Thread: Engine rebuild tips and help

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Okay Vinny – here’s a few thoughts/ideas:

If your rear end is stock, it’s probably a 2.56 as there were a gazillion of them installed in corporate GM 10” rear ends in this era. It’s a fine ratio for the intended purpose (family fun car of the late 70’s) but it will never be what you want in terms of snap off the line unless you throw 600 horses at it (which will blow it to smithereens). You need to get to numerically higher ratio – unfortunately it may require a rear end swap. I would go with a 3.73 and since you’re spending money there, go with a good aftermarket posi-traction. Have this work done at a competent axle shop and be prepared to spend $800-1200.

You said you have a higher stall converter – do you know what RPM it is? (Stock would have been 1800 so anything in the 2000 range would be higher). Depending on final head/cam selection you may want mid 2,000’s.

It sounds like you do not want to disassemble your engine – that’s okay but you will need to check a few things prior to selecting heads.

1. Accurately measure the bore. Stock is 4.000” and if the block has been bored, cylinders will probably measure 4.030”
2. Measure the distance down in the cylinder that the piston stops its upward travel. A stock 350 block leaves the factory at 9.025” and the stock stroke on a 350 is 3.48. Most aftermarket pistons have an extra .020" of deck clearance built in; on top of the usual .025" that is present in a stock (9.025) block. As such, you may have as much as.045" at TDC. This is an important measurement and it should be done at all four corners (#’s 1, 2, 7, and 8). While nowhere near as accurate as measuring the block outside the car, it does give an indication if the block is square.

If the four corners are all within .002 than you’re probably okay to just bolt up a pair of cast iron Vortec heads. I’d opt for L31 Vortecs, casting number 12558062 or 10239906. They were used on '96-'99 Chevy trucks with the L31 5700 Vortec engine and are readily available in wrecking yards and on Craigslist / eBay (if you buy them on-line, make sure they’re genuine GM heads – not knock offs!). These heads use rail rockers, so get the rockers with them if you can. These are some of the best flowing production heads that Chevy ever made. Have your machine shop pin the studs, install new seals, and perform a 5-angle valve job. You can buy valve springs and retainers that complement your cam and you have a great set of heads.

You could also buy new Vortecs (GM Part # 12558060) from Speedway, Summit or JEGS for about $440 each with free shipping - which may be a better deal than reworking bone yard heads.

So with rear end work and heads we’re past $2K and we have not even talked about a cam yet. A new cam needs to be a roller and your 1969 block was made for a flat tappet cam. The good news is that there are some great kits (like Comp Cams K11-600-8) that include the cam, lifters, valve springs, new push rods (different length than flat tappet), roller cam button (to prevent the cam from moving), timing gears and double roller chain, and even a new pushrod for the fuel pump. The bad news is that you’ll have another $1000 tied up here.

Buy some Hooker 1 5/8" long tube, equal length headers that fit the car and route through Flowmaster 40 series mufflers – I really like ceramic coated for looks, longevity and heat dissipation. Add another $750.

Stay with the stock fan setup and shroud – resist the temptation to use an electric fan. They do not save horsepower nor do they cool anywhere near as well as the stock GM fan.

The reality is that $2K will not get you where you want to be. A turn-key 383 crate engine that produces 430 HP is about $5200 and its real tough to beat price with a home build. I've built a lot of SBC engines and it always costs more than you want it to and remember that big HP almost always equals big $$'s.

So another option would be to drive what you’ve got and bank some money to get either all the pieces or a complete replacement engine.

As mentioned above, late model LS engines and transmission combos are available at bone yards at reasonable prices as well.

Others will continue to chime in so you'll get a lot more advice!

Regards,
Glenn

Originally Posted by glennsexton

Okay Vinny – here’s a few thoughts/ideas:

If your rear end is stock, it’s probably a 2.56 as there were a gazillion of them installed in corporate GM 10” rear ends in this era. It’s a fine ratio for the intended purpose (family fun car of the late 70’s) but it will never be what you want in terms of snap off the line unless you throw 600 horses at it (which will blow it to smithereens). You need to get to numerically higher ratio – unfortunately it may require a rear end swap. I would go with a 3.73 and since you’re spending money there, go with a good aftermarket posi-traction. Have this work done at a competent axle shop and be prepared to spend $800-1200.

