LT1vette

Hi.... a couple of quick questions. Will LT4 heads bolt up to a LT1 intake manifold without mods I have access to a set of LT4 heads.
Which will show the best gain? Porting LT1 heads or bolting on "stock" LT4 heads.......if they do bolt up.


TIA B

MarkBychowski

Unfortunately, the intake ports will not line up. You have to use an LT4 intake with LT4 heads. Even with porting it doesn't work because there's not enough physical material on the LT1 intake manifold.

d48mclain

To be candid I've put LT4 intakes on LT1 heads, but never visa versa. With a little bit of metal welded in certain areas I can't see why not. The last time I stopped by Lloyd Elliott's shop Lloyd was saying certain LT1 intakes actually had more metal that could be removed by porting than LT4 intakes. So??

The LT4 heads are for sure better and if you can get a set reasonably, I'd jump on them in a heartbeat.

Tell ya what I'll do. Send Lloyd an e-mail and see what he says as he's seen/tons of LTx combinations and get back to the list but in my mind it wouldn't take that much to make the intake work.

VenkmanP

No. You have to modify the intake.


Ported LT1 heads have far greater flow than stock LT4 heads.


Try a search for these questions on this or any other LT1 forum you will find plenty of past threads.

Carpenter

I am led to believe both intakes have the exact same casting #'s?
Does GM then 'port match' the LT4 manifold at the factory? Or do they simply not bother to change the casting # for the LT4 pour?
Or, am I mis-informed?

rocco16

That's a pretty bold statement to make, not knowing how much porting was done or who did it.

For instance; I, myself, could port a set of LT1 heads and not only would they flow worse than stock LT4 heads, they'd probably flow worse than they did as stock LT1 heads!!

Stock LT4 heads are, essentially, welded-up and ported LT1 heads, wouldn't you agree?? So, why would welded-up and ported LT1 heads have "far greater flow" than welded-up and ported LT1 heads (LT4 heads).

I believe you'd spend a LOT of money before LT1 heads outflowed stock LT4's. Also, keep this in mind: max flow doesn't necessarily equal best street performance.....

Larry
code5coupe

d48mclain

If properly ported......absolutely. Your best bang for the buck will always be porting a set of LT1 heads. Hope I didn't mislead anyone with my answer above as my assumption was you were going to port both. Properly ported LT4's compared to properly ported LT1 heads are good for 15+ cfm. If funds are limited or you're looking at value, a good set of LT1 heads is hard to beat.

No....home ported heads do not count. Unless you're very savvy, only a fool would try to port their own heads without experience or a mentor and the proper equipment to check progress. The only exception I've seen is Jordon Musser who ported his own AFR 210s' but had exact instructions; port dimensions from a mentor and has an engineering degree. He made 472 rwhp with home ported heads which is absolutely a freak of nature and a fantastic accomplishment.

Wow…… almost don't know where to begin on this one. Stock LT4 heads are a completely different casting and in fact, aware of at least two different aluminum LT1 castings. One of the LT1 castings has more metal and can be taken out more to flow better so there is even a difference in LT1 heads. Both LT1 heads with stock valves and decent porting will outflow stock LT4's so there is not a lot of hoops to jump through to make them work.

Again, got an e-mail into Lloyd Elliott to get a true professional answer but if memory serves me correctly, the upper lip on the LT1 intake makes a very thin seal on LT4 heads. I could be wrong, as I think they will bolt up but you run a risk of a leak. Really believe all you need to add material and match the ports, but I'll let someone whom knows better qualify if and how it works.

Give Lloyd a while……he always returns e-mails but is probably porting heads right now.

VenkmanP

You appear to be completely ignorant on the differences between LT1 and LT4 heads as well as the cost of LT1 porting vs. the cost of LT4 heads.

[edit]typo[/edit]

VenkmanP

LT1 and LT4 intakes are a different casting.

d48mclain

Just like the heads, believe there are even a couple of different LT1 intake castings but didn't want to post it until I had heard back. The LT4 intake, is the LT4 intake!!! Whew! How did that get started??? Just painted red, huh. Well......now I know.

Not meant to neither be offensive to anyone nor mean spirited, but this list is not known for its technical expertise at times. Know someone posted they wished a few more of the really technical guys would post on this list but not sure how those vendors (what they really are) feel regarding how this list fairs compared to other general automotive community lists.

Unfortunately usually those people are making money off the members or it's a waste of time for them to go into such detail. Tony Momo of AFR did make a grand announcement on his new heads and it sounded like a few people actually thought you could make an extra 120 rwhp from just bolting on a set of heads. All I'll say is…….If that's what ya really believe, just go out n buy ya some of um. Another whew!!!

BTW.. he didn't make the same post on another list that comes to mind. Wonder why?? Somehow "blown out of the water by the members" also comes to mind.

