[urhere2]

I just bought my Tempest not too long ago and am VERY new at building these things. I pulled my engine yesterday and cleaned it up so now I can read the numbers on the block. It is a Pontiac 400 (from a Firebird), YS code from 1975 (185 HP). Installed on it are 1967 670 heads, an Edlebrock performer intake, and an Edlebrock #1406 600cfm carb. When I pulled the oil pan, I found a double roller timing chain and what looks like an aftermarket cam. I have no idea if its been bored or if any of the internals have been replaced.

1) Assuming the internals of the block are stock, (including the cam)and the heads have not been machined, what would the compression ratio and approximate HP be?

2) Is there any way to tell what cam is in the engine without removing it from the block?

3) I am almost positive that the jets in the carb have been changed. How can I tell what size jets are in it?

4) How many RPM's can I go to safely?

Thanks in advance for your help! [img]/infopop/emoticons/icon_smile.gif[/img]

[ March 03, 2002: Message edited by: urhere2 ]</p>

[urhere2]

I just bought my Tempest not too long ago and am VERY new at building these things. I pulled my engine yesterday and cleaned it up so now I can read the numbers on the block. It is a Pontiac 400 (from a Firebird), YS code from 1975 (185 HP). Installed on it are 1967 670 heads, an Edlebrock performer intake, and an Edlebrock #1406 600cfm carb. When I pulled the oil pan, I found a double roller timing chain and what looks like an aftermarket cam. I have no idea if its been bored or if any of the internals have been replaced.

1) Assuming the internals of the block are stock, (including the cam)and the heads have not been machined, what would the compression ratio and approximate HP be?

2) Is there any way to tell what cam is in the engine without removing it from the block?

3) I am almost positive that the jets in the carb have been changed. How can I tell what size jets are in it?

4) How many RPM's can I go to safely?

Thanks in advance for your help! [img]/infopop/emoticons/icon_smile.gif[/img]

[ March 03, 2002: Message edited by: urhere2 ]</p>

[Will]

Don't know how well I fit the qualifications outlined in the title of this thread, but I'll give it a shot...

1) CR will be in the neighborhood of 9.6:1 with a completely stock bottom end and assuming the heads have not been significantly milled. With the stock 185 HP cam and those heads, you're probably in the neighborhood of 220-240 honest horsepower, maybe a bit more if you have headers and a good exhaust.

2) Probably not unless you have a degree wheel and a dial indicator. Your best bet is to look on the end of the cam you can see for stampings or other identifying marks. If you do have a degree wheel and dial indicator, you can measure the cam lobes directly to determine how much lift and duration you have.

3) By pulling one jet out and looking at the numbers on it.

4) Probably more than you need to. Assuming a completely stock bottom end, I'd not rev above 5500, and I'd avoid that limit if at all possible. With a good rebuild, ARP bolts, forged pistons, better oil pump, etc. it will be good for 6000 RPM with stock rods. Again, unless you've got a healthy cam, it probably won't need to rev that high.

Hope that helps.

[78 GHOST]

What Will said, I won't comment further as I'm neither experienced or knowledgeable. -Matt [img]/infopop/emoticons/icon_wink.gif[/img]

[Half-Inch Stud]

urhere2,

Did you do a compression test,, on all 8 cylinders?

I would like to know the compression readings before advising on a tear down.

If the motor was a blowin smoke, at this rate I'd recommend Intake valve seals....

H.I. Stud

[urhere2]

Thanks for the info. That's what I wanted to know.

[Blackcat]

1) Assuming the internals of the block are stock, (including the cam)and the heads have not been machined, what would the compression ratio and approximate HP be?
Most likely around 300 hp
If the engine is using flat top pistons 10.5 to one. If using the sholdered pistons 9.5 to one Approximate. If the engine has been bored the number will be slightly higher.

2) Is there any way to tell what cam is in the engine without removing it from the block?
Not really unless you use a degree wheel. Best guess is something around a HO cam

3) I am almost positive that the jets in the carb have been changed. How can I tell what size jets are in it?
If you take the carb apart you will find the jet size stamped on the jet's themselves.

4) How many RPM's can I go to safely?
5500