Stock Poncho 400 HO question

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Stock Poncho 400 HO question

Post by My427stang » Sat Dec 09, 2017 8:22 pm

I am working on a resto 67 GTO 400 HO 4 barrel. A favor job, so of course I keep finding more things to fix...

Question for the Poncho guys. This looks to be a stock engine that was rebuilt with someones "handiwork" inside inside. I am fixing a lunched cam.

Went to check the springs today and certainly found some issues, rockers were hitting retainers here and there but an odd thing was the valve tips were barely above the retainers.

Installed height on a Pontiac of that era is 1.59 or 1.60 depending on the book. These were 1.728 measured with no oil deflector, and no shims using a spring mic. With the shims that were in the engine (.055) and the oil deflector (.025), it came out to be 1.648 mathematically. So the retainers seem to be sitting very tall and/or the valves are sunk way more than I'd expect for a fresh rebuild. (We have not had the heads off, it was bought that way)

The valves are 2 groove look factory, the keepers were single groove, the question I have is, what was the stock keeper for a 2 groove Pontiac look like? I haven't yet figured out if they are +.050 keepers, or just the wrong keepers. Ran out of time today

Also, the second question is, although I can do whatever I like as I set up for the cam change, did the 670 heads use a spring cup?

I am not concerned with getting installed heights and pressures correct, I will do whatever it needs to get it where I want it, but the the fact that with a .025 deflector AND a .055 shim on all 16, the installed height was still .048 tall AND the stems were buried in the retainers have me interested. Ideas?
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Re: Stock Poncho 400 HO question

Post by Keith Morganstein » Sat Dec 09, 2017 8:40 pm

The valve tips do not protrude much on Pontiacs.

+.050" Valve locks are often a problem.

Fortunately the spring pads are thick. No problem going down .060".
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Re: Stock Poncho 400 HO question

Post by tjs44 » Sat Dec 09, 2017 8:44 pm

IMO the first thing is to get new one pc valves.The factory were 2 pc.I dont think any of the pass car heads used a spring cup.I know my RA Vs did.I dont have specs on the 670s and they could have been diff than the 69s that I do have specs on.Tom

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Re: Stock Poncho 400 HO question

Post by GOSFAST » Sat Dec 09, 2017 8:50 pm

The "670" were sort of special heads from Pontiac, they were one of the few heads to use longer-than-normal valve lengths, RA-V aside!

The intakes were 5.097" and the exhausts were 5.090". If yours are under 5.000" they are wrong?

I would make certain you have the correct valves going in?? And there are no spring cups from the factory!

Thanks, Gary in N.Y.

P.S. We still move a bunch of these head parts (valves/springs) being heavily into the 100% stock-appearing crowd!
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Re: Stock Poncho 400 HO question

Post by SupStk » Sun Dec 10, 2017 2:24 am

As mentioned Pontiacs don't have a lot of tip above the retainer. I don't recall 670 heads having longer than "normal" valves. RA IVs were longer. 1.660 is the most common installed height for D port heads. Have some stock retainers in case you want a pic, they look different than everything else.
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Re: Stock Poncho 400 HO question

Post by Geoff2 » Sun Dec 10, 2017 3:05 am

Couple of points/comments.

- 670 heads had some of the shortest valves used by Pontiac because they were a one year only closed chamber 'bathtub' head that meant the chamber was quite deep, hence shorter valves reqd.

- valve tip protrusion above the retainers. Whether it is high or low depends........on your perception of what is high & what is low. Typically 1/8 - 3/16" with factory retainer & keepers.

- Pontiac did not use locators under the springs

- springs pockets are quite thick. Can be machined 1/8", have done it a few times, gives more installed height & greater spring selection.

- tip. Use RA4 valves, which are about 1/4" longer than the 670 valves. This gives you an installed ht of ~1.8" & you can use Beehive springs, which with their reduced spring tension, will make life easier for the valve train. If using roller rockers, use SB Ford rockers, more choice, usually cheaper. They are a little shorter than the P rockers, which will be reqd if going to RA4 valves. I did this build recently, used the Comp steel 1.7 rockers.

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Re: Stock Poncho 400 HO question

Post by blown265 » Sun Dec 10, 2017 4:44 am

The photo below is a set of RA4s I'm working on now. As mentioned, tip height is relative, but these are certainly shorter than the Mopar heads I'm more familiar with.
Thanks for the tip on roller rockers Geoff- I need to buy some soon- do you have a part number?
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Re: Stock Poncho 400 HO question

Post by mag2555 » Sun Dec 10, 2017 7:16 am

We have after all of these years ( us Pontiac nuts) finally figured out the mid 1967 400 cid heads and there valve and spring veriations from looking at old factory parts catalogs from back then.

There where 3 different set up from the factory.
I big part of the mess stems from the fact that in 1967 these 670 casting where also used on the 428 cid motors!

