#21  
Old 11-16-2023, 01:45 PM
'ol Pinion head 'ol Pinion head is offline
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Originally Posted by 78w72 View Post
OP stated in the 1st post his engine already has 6x-4 heads...
Missed that, read right passed it! That noted, with the 6X-4's, as long as the shortblock is untouched, static CR is going to be quite low. Short of rebuilding with a forged flat top .030 or .040 pistons & a zero decked block, milling a pair of 6X-4's the reasonable amount of .030-.035 isn't going to get static CR up. That brings it back to one solution & that's increasing dynamic CR through a small cam with quick ramp speed. Personally, I don't like the XE's but they do have a use in a really low CR builds. Have no use for them in higher CR builds. just have seen results of a few street builds that had way too much CR to run the XE's (last example was a local that listened to the wrong folks, & had a moderate sized Comp XE installed a fresh built '67 .030 400 670 head combo.

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Old 11-16-2023, 02:04 PM
78P-T/A 78P-T/A is offline
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Originally Posted by Stan Weiss View Post
What is the duration and lift of the present cam.

Have you done a cranking compression test? If so what psi have you seen.

Stan
I don't really know anything about the camshaft that is in it now. I assume it is original. I think it was changed when the heads were overhauled sometime in the 90s, but that it was put in an original camshaft. I haven't done a cranking compression test... should I?

  #23  
Old 11-16-2023, 02:24 PM
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Originally Posted by 78w72 View Post
.050 milling and only .5cc reduction?? something seems off on that, unless smoothing the ridge in the chamber was a big reduction in volume to make a .050 milling only reduce .5cc.

The last set of 6x-4 on my 400 CCd at 92cc and .030 was right about what wallace head milling chart shows, ~5-6cc. Same results from most of what Ive read over the years too. Everyones results will vary based on what is actually done & the combo of other parts used.

If the OP doesnt want to pull the heads to mill, there are still cams that will work good at the estimated 8.5 compression.
Chambers had some grinding too! Ridge taken down some. Kind of similar to Jim Hand's inhis book

Also remember the same cut on a 6X-4 will get less reduction than a 6X-8 as the diameter is smaller. h equals the cut.
V=πr2h

2801 is pretty mild in this low compression 400.

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Old 11-16-2023, 04:07 PM
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In terms of the width of the chambers ( spark plug side to quench side ) in the 6X-4 heads I have, over the decades more then proven to myself each time that a mill of .006” will take out 1 CC.
.030”/.006= 5 CCs.

The wider chamber of the -8 heads will get you 6.2CCs removed for every .030” milled off.

The very wide chambers of the short lived 061 heads will get you 7 CCs taken off for a ,030” mill.

All of these I have posted about are with the factory supplied face valves.

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Old 11-16-2023, 08:28 PM
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Originally Posted by 'ol Pinion head View Post
Missed that, read right passed it! That noted, with the 6X-4's, as long as the shortblock is untouched, static CR is going to be quite low. Short of rebuilding with a forged flat top .030 or .040 pistons & a zero decked block, milling a pair of 6X-4's the reasonable amount of .030-.035 isn't going to get static CR up. That brings it back to one solution & that's increasing dynamic CR through a small cam with quick ramp speed. Personally, I don't like the XE's but they do have a use in a really low CR builds. Have no use for them in higher CR builds. just have seen results of a few street builds that had way too much CR to run the XE's (last example was a local that listened to the wrong folks, & had a moderate sized Comp XE installed a fresh built '67 .030 400 670 head combo.

Pretty sure the stock 6x-4 78 400 was 8.1 compression, i just estimated that with a .030 milling of the heads that would get it up to the 8.5 range, can go more if needed, then an XE or other cam to work with the lower comp would be a nice upgrade being on a budget. Even if the heads arent removed and milled the right cam can make a decent upgrade.

  #26  
Old 11-17-2023, 12:57 AM
78P-T/A 78P-T/A is offline
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Originally Posted by 78w72 View Post
Pretty sure the stock 6x-4 78 400 was 8.1 compression, i just estimated that with a .030 milling of the heads that would get it up to the 8.5 range, can go more if needed, then an XE or other cam to work with the lower comp would be a nice upgrade being on a budget. Even if the heads arent removed and milled the right cam can make a decent upgrade.
I probably have neither the knowledge nor the opportunity to pull the heads to get them milled, although it is tempting! Maybe sometime in the future... So then I'm back to the question which camshaft can be recommended if it can help a little and not least be worth it? 😅 I should probably be able to get a camshaft replaced with a little help 😊

  #27  
Old 11-17-2023, 01:49 AM
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An XE262H will be a good choice
https://butlerperformance.com/i-2445...-51-222-4.html

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Old 11-17-2023, 02:07 AM
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If I eventually go for this one, is it only the cam and lifters that I need to replace or are there other things that need to be replaced at the same time?

