swapping engines

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jrinchitown

Junior Member
Oct 14, 2013
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I have a 99 chevy Express with a vortec 305 that locked up. I got a great deal on a rebuilt 1970 chevy 350 with a 4 barrel carb. I thought the intake from the 99 would fit the 350 but doesn't so I was wondering if anyone can help show me how hook up the intake with the carb. Do I have to modify the fuel lines to the carb, do I have to put the fuel pump back on the block?
 

phucheneh

Diamond Member
Jun 30, 2012
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I am not a GM guru, but I would think that a 99 would be port injected? Seems late for TBI.

Either way, the major requirements are going to be the same- fuel pressure must be toned way down (most carbs want around 5-6psi), first off. You can switch to a mechanical pump or run a regulator. You'll of course want to accompany the carb with a fully-independent distributor; probably a 70's HEI. Mechanical and vacuum advance.

With the motor pretty much functioning on its own, it's then just down to rigging everything around it. Exhaust fitment, intake clearance, correct oil pan, ect. And whatever you're going to do about the PCM. You'll still need some selective functionality to get the car to start, I would think. Plus gauge functionality and all that.

I think it's legal to do that, so long as you keep catalytic converters on it. And the evap system, I guess...you could make it function if you really wanted. Though I highly doubt you'd ever be cited for it, you can get some big fines for any missing OEM emissions stuff. Whether fuel injection and computer control in general would fall under that, I dunno.

But more importantly, do you not have inspections and/or emissions testing where you are? 1996+ typically needs to pass OBD2 readiness. Pre-96 is usually a tailpipe sniffer.
 

XavierMace

Diamond Member
Apr 20, 2013
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In my limited research, while it varies from state to state, most laws say the new engine must be as new as the vehicle or newer.
 

Zenmervolt

Elite member
Oct 22, 2000
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I think it's legal to do that, so long as you keep catalytic converters on it. And the evap system, I guess...you could make it function if you really wanted. Though I highly doubt you'd ever be cited for it, you can get some big fines for any missing OEM emissions stuff. Whether fuel injection and computer control in general would fall under that, I dunno.

The way the EPA regs are written it's technically illegal to remove any "emissions control device" from a vehicle. I'm pretty sure that more than just the evap and catalyst systems are included in that. I'm pretty sure that OBD-II is considered an "emissions control device" and he's definitely going to lose that with the older engine. Plus, since a 1970 engine would not have had catalytic converters to begin with, it's probably going to run rich enough to foul a cat over a relatively short period (a few years probably). Catalytic converters are rather picky about mixture control and the simple 1970 carb is probably not going to hit that ideal mark like EFI does.

I do agree that the chances of getting caught are low unless there are emissions inspections where he lives (and if he's in CA, being caught is a virtual guarantee), but if he does it's $$$ in fines.

In general, I want to say that the OP really should stick with the "same" engine that used to be in the vehicle.

ZV
 

Jimzz

Diamond Member
Oct 23, 2012
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You can't swap them, at least easily. The bolt pattern is different, the rear seal is different, I think the balancer is different, fuel system is different(electric vs mechanical), etc...

Find another late 90's motor and start from there.
 

exdeath

Lifer
Jan 29, 2004
13,679
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If you have to ask its probably too big a project.

If you're doing it for the sake of having a project and wrenching for fun, ok, but not worth the hassle if its just maintenance and having a running vehicle.
 

BUTCH1

Lifer
Jul 15, 2000
20,433
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Just go to a bone-yard and buy a used engine from the same type/year vehicle, much less headaches in the long run. Put the 1970 350 on CL, someone with and old truck would snap it up in a second.
 
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