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Discussion Starter · #1 ·
19 minutes ago#1
Pleze1988
Pleze1988New Member
Hello everyone. Just a little info, I have a 1978 Camaro sport coupe that has the original 305/350 combo. This winter I'm going through the motor. The parts I have so far:
Edelbrock Performer Intake
Lunati BareBones 280/290 Cam
Older Quadrajet
Headers and 2.5 inch full exhaust
Now the issue. I have access to a low mileage 1991 TBI 350. I wouldn't want to rebuy anything so I would use a set of 416 heads I already have so the intake and carb would be useable. Would it be worth the trouble or should I just stick with the 305? How much power would you ballpark both combos. I figured 200hp out of the 305 combo and probably 250hp out of the 350. Am I close? Thank you for the info and advice. Either way I'm excited to have this car back on the road, it's been a long time coming.
 

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The TBI 350, all the way. Toss the TBI head and use the 416's of the 305.
The 305 just can't compete with 45 more cubic inches. It will be down 50 ft lbs on torque and at least 35 hp down versus the 350.

305's big problem is it's tiny bore size.

This will work best if the 416's have at least 1.84" intake valve though and not the tiny 1.72" valve....so you may need to get those rebuilt......which brings up a whole new subject which is the fact that the cost of rebuilding and bigger valves is the same as the cost of a set of aftermarket aluminum heads that are 5 times better.

Rebuilding stock old iron heads is no longer worth the cost unless they are for a numbers matching restoration
 

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1979 Chevrolet Malibu 496-TH400-9" (cruiser). 1992 Chevrolet S10 355-700r4-7.625" (daily driver).
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The TBI 350, all the way. Toss the TBI head and use the 416's of the 305.
The 305 just can't compete with 45 more cubic inches. It will be down 50 ft lbs on torque and at least 35 hp down versus the 350.

305's big problem is it's tiny bore size.

This will work best if the 416's have at least 1.84" intake valve though and not the tiny 1.72" valve....so you may need to get those rebuilt......which brings up a whole new subject which is the fact that the cost of rebuilding and bigger valves is the same as the cost of a set of aftermarket aluminum heads that are 5 times better.

Rebuilding stock old iron heads is no longer worth the cost unless they are for a numbers matching restoration
100% agree with this. 350>305. The bang for your buck on the cylinder head upgrade is money well spent.
 

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Screw the 305 or weak 5.7 tbi heads.
Dont mess with spending $1000 on vortecs, intake, and a carb.


5.3 bolted to a th400 and a fuel cell in the trunk.
Plan on around 2-3k to do it all right. Several write ups out to show you the headaches and such.

Get it moving with a 200k engine(vats and egr removed) then throw in a cam/tune later.
Easy 300hp out the gate with 330 to 350 hp not far away for around what a carburated vortec conversion will cost.

Better driveablity and mileage as well as much easier to find longblocks.
 

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You’ll find the flow of the 350 TBI head’s and that of the small port and valve 305 head’s to be the same and insufficient to the performance needs of a 350.

You will hit two trouble spots with either head.
1. The 305 has a very small combustion chamber which will detonate from too much compression on a 350. A common problem with 305 head’s on 350s that don’t get some chamber relieving.

2. The Swirl Port, TBI head’s while using what looks like the standard SBC intake pattern isn’t the same as the pre 1987 heads and will not take your old intake. The bolts alongside the plenum change their angle from 90 degrees to the head’s intake mounting face to 72 degrees so your old 1978 intake will not bolt up without some carving on the head or the intake. To change the head an inexpensive solution is to cut off a suitable length of 5/16ths coarse threaded rod or a same threaded length of bolt then glue it in with epoxy or high strength Lock-title then redrill and tap for the old bolt angle. Or egg the intake holes and relieve the landing pad so the bottom of the bolt head lays flat against the boss when torqued down.

