[eodcoduto]

I have read most threads on here about heads, and here is my situation. I had a 1969 XH 400 with matching 62 heads for my '74 T/A but a fella has 69 GTO missing an engine and my date code was the same month as his car so I swapped him for his 1973 Y4 400 with 4x-4 heads and some other parts. This was done because I think it is better he has a closer engine to factory than running it in my car. So this sweet Y4 400 is the 180hp 2bbl version, 55K miles with a stock bore, crank, rods and a ton of crud from the little old lady driver. But there isn't a ridge in the engine and the bearings are good.

I know that I can shave the heads to my goal of 9.2 compression, but I am looking for other options as well. I am keeping the 8 valve relief pistons so my math says I can run 72cc heads and hit close to my goal, but I always ask for other options first. I haven't been able to find any 6x-4 or 4x-3,7 heads within 250 miles of me. There is a set of 7k3, and I won't run headers so that may work. This is a super cheap build, gaskets and bearings and make it run is all I'm after now. Any advice is appreciated.

[Mike Davis]

No way I would put a set of 72CC heads on a set of old cast pistons. You would be better off using 6x-4 or -8 shaved down to about 94CC. I would spend the money on new pistons no matter what heads IMO.

[72LuxuryLeMansLa.]

Originally Posted by eodcoduto

I have read most threads on here about heads, and here is my situation. I had a 1969 XH 400 with matching 62 heads for my '74 T/A but a fella has 69 GTO missing an engine and my date code was the same month as his car so I swapped him for his 1973 Y4 400 with 4x-4 heads and some other parts. This was done because I think it is better he has a closer engine to factory than running it in my car. So this sweet Y4 400 is the 180hp 2bbl version, 55K miles with a stock bore, crank, rods and a ton of crud from the little old lady driver. But there isn't a ridge in the engine and the bearings are good.

I know that I can shave the heads to my goal of 9.2 compression, but I am looking for other options as well. I am keeping the 8 valve relief pistons so my math says I can run 72cc heads and hit close to my goal, but I always ask for other options first. I haven't been able to find any 6x-4 or 4x-3,7 heads within 250 miles of me. There is a set of 7k3, and I won't run headers so that may work. This is a super cheap build, gaskets and bearings and make it run is all I'm after now. Any advice is appreciated.

No way, No how! Those pistons have to go. Buy forged flat tops and re-calculate.

[Goatracer1]

According to you this is a budget build so I assume you are not beating on this car. So use the pistons that are in it for Pete's sake. If you don't want late heads can you find another set of #62's?

[Cliff R]

If the engine showed up with 8 valve relief pistons it's not a "stock" 400 2bbl engine with 55K miles on it. Are you replacing the original pistons with aftermarket cast 8 valve relief pistons or am I reading this wrong?......

[eodcoduto]

As I was, it has 4 relief pistons in it and I can’t confirm they are stock, but I mic’d the bore and its std, plus none of the fasteners show use. This car will become a daily driver, 22 miles each way all highway with 2 stop signs. 3.08 gear and a th400. I know down the road I’ll make it quicker, but thats down the road.

[jhein]

Ah! You meant "8", 4-valve relief pistons.

[25stevem]

Since it’s only a daily driver and as you have stated will up grade the motor at a later point for more performance then for God’s sake for now just rebuild your 4X heads if they pass a mag tests and Mill then .030” if the bucks are there for that.

If you did not keep track of the order of the push rods to there rocker mate you will need to inspect them close for ware, to reuse them, or just take the safe route and replace them.
In terms of finding and just plopping on a used set of heads I would in no way due such unless I had heard the motor run in person!

Please rebuild your 4X heads and run those for now.

[25stevem]

If you do rebuild your 4X heads and they need a few intake valves then replace all of stock 1.96” valves with 2.11” valves , as this alone will help to increase compression.

If this is done then be sure that the valve job is done to get the OD of the 30 degree seat out 2.08” with a nice deep 60 degree bottom cut done to narrow the main 30 seat to .065” wide.