You said you have a higher stall converter – do you know what RPM it is? (Stock would have been 1800 so anything in the 2000 range would be higher). Depending on final head/cam selection you may want mid 2,000’s.

It sounds like you do not want to disassemble your engine – that’s okay but you will need to check a few things prior to selecting heads.

1. Accurately measure the bore. Stock is 4.000” and if the block has been bored, cylinders will probably measure 4.030”
2. Measure the distance down in the cylinder that the piston stops its upward travel. A stock 350 block leaves the factory at 9.025” and the stock stroke on a 350 is 3.48. Most aftermarket pistons have an extra .020" of deck clearance built in; on top of the usual .025" that is present in a stock (9.025) block. As such, you may have as much as.045" at TDC. This is an important measurement and it should be done at all four corners (#’s 1, 2, 7, and 8). While nowhere near as accurate as measuring the block outside the car, it does give an indication if the block is square.

If the four corners are all within .002 than you’re probably okay to just bolt up a pair of cast iron Vortec heads. I’d opt for L31 Vortecs, casting number 12558062 or 10239906. They were used on '96-'99 Chevy trucks with the L31 5700 Vortec engine and are readily available in wrecking yards and on Craigslist / eBay (if you buy them on-line, make sure they’re genuine GM heads – not knock offs!). These heads use rail rockers, so get the rockers with them if you can. These are some of the best flowing production heads that Chevy ever made. Have your machine shop pin the studs, install new seals, and perform a 5-angle valve job. You can buy valve springs and retainers that complement your cam and you have a great set of heads.

You could also buy new Vortecs (GM Part # 12558060) from Speedway, Summit or JEGS for about $440 each with free shipping - which may be a better deal than reworking bone yard heads.

So with rear end work and heads we’re past $2K and we have not even talked about a cam yet. A new cam needs to be a roller and your 1969 block was made for a flat tappet cam. The good news is that there are some great kits (like Comp Cams K11-600-8) that include the cam, lifters, valve springs, new push rods (different length than flat tappet), roller cam button (to prevent the cam from moving), timing gears and double roller chain, and even a new pushrod for the fuel pump. The bad news is that you’ll have another $1000 tied up here.

Buy some Hooker 1 5/8" long tube, equal length headers that fit the car and route through Flowmaster 40 series mufflers – I really like ceramic coated for looks, longevity and heat dissipation. Add another $750.

Stay with the stock fan setup and shroud – resist the temptation to use an electric fan. They do not save horsepower nor do they cool anywhere near as well as the stock GM fan.

The reality is that $2K will not get you where you want to be. A turn-key 383 crate engine that produces 430 HP is about $5200 and its real tough to beat price with a home build. I've built a lot of SBC engines and it always costs more than you want it to and remember that big HP almost always equals big $$'s.

So another option would be to drive what you’ve got and bank some money to get either all the pieces or a complete replacement engine.

As mentioned above, late model LS engines and transmission combos are available at bone yards at reasonable prices as well.

Others will continue to chime in so you'll get a lot more advice!

Regards,
Glenn

Thanks for the info!

To start, the rear end is stock, so 2.56 sounds right. It’s something I’ve been meaning to change for a while. Regardless of an engine swap or just a top end rebuild, I’ll be swapping that out in the future.

Torque converter is 2500rpm stall.

I’ll look into measuring my block like you describe. Doesn’t sound too bad and probably something I should do.

Now for head selection, for every guy I find that says to use a set of vortec heads, I find another that says don’t waste your time with them. Ultimately I’d like to just buy some kind of aftermarket head that’ll just bolt right on. I don’t have the ability or means to machine something like that myself, and it gets costly quick having someone else do it. I’ll keep in the back of my mind for sure though.

I don’t really have a preference toward flat tappet or roller cams, but you mentioned this my block was made specifically for a flat tappet cam. Are they not interchangeable? Assuming you change the lifters too of course.

Headers are something I’m on the lookout for, but I figured those can wait a bit.

Now someone mentioned an Edelbrock rebuild kit. I didn’t know these existed, but do you have any opinion on them?
Here’s the one I was looking at:
https://www.edelbrock.com/performer-...hevy-2098.html

Personally I feel like it’s not really fair to include the price of headers and the rebuilt rear end in the price estimates since both of those would have to happen regardless of if I kept my 350 or swapped it for something else. If that’s the case, that would bring your estimate down right about to 2k wouldn’t it?

Again thanks for your help. I really do appreciate your time.