Bogie
 

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Discussion Starter · #7 ·
Okay fellas, I got the engine this afternoon. Here are the goods. It's supposedly a 1991 Chevy truck engine. The numbers are 14093638. I cannot get to the suffix codes as of yet due to the ac compressor bracket. The heads are 193s. Not the best heads or so I've heard. I'm curious to know if this is a 4 bolt block. I'd assume it is but the suffix code should give me that info. If I do keep the 193s I will buy a new intake and sell the performer I have or shelf it (can't have too many). I will be using the BareBones lunati 280/290 for now and plan for a roller build in the future. I'm excited to tear into this thing and see what I got. Thanks
 

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Something worth mentioning too: a stock 350 TBI gives a whole lot of torque at a very low RPM, that is what it was designed for. This means that it is a very, very pleasant engine, with a lot of low end grunt. Add to that a better aluminium intake (Edelbrock...), a stock QJet in good condition (or rebuilt), maybe a distributor (stock HEI) re-curve and a dual line exhaust system (no need for headers for such a low RPM engine), and your Camaro will be fun to drive, for cheap.
For more good ideas about the 350TBI, for all you need to know (pretty much), go read that site: Recommended 350 TBI modifications | TBI
 

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Don't get locked in to any parts "just because I already have them". If you know your cam or anything else is not a good choice as you learn more, then sell them and buy the better parts. Using something you already have often negates what you can derive from other add on parts. As you increase displacement, a hot cam becomes a mild cam.
 

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The 305 is 87% the size of a 350, but it does NOT have 87% the performance potential due to it's tiny bores. Spending money on a 305 is pointless as you have discovered. By the time you buy an intake and a cam for a 305 to get 10 more hp, you could have bought a good running 350 for the same money and have 75 more torques

The 350 TBI is a well-matched set of components. The problem is, they are all matched for the really wheezy 190 hp so it's not like you can just swap an intake or cam and make magic HP. The TBI engines really need a comprehensive re-outfitting of everything from the cam up to be decent. The swirl port heads are downright awful. The cam specs out in the 160s duration, the pistons are dished, and the TBI unit itself doesn't flow nearly as much as the internet would have you believe. People will tell you that they flow 500-600 cfm which is true... if you remove the nozzles. WIth nozzles in place, wet flow is more like 390 cfm.

Having said that, you could drop in the TBI 350 as-is and run circles around the 305, AND have a decent platform for a future build.

My first suggestion is to do just that. Snag a cheap ECM and harness and drop in the TBI 350 as-is.
Second suggestion is to go ahead and do some mods to the TBI before dropping it in, but be aware, that can have some expense as it means cam, heads, and associated intake/carb
 

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Discussion Starter · #11 ·
I've tore into the new to me 350. It's a 2 bolt main block but very clean. The truck it came from said 50,000 miles but wasn't sure if it was true. I'd say, from the look of the intervals, it could be. Either way in going to go with the lunati BareBones 280/290 cam. It's rated for idle to 5000 so it will be a decent match for the either the 193 swirl port heads or the 305 heads. The 305 heads do have the 1.84 valves. They are also in great shape and I have valve seals for those around here somewhere as well. New heads just aren't in the budget right now. Just some more info if anyone is following the thread.
 

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If you've got to choose between the 1.84" valve'd 305 heads and the Swirl Port heads, use the 305 heads.
They will raise the compression about 1/2 a point, and won't flow any worse than the Swirl Port TBI 350 heads did. Probably are a little better on flow, but you'd have to search for that info.
 

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Discussion Starter · #13 ·
Thanks for the info Eric. All the info I've dug up on stock flow bench numbers show a bit better flow from the 601s vs the 193s. The 193s respond well to porting or so I'm told but I don't want to spend that kinda money in em. Plus the performer Intake wouldn't fit the TBI heads. Even if it's a mediocre gain from those, it just wouldn't be worth the extra money for an intake or the hassle of drilling a really good intake.
 

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Discussion Starter · #15 ·
Good to know Bogie. Think I will stick with the 601s. I know they are not the best heads but for the application, I think they will be fine. Main goal is a fun driver that would out perform the stock 305 so it's a win to me. I will post more info and some pics soon. Thanks for the info everybody.
 

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Discussion Starter · #19 ·
I like that analogy Bogie! Don't forget Yellowstone comes back tonight if you are a Kevin Costner fan. I'll keep posting pics along the way. I have to tear down the 305 too. It's supposedly got an aftermarket camshaft and some port work already done to the heads so I'm curious to see if he was truthful. I assumed it was a stock 305 but who knows.
 

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Discussion Starter · #20 ·
I've decided to go ahead and rering the stock shallow groove pistons and hone the cylinders. I also order clevite main and rod bearings since I'm taking it all apart. Figured it'd be a good investment at this point.
 
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