How do you tell if you have the regular passenger 454 Mark IV block or the Bowtie Mark IV block? I've heard that the Bowtie blocks have siamese cylinders and are better but am not sure why. Any responses to better understand this are appreciated. My 91 crate engine casting number is 10051107 which I was told is a Bowtie block. I have the GM rectangular port iron heads and a GM hirise alum intake. I'm pretty sure I have a GM mild hydraulic flat tappet cam and am considering a new roller cam but am not sure whether to go hydraulic or solid. I've heard that solid lifter cams are more maintenance but am unsure what that means. I'm considering a cam/intake upgrade. Again, your patience and comments with me (engine/cam challenged!) are greatly appreciated. This is not a daily driver and visits lots of cruise-ins and the strip 4-5 times a year. Other relative info is in my sig. Thanks for your help.

 

I'll try to help some.

It sounds like you have a crate LS-6 motor. It should have 4 bolt mains, 7/16" rods, forged 10.2 compression TRW's, open chamber iron rectangular ports heads and depending on production date either a hydraulic or solid flat tappet cam. I know they changed to Hyd. in the later ones, but I'm not sure when. I remember seeing a dyno test between the two and they were nearly identical.

You have all the "good stuff"!

The bowtie blocks were never used in crate motors as far as I know. It is a heavy duty piece designed for racing. It has siamesed bores meaning that there is no water flowing betweent he cylinder bores. This alows the cylinder walls to be much thicker which allows larger overbores (4.625") and can maintain good cylinder shape at big bore sizes and make more power. It also has much more metal everywhere to make it an overall stronger piece. The oiling system is a little different too. If you are building the ultimate bad boy race motor it's a great choice!

For what you are doing you have a great basis. You could slip a real cam in there ( I prefer solid rollers) and do some mild port work and have a monster. 600 Hp would not be too hard to get!

Maintenance on solid cams is blown way out of proportion. Get a good set of rockers, and a stud girdle if you want to really get crazy and they are no big deal. You set them and they will stay just fine. Average street toy... set them a couple of times a year and forget them.

Your intake isn't all that bad. I've seen guys go 9's with that factory high rise.
Don't be too quick to get rid of it on a 454 based engine. There are others that will make some more power, but I'd spend the money somewhere else
first.

JIm

 

427Hotrod - After finding a better listing of serial numbers, I've found that mine is indeed the Bowtie block (YeeHa!). This motor is meant to run on pump gas and I'd like to continue that. Because of this I'm guessing I have between 8.5 and 9cr and may not have the 10.2 forged TRWs. The question is what would you do first - have the block bored to a bigger size or do the new cam. Define what you mean by 'mild' porting. I was told that the guy that put the engine in it took it to a NASCAR shop here in NC and had the heads polished and ported and the engine blueprinted but I have no way to verify it. I've read where others have the solid lifter roller cams and are up near or beyond 500hp. Is this possible while still having a relatively smooth idle on 92 oct pump gas with my block and heads? Other than the cam, what else would need to be replaced vs my present hyd setup? As always, I appreciate yours and anyone elses feedback! :cheers:


[Modified by Marks69BB, 6:23 AM 10/11/2001]


[Modified by Marks69BB, 6:38 AM 10/11/2001]