searching around this site for quite some time and have found most of the info I’ve been looking for regarding my newly acquired 1984 C10 with a CA emissions 305. I’m a Ford diesel guy at heart but I picked this truck up on the cheap to rebuild/restore for, (and with), my 15 year old Son who will be driving by this summer. What I’m in the process of doing is swapping out the now seized up 305 with a GM crate 350. I just wanted to post the general game plan on here so that if I have anything screwy or if I have overlooked something in my research, someone can chime in and stop me from doing something that isn’t going to work. I’d much rather learn from your guy’s mistakes than my own. No offense.

The foundation of the build is going to be the GM 260hp/350tq, (yeah right), crate motor (Part #10067353 off Ebay. Crazy but it’s from Jeg’s and cheaper than their website). I plan on pulling the cam/lifter/springs out of it and replacing it with an Edelbrock 3702 cam, (includes CARB EO#), and 5903 springs, also from Jegs. So far, as long as the smog guy isn’t looking at casting numbers or checking cylinder volume, I’m good to pass the visual. The intake I’m looking at is a Holley/Weiand 8000. I see a few used ones on Ebay for cheap which is about the only place I can find them. I think they are out of production. That intake has an applicable CARB EO# and I haven't been able to find another that does. It’s got to better than the stock 305 one though, right?

Still haven’t quite got the carburetor nailed down which I think will be a big determining factor of what comes out of the pipe for the sniffer test. The Carb # is 17084527 which apparently only came on CA emissions trucks. I’ve chatted with Ted via email over at Mountain Man Fuel Systems in Hackett Arkansas about rebuilding my carb. He seems to think that a simple rebuild to factory specs will be fine with the cam/induction combo we’re going with but can’t guarantee it’ll work because he hasn’t done this combo himself. I can respect that. My thoughts are that the cam lift/duration isn't that much of a deviation from the 305 cam so the computer should be able to compensate for the added cubes. No? It should also have as good if not better vacuum production as stock. No? Another thought is if Chevy put a CCC Quadrajet on a CA emissions equipped 350 in 1984, wouldn’t that carb work? I would think it would visually look identical as the one on the 305 but perhaps have more flow on the secondary side during WOT. Just guessing, I don’t know. I’m still a little perplexed on why there is a CCC carb, a 4 wire distributor and an O2 sensor but no knock sensor. I looked. On both sides of the block. Where Google images told me to look. All I found were plugs. Is that normal? As far as spark goes, I’m sticking with a factory replacement distributor, nothing fancy plug wires and whatever spark plugs. This build isn’t going to be a ball of fire by any stretch of the imagination.

After saying that, one would wonder why we’re going with Headman 69891 LT headers, Magnaflow Super Cat and a Flowmaster. The answer to that would be I also got those on the cheap off Craig’s List. I couldn’t turn it down, especially because the headers and cat have CARB EO#’s that get me through smog inspection. Can’t hurt, right? I'm thinking of using a "not for application" 2 1/2" vacuum operated exhaust valve in place of the factory restrictive efe valve. It looks pretty darn close to factory and I'm sure I can sneak it by. I'll have to weld in a bung on one of the collectors on the headers for the O2 sensor as well.

I plan on putting a 4 row aluminum radiator from Champion (MC716) in it to help with the cooling. Not the best, I know. But it is cheap; like me. We're in the central valley where temps are regularly in the triple digits in the summer.

I’m looking at a rebuilt 30 spline, (that is if I already have the 30 spline and if not can swap in a 30 spline just by using the correct torque converter), 700r4, (a rebuilt one from a local shop that has them for $400), behind all this with a tranny cooler to again, help with the valley heat.

Seriously considering lower this ranch truck with a Western Chassis 2.5/4 kit using front spindles and rear drop leafs. From what I read on this and other forums, that drop seems to be o.k. with long tube headers and ground clearance. The only down side to that I see is a 16 year old boy and speed bumps in the high school parking lot.

Other than putting all the smog junk and typical misc. parts, (fly wheel, starter, engine acc...etc), that’ll just swap over, am I missing anything specific that’d be needed for the swap? Thanks a head of time for any positive criticism/feedback and for all of you who unknowingly have already helped me out thus far.

[frank69]

If I was doing it I would forget about the headers and go with the stock exhaust, unless u enjoy relacing gaskets and working around the pipes everytime u have to fix something like the starter.

