[mrrat1]

I also have one with a 2802 & stock 96 heads.........

[lethal-428-lemans]

Stock 670's on a 400 . I'd guess the compression is around 10 to 1. If anyone knows for sure feel free to speak up.

[GTOLiam]

Originally Posted by lethal-428-lemans

Stock 670's on a 400 . I'd guess the compression is around 10 to 1. If anyone knows for sure feel free to speak up.

More like 11+ to 1
depending on many factors
The 670's are listed at 72cc but you will have to cc your heads to confirm

Use this and enter the details for your engine
http://www.wallaceracing.com/cr_test2.php

[lethal-428-lemans]

Originally Posted by GTOLiam

More like 11+ to 1
depending on many factors
The 670's are listed at 72cc but you will have to cc your heads to confirm

Use this and enter the details for your engine
http://www.wallaceracing.com/cr_test2.php

What do they mean by gasket bore diameter ?

[pastry_chef]

Originally Posted by lethal-428-lemans

What do they mean by gasket bore diameter ?

The bore hole in the gasket is larger than the cylinder.
You could just put 4.2 will be close.

[lethal-428-lemans]

That's showing me a 10.32 ........ Looks like I'll be buying aviation fuel again.

[AG]

My 0.060" 400 with a 0.025" deck, 68 cc heads had a meaured CR of 10.2:1. Don't assume anything, just measure everything if you want to knw the exact CR. Ran my motor with 91 octane without any problems and confirmed it by checking bearings and rings.

[lethal-428-lemans]

How do I check the deck ? It's a stock 400 are they all the same or are different years decked different? I see yours was 0.025

[mrrat1]

I have been running a 50/50 mix. After this tank is run down. I'm going to try just 93 and see how it goes. $120 fill ups is why it sat for 3 years!

[lust4speed]

Originally Posted by lethal-428-lemans

If I go with the 2802 should I use stock rockers or upgrade to a 1.52 or 1.65 ? Also are the stock valve springs good or should they get an upgrade ?

The pushrod holes need to be elongated (oval shaped) before swapping to 1.65's - so you don't want those until you do the other work necessary to run them. The 1.65's also increase valve lift by 10%, and everything must be taken into account.

The 2802 is going to require a better spring than what is in the 50 year old engine. Also there is much much lift with this cam, and you will be at or beyond coil bind with stock springs. My spec sheet on the 2802 shows .465/.488" lift while stock cams were around .408" lift.

[steve25]

The only 400 cid motors that rolled out of the factory with over 10 to 1 compression where the 1969 RAIII motors fitted with the 66 CC version of the casting number 48 head.

There was never a 1967 400 with over 10 to 1 comp, and seing that the motor is 5 decades old your compression is more like 9.4 to 1, but that does not mean that you can't stuff a Cam in it that will make it knock and ping!

[AG]

Originally Posted by lethal-428-lemans

How do I check the deck ? It's a stock 400 are they all the same or are different years decked different? I see yours was 0.025

Put the piston at TDC and measure from the block deck to the middle of the piston using a dial indicator, a piston bridge makes it easy. There is also a method that measures the piston to deck on the exhause and intake side of the piston rocking the piston down on each side and calculates the exact deck height but I forget the formula now.

[lethal-428-lemans]

Originally Posted by steve25

The only 400 cid motors that rolled out of the factory with over 10 to 1 compression where the 1969 RAIII motors fitted with the 66 CC version of the casting number 48 head.

There was never a 1967 400 with over 10 to 1 comp, and seing that the motor is 5 decades old your compression is more like 9.4 to 1, but that does not mean that you can't stuff a Cam in it that will make it knock and ping!

Why would a new cam make it knock and ping ?

[lethal-428-lemans]

Originally Posted by AG

Put the piston at TDC and measure from the block deck to the middle of the piston using a dial indicator, a piston bridge makes it easy. There is also a method that measures the piston to deck on the exhause and intake side of the piston rocking the piston down on each side and calculates the exact deck height but I forget the formula now.

I will have to check that out when I pull the heads.
Thank you

[Tom Vaught]

Originally Posted by steve25

A more realistic peak flow@ 28" to HP conversion for non race built motor is to divide the Intake flow number by 4.
200 cfm stock D ports can make 400 hp.

I have been using the cfm times 2 or 200 x 2 = 400 hp (similar to above equation) and then if right camshaft, right intake/carb do a multiplier above that 102%, 104%, 106% depending on the engine size etc. I can usually hit the dyno number within 10 hp.

Tom V.

[Tom Vaught]

Originally Posted by lethal-428-lemans

Why would a new cam make it knock and ping ?

Cylinder pressure is related to trapped volume in the combustion chamber prior to ignition as well as other variables. A poor camshaft choice can have a effect on a engine with the wrong compression ratio for today's fuel octane at the pump.

Tom V.

[mr67gp]

Originally Posted by Tom Vaught

Cylinder pressure is related to trapped volume in the combustion chamber prior to ignition as well as other variables. A poor camshaft choice can have a effect on a engine with the wrong compression ratio for today's fuel octane at the pump.

Tom V.

As Tom says, there are other variables affecting knock and ping, but dynamic compression is determined by the cam chosen. Overlap between closure of the exhaust valve and opening of the intake allows cylinder pressure to bleed off. How much depends on how much overlap. Dynamic compression is the important factor affecting an engines tendency to knock or ping. Static, or calculated compression AFFECTS dynamic compression, but that number is not what the engine "sees".

[lethal-428-lemans]

I was looking at a spotts performance cam called an HCP01 . Would this be a good choice with 1 degree overlap ?

[steve25]

That Cam and its valve lift is fine if the heads are not on the motor as you need to run different valve springs and cut the tops of the valve guides for postive seals and then ditch the stock spring retainers and steel oil shields.

[chiphead]

As promised, here is the flow data on my 670 heads. This is with a bowl blend only, otherwise stock 670 heads. By the way, the chambers on these are going to be 75-79CCs. The published data of 72cc is a dead lie. Mine are 76CC after being milled .020".

LIft Int flow EX flow
100 75.5 57.2
200 144.3 106.2
300 182.5 146.1
400 198.5 168.2
500 204.5 180.8
600 207 192