400 engine combo what will it do?

[tony evans]

Hi every one i just bought a nice shiny 400 aly headed angine to liven up my 79 trans am but im not sure what to expect from the engine it has afr 210 cc aly heads with a comp cam solid lifters grind 294s which is good for 2500- 6500rpm range and an edelbrock rpm air gap inlet with a 750 vac sec carb,the worrying thing is i bought this a street motor and when i run the numbers through a cam quest software program it suggests a 3000 plus torque convertor im wondering have i bought something that will be a pig on the street as i have never driven any thing other than a stock convertor box.
any body got any ideas.
cheers

[rumrumm]

It sounds like a nicely matched combination for a street/strip car, but the cam and heads are a little big for my liking, especially if you have high gears in the rear. I think you would be happier with AFR's 195 heads which would give you better acceleration at lower rpms, and I would consider changing to a hydraulic cam around 230 degrees duration, something like a Magnum 280. But without knowing what type of pistons and the cc of the head chamber, it is hard to make a suggestion. Can you provide these details?

[tony evans]

HI thanks for the reply yes the heads are a 65cc as for the pistons i dont know im afraid as just bought the engine complete and assembled.
the cam specs suggested it be run at 9.5 or higher so i assumed it is 9.5.
dont want to change the heads but if need be bfore the motor goes in i would consider a cam cahnge (more money )

[tony evans]

HI thanks for the reply the heads are 65cc but im not sure on the pistons the spec on the cam called for a minimum of a 9.5 comp ratio and ive assumed thats what it is.

[tony evans]

sorry for the delay but i keep replying but it dissapears?
any ways the heads are 65cc but i dont know the pistons the cam calls for a minimum 9.5 1 ratio so i ve assumed thats what it is

[tony evans]

hi thanks for the reply it has 65cc heads but i dont know the pistons in the cam specs it called for a ratio of 9.5 -1 so i ve assumed thats what it has
cheers

[tony evans]

64cc head pistons 9.5 -1 did try to reply several times keeps dissapearing with some moderators message
cheers

[rumrumm]

64cc heads and 9.5:1 would mean dished pistons. You could switch out the cam to the one I run--a CompCams Magnum 280--which has an rpm range of 1800-6000 rpm. My 383 idles at 800 rpm and runs fine at lower rpms cruising around town. I use a 2500 stall converter which is a lot more street friendly than a 3000 stall converter. You should be able to sell the 210 heads fairly easily and I would recommend purchasing a set of AFR's new 195's which produce gobs of hp and torque. I had my engine dynoed, and it produced 450 hp an 468 ft. lbs. of torque. Those kind of numbers would make your Firebird a real street monster. With the 195 heads, you should be up closer to 475 hp and 500 ft. lbs of torque.

[tony evans]

many thanks for the advice although having just bought the engine its not what i wanted to hear as it means more money i thought id bought something i could just drop in and go.
if i change the cam to the one you us would it mean i have to also change the lifters and roller rockers?

[Dave Severson]

Kind of big runner sizes on the heads--and I'm with rumrumm on the cam being a bit much... IMO a bit of a mis-match--camming and runners that are good for a 7500 rpm engine and trying to get the power to work with a very streetable intake and carb at street rpm levels......

[techinspector1]

Hello Tony. I welcomed you on your initial thread and am pleased to see a rodder from the other side of the pond and to trade ideas back and forth.

I am what you might term the resident self-proclaimed math rat here on CHR. I take great delight in crunching numbers because to me, numbers are the definitive answer to any problem.

Now, with that explanation aside, I'll take a shot at your combination. I have to agree with the others that the heads are a little bit on the large side according to a rule of thumb I use. (CID x 0.5 = intake runner volume) for a street motor. For a more agressive motor, (CID x 0.55). Your heads fall right in the middle of this and in my opinion, can be made to work on the street with enough cam, static compression ratio, converter and gear.

When cam grinders post the operating range of a cam for a SBC, they are using the most popular motor used for hot rodding, the 350 CID motor. A cam which seems about right for a 350 under certain operating conditions will appear more tame when bolted into a larger motor such as your 400. Your 294S (I'm assuming this is the Comp 12-224-4 cam) is not necessarily too big for a 400, depending on operating rpm's, but it is too big for a static compression ratio of 9.5:1.