This will increase air flow at the lift point where a stock cam spends the most open time.

[grivera]

Is this an engine that was running before you received and you removed the heads or did you get it disassembled? Being this far into it and with the amount of crud, I'd want to disassemble, clean oil passages, put new bearings in, new cam/lifters, timing chain, oil pump gaskets. Also, I'd definitely look for some advertised "72cc" heads rather than sinking money into the 4x.

[67Fbird]

Just went down this kind of road. Kinda like a roller coaster of direction changes and problems......finally got to the END...Everything I opened up...was screwed up causing a change in "the plan". Either give it a FULL freshen up now BEFORE you even get started...or deal with it EVERY TIME you drive it. Plans change, be HONEST with your expectations and your budget and you too will get to the end point.

[Cliff R]

4X heads were also prone to cracking. The smaller valve versions the 2bbl used not quite as much as the larger valve versions but the exhaust seats on the center cylinders should be bead blasted gently and visually inspected or even magged if you have the means.......

8 FOUR VALE RELIEF pistons makes more sense if it is truly a 55,000 miles unmolested little old lady driven it's entire life engine..........I'd re-use them and wouldn't worry about the cast rods they are connected to for a second.......

[Goatracer1]

By all means stick with the stock heads for a daily driver. Also stay with the small valves. They will give you better low speed air flow velocity for better gas mileage and pickup. You don't need bigger valves until much higher rpm.

[25stevem]

In regards to the opinion about valve size in the post before this ( number 13 ) I have a question, that being so why did Pontiac use 2.11” intake valves ?

This size valve was used in literally hundreds of thousands of heads that they bolted to motors over the course of some 11 years!

[Stan Weiss]

Since velocity is a function of flow (cfm) and CSA. The throat, valve area and curtain area velocity will be different with a 1.96" verses 2.11" intake valve, but the port velocity will remain the same.

Stan

[Sirrotica]

By the same token they used the 1.92 intake valve for just as long of a period of time period on 389 and 421 engines. A few select 421s used a 2.02 intake valve......

In 67 they did a complete re design on the cylinder heads, and yes, a 2.11 valve was used along with a 1.77 exhaust, which was later downsized to a 1.66 exhaust. The smaller cubic inch engine, along with the lower performance engines had smaller valves also.

The post 1967 heads weren't all the same size valves it depended on their target usage in the car they were installed in.

[grivera]

My numbers matching 400 has 62s on it which are 75cc and and an XE268 cam - there are zero issues with low end performance in that engine. 4x4s would be pretty low compression on a 400….

[eodcoduto]

I appreciate the comments and passion. I’m going to have these checked for cracks and make a plan after that while keeping an eye open for better options.

[Goatracer1]

I never said there was anything wrong with big valve heads. I said they weren't needed on an every day driver. He said this was a budget build. Why spend money on something you are never going to need.

[Cliff R]

For those of you worried about not having big valve heads it's not really holding things back anyplace on a build like this.

A few years back we had a really nice 455 short block here in the shop ready for a set of SD Performance ported KRE aluminum "D" port heads and one of his custom cams but they were not going to make it in time to get the car to the Tri Power Nat's at Norwalk.

So I pulled out a set of #46 heads from a 1969 428 engine from under the bench and a used Crower cam from a shelf in the parts room. The heads got better springs and screw in studs, and I quickly ground the valves and seats, not a grinder or sanding roll touched them anyplace, not even a port match to the intake gaskets.

The cam went in dot to dot, didn't even bother degreeing it, on went the intake, HEI and I set up a late 70's Olds Q-jet for it (850cfm).

The car was well set-up, TH350 done here, custom Continental 10" converter, etc. I was expecting maybe low to mid 12's out of the car and would have been happy with that, but at least we would make the event.

Right off the trailer it went high 11's and ran there all weekend even in the hot/humid August weather! I've seen folks with ported big valve heads on similar engines not run that quick at or close to the same race weight and drive train parts, etc. So when building one of these engines on the cheap I'd use what was available and not give the valve size a second thought..........FWIW......