The standard 670 head had what was to become the normal D port type head with a 1.586" installed height.

The next higher performance motor that year with a 670 head was the HO motor which got the 068 Cam and a tad stiffer springs still at the same installed height.

Next up was the 400 with the ram air package .

This motor came with 670 heads that had the casting 6 and 7 ground off and and restamped to make it 97 casting.

These Heads had the 744 Cam , longer valves and a different spring package and many of these where known for busting springs.
Next was the 670 casting recast for the RA package with with 997 near the spark plugs , not in the normal location of on top of the Exh port.
With these Heads they got a hold of the spring brakage issue and had smooth sailing!

If you go with replacement valves you can not use the factory O ring so you must delete the oil splash shield from under the retainer when you also run a guide mounted seal otherwise the oil splash shield will run the valve too dry , especially the Exh valve.

Many replacement duel valve spring set ups come with a flat wire damper and they are more trouble then they are worth!

On motors that will not top 5500 rpm and not apply more then .470" lift I just remove the flat wire damper and shim the spring set up a tad more.

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Re: Stock Poncho 400 HO question

Post by My427stang » Sun Dec 10, 2017 7:52 am

Thanks everyone. It is a 400 HO, 4 speed, 67 GTO, originally 068 cam. Interesting info on the deflectors, it's got modern Viton seals on the intake side, o-rings on the exhaust. I was planning to add seals on the exhaust side, and considered taking off the deflectors, I will likely now.

It's got unknown dual springs no damper. The springs like those Blown 265 posted and felt pretty loose closed, I will check them out this week and see if we need to pick a new spring. I have plenty of height to work with at 1.728, the cam is mellow, it's only .460 lift with a 1.50 rocker and we don't intend to change the rocker. It's sort of a "Day 2" resto, 67 GTO, 400 HO, 4 speed, 3.55 posi, Doug's headers, recurved HEI.

I'll post a picture later, I think the valve tips are a little lower than the picture below, but hard to tell, but a few of the rockers are hitting the retainer. More to come, thanks for the help!
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Re: Stock Poncho 400 HO question

Post by My427stang » Sun Dec 10, 2017 9:14 am

Here is what I have, you can see on the front spring that the rocker is just barely rubbing, I have matching marks on a few rockers but not all

Image

In the even the springs are not good for the cam, I'll get new springs for the 1.728 installed height, but if it works out, I have lot's of options. I can get a -.045 keeper, a -.075 keeper, and I have the current .055 shim in it and the .025 deflector. So, if the springs are good, I should be able to get where I want.

I still don't know why there is so much room, but despite the motor being in pretty decent shape, he intends to have me build a stroker in the next year or so, so I likely will not dig much deeper into the engine than I need to to make a street car run well.
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Re: Stock Poncho 400 HO question

Post by tjs44 » Sun Dec 10, 2017 9:28 am

While your at it you might want to get rid of the bottle neck studs and get 7/16 with polylocks.Tom

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Re: Stock Poncho 400 HO question

Post by My427stang » Sun Dec 10, 2017 10:23 am

Thanks Tom, this thing is pretty mild and on a budget, and closer to a "parade car" than a racer. Also, with another engine on the horizon, I'd likely only do that if I have to move the rocker with longer push rods.

In fact, the car had polylocks, but our thought is that the previous owner used the to try to adjust away the noise, which was likely the rockers hitting the retainers and later ended up as a bad cam
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Re: Stock Poncho 400 HO question

Post by Geoff2 » Mon Dec 11, 2017 4:53 am

Paul/blown 265.

The 1.7 SBF rockers came from Summit. I built the engine, owner did the ordering & paying the $$$. The rockers are the Comp all steel full roller rocker, light weight.

These might not work in your build, if you are using RA4 heads. The engine I built was a 455 HO, had the short 4.9" valves. So going to the taller 5.2" RA4 valves gave me an extra 0.200"of installed height AND moved the valve tip closer to the r/stud [ valve is on an angle to the stud, not parallel ].
So in your case, the shorter SBF rockers probably will not work without an exceptionally long p'rod, so introducing more problems. Holden 308 rockers are identical to Pontiac, Yella Terra sell them.

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Re: Stock Poncho 400 HO question

Post by Geoff2 » Mon Dec 11, 2017 4:56 am

Stang,
If you go to 1.65 rockers, you will probably have to elongate the p'rod holes. Also, with 1.65, check that the p'rod does not rub at the back of the guide plate slot.
Crower 68404 springs are often used with 1.6 IH on Pontiacs with FT cams, & the 68405 springs are 1.7 IH.

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Re: Stock Poncho 400 HO question

Post by PRH » Mon Dec 11, 2017 11:34 am

With that much installed height, and since you say the heads have been done before, and there is rocker contact, I'd say it likely has the wrong valves(longer than OE) in the heads.
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