In order to generate good cylinder pressure (BMEP), the intake valve must close at a certain point commensurate with the static compression ratio built into the motor. The 294S cam would work well in a 10.5 to 12.0 environment. I figured the 0.050" tappet lift valve events of the cam based on information given on the Comp cam card. They are: intake opens 18* BTDC, closes 50* ABDC. Exhaust opens 58* BBDC, closes 10* ATDC.

Using the DYNAMIC compression ratio calculator on the Keith Black Piston site, I calculated your DCR at 7.63:1. Tony, this is leaving quite a lot on the table and I think you'll be disappointed with the performance characteristics of the motor. There are three scenarios:
1. Increase static compression ratio to more closely match the intake closing point of the cam and bring DCR up to 8.3 to 8.5. Install 3000 stall converter. A SCR of 10.5 would generate a DCR of 8.41 with the 294S cam. I might even be tempted to raise the SCR to 11.0 if I knew the motor had a good tight squish of 0.035" to 0.045" and that good fuel was available to prevent detonation. That SCR would generate a DCR of 8.8. You'd also need pistons with a large, flat area on the crown to mate up with the squish pad on the underside of the cylinder head in order to generate a good squish. Aluminum AFR's are recommended to use the Fel-Pro #1003, which is 0.041" compressed thickness, so the piston deck height would have to be zero or very near zero in order to create the necessary squish. I don't know what heads you have. You just said aluminum.
2. Decrease cam timing with an earlier intake closing point to more closely match the available 9.5 SCR and bring DCR up to 8.3 to 8.5. Install 2500 stall converter. A cam which closes the intake valve at 35* ABDC @ 0.050" tappet lift would generate a DCR of 8.4 with the available 9.5 SCR. Problem here is, the motor would run out of cam before it ran out of heads.
3. Bolt in a 3000 stall converter with the present configuration and hope for the best with your 7.63 DCR.

I don't intend to sound mean-spirited here, but perhaps that's why the motor was for sale.

If you'll post a detailed list of parts and dimensions, I'll be glad to run your combination on my DynoSim software and publish the results.

[tony evans]

wow!! didnt expect such an indepth response many thanks for that.i think the engine was origonally built with circuit racing in mind,but i innocently saw big hp numbers and torque and was told it was configured to pull well out of the bends so would be good for my street use.
i wanted to come up with the most streetable solution for as litlle extra outlay as possible,having just bought it.
i found the camp coms calculator and it says if i put in a 12-404-4 cam then ill get 425 hp at 5500 and 473 lbs at 4500 that would suit me fine although i would rarely use 5500 rpm the torque would get me moving fine.
Im not sure how accurate this all is!
the heads i have are the afr aly heads with 210 cc and 65 cc chambers.
the bottom end is freshened but standard pistons and crank and standard bore
im not able to calc compression i just guessed it would be up slightly on standard as the heads have smaller chambers the engine is a 2 bolt mid seventies,i think the origonal heads may have been 79cc.
it has the cam you thought it might be with the solid lifters the intake is the edelbrock rpm air gap and the carb is an edelbrock 750
dont know much more about it.
i spotted some little collars to insert to change the timing of the cam by up to 8degrees to move the operating range is this an option ?
once again many thanks
i lookm forward to hearing your response.

[rumrumm]

Check with the guy you purchased it from and ask what kind of pistons are in it. If they are flat tops, this engine will never run on pump gas. If they are dished, find out the manufacturer and part number so you can determine how many cc's the dish is. You really have to know this in order to make an informed choice about a camshaft.

[tony evans]

many thanks for that rumrumm i checked with him he said the pistons are the standard 400 whatever they were?
i will remove a plug later and have a look with a torch to see what i can see

[tony evans]

well had a look this morning with a torch in the plug holes cant see a thing only the valves.
im beginning to think the only way forward is to tear the thing apart and start again!
this in itself brings other questions having never done this.
1. can i remove the sump and remove a piston but leave the heads on?
2. if i do this is the sump gasket reusable
3. should i remove the heads and inlet to see the piston and then i can measure the deck height,would the gaskets be reusable on the intake and heads?although fully assembled the engine has never been run.
wonder how much a gm crate motor is?lol.
my brain is boggled i find this all very interesting but id rather be installing it.