Vortec head question

[Jaysonb]

I'm going to install vortec heads on a 400 for my project stepside. I have been trying to gather all the info I need now, so there is no surprises when I wrap this thing up. The heads are at the machine shop getting steam holes drilled, and measured for retainer to seal clearance. I bought a vortec intake, and self alining rocker arms. What I'm not sure about is the coolant bypass. The truck will have the heater core hooked up, and there will be no valve in the heater hoses. Is that good enough, or do I also need to run a short hose from the intake to the water pump?

[68c10owner]

Originally Posted by Jaysonb

I'm going to install vortec heads on a 400 for my project stepside. I have been trying to gather all the info I need now, so there is no surprises when I wrap this thing up. The heads are at the machine shop getting steam holes drilled, and measured for retainer to seal clearance. I bought a vortec intake, and self alining rocker arms. What I'm not sure about is the coolant bypass. The truck will have the heater core hooked up, and there will be no valve in the heater hoses. Is that good enough, or do I also need to run a short hose from the intake to the water pump?

The vortec head swap has been done since the heads came out. Only recently and only on this forum have I heard anything about this bypass hose. It is not needed. The vortec block uses the same water jacket as the early blocks. Plenty of people have used the vortec block for builds using non vortec heads without issue.

With that said, you need to address the lack of clearance between the guides and the bottom of the retainers. And fi d a deep dish piston if you want to run pump gas because a 64cc head on a 400 block builds some compression.

[Jaysonb]

The block is a stock bore 400, with the stock dish pistons, I'm pretty sure the cr will be ok. The cam has .466 lift, and the machine shop is installing new springs, and measuring the retainer to seal clearance.

[68c10owner]

Originally Posted by Jaysonb

The block is a stock bore 400, with the stock dish pistons, I'm pretty sure the cr will be ok. The cam has .466 lift, and the machine shop is installing new springs, and measuring the retainer to seal clearance.

Stock dish pistons may not be deep enough. You need to measure. Guessing is not the correct way to do any engine. If its worth doing, its worth doing right.

[Jaysonb]

I bought the block and heads from the same shop, he told me the compression ratio will be 9.2 to 1. I will make sure he measured, and not just guessing. Thanks for your input, is there anything else I need to double check? I want this done right, as I already blew the budget for the motor part of this project.

[Tom]

No need to measure things about. You've got stock pistons, a known value. Your putting on vortecs with 64cc chambers, another known value. What checking is needed? Its not like your running on the ragged edge of octane tolerance.

[MikeB]

Originally Posted by Jaysonb

The truck will have the heater core hooked up, and there will be no valve in the heater hoses. Is that good enough, or do I also need to run a short hose from the intake to the water pump?

Man, I wish I would have made notes on this when I built a 355 last year using a 1997 block and 062 heads, but I believe neither Vortec heads nor 96-up 5.7L blocks have bypass holes. But if your heater does not use a coolant valve, then you're good to go.

[Jaysonb]

Thanks Mike, that's what I needed to know.

[68c10owner]

Originally Posted by Tom

No need to measure things about. You've got stock pistons, a known value. Your putting on vortecs with 64cc chambers, another known value. What checking is needed? Its not like your running on the ragged edge of octane tolerance.

How do you know for sure Tom? We dont have a known value for the stock pistons. Do you know how many CC`s the dish is? The OP hasent listed any. This is a important measurement to know when calculating the compression.

Using 12.5 cc`s which is what the speed Pro replacement pistons are I come up with 10:1 compression. OP mentioned a .466 lift camshaft so I`m guessing short duration as well. Mix that with 10:1 compression with iron heads and you are looking at cylinder pressures much higher than stock and will create serious issues trying to run on pump gas.

Pretty bad advice you are giving out Tom. Info like that can cause a guy to ruin his engine. Just because you give the answer that the OP wants to hear doesnt make it the right answer.

[Jaysonb]

I will measure the pistons, the engine is from a 78 k10, if nothing was changed it should have 19.5cc dish pistons. I will measure to make sure. The cam specs,Cam Style: Hydraulic flat tappet
Basic Operating RPM Range: 1,600-5,200
Intake Duration at 050 inch Lift: 214
Exhaust Duration at 050 inch Lift: 224
Duration at 050 inch Lift: 214 int./224 exh.
Advertised Intake Duration: 288
Advertised Exhaust Duration: 298
Advertised Duration: 288 int./298 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.444 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.466 in.
Valve Lift with Factory Rocker Arm Ratio: 0.444 int./0.466 exh.
Lobe Separation (degrees): 112

[Jake Wade]

Ask the guy what the dish volume is for the pistons in the short block, better yet, ask him the particular brand and part #.

Most of those Vortec heads I have CC'd actually measure closer to 62cc's than the advertised 64.

You have to be careful here, I would want a 22cc dish piston and somewhere in the .038-.044 piston to head clearance including gasket.

[Jake Wade]

Is this an aftermarket block or an OEM block? Very hard to believe you found a OEM 400 block that has a standard 4.125 bore still within spec after at least 35 years since being produced.

[Jaysonb]

It is a stock bottom end, there was no ridge at all in the bores. It's going back together with the stock pistons. When I get home, I will measure the piston cc, plexiglass sealed up, and a medicine dropper should get me close, right?

[Jake Wade]

Assembled in the block? Not really, the pistons will be below the deck and if you measure off the deck surface, your numbers will be exaggerated.

[Jaysonb]

The block is bare. It was cooked, then new cam Bearings and plugs installed. The pistons are cleaned up and ready for new rings. I thought if I sealed up the dish of the piston with a piece of plexiglass, with grease, then used a cc dropper and filled up the dish???

[Jake Wade]

If the pistons are without a doubt the pistons that came in that block as installed from the factory, or ones with the same dish volume as the originals, you should be fine.

Those engines were somewhere in the low 8's CR with the factory 76cc heads.

With no other changes, swapping to a 64cc chamber head should put you somewhere in the low 9's.

[Jaysonb]

I used the better of 2 400 blocks, both were factory original, and they both had the same pistons. Do the specs of my cam look ok?

[Jaysonb]

Had the wife run out and snap a pic of the pistons.

[Jake Wade]

Originally Posted by Jaysonb

Do the specs of my cam look ok?

Depends on what you want to do. That's an old school grind that is a step or two above a RV cam for a 350. The 400 will swallow it up and I consider it an RV style cam for those cubic inches.

It will do fine in your truck for daily usage, good manners, and gobs of low-mid range torque.

[Jake Wade]

They appear to have a fairly large(safe) dish volume. No way to know the exact figure unless you measure.

Just looking at them, I see no problem with too high of a CR.

[Jaysonb]

Thanks guys, all I am after is just a little more snort than stock. I bought the standard edelbrock performer vortec intake, a 1406 carb, and some standard ceramic coated long tube headers, and a rebuilt th350, with a little shift kit, and a 2000 stall. The truck has 342 gears in it. It sure seems like kind of a hassle to put these vortec heads on, but it should run good.(I hope!)