I have a new set of Dart Pro1 aluminum heads that I am planning to install with Cometic head gaskets. Cometic recommends a surface texture of 50 Ra or less. I'm having a difficult time locating someone locally that can check the surface texture on these heads. Do you think these heads will be smooth enough "out of the box"?

 

No. My brodix heads were not smooth enough out of the box. I have a guy who can do it. I'll pm you his #.

 

I know mine didn't leak and my block surface wasn't very smooth. The head surface was good though.

 

I just got back from a local non-automotive machine shop. The owner looked at the deck surface and in his opinion, the surface is smoother than 50 Ra. He doesn't have a profilometer, so we couldn't measure the actual surface texture. All he has is a plate with different finishes to compare the surface against. I believe the checking plate had 16, 32, 64, 128, etc. finishes. I looked at this plate vs. the cylinder head and couldn't draw any definitive conclusions.

I want to emphasize that this was strictly his opinion based on his experience and the feel of the surface.

I don't think I'll have a definitive answer unless I can get these measured. Gotta love long, drawn-out hot rod projects!

 

Greg. If you still need the number for my head guy I'll get it, just let me know.

We put my heads in the machine and were shocked at how un even the surface was. It took 3 passes to get them completely flat. One side was very high like the head had been dropped on it's end sometime before it got to me. Although with a flat edge laying on it everything looked OK to the eye

 

I just returned from a tour of local automotive machine shops checking this out. I found one guy who had a profilometer and we measured the Ra anywhere from 46 to 52. This is right on the borderline for what Cometic recommends and we didn't check every square inch of surface on the head.

Another weird thing is that the finish on the deck surface almost looks like it was sanded after the milling operation. Every shop I took the heads to thought that something didn't look right about the surface finish when compared to other heads that they have seen. I bought these brand new from Summit, but who knows how the finish ended up this way.

Based on your experience, Dustin, I think I'm going to have the deck surfaces cleaned up. Like you said, there is no guarantee that the surface is flat, even on a brand new head. There are a few shops locally that I think can handle the job. We are planning to feed the cutter as slow as possible to obtain a smooth finish. Any other recommendations/warnings on this would be greatly appreciated.

It seems that the biggest complaint that I heard today about the MLS gaskets is the problem of water seepage. One shop said they had seen nothing but problems with MLS gaskets and that I should steer clear of them. The machinist at another shop said that he sprays permatex copper spray on the gasket and has had no problems with seepage. Cometic recommends a dry installation. Does anyone have any advice on this? Am I screwing up by using these MLS gaskets vs. a composition gasket (i.e. Fel Pro 1014)?

 

never had problems with them...

have been running the same set for 3 years now on 200 shot.

I am running r-302 block 342 with TFS street heats

 

:agree: didn't have a problem with seepage either and I also sprayed a 200 shot. Like I said, the deck on my block wasn't even close, my deck height ranged from .017 to .021

When I pulled the heads the gaskets still looked like new and there were no signs of seepage. I installed them dry.

Maybe I just got lucky.

 

running Dart Pro 1 CNC's on a BB Chevy with Cometics for 3 seasons.This year with twin turbos on pump(1600+hp already).Never had a set of Cometics leak anything.You HAVE to have a real smooth surface to make these work on the block AND heads.If you can see any swirl marks in the head or block then it's too coarse.I like to go over the heads with 1200 grit wet and dry on a sanding block every time the heads come off.....
Go with them as they are the best gaskets i've ever used....

www.redvictor1racing.co.uk

 

I had the heads touched up and of course the block was decked for the cometics. I used the .040 Cometic with the copper spray on them. I let them hang in the shop for an hour or so until they were very tacky yet almost dry and put the heads on. This was the way Steve Petty told me to do it at the time. I later had to remove one head and I just cleaned the copper spray off, recoated it, let it dry again and put the head back on. Sealed up just fine and no leaks.

 

I'm not biased in any direction but no matter what I did I could not get my SBC Dart Pro1s to seal w/ the Cometics and I had the surfaces done at the correct RA. Had a machine shop build the motor 1st, after it was leaking I went and had everything checked, tried to reassemble myself and the same thing. Went to the Felpro loc-wires and no problems since. On the corners of the head and gaskets there were slight variations and I've seen it brought up in a thread before and it may have been the issue?

 

I talked to Rick at Dart Machine today and made some interesting discoveries. The first is that the "sanded" appearance on the deck and intake surface was a process that was done by Dart. They ran a flat sanding board across these surfaces (with a machine) to rough them up for better gasket seal with a standard composite gasket. Apparently people complained about the finish so much that they discontinued that process. My heads were purchased in late 2004, so they were produced using this technique. The currently production Dart heads are milled to a 60 Ra finish.

