Re: Help Me Pick Some Heads For Christmas Present
 

I thought about some port work but these will be such an improvement over stock I'm going to hold off. Think I'll just disassemble and clean/inspect for now.

Re: Help Me Pick Some Heads For Christmas Present
 

Needed to give this discussion an update since it's been a few months.

Over Christmas we got the engine/trans pulled and have had a chance to tare down the top end to take measurements and confirm our starting point before bolting on any new parts. The pulled motor stats are:

1. Verified a 4.00" bore x 3.48" stroke
2. Piston deck height of 0.032"
3. Head Gasket thickness of 0.039" compressed (scratching my head as to why the PO used such a thick head gasket:crazy:)
4. Stock heads with 76cc chambers

Using a dial indicator to ensure TDC I am confident that my piston desk height is accurate but I'm confused about a few things I'm seeing and would like some feedback:

1. Since the mileage of this engine has been in question from the get-go (This is a 1973 truck and odometer says 21k miles which could be 121k, 221k, etc...) I'm looking for evidence of any level of rebuild. Though the bore is still at 4.00" I'm seeing markings on cylinder wall as if its been honed (see photos). Hone & re-ring????
2. Also the current pistons have 4 valve reliefs (see photos) which is excessive for these two-valve stock heads

Thoughts?

Attachment 1758816

Attachment 1758817

Re: Help Me Pick Some Heads For Christmas Present
 

A 4 valve relief piston is the standard configuration. That way the pistons will fit either side of the engine. Those pistons look to be dished to me. A set of heads with 64cc chambers and a thinner head gasket would help.

Re: Help Me Pick Some Heads For Christmas Present
 

Yep these are slightly dished. Not stock right?
I can post up a better pic but these pistons have approx 1/4" wide crown and a 0.065" dish to them.

Re: Help Me Pick Some Heads For Christmas Present
 

Yes, dished pistons are stock. This is probably an 8:1 or less engine with those large chambered heads.

Re: Help Me Pick Some Heads For Christmas Present
 

Can anyone shed some light on if this looks like a stock piston for this gen I and 350?

This morning I was able to verify bore roundness/taper and though Im approaching 75% of allowable limits, I'm still within allowable tolerance. With that said, it doesn't really matter what the previous owner did. I know now that this block is down to its last ~50k miles and will run it as is (no rebuild) until it gives.

With a piston deck height of 0.032" I picked up a felpro 0.015" steel shim to drop the head into a respectable quench range. Should have the decks prep'd and heads on in the next couple days. I'll post pics as progress develops.

Re: Help Me Pick Some Heads For Christmas Present
 

Cap'n, any idea on the volume of these pistons? I've read somewhere between 5-7cc.

Re: Help Me Pick Some Heads For Christmas Present
 

looks like 423np

https://www.summitracing.com/parts/stl-423np

Re: Help Me Pick Some Heads For Christmas Present
 

Looks very much like it. In that case (and check my math) the piston would have a volume of 8.6cc

If that's the case, and I have the following inputs:

Bore 4.00
Stroke 3.48
Head chamber (new) 67cc
Valve reliefs 8.6cc
Gasket 0.015
Deck clearance 0.032

Then I get a SCR of 9.4 which is in the ballpark of what I'm shooting for with these new iron vortec heads. Am I overlooking anything?

Re: Help Me Pick Some Heads For Christmas Present
 

are you entering the valve relief volume as a negative?

-8.6cc

Re: Help Me Pick Some Heads For Christmas Present
 

On the calculators that call for it.:metal:
I'm using Performance Trends CR calculator.

Re: Help Me Pick Some Heads For Christmas Present
 

A dish in a piston should be a positive number. A domed piston's dome volume would be a negative.

Re: Help Me Pick Some Heads For Christmas Present
 

Update!
Finally making some progress after a long week. Heads are torqued down, manifold mocked up, and rockers going in tomorrow. Waiting on a few parts from Mr. brown but should be ready to put the motor back in shortly.:metal:

Attachment 1761544

Attachment 1761545

Re: Help Me Pick Some Heads For Christmas Present
 

Nice!

Re: Help Me Pick Some Heads For Christmas Present
 

Looking good :thumbs:

With such a nice engine. Please post a pic of the truck that you are going to put this engine in. Did you indicate a 1973 pickup ? Show us some pics. Thanks !!!!!
Posted via Mobile Device

Re: Help Me Pick Some Heads For Christmas Present
 

We're pushing to get the laundry list of things done and motor back in by this time next month so I'll post wrap up pics then.

Re: Help Me Pick Some Heads For Christmas Present
 

Since we used VHT ceramic paints I need it to bake the coatings to improve the cohesive strength but we don't have a big enough oven to throw the parts into so we had to improvise. Had to go build our own redneck ez-bake oven:laughing

Grabbed a double-walled cardboard box that I could fit right over the engine stand, pulled out my weed burner (no not that weed burner) and went to town.

Was able to heat cycle everything up to 200, cool, then back up to 250F without burning the house down.

Attachment 1766715

Attachment 1766716

Attachment 1766717

Attachment 1766718

Re: Help Me Pick Some Heads For Christmas Present
 

Figured I'd try and push the limits of this easy bake oven so I set it up on the back patio to cook the headers at as close to 400F as I could. Though cardboard self ignites just north of 450F I wasn't sure how the adhesive would hold up. Let's just say that $h!t got real right at 400 so I held it at 390F for 30 min. At this temp i could bake my own powder coat, Not bad!:metal:
Attachment 1766719

Attachment 1766720

Re: Help Me Pick Some Heads For Christmas Present
 

Are you upgrading the transmission as well since you already have the engine out of the 1973 pickup ?

Re: Help Me Pick Some Heads For Christmas Present
 

Here's a couple of wrap up pics of the truck now that the heads are on and everything is back together. Thanks again for everyone's help on this project!!

So much prep and paint that my fingers are literally bleeding and my back feels like Im 100 yrs old.
Attachment 1780538

Wiring cleaned up, carb and timing are dialed and the jewel is ready for the lid.
Attachment 1780539

Couple of shots from this weekend's car show. This was his first show with his truck which was held at his high school.
Attachment 1780540

Attachment 1780541

Re: Help Me Pick Some Heads For Christmas Present
 

That looks great :thumbs: nice job.

Re: Help Me Pick Some Heads For Christmas Present
 

Very nice!

-klb

Re: Help Me Pick Some Heads For Christmas Present
 

Thank you, and Thanks again for the help Cap'n!