Stock Poncho 400 HO question

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My427stang
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Re: Stock Poncho 400 HO question

Post by My427stang » Mon Dec 25, 2017 10:21 am

Some feedback on where we ended up.

I don't know who built the heads, but, measuring without the deflector and no shims, retainer height ranged from 1.78 to 1.71, but every valve got a .060 shim along with the .025 deflector. The setup had some very soft dual springs, no damper, that were likely barely usable at 1.60, but not nearly enough spring for the installed height. The intake guides were cut, and intakes got Nitrile positively located seals and also had o-rings, just O-rings on the exhaust. Most of the rockers were not hitting the retainers, but there is evidence of 3 that were making contact. He is very lucky it didn't spit a lock, my guess is it was just making light contact low-mid lift and then it would roll onto the valve stem.

I first considered using spring cups to get the installed height back to 1.60 to make the springs work, but that wouldn't have helped the rocker contact. So I then considered a -.050 or -.045 lock to drive the retainer down, but in the end, those springs limited choices for exhaust seals with the small inner spring, plus we really didn't know the history of the springs.

So we are going with a Crower spring at a 1.65 installed height, single spring with flat wire damper, modern Viton valve seals intake and exhaust, no o-rings and getting to the installed height using a -.075 valve lock and shim accordingly.

It gets me my installed height, a real valve stem seal on both sides, eliminates the oil deflectors and drives the retainer down to give me some rocker clearance.

It's a relatively mild cam, custom ground Comp, but not far off a 280H Magnum, pretty much a parade and cruise night 67 400 4 speed GTO, but should work out pretty well. Thanks for the help!
70 Mustang, 489 FE, TKO-600, Massflo SEFI, 4.11s
71 F100 SB 4x4, 445 FE, hot rod 4x4

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Re: Stock Poncho 400 HO question

Post by rfoll » Mon Dec 25, 2017 12:29 pm

I would think a .050" keeper would solve some problems. The retainer will sit lower on the valve stem, and add .050" worth of compressed valve spring. Hopefully the retainer would not hit the guide seals.
So much to do, so little time...

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Re: Stock Poncho 400 HO question

Post by My427stang » Mon Dec 25, 2017 3:04 pm

-.050 or -.075, either would do it, just changes the shim I need on the bottom. I am using the .075, we'll see.

I don't think I will have an interference problem, lift is low at .460 and I have a ton of room now, but I'll keep an eye out. This little poncho is a freebie and loves to push back LOL
70 Mustang, 489 FE, TKO-600, Massflo SEFI, 4.11s
71 F100 SB 4x4, 445 FE, hot rod 4x4

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Re: Stock Poncho 400 HO question

Post by Geoff2 » Tue Dec 26, 2017 4:41 am

If you use 050 keepers, check them. I found they often only change intalled height by about 035".

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Re: Stock Poncho 400 HO question

Post by My427stang » Sun Jan 14, 2018 10:07 am

Just an update to the Poncho, nothing earth shattering but it all worked out. This job was delayed due to parts and working into two crazy schedules

I used a -.075 keeper that with a shim here and there put installed heights at 1.60. Ironically, at disassembly, with the old keepers, oil deflectors and shims, installed heights were all over the place, but with my combo the largest shim I needed was .015, they came in pretty nice. That height worked out to 100 closed/270 open on a .470 lift cam. These are Crower single springs with a damper.

The drop keeper gave us lots of room for rocker/retainer clearance. I removed the oil deflectors and O-rings on all valves, and put a Viton positively located seal on the intakes, but because the original builder only cut the intake guides, I used 11/32 Viton umbrellas on the exhaust. I couldn't find a positively located seal that fit on the unmachined guide and the ID of the damper and I did this in the car. It didn't have any oil use issues and should be significantly better than O-rings half missing the other half hard

The engine is a stock 67 400 HO, advertised to be 10.75:1 but likely lower, headers and duals, stock 670 heads, iron intake, Q-jet and recurved HEI in a 67 GTO with an M21 and a 3.55 gear. The cam we used was a custom grind, but not far off a 280H and Crower Camsaver lifters.

One odd thing, I wanted to just run factory lock nuts to make it easy, but when I mocked it up, I had to use the poly locks to get to .060 preload. Although I do not know valve length, with all the components verified to factory measurements OTHER than the valve, this likely points to a longer valve as was pointed out here before. Break in was uneventful, it sounds healthy hitting on all 8 and adding a bit more overlap, but hardly "cammy", it should work out pretty well.

