HI-PERF or PERF ??

[frank Bernier]

what is the dirrerence between HI-PERF and PERF ?

my 427 L-68 3x2 400HP 1969 as a 2 bolt 3935439 block casting number and it say only PERF ??? why is that ?? is it normal ???

thanks alot
Frank

[Mike S.]

Re: HI-PERF or PERF ??

390hp,400hp,where two bolt main blocks that say pass perf,435hp,430hp,were 4 bolt main blocks that say hi-perf.also had external oil passages drilled in blocks above oil filter for external oil cooler for racing.

[Terry F.]

Re: HI-PERF or PERF ??

It is just fine with 2 bolt mains. Though I am not certain, I believe that block can be configured either way (2 or 4 bolt). Someone else may comment on this also. My 390 hp is 2 bolt and original. Terry

[mike mccagh]

Re: HI-PERF or PERF ??

have seen 2 bolt's with either perf or hiperf. have seen 4 bolt blocks with either also. haven't seen any 396 4 bolt 962's with any thing other than hiperf. ain't seen em all though. mike

[Jack H.]

396 FYI

Early versions of the 396 '962 block read PASS while later versions for Corvette read HI PERF with the change coming on-stream approximately May of 1965...

[Mike S.]

Re: HI-PERF or PERF ??

do they say pass hi-perf,or just hi-perf?all pass hi-perf i have seen where 2 bolt mains and if only said hi-perf and not pass hi-perf where 4 bolt mains.mike

[Norris W.]

Re: HI-PERF or PERF ??

I don't think the perf or high perf definition has anything to do with the configuration 2 or 4 bolt wise. Most of my 427/454 stuff is 512 blocks and with the exception of the 351's in my 2 67's I don't have much other experience, BUT the 2 bolt/4 bolt configuration is nothing more than how the blocks are machined AFTER they're cast and anything that happens in the mold doesn't seem to follow an intended application trail. In addition to the oil cooler line threads machined above the oil filter, (both blocks have the same casting in that area) the 4 bolt applications in 427/454 blocks had reliefs or chamfers in the tops of the cyl walls to unshroud the valves that WERE NOT present on the two bolt blocks. From what I've seen (again somewhat limited experience) ALL 396 blocks were chamfered in that way regardless of 2 or 4 bolt application.

[Robert M.]

Re: 396 FYI

I agree with Jack. My 396 "962" block was cast March 15th. It has PASS not HI PERF.

[Jay Garris]

Re: HI-PERF or PERF ??

I have a 1969 Camaro SS 396 X-22, with a replacement 65 396 Block. Built late Feb of 65, Hi-Perfomance 4-bolt main, Solid lifter, definetly NOT a Z-16, seems like an old Vette 396. Hi-Po configeration.

[Mike McKown]

Re: HI-PERF or PERF ??

All I recall seeing was either "pass" or "hi-perf". Friend bought a new '69 Chevelle 325/396, Block was cast "hi-perf".

[Dan A.]

Re: 396 FYI

I had a C 15 5 cast 962 block and it had PASS and Hi Perf. I woud post a picture if I knew how.

[Wayne M.]

2-bolt 961 block E_14_5 has PASS at the ....

bellhousing flange (right side) and has PASS (and directly under) HI-PERF under the timing cover to the left of the cam journal.

[Mark #28455]

I have one that says "HI PERF ASS"

I guess the "P" got lost somehow! I currently own at least 20 BB engines and there seems to be no rhyme or reason to which ones say what and where. You can commonly find these marks in the timing cover area, on the side of the block over the oil filter, on the rear of the block in the bellhousing, and on the upper face of the bellhousing flange. Some also say "TRUCK" inside the bellhousing. More likely these were just used at the foundry to tell the sand cores apart from the truck ones - but some cores were interchangeable apparently such as the inside of the bellhousing and possibly the timing cover area.

Mark