Rufus_911

Hello folks,

Currently my 1991 car has a new HT383 (ramjet cam, vortec heads) with TBI. (I found what I think were the last 2 remaining brand new cop car TBI injectors in the country.) It also has Rbob's engine computer.

I should probably just enjoy the car as is. But since I already have a complete speed-density TPI setup in my basement, I'm wondering..... would a set of new ZZ4 heads fit on this engine with no problems?

Anyone have experience with ZZ4 heads on a 383? Or would it be too much compression for pump gas?

Thanks in advance.

Rufus_911

I just looked at a similar thread by someone else and got some info. I should mention the pistons, if I'm not mistaken, have a -18cc dish.

InfernalVortex

iTrader: (4)

-18cc will net you about 9.5:1 compression with 64cc heads on a 383. Which ZZ4 heads are you talking about? There are apparently 3 different ZZ4's. SOme have fast burns, some have Vette L98 heads, etc. But if the heads are 58cc I would imagine that would put you in the mid 10s as far as compression, which would be perfect.

Just depends on your quench and gasket thickness etc, but it seems like it'd put you in a nice compression ballpark to me.

I remember trying to figure out what I would need to do to make my vortecs work with a 383, and between 15 and 20cc dish was the range I was looking at, and I think 18cc was perfect for 9.5:1 compression by my calcs if I recall, and in my opinion 9.5:1 is as high as you wanna go for a daily driver street car. You want one full number point higher with aluminum heads.

vetteoz

iTrader: (13)

Only ever seen one ZZ4 head listed and that is the 58cc version based on the Vette L98 casting

http://www.ls1tech.com/forums/3412016-post9.html

If a crate engine has Fastburn heads it is called a Fastburn

vetteoz

iTrader: (13)

Popular thinking is the Vortec heads are way superior to the ZZ4 heads except for weight

http://corvette.wikia.com/wiki/Head_and_Cam_Comparison

https://www.thirdgen.org/forums/post...52-post12.html

cuisinartvette

Going backwards with that swap imo

InfernalVortex

iTrader: (4)

Maybe they consolidated them? They have a 350hp zz4, a 355 hp zz4 (seem redundant to anyone else?) and a 385hp zz4.

350hp:
http://www.summitracing.com/parts/NAL-19201330/

355hp:
http://www.summitracing.com/parts/NAL-24502609/

385hp:
http://www.summitracing.com/parts/NAL-12496769/

To me the mystery is what exactly are the heads on the 350hp version. Surely they dont go through the trouble of making two versions with L98 heads with only a 5hp difference? Or bother with a different cam for a 5hp difference?

Damon

The first two are the same engine. Once "turnkey" the other a longblock. Not sure why they are rated 5 HP different but they are identical from the the valve covers down.

The last one is the "Fastburn 385" which has the factory ZZ4 heads replaced with factory "Fastburn" heads. Fastburn heads are like aluminum version of Vortec heads but with bigger ports and valves. Those heads are worth 30 HP over the lesser ZZ4 aluminum heads with no other changes.

NONE of those heads will allow your 87-up TPI system to bolt right up. The ZZ4 heads use the older 85-down intake bolt pattern and the Vortec and Fastburns have Vortec style ports and bolt pattern. Very few heads come in the now-defunct 87-up intake bolt pattern. I know Edlebrock sells a version of their Performer heads and I think AFR has an 87-up bolt pattern option on some of their entry level heads. A BETTER option would be simply to open up the 2 center bolt holes on each side of your TPI lower manfold so you can bolt it onto an older set of 85-down patttern heads and then select from zillions of different heads. Including the ZZ4 heads, with the exception that they lack an exhaust crossover port so your TPI's EGR system won't work.

Decisions, decisions!

vetteoz

iTrader: (13)

Very common for the likes of Summit and Jegs to mix names, info or mis-name completely.

As Damon says above; the Fastburn 385 uses the same ZZ4 shortblock as the ZZ4 crate engine

http://sdparts.com/details/gm-perfor...parts/12496769