Approx Cost to Re-build a 425 GS motor

[Guest Rob J]

What do you think would be an approx cost range to do a complete re-build on a 65' 425 Dual-Quad motor these days? Keeping it stock, just freshened.

How about on the BS code transmission, and the 3.42 posi rear end?

Rob.

[JZRIV]

Sorry for the long answer to what seems like a simple question.

Its very difficult to just "freshen" an engine because everything is related and rebuilding one area and not another can cause problems. Going through all the work of pulling an engine and rebuilding it justifies making sure all the important areas are addressed and cutting corners in some places just doesn't make good sense. But....you have to draw the line somewhere depending on your personal goals and budget. For that reason and others rebuild costs can vary greatly.

Are you doing the assembly work or are you paying someone to do a turnkey engine for you? There are many cost adders with all the exterior bolt-ons after all the internal work is done. Also a factor is the current condition of the block, heads and crankshaft. Untill you get it apart, you really don't know for sure.

There are many decisions you will make when rebuilding an engine that all affect cost. Based on a complete engine that is ready to drop in and start:

Doing all the assembly yourself and assuming new pistons you should plan on being in the $3000 range but be warned that can significantly change as you go through the process. For example just having the carbs "professionaly" rebuilt will cost $700-$900. you might not have thought of carb rebuilds as part of the engine work but at that cost it needs to factor into your budget. You might think the carbs are working "OK" but having them done professionaly can make a huge difference in performance especially on the 2x4 cars.

Here is a small sampling of questions that will arise: Do you want the crank mains align-bored or leave it as-is? Do you want to buy new push rods or use the originals. Do you want completely rebuilt rocker shafts with rebushed arms or inspect originals and only replace ones that have too much wear? All new valves or check originals and replace only those with wear out of spec? If someone else is assembling do you want documentation of all of bore/piston measurements, all bearing clearances, valve guide clearances, etc? Usually you won't get this but its very important information to have and helps validate the shops work. The list goes on and on with each decision affecting the bottom line.

If you are paying someone to do all the labor plan on $5000 min. Keep in mind this is really a generic number and I'm even hesitant to throw one out there. So much depends on what decisions you make along the way on how far to go during the rebuild. You can really get carried away.

If you are having someone do the assembly, be very careful when selecting a shop. Do NOT assume anything and stop in once a week to ask questions and check progress. If they will be irritated by this find another shop. Find out who is actually doing the work. Is it a young kid getting a little direction from an experienced guy or is it the experienced guy? Maybe you know all this but I wanted to mention it because it seems like I have seen more disappointed people than satisfied when it comes to having an engine done.

I had my BS tranny done for $550 by a guy who does it for a living but did it on the side at his home. Expect to pay $1000-$1200 at shop.

Not sure about the axle. I know what it cost me in parts so will make an assumption and keep in mind it is just that. All New bearings, seals, a clutch kit, + labor and setup could cost $1000. Depending on mileage you may not need a total rebuild. If the clutch pack for the posi is not worn I would not replace it. If the axle is performing OK I'll visually inspect the bearings and races for degradation. If they look good I do not replace them. I do replace the outer axle bearings because they are sealed and after 40+ years the grease dries out.

Edited November 20, 2010 by JZRIV (see edit history)

[Guest jonly]

Sorry for the long answer to what seems like a simple question.

excellent answer, long or not it's the sort of explanation that makes the internet valuable.

I did all the work myself with the exception of milling, planing, honing and micing on my 425 and I'm sitting at 3500. you have another carb to deal with so adjust for that, as well as varying rates in your area.

[Guest Rob J]

Thanks for the insight Jason. Yes, I have been considering a lot of the points you bring up, as they are very valid. I am looking at a 65 GS now, but there is really no way to know what you really are getting until you get it, and start going through it. At least I want to start getting an idea as to what complete OEM spec rebuild's will cost on these cars. I've restored a 72 Vette, built a Factory Five Cobra Replica, and worked on lots of Fox body Stangs in the past, but the Riv will be a first for me. I want to have a nice GS as an end result, but I don't want to invest more into it than it will be worth. How difficult is it for a DIY'er to rebuild one of these 425's say compared to a Small block Chevy 350, or a Ford 351 Windsor? I'd have a machine shop do all the machine work ect, and I'd like to do the re-assembly.

Edited November 20, 2010 by Rob J (see edit history)

[Dales90]

Hi folks,

This thread reminds me of the 71 Riv GS engine heads I had rebuilt a long time ago. I had done the typical things to fix a slightly rough idle. plugs, points, carb, etc, and nothing seemed to lessen the slight roughness. the car ran fine after idle speed and was a real runner.

Someone finally suggested a valve job, but I felt it may not need one, as the idle was not very rough.

Pulled the heads, took them to my favorite shop for bench work,and when I picked them up, the owner showed me a very bad exhaust valve, a real chunk missing from the top, and asked me if this car war running when i pulled the heads.

I said, "yes, why?" and he stated, "It shouldn't have been!"

Love those 455's!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Dale

[JZRIV]

How difficult is it for a DIY'er to rebuild one of these 425's say compared to a Small block Chevy 350, or a Ford 351 Windsor? I'd have a machine shop do all the machine work ect, and I'd like to do the re-assembly.

Not any more difficult really. The only real concern is if the valve seats are in such bad shape they need inserted. If don'e incorrectly they may hit the water jacket. You want to avoid inserting if at all possible. Also you really don't want to go more than .030 over bore in a 425.