[rich weyand]

That cam looks like an older grind. The ramps are slow. Subtract the "duration at 050" from the "duration as advertised" and you get 50 degrees on both intake and exhaust. That's time the cylinder can't be filled on intake and shortens the exhaust stroke. Also, the rpm range beginning at 1500 means it will be low on torque in the bottom. Their claim of 245 lbft is way low for what you should get from that engine, or even from a 305. It's also a TBI cam and you are putting it on a carb engine. This cam is a really bad fit for your truck.

Use the Comp Cams 12-235-2 instead. First, it's a carburetor cam. This cam was recommended to me by Sean at SMI and he knows his stuff. I've run it through a dyno simulator on that engine with a similar setup to what you are talking and got 415 lbft of torque at 2500 rpm and 290 hp at 4000. RPM range is 1000-5200, which is a function of that torque number. Also, better low end should result in better idle emissions numbers than a cam with a higher rpm range. Ramps are 44 degrees instead of 50, which means it's a more modern grind, and gives better flow and performance. It also has a CARB EO# and is 50-state legal on '93 and earlier SBCs. Other people on chevy pickup forums have used this cam and love it.

[Ziegelsteinfaust]

Smogger Q-jets still have enough cfm for close to 400 hp. So I wouldn't swap carbs, but rather concentrate on making the one I got 100%.

The Weiland intake doesn't hurt, and they do flow a bit better then a stock iron one. I have a Edelbrock on my truck, and I used a 1" spacer to help with power. On my C20 I had 4.11 gears so it helped my driving rpm power out quite a bit. I now have the same set-up on my new engine, but haven't driven it yet due to overwhelming project status.

Its been quite a few years since I had to smog anything besides new cars, but the smog nazi's do not like anything that shine's. So I painted everything black, and never had a problem.

[CAChevy]

frank69; thanks for the input. I don't mind so much working around the headers. I had a set on my '74 F250 w/428 and they didn't pose to much of a hassle, though you're right, I constantly fought leaks on the flange style collectors that they had. The flange on these for the C10 are 3/8" thick and the collectors are a ball/socket type so it should seal up and stay that way for a while. Hopefully. Anyways, alread bought them, might as well use em'.

Rich, thank you very much for that ino! The specs on the Comp 12-235-2 look much better than the Edelbrock 3702. I read this "Engine Application: 305-350 V8 T.B.I. & LG-4" off the cam card for the 3702 and thought I'd be ok with it. Do you know of anyone running the CCC Quadrajet and stock programming with the 12-235-2 cam? My fear here is freaking out the ECM with a cam that's that's too far off from factory. I found a thread where you went with the 12-300-4 in your truck. But I also see you're not running the CCC Q-Jet. But the 12-300-4 has an EO# as well. Dang it! Now I'm all confused.......

Ziegelsteinfaust; I agree that the Q-Jet will flow enough cfm. I guess I'll just need to learn how to change out metering rods or whatever to get the A/F ratios where they need to be.

Thanks guys for the input.

[CAChevy]

OK, correct me if I'm wrong here. The Electronically controlled Q-J that I have has a mixture control solenoid. So, there isn't anything I need to do to it because the computer takes the A/R ratio from the O2 sensor and adjusts accordingly right? So I'd most likely be ok with just a rebuild and good to go?

[rich weyand]

Originally Posted by CAChevy

frank69; thanks for the input. I don't mind so much working around the headers. I had a set on my '74 F250 w/428 and they didn't pose to much of a hassle, though you're right, I constantly fought leaks on the flange style collectors that they had. The flange on these for the C10 are 3/8" thick and the collectors are a ball/socket type so it should seal up and stay that way for a while. Hopefully. Anyways, alread bought them, might as well use em'.

Rich, thank you very much for that ino! The specs on the Comp 12-235-2 look much better than the Edelbrock 3702. I read this "Engine Application: 305-350 V8 T.B.I. & LG-4" off the cam card for the 3702 and thought I'd be ok with it. Do you know of anyone running the CCC Quadrajet and stock programming with the 12-235-2 cam? My fear here is freaking out the ECM with a cam that's that's too far off from factory. I found a thread where you went with the 12-300-4 in your truck. But I also see you're not running the CCC Q-Jet. But the 12-300-4 has an EO# as well. Dang it! Now I'm all confused.......

Ziegelsteinfaust; I agree that the Q-Jet will flow enough cfm. I guess I'll just need to learn how to change out metering rods or whatever to get the A/F ratios where they need to be.

Thanks guys for the input.