The most interesting (and important) thing I learned has to do with the Cometic gasket compatibility with the Dart heads. Rick mentioned that one of the owners of Dart had issues with some Cometics awhile back. After talking with Kevin at Cometic, it seems that Cometic gaskets manufactured more than about a year ago were made so that the 3 raised embossments that seal the coolant passages between the cylinders on the intake side are incompatible with Dart Pro1 and Iron Eagle heads. The Dart head coolant passages are sort of triangular shaped and the gasket embossments are somewhat "mushroom" shaped. The corners of the Dart passages are not contained within the embossment and a leak will certainly occur here no matter what the surface finish. The early Cometics will work fine on all heads except the Darts. A design change was made about a year ago to the Cometic gaskets to make them compatible with all SBC 23 deg. heads.

This is a case of good luck/bad luck. Good luck that I found out about this before trying to fire the engine. Bad luck that I now have a $140 set of gaskets that are shop ornaments. The guy at Cometic said that he couldn't exchange them (even thought I called them back in 2004 and told them what heads & block I am using and they told me the part # to buy). Maybe someone else with non-Dart heads can use them. I'll make someone a good deal on them. The part# is C5327-040.

Has anyone tried some of the other MLS gaskets (Fel-Pro, Mr. Gasket)? Any pros/cons on these brands vs. Cometic. I'm a little pissed at them for not standing behind their product and would rather not put any more money in their pocket.

Thanks to everyone for the responses.

 

Dart block and AFR heads. I wouldnt worry about the specs so much. They will seal just fine.

 

A local builder uses the Fel-Pro MLS gaskets and likes them. Majority of his small block motors use Dart heads.

 

Dustin,

I sent you a PM - I'd like to contact the guy that uses the Fel-Pros to make sure I get the correct part #.

Thanks

 

I have run fel pro MLS gaskets with good luck at the 750 HP level. I recently had the engine apart and had read some info too about water passage compatability. The felpro gaskets were fine in respect to the sealing hump to the port but i compared them to a corteco composite gasket and noticed that the hole sizes were RADICALLY different between the two and members on this board had claimed overheating issues with the MLS and and DART heads. For monetary reasons, i switched to the corteco's and did notice some improvement in cooling but not a huge difference. As far as sealing, the MLS gaskets did a good job but i noticed the rubber coating kinda looking distressed between the cylinders to the point that i wouldn't have felt good about re-using them. They had about 20 passes on them in the low 10 sec. range. The heads are alum. DART 200 cc on a SBC 350.

 

I bought my Cometics about 8 months ago. I also have dart pro 1 heads. Do you think I will be ok?

 

After a bit of further research, I have purchased a set of Fel-Pro MLS gaskets (P/N 1144). Like you said, the embossments completely cover the head passages on the Dart heads. I also agree that the coolant hole sizes seem to be pretty small. On mine, the exhaust side coolant passages don't completely line up with the small hole in the gasket. I'm thinking of enlarging these holes slightly to promote better coolant flow.

Another thing I noticed about the Fel-Pros is that a couple of the rivets overlay either the block or head surface. I have seen somewhere that guys cut these rivets off in certain cases. Since I don't have a situation where a rivet is "sandwiched" between the block and head, do you guys think I will be ok to let it ride?

You may want to do some further investigation on this. I may have been incorrect in my earlier reply about the gasket being redesigned. When I talked to Cometic the next day, they indicated that the correct P/N for the Dart heads is a 5880. If you look at their web site, the 5880 is listed for the Dart iron heads. I think the aluminum Pro 1 and the Iron Eagle have the same water passage design, but I'd check with Cometic first. The 5327 may be incompatible no matter when it was produced. Sorry for the mix up in my earlier reply.

I didn't bother to get to the final answer because Cometic really pissed me off by advising me to order the 5327 in the first place. When I talked to the office manager, she acted like it wasn't their fault and wouldn't help me out in any way to rectify the situation. I try to steer clear of companies that operate like that and that's why I have gone with the Fel-Pro. I realize that a lot of time has passed since I purchased the Cometics, but IMO it's never too late to do the right thing.

I would call Kevin at Cometic (800-752-9850) and ask him to clarify this situation. He seemed pretty knowledgable and I think he could get you going in the right direction. If possible, please post the results in this thread so we can hopefully save any other unsuspecting enthusiasts from making the same mistakes. Once I get my hands on a digital camera, I'll post some pics of the misalignment on the 5327 gaskets.

 

Ok, I just pulled out my set of gaskests. Here is What I got. Seems to be a little diffrent that what you got. My block is 4.040 Bore. I guess the gasket has to be a little bigger than the bore size

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Well I finally figured out how to modify my pics & post them.

The areas highlighted with the green ellipses in the images below show where the problems are between the Cometic 5327 gasket and a Dart Pro1 head. If any part of the water port sticks out passed the raised embossment, you will have a leak.

It looks like your gasket is designed exactly like the 5327 with only the bore size being different. I wish it weren't so, but that's what it looks like.

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