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Old 11-17-2023, 10:37 AM
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Originally Posted by 78P-T/A View Post
If I eventually go for this one, is it only the cam and lifters that I need to replace or are there other things that need to be replaced at the same time?
probably a good idea to replace the valve springs too since the cam is bigger than stock and the springs on there are almost 30 years old if they were changed when heads were serviced in the 90's... 45 some years old if original.

If you can do a cam change or pay a shop to do it, its not much more work to pull the heads and have a shop mill them "x" amount.

Another suggestion in the link posted is the crower 60240 that will work good in a lower comp 400 with a stock converter

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Old 11-17-2023, 12:45 PM
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probably a good idea to replace the valve springs too since the cam is bigger than stock and the springs on there are almost 30 years old if they were changed when heads were serviced in the 90's... 45 some years old if original.

If you can do a cam change or pay a shop to do it, its not much more work to pull the heads and have a shop mill them "x" amount.

Another suggestion in the link posted is the crower 60240 that will work good in a lower comp 400 with a stock converter
Ok, yes I understand. Can investigate a bit later on mill the heads. But I have to travel quite a distance to be near someone who does this kind of thing. The crower 60240, how does it compare to the xe262h? Know it's hard to just estimate numbers, with or without milling the heads, and one of those camshafts, what numbers hp do you think I can expect? understand of course that it is not very much but 😅

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Old 11-17-2023, 01:04 PM
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Hard to guess at power, im sure some others can make an estimate, some members here have a tool that can estimate HP based on specs.

The stock hp was 180-220 hp on these mid to late 70s 400s, i would guess a mild cam upgrade with headers & good exhaust could be at or close to 275-300hp, which is pretty good for a smog'd low comp late 70s 400.

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Old 11-17-2023, 02:21 PM
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Originally Posted by 78P-T/A View Post
I don't really know anything about the camshaft that is in it now. I assume it is original. I think it was changed when the heads were overhauled sometime in the 90s, but that it was put in an original camshaft. I haven't done a cranking compression test... should I?
JMO It will give you and idea about the state of your engine and also might help with cam selection.

Stan

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Old 11-17-2023, 02:26 PM
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Ok, yes I understand. Can investigate a bit later on mill the heads. But I have to travel quite a distance to be near someone who does this kind of thing. The crower 60240, how does it compare to the xe262h? Know it's hard to just estimate numbers, with or without milling the heads, and one of those camshafts, what numbers hp do you think I can expect? understand of course that it is not very much but 😅
I have not run neither cam. Looking at the numbers the XE262 is more aggressive. It has less Adv seat-to-seat duration but more 0.050" duration and more lift than the 60240.

Stan

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Old 11-17-2023, 03:09 PM
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JMO It will give you and idea about the state of your engine and also might help with cam selection.

Stan
Okay👍 which numbers are most desirable to see on such a test?

  #35  
Old 11-17-2023, 03:10 PM
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I have not run neither cam. Looking at the numbers the XE262 is more aggressive. It has less Adv seat-to-seat duration but more 0.050" duration and more lift than the 60240.

Stan
Understand that you say the xe262 is more aggressive. But unfortunately I don't understand anything about those numbers 🙈

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Old 11-17-2023, 03:44 PM
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Okay👍 which numbers are most desirable to see on such a test?
You need to do the cranking compression test on all 8 cylinders and then post the result.

Stan

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Old 11-17-2023, 03:55 PM
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I put an XE262 on a 112 LS in my original 400 from the 78(180 HP 6x-8 heads 97.5cc) in the 81. The 2801 is every bit as good a cam. And it degreed perfect dot to dot!

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Old 11-17-2023, 05:22 PM
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You need to do the cranking compression test on all 8 cylinders and then post the result.

Stan
Then I will take a compression test and post the result. Will be a couple of days until I have time to do it.

