Author Topic: pontiac 400 HP guestimate  (Read 1462 times)

Offline Tesla50

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pontiac 400 HP guestimate
« on: July 31, 2023, 08:17:21 PM »
Good evening. Due to having 3 engines disintegrate on me at a cost of $5000 each,
I had an engine builder just build be a basically stock 400 for my 71 firebird.
I'm just curious if someone would have an idea on how much hp it would be making with specs
 I have. It's a 400 bored .060, 1974 #46 heads milled to 90cc, and machined for large valves, kb pistons w/6cc reliefs, Howards cam HRCCL414645-10 213/221@.050 ,110 lsa, 485/475 lift.  I'm guessing compression is around 9:1. Also looking for advice on a timing curve for my distributor since I will be using pump gas now. Thanks in advance.

Offline Cliff Ruggles

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Re: pontiac 400 HP guestimate
« Reply #1 on: August 16, 2023, 03:07:13 AM »
#46 heads are excellent for "D" ports but don't make much compression on a 400 build. They are the hot-ticket for a 455 build with flat top pistons and often kicked aside by folks looking for big valve heads instead. 

I don't build Pontiac engines with compression that low, or use tight LSA cams in them so I'd be guessing at the power production.  It should make around 330-340hp (best guess) and 430-450 ft lbs torque.

The same engine with #16 heads (well prepared but no porting) and Crower 221/229/112 cam with make 419hp/453tq.  With the larger 228/235/112 cam 424hp/465tq.

With the Summit 2802 cam (224/234/114) 385hp and 445tq.

I also did a 400 once with a factory 068 cam and 670 heads but didn't dyno it.  It made great power, but not as much as any of the examples above.

The 400's are capable of great power.  Below is a link to a drag strip run that I helped out with.  I supplied the parts for the Q-jet, and built the TH350 for it.  It's nothing "fancy", has ported #48 heads, flat top pistons, steel rods and a solid flat tappet cam......

 https://www.facebook.com/100061932521804/videos/pcb.662098362531242/821130332784502