The 12-235-2 may be better for most people, I think. I went with the 12-300-4 for even higher torque, but I gave up horsepower and rpm on the top end. It works for me; I just don't wind it that tight, and I have over 420 lbft on tap at 2500, with over 400 lbft of torque coming off idle. Now that I have a tach in it, I can see that I never go over about 3000 rpm. No need. If you do put in the 12-300-4, you need to mod the governor in the transmission so it doesn't hang on to gears too long. I have an extra of the piece you need if you go that route.

The different Q-jet shouldn't have any problems with either the 12-300-4 or the 12-235-2. They aren't that far off the stock 350 cam, truth be told, compared to some high-duration cam set up for horsepower at high rpm with a crummy idle and low torque in the bottom. That base 350 is set up for nice low-end torque from the factory, these two cams just use modern grinds to get better numbers from the same design philosophy.

All carbs are open-loop systems trying to get to the correct A/FR, and all carbs have errors in the A/FR. As opposed to fuel injection, which is a closed-loop system that controls the A/FR exactly. The solenoid Q-jet basically uses an O2 sensor to pick between two setups, depending on which one will be closer to the correct A/FR. That is, it minimizes the error by having more than one setup to choose from, and chooses based on the O2 sensor. So yup, rebuild and good to go.

P.S. Modding the governor is no big deal. It pops out from the side of the transmission. It's behind a little cap with a spring-loaded clip to hold the cap on. You just pull it out, take out a hinge pin on the flyweight, and put a new pin in it (a #6 finish nail -- no, I am not kidding) and pop it back in there. The extra flyweight I have is a bit heaver than stock -- you only replace one of the two, which is why I have one extra -- and it will move your WOT shift point down about 500 rpm. This is all on a TH350; I think the 700R4 has a similar setup, but the flyweight may or may not be the same.

[CAChevy]

Do you think I can still use the lifters/springs/rockers/rods that come in the GM crate motor with the 12-235-2 cam? I don't know if GM runs those crate motors after build or not. Or, at the very least pick up a set of Comp 812-16 lifters to go with?

[rich weyand]

New GM crate engines have never been run, they've never even had oil in them. The 12-235-2 cam has about the same lift as the 350/290 engine, which has the same springs and lifters as the 350/260 engine, so no worries there in terms of needing stronger springs or whatever.

As long as you don't fire it up AT ALL, you just swap the cam in and you're good to go.

When I did my 12-300-4 swap in the 350/290, I did replace the lifters, but it had been in there a year and I had over 5000 miles on the new engine. Lifters and cam bed into each other very quickly -- within minutes.

Make sure you follow the break-in procedure on the engine. This includes running it at various speeds for a half hour, then changing out the oil and filter, then changing the oil and filter again at 500 miles, and again at 1000, and using ZDPPPlus or some other zinc additive in the oil every time, etcetcetc. I don't remember all the details, but it is in the instructions you get with the engine. Don't skimp there, 'cause it'll cost you: You'll flat-lobe that cam, and they're a lot harder to change once the engine's in the truck.

I can recommend ZDPPPlus additive. One little bottle in each oil change, including the first load of oil you put in the engine. Also, I can recommend Mobil1 10W30 (full synthetic) as well as full-synthetic ATF (better shifts, more efficient which is more power to the wheels and less transmission heat) and full-synthetic power steering fluid (much better steering including easy steering even when stopped at idle).

[Ziegelsteinfaust]

Valvoline VR1 racing oil has zinc in it. Which is what I run in my old vehicles.

[CAChevy]

O.K...so, I got the motor in the garage yesterday and took the heads off it. Man o man o man...there is no way this thing will build 8.5:1 compression. Now I don't know exactly how many cc's those dished pistons are but after putting a depth micro on them they're sitting between .031"-.029" below the deck. It's hard to tell but the head gasket GM used look to be around .028"-.035" compressed. Add to that the 76cc heads and I come up with arounf 7.87:1 Ugh. Sure that's all fine and dandy to run 87 octane but the quench is way off at an average of .062".

I don't want to deck the block...I want to leave as much material on there as I can for future uh-oh's. What I'm thinking about doing is changing out the pistons to a 5cc flat top, (Sealed Power H345DCP), and put a .015 head gasket on it. That'll get me a quench around .042 (not great but better), and a CR around 9:1....still pump gas 87-89 friendly.

You guys think all that along with the Comp 12-235-2 cam is to much for the stock ECM?

[rich weyand]

I'd leave the rotating assembly alone (You gonna rebalance that?), and just go to the thinner head gasket, put in the 12-235-2, and call it done. That'll have plenty of pop.