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Old 11-20-2023, 11:00 AM
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A boost of everthing for the low compression 400
I would recomend you try the Lunati LUN-10510701
I have it in 350 with a baby stall converter, works very good IMO

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Old 11-20-2023, 02:01 PM
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Ok, yes I understand. Can investigate a bit later on mill the heads. But I have to travel quite a distance to be near someone who does this kind of thing. The crower 60240, how does it compare to the xe262h? Know it's hard to just estimate numbers, with or without milling the heads, and one of those camshafts, what numbers hp do you think I can expect? understand of course that it is not very much but 😅
Here is an actual dyno test of a '79 W72, but with an actual 8.1 to 1 static compression ratio. The purpose of the rebuild was to keep the engine as original to factory production as possible. So, this would give you a good idea of what to expect in power output.

"Here are some real-world results of a stock W72 400 rebuild that was relatively low miles (51,000) and starting to lose the original cam. This was Dan’s red ’79 TA W72/WS6 (that he subsequently traded for his current 25,000 mile all original black WS6 TA). Dan pulled the engine due to a little rocker noise and discovered all of cam lobes starting to wear, so decided to tear it down, install new rings and bearings, resize the stock rods, polish the crank, and re-balance the stock rods, pistons, & new rings. His intension was to keep it stock, so he needed a new cam and ordered a custom ground Comp Cams that is somewhat close to the factory cam with 202/219 (255/261 adv.) duration at .050” lift with .420”/.450” lift ground on a 110 lcl. Dan degreed several lobes of the original cam at 199/216 @ .050 and .397”/.406” in worn condition.

He didn’t deck the block to preserve the piston size stampings and measured the factory pistons to be and average of .0114” down (yes, the pistons have the perimeter chamfer). The 6X-4 heads got a slight cut of .002/.003” to true up and new guides and seals with the original valves and springs (that checked out great). The heads measured 91.8 cc’s average and the valve reliefs, above ring and crown chamfer measured 9.8 cc’s that calculated out to 8.1 to 1 static compression…just as advertised. Dan used .046” head gaskets to keep the compression at factory advertised and quench at a high .0574”. Using the Felpro 1016 gaskets with .039” thickness would bump the compression up to 8.22 and lower the quench to .0504”.

The first dyno session they made 23 pulls and found the engine power dropping the last several pulls. Worried, they pulled the valve covers and found lots of glitter! The bearings were toast due to the rod big ends going out of round, even after resizing and using new ARP rod bolts! So, Dan rebuilt the engine with Eagle forged H-beam rods with the original cast pistons…obviously new rings & bearings were installed. (This is the second motor that lost the bearings due to the cast rods going out of round!)

After he reassembled and broke-in the engine he took it to the engine back to the dyno to continue the testing…in 6 variations:

1) With the original ’79 exhaust manifolds through the factory Y-pipe, no ac base
2) With the original ’79 exhaust manifolds through the factory Y-pipe with ac base
3) With ‘71/72 A/F-body log exhaust manifolds with dual 2.25” headpipes with ac base
4) With factory A/F-body Ram Air manifolds with 2.5” mandrel headpipes with ac base
5) Same as 4 with TA air cleaner no scoop
6) Same as 4 with TA air cleaner with scoop (not opened up)

Dyno results (2800 to 5000 rpm):

1) 397.3 tq @ 3400 / 300.0 hp @ 4900
2) 402.0 tq @ 3400 / 305.6 hp @ 5000
3) 413.0 tq @ 3400 / 328.8 hp @ 4900
4) 420.2 tq @ 3700 / 335.3 hp @ 4800
5) 417.6 tq @ 3400 / 331.8 hp @ 4800
6) 412.2 tq @ 3400 / 322.8 hp @ 4700

This is not a max’ed out PSMCDR engine build by any stretch, just a good street rebuild that will perform a little better than original. If you are going to run the stock heads and compression, the Summit 2800 cam (204/214/112 @ .422”/.444”) will be fairly close to these numbers. Since the custom CC cam has the quicker ramps it did build cylinder pressure faster, so is a good cam to use with really low (under 8.5) compression. The Crower 60240 cam is a good choice too, but maybe a little softer down low. Dan was interested in seeing what a very-close-to-factory-original W72 400 would make for power. Installed back in the heavy (loaded) TA with the factory exhaust manifolds, Y-pipe, and test pipe in place of the catalytic convertor, it felt like a low 14 sec. car."

Dennis
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