New heads

[HawkX66]

I've been looking to get some extra power out of my 69 Camaro. I'm running a 408 (402 +.030) I R&Rd the heads on it last weekend, but then I calculated what the compression ratio would be when I put it back together. 8.3:1... My new cam wants 9:1 or better so I picked up some 290 heads for $200 last night. I think I did pretty good all things considered. Now the question is, what to do with them? Most of the seats are perfect, but two have a couple of small pits that I'd like to see gone. Should I replace all the seats with hardened seats and re-use my 2.06/1.72 valves or should I go to 2.19 or 2.25 valves? Money is an object... What would I be looking at in machine shop costs for either option? I don't have much for machine shops near me to I'll need to go closer to Detroit I think.
I compared the factory pistons in my born with 350hp 396 to the replacements that are in the 402 I'm playing with. There should be zero clearance issues. The replacement pistons are supposed to be a stock replacement piston, so I figured that was the case.
Thanks for any input.

My virgin born with 396 piston compared to the replacement Silvolite 1445





New Heads 3964290 (H 11 9 & I 23 9 A month newer than mine)









My new cam & springs. Head gasket will be .020.

[ssl78]

Changing valve seats on a big block Chevy is very risky since it is very easy to go into the water jacket. Then your head in junk.

[HawkX66]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ssl78</div><div class="ubbcode-body">Changing valve seats on a big block Chevy is very risky since it is very easy to go into the water jacket. Then your head in junk. </div></div>
I thought that was a pretty standard practice. Do you mean enlarging them is risky?

[VintageMusclecar]

Do NOT try to have hardened seats installed unless it's absolutely necessary--there's water JUST under the valve seats on a BB head and it's easy to break through when cutting the seats for the insert. I would go to a 2.19 on the intake but leave the 1.72's in the exhaust. If it's in the budget, a pocket port job and a little chamber work will pick up a nice little chunk of power.

As far as that cam goes--that's going to be a pretty lumpy cam in a 402. You're going to need a 3500 converter or a 4 speed and a 4.10+ gear to take advantage of it.

Also, do not take for granted it will have sufficient piston to valve clearance--you really need to check it with those rebuilder pistons as the reliefs tend to be fairly shallow.

[HawkX66]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: VintageMusclecar</div><div class="ubbcode-body">Do NOT try to have hardened seats installed unless it's absolutely necessary--there's water JUST under the valve seats on a BB head and it's easy to break through when cutting the seats for the insert. I would go to a 2.19 on the intake but leave the 1.72's in the exhaust. If it's in the budget, a pocket port job and a little chamber work will pick up a nice little chunk of power.

As far as that cam goes--that's going to be a pretty lumpy cam in a 402. You're going to need a 3500 converter or a 4 speed and a 4.10+ gear to take advantage of it.

Also, do not take for granted it will have sufficient piston to valve clearance--you really need to check it with those rebuilder pistons as the reliefs tend to be fairly shallow. </div></div>
Thanks a lot Eric. That answers that about the valve seats anyhow. I always thought hardened seats were a must have in the long run. That'll save me some cash now. I didn't realize they were that close to the water jackets. I was planning on leaving the exhaust. Thanks for confirming it. Now all I'll have to do is concentrate on the intake valves. Going up to 2.19 will take care of the couple of small pits I saw. Perfect. That was the big reason I was looking at changing the seats.
I'd love to port them etc, but that'll will have to wait for another day. The cam is what Comp Cams recommended, so that's what I went with. I do have a 4 speed, so I'll be good there. Only factory 3.31s though...
I definitely wasn't going to take clearances for granted. Even though I'm sure they're ok, I'd still double check it.
I know she's not going to be a 10 sec car, but I'm alright with that. I was just looking for a lot better than the truck heads and smaller cam I've been running.
This was some great info. I really appreciate it. Obviously I'm just getting into learning about heads, cams etc...

[WILMASBOYL78]

Great advice from Eric...those 290's are a semi-open chamber design and with a little work, they will help make some decent power. As he mentioned, that is a lot of cam for a baby rat...I would consider something else if you can.

I don't understand the compression calculation?? if you are using 396/350hp pistons and the closed chamber heads, the factory ratio would have been 10.25 to 1. How do you get down to the 8's [img]<<GRAEMLIN_URL>>/dunno.gif[/img]

Check with Eric on a cam recommendation and make sure you have the compression ratio figured correctly.

-wilma

[ban617]

Since they are semi open won't the compression ratio be lower ?

[WILMASBOYL78]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ban617</div><div class="ubbcode-body">Since they are semi open won't the compression ratio be lower ? </div></div>

The #290 head was a closed chamber head that the factory added a little 'breathing room' to. It was used on the 396/350hp and 454/360hp big block applications in 1970. It was identical to the #063 used in 1969 except for the newer 'peanut spark plugs'.In both cases the advertised chamber volume [101cc] is the same in these heads and even #215 which came before that. These heads were all designed to work with a small dome piston that produced a 10.25 to 1 compression ratio.

As was mentioned, they are a great platform for a street build...with a little work these oval ports, combined with other properly selected pieces can really make good power.

-wilma

[earntaz]

I am running 063 and they have ccd a skoshi over 100 cc. Totally agree with Wilma ... TAZ

[HawkX66]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: WILMASBOYL78</div><div class="ubbcode-body">Great advice from Eric...those 290's are a semi-open chamber design and with a little work, they will help make some decent power. As he mentioned, that is a lot of cam for a baby rat...I would consider something else if you can.

I don't understand the compression calculation?? if you are using 396/350hp pistons and the closed chamber heads, the factory ratio would have been 10.25 to 1. How do you get down to the 8's [img]<<GRAEMLIN_URL>>/dunno.gif[/img]

Check with Eric on a cam recommendation and make sure you have the compression ratio figured correctly.

-wilma </div></div>I hear you guys on the cam. I contacted Comp Cams when I bought it, and it's what they suggested. Lunati suggested something similar, but solid lifter. I'm not using my L34 motor. She's bagged and stored in the corner. The 402 +.030 (408) short block I'm using has Silvolite 1445 pistons at -8cc. They're in the second picture. I'd swap out the pistons for some more like the originals, but I'll eventually build a bigger cube engine I'm sure. This should be fine for a while to keep a grin on my face.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: WILMASBOYL78</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ban617</div><div class="ubbcode-body">Since they are semi open won't the compression ratio be lower ? </div></div>

The #290 head was a closed chamber head that the factory added a little 'breathing room' to. It was used on the 396/350hp and 454/360hp big block applications in 1970. It was identical to the #063 used in 1969 except for the newer 'peanut spark plugs'.In both cases the advertised chamber volume [101cc] is the same in these heads and even #215 which came before that. These heads were all designed to work with a small dome piston that produced a 10.25 to 1 compression ratio.

As was mentioned, they are a great platform for a street build...with a little work these oval ports, combined with other properly selected pieces can really make good power.

-wilma</div></div>
These heads were also used in 69 at least on the &quot;C&quot; prefix motors which started ~July. My born with motor is a &quot;C JF&quot; coded or 350hp 396 4 speed built 7/28/69. The heads are original to that motor.
I did a lot of reading on the 290 heads after a lot of guys told me I should use my originals. The high reviews they got for being iron convinced me to buy this set. I figured for $200 I'd be doing ok. I'm going to put 2.19 valves in and leave the 1.72 exhaust.
I just re-curved my distributor this weekend. Here's what I came up with. We'll see if 20* initial is too much...