Frankly a big part of viewing various lists is for me to learn things myself and this list can be a bit lean at times technically.

bobmic93

If you have Lt1 heads ported , they will outflow Lt4 stock heads! Are you on a budget with all this? Have a pro port your LT4 heads and by the new eddlebrock LT4 intake since you have the LT4 heads. With the right cam your going to turn your car into a rocket.

rocco16

No, not completely. (and I'll ignore your insult...for now)
I've seen the cutaways of the LT1 and the LT4 intake and exhaust ports. The LT4 ports are larger, straighter, and higher. It appears that it would take welding up LT1's to achieve the same configuration.

You may have misunderstood what I was saying in the previous post. I didn't mean to say that LT4 heads are just welded and ported LT1 heads, I said that's "essentially" what they are....that the LT4's can be equal to a ported LT1 head (with larger valves.) Of course they have a different casting number, are a different casting, and are a different head than an LT1 head.....that's what makes them an LT4 head!

While I haven't gotten quotes on LT1 porting, I do know that port work by proven specialists, with welding, does not come cheap. I'd bet that you could buy a set of LT4 heads for just about the same money that you'd spend to have a set of LT1 heads reworked to flow equal to the stock LT4's. After that, you could go even further on the flow numbers with additional work/$$, and you could do this with either head.

Is it cheaper (or better?) to achieve XXXcfm with inexpensive LT1 heads and $ZZZ in port work, or achieve the same XXXcfm with LT4 heads that cost the same $ZZZ? That's my question.

Larry
code5coupe

VenkmanP

It is a question?

It keeps coming across as a declaration that it is cheaper to get the LT4 heads. That is incorrect, and it is a FAQ.


Again, you haven't got a clue.

Stock LT1 (372 casting - the worst flowing in stock form) flows about 215/155 @0.6

Stock LT4 flows about 245/175 @0.6 list price $1350, can be had for $1200

"Budget LE1" ported LT1 flows 255/180, price $750 (and Lloyd generally sandbags on the flow numbers)

http://www.chevyhiperformance.com/te...ase/index.html

http://eportworks.com/index.htm

VenkmanP

Amen, Brother.

bobmic93

I have to disagree with you on all this. What do stock LT4 heads flow? If your going to tell me over 260 you may have a argument. My Lt1 heads peak 275(ported) and some guys reach 300.
We need to know Lt4 stock flow #s help us out here.

VenkmanP

I think you're right on that. There is an early and a late port shape on the intakes. There is also the L99 intake, which if I recall correctly is similar in port shape to the later LT1 intake.

One of the LT1 intakes is better for matching to the LT4 heads. Off the top of my head I don't recall which one. A search on camaroz28.com or impalass.com would answer this.

96Eric

There is an in depth comparison between LT4 heads and LT1 heads at the grandsport registry site. LT4 heads are superior and leave room for additional porting. Even the best ported LT1 heads won't flow as well as a good set of ported LT4 heads. Stock for Stock LT4 heads flow measurably better than LS1 heads.

link: http://www.grandsportregistry.com/lt1vslt4.htm#HEADS

bobmic93

We dont doubt that, but theres a comparison between ported lt1 vs stock lt4.

mffi115

I have LT4 heads, LT4 intake and the hot cam kit and have been screwing around putting off installing it on my 94 LT1. I plan to have a pro port match the heads and intake. Will I be wasting my time/money or is it worth the effort. BTW, I plan to eventually, if not when I do the install, put on LT headers and a PCM tune. The car will be a street DD.

ALLT4

I took the pictures from the Grandsport Registry and did some playing around with them. I know an LT1 intake will bolt to an LT4 head, the real question is will it cover and seal the top part of the LT4 head's intake port?

I think it will looking at the pictures, as long as the head's intake port opening at the roof does not protrude above the intake's flange there. Don't worry about sealing off the top of the head's (LT4) intake roof a little, if you could see how much the head's intake roof is covered stock, you'd be surprised. I saw it myself when I disassembled mine.

I believe the general theory goes; there was no power increase opening the intake manifolds roof to match the head's intake roof. It remains covered by the stock gasket and manifold.

Essentially a stock LT4 intake manifold port design matches the LT1's exactly. So there would be no detrimental effects (power wise) in using an LT1 intake as opposed to an LT4 intake. The only difference is the extra material at the roof of the port where it mates to the head. The stock cam the engineers decided to use did not warrant opening this area up to match the head.

Since the cast was already made that way though, it was left as is and the red powder coat differentiates the two. Also the extra meat up there allows opening it up and matching the head at a later time. Usually when you add headers along with that big winded cam that makes your pecker bigger and leaves stains in your pants.

BTW, don't worry about the angles; they look different in the picture. I assure it's just the way they were shot.