Thanks for the advice along the way
70 Mustang, 489 FE, TKO-600, Massflo SEFI, 4.11s
71 F100 SB 4x4, 445 FE, hot rod 4x4

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Re: Stock Poncho 400 HO question

Post by My427stang » Sun Jan 14, 2018 2:35 pm

BTW, cam was 278/226 @ .050 Thumpr lobe intake, 280/230 Magnum lobe exhaust, 110 LSA on 107 ICL. Brent Lykins was great getting this delivered to me as I wanted it, and the specs came in exactly as expected. This was a unique application/customer and we both likely would have done it different if starting from scratch, but this took the car exactly where the owner wanted it to be.
70 Mustang, 489 FE, TKO-600, Massflo SEFI, 4.11s
71 F100 SB 4x4, 445 FE, hot rod 4x4

tjs44
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Re: Stock Poncho 400 HO question

Post by tjs44 » Sun Jan 14, 2018 6:12 pm

is it a slug from a stop sign with the 2.20 first gear and a 3.55?Tom

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Re: Stock Poncho 400 HO question

Post by GARY C » Sun Jan 14, 2018 6:30 pm

My427stang wrote:
Sun Jan 14, 2018 10:07 am
Just an update to the Poncho, nothing earth shattering but it all worked out. This job was delayed due to parts and working into two crazy schedules

I used a -.075 keeper that with a shim here and there put installed heights at 1.60. Ironically, at disassembly, with the old keepers, oil deflectors and shims, installed heights were all over the place, but with my combo the largest shim I needed was .015, they came in pretty nice. That height worked out to 100 closed/270 open on a .470 lift cam. These are Crower single springs with a damper.

The drop keeper gave us lots of room for rocker/retainer clearance. I removed the oil deflectors and O-rings on all valves, and put a Viton positively located seal on the intakes, but because the original builder only cut the intake guides, I used 11/32 Viton umbrellas on the exhaust. I couldn't find a positively located seal that fit on the unmachined guide and the ID of the damper and I did this in the car. It didn't have any oil use issues and should be significantly better than O-rings half missing the other half hard

The engine is a stock 67 400 HO, advertised to be 10.75:1 but likely lower, headers and duals, stock 670 heads, iron intake, Q-jet and recurved HEI in a 67 GTO with an M21 and a 3.55 gear. The cam we used was a custom grind, but not far off a 280H and Crower Camsaver lifters.

One odd thing, I wanted to just run factory lock nuts to make it easy, but when I mocked it up, I had to use the poly locks to get to .060 preload. Although I do not know valve length, with all the components verified to factory measurements OTHER than the valve, this likely points to a longer valve as was pointed out here before. Break in was uneventful, it sounds healthy hitting on all 8 and adding a bit more overlap, but hardly "cammy", it should work out pretty well.

Thanks for the advice along the way
It should run good, is that a big valve 30* seat head?

I have a .060 over Pontiac 400 with a 6X-4 head with a little work done to them, it's a little over 9.1 with a Comp 268 AH-8 Hyd Flat.
268/222 276/226 108LSA IN.3100 EX.3090 with 1.65 rockers.

79 4sp T/A 3.42 gear and 28" tire.

I found 18* initial timing made mine pretty calm and gave me the best vacuum.
He should be happy with it.

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Re: Stock Poncho 400 HO question

Post by My427stang » Mon Jan 15, 2018 2:22 pm

Tom - Considering my own toy is a 489 inch FE with a 4.11 and 2.87 1st, it's a bit mellow for my tastes, but that's how the car came and he doesn't know it any other way. It was the reason for the short cam. Ironically the stock 068 cam for it was 288/302 adv, 116 LSA on 113 and a slower/later timing curve, so it's GOT to have a little more torque than before! Unfortunately we got hit with snow, so we won't see for a bit.

Gary - I am not a Pontiac guy, but I think the 670 head is a decent one 400HO and RA3 for 67. 2.11 / 1.77 valves, 72 cc advertised chamber size, screw in studs, but I did not have these off to see what it has for a valve job or bowl work, from the port they looked real stock. I'll try the timing again, it was late and we were post break in with the tail of the car outside when I set the timing and it was real cold. We basically packed up, cleaned up, and put tuning to another day

The engine had a Crane HMV 278 in it, sort of an odd cam, 114 LSA on 108, 278 adv / 290 exhaust, but they rate their advertised duration at .004 so that cam was smaller than the specs sounded and I think had more exhaust duration than the engine needed. That being said, it ate a lobe, either from bad break in procedures, wrong oil, or the rockers hitting the retainers. More likely the first two, the owner can't remember when he heard the valve noise start but was using cheap filters and whatever oil he had. We are running Brad Penn now and taught him the difference :)
70 Mustang, 489 FE, TKO-600, Massflo SEFI, 4.11s
71 F100 SB 4x4, 445 FE, hot rod 4x4

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