[Mwieczorek]

Guys,

I'm looking at a 400. It's a 1970 XH code 400 with 13 heads. It was rebuilt several years ago. The engine shop used TRW L2262F30 pistons, reconditioned the stock rods and installed ARP bolts, turned the crank 0.010/0.010, rebuilt the heads with new valves, guides, etc. Apparently it was not zero decked and the heads only had a skim cut taken. The cam is a Wolverine Blue Racer, 224/234 @ 0.050, .465/.488 lift, 112 LSA.

The only thing that scares me about the engine is the compression ratio. Doing the math it should be around 9.9:1. That violates the old "thou shalt not exceed 9.5:1 and run on pump gas" rule.

Would you guys run 9.9:1 on pump gas? We can get 93 octane in my area.

Thanks!

Matt

[25stevem]

Your fine as is!
I will bet that in your compression math you did you did not factor in.

1) 1.5 CCs for ring land volume.

2) 1 CC. For sinking the valve during the valve job.

3) and maybe 1 CC for the intake valve notch in the top of the bore if your motor has such.

Your much closer to 9.5 then 9.9 and this is assuming that your heads where 72 CCs to start with, when they where larger then that.

At best they where 74 CCs.

[John Milner]

Agree with Steve, you should be fine. That camshaft will be about perfect for the engine. I ran one in a 69 XH 400, 62 heads, 4 speed and 3:55’s. It was a very simple build but made great power in a 66 gto.

[Mwieczorek]

That makes me feel a bit better about it!

I didn't build the engine. It is a used one. The guy has all his receipts and stuff, and I'm going to go over it as far as he will let me go. I can't build any engine for the price he is asking, so I'm at least going to go look.

This is for my 66 Bonneville. The ol' 389 is pretty tired. It has a lot of blow by and the rear main is leaking pretty bad. Its to the point where I don't want to drive it to anyone else's house because it leaves a puddle of oil behind. I am in the middle of replacing the rear end and doing a bunch of other upgrades, so this is a perfect time to replace the engine. I have a 455 block in my stash, but my plan for that is a forged rotating assembly with a hydraulic roller cam and whatever other goodies I can get away with, and its gonna take some time to save up for that. If I can buy and install this (what looks to be a) reasonably built 400, I may just do it. Obviously I'll drop the pan and check things internally and pull the valley pan and check for any wiped cam lobes and whatnot before dropping it into my car.

While I'm bugging you guys... Assuming it checks out, how do you think that engine will work with this combo? 1966 Bonneville, TH400, 3.08:1 limited slip rear, 225/70R15 tires, Holley Sniper EFI and Hyperspark ignition, Ram Air Restoration B body long branch cast manifolds and 2.5" dual exhaust. The cam card says 2200-5700 is the power band. So would this engine work ok with my car and a mild stall converter, or am I way off base? I treat my Bonneville more like an overgrown GTO and less like a cruiser. It may actually go to the strip once I get it dialed in with the new rear end and whatnot.

Thanks!

Matt

[b-man]

The #13 heads have the largest combustion chambers of any of the ‘67 -‘70 400 high compression 72cc heads. From what I’ve read here on the forums they can come in anywhere between 77 and 82 ccs.

So more than likely your 400 has about 9.5:1 or a little more.

[Stan Weiss]

Are you able to do a cranking compression test on this engine?

Stan

[Mwieczorek]

Originally Posted by Stan Weiss

Are you able to do a cranking compression test on this engine?

Stan

I don't know yet. I may try to throw together a kit for just that purpose though. I have a spare battery and a Pontiac starter in the barn...

Normally I would only buy a used engine as a core planning on a full rebuild. This guy claims very low miles since the rebuild and has a pile of receipts. If its all on the up and up it could be a decent deal, especially considering how long it is taking to get machine work and parts lately. The engine from my tractor has been at the machine shop since JUNE of last year. I had all the parts, but the crank needed to be ground and there is only one crank grinder left in the area and his waiting list is months long now.

The things I worry about are stuck rings, a wiped cam lobe, trashed bearings...

[25stevem]

Where has this 400 been stored that your going to look at?

Even if it happens to be indoors when you look at it and even if it has the carb on it be sure to open up the secondary’s and tilt the air flap open to look for signs of water getting in.

In addition to your crank over kit I would bring a few gallons of water.

I would remove the plugs get set up to crank the motor , but first pull out the thermostat and pour as much water into the motor that you can before it comes out the lower road hose port.
Next crank it over and look for water spitting out of the cylinders or coming out the sides of the block.

[Lee]

Originally Posted by b-man

The #13 heads have the largest combustion chambers of any of the ‘67 -‘70 400 high compression 72cc heads. From what I’ve read here on the forums they can come in anywhere between 77 and 82 ccs.

So more than likely your 400 has about 9.5:1 or a little more.

Agree, I've personally cc'ed several pair, all of which were right at 77cc's.

In the late 80's to mid-90's, my cousin had a set of 13's on his 400. The cam was a bit bigger. It was his daily driver for years that way, and ran great. Consistent mid-13's with a best of 12.9 (street tires, drag radials didn't exist and we were too cheap/poor to buy slicks).

[hurryinhoosier62]

The 112 degree LSA of the cam effective lowers the dynamic compression ratio. If you'll notice, most (if not all) of the OE cams used 112-116 degree LSA. This lowered the dynamic compression ratio to a more manageable level. As has been previously stated there are many more factors figured into calculating the actual static compression ratio that the chamber volume, deck height and bore size.

[Stan Weiss]

Originally Posted by hurryinhoosier62

The 112 degree LSA of the cam effective lowers the dynamic compression ratio. If you'll notice, most (if not all) of the OE cams used 112-116 degree LSA. This lowered the dynamic compression ratio to a more manageable level. As has been previously stated there are many more factors figured into calculating the actual static compression ratio that the chamber volume, deck height and bore size.

The greater LSA reduces overlap. But if the same lobes are on a 110 LSA and a 114 LSA with both cams installed @ 108 ICL they will have the same DCR.

Stan

[Tom Vaught]

Originally Posted by Stan Weiss

The greater LSA reduces overlap. But if the same lobes are on a 110 LSA and a 114 LSA with both cams installed @ 108 ICL they will have the same DCR.

Stan

X2 Stan.

Tom V.

[hurryinhoosier62]

Originally Posted by Stan Weiss

The greater LSA reduces overlap. But if the same lobes are on a 110 LSA and a 114 LSA with both cams installed @ 108 ICL they will have the same DCR.

Stan

IF you advance the centerline. I do believe Mac had forgotten more about camshaft design and operation than most of us have ever known. Never have seen an OE can advanced four degrees from the factory.

[Stan Weiss]

Originally Posted by Mwieczorek

Guys,

I'm looking at a 400. It's a 1970 XH code 400 with 13 heads. It was rebuilt several years ago. The engine shop used TRW L2262F30 pistons, reconditioned the stock rods and installed ARP bolts, turned the crank 0.010/0.010, rebuilt the heads with new valves, guides, etc. Apparently it was not zero decked and the heads only had a skim cut taken. The cam is a Wolverine Blue Racer, 224/234 @ 0.050, .465/.488 lift, 112 LSA.

The only thing that scares me about the engine is the compression ratio. Doing the math it should be around 9.9:1. That violates the old "thou shalt not exceed 9.5:1 and run on pump gas" rule.

Would you guys run 9.9:1 on pump gas? We can get 93 octane in my area.

Thanks!

Matt

Originally Posted by hurryinhoosier62

IF you advance the centerline. I do believe Mac had forgotten more about camshaft design and operation than most of us have ever known. Never have seen an OE can advanced four degrees from the factory.

Is the that an OEM cam and did Mac have anything to do with its design?

Stan

PS Speaking of OEM cams. Lets take the 068 cam. What was the CR of most engines Pontiac installed the 068 cam in and was the octane rating of pump gas at the time?

[hurryinhoosier62]

Originally Posted by Stan Weiss

Is the that an OEM cam and did Mac have anything to do with its design?

Stan

PS Speaking of OEM cams. Lets take the 068 cam. What was the CR of most engines Pontiac installed the 068 cam in and was the octane rating of pump gas at the time?

Advertised or actual CR? Do you always revel in starting arguments with me? I am quoting what Pontiac guys from Mac McKellar to Jim Hand have been saying for decades. Pontiac used the 112-116 LSA to lower dynamic compression ratios. They dealt with REALITY; not computer simulations.

[Stan Weiss]

Originally Posted by hurryinhoosier62

Advertised or actual CR? Do you always revel in starting arguments with me? I am quoting what Pontiac guys from Mac McKellar to Jim Hand have been saying for decades. Pontiac used the 112-116 LSA to lower dynamic compression ratios. They dealt with REALITY; not computer simulations.

The reality was back then you could run more CR than Pontiac advertised and still pull into any gas station and buy gas with the octane you needed.

Again greater LSA less overlap, better idle, more vacuum at a give idle RPM.

Stan

[Cliff R]

" That violates the old "thou shalt not exceed 9.5:1 and run on pump gas" rule."

That statement is absolute and utter BS right to start with and I'm still not sure where it came from/originated. I can say that whoever uttered those words needs to leave all the Forums and go as quickly as they can back to their "day job"......FWIW.....

[Stan Weiss]

I seem to remember someone, don't remember if it was Ace Wilson or Royal Oak selling a steel shim head gasket to raise your CR for the 389's back in the mid 60's. Anyone else remember this?

Stan

[Mwieczorek]

Originally Posted by Cliff R

" That violates the old "thou shalt not exceed 9.5:1 and run on pump gas" rule."

That statement is absolute and utter BS right to start with and I'm still not sure where it came from/originated. I can say that whoever uttered those words needs to leave all the Forums and go as quickly as they can back to their "day job"......FWIW.....

Cliff - I saw you say something similar in another thread. I am genuinely curious as to what static and dynamic compression ratios you consider safe with pump gas. I know having good quench helps, and ensuring you don't have any sharp edges that can create detonation ignition points helps, but what is the real limit? 9.5:1 static CR seems to be the number that gets tossed around as the rule of thumb with iron heads and modern premium fuel. If that's not right, I want to be enlightened!

My day job is suspension engineering, I'm just a knuckle dragging chassis rat, not a high flying powertrain engineer.

Thanks,

Matt

[turbo69bird]

What you can get away with on a particular fuel will also be determined by how rich or lean you run and your timing curve . I can run a 12 to 1 motor on pump gas if I drown it in fuel and take all the timing out. Fat and lazy make it run On pump gas but that doesn’t mean it’ll make peak HP it could on other fuels.

So that 9.5 rule is attached to a certain state of tune. And at that point just a simplification for the general masses. It saves engine builders from people who can’t tune, is what it does and that’s a good thing because people blamed Pontiac engines for their own